got a cross fire corvette


Staff member
Got these pics from another forum; they are of the new Renegade manifold for the CFI installed on a 1984.
The following is a statement from the makers DCS:

Please note that we are not releasing any internal pics or technical specs at this time. The reason for this is the design is not 100% finalized - we are still tweaking things. But here is some basic info.

* Runner cross sectional area is presently approx 30% larger.
* There is a 20% taper from inlet to outlet.
* True Crossram design style with optimized runner configuration but modified for our application.
* The outlet is slightly smaller than a 1205 gasket. This is done to make sure there are no leaks and a good seal is obtained.
* Plenum area is 20% larger than stock.
* True OE design on the top plate. All brackets are in their stock locations. Just bolt it on and everything is located where it should be.
* Same overall height as the stock manifold.
* EGR is built in if it is needed.
* No issues with removing valve covers. ... olish.html
1.94/1.50 2.02/1.60

heads tend to crack if over heated or incorrectly torqued
if you have zero deck to head distance I'd suggest a .040-.042 thick head gasket should be used

for a 9.3 compression, 327 with a 3.08 rear gear, and auto trans, Id suggest a cam like a crane 114132

with the correct matched components 350 hp should be doable, btw mild port and bowl area clean-up can allow these heads to have improved flow, they will never be a great choice but they can be improved
use of long tube headers a low restriction exhaust and a cam with a bit more lift and duration can help compensate for the restrictive ports some what.
I would certainly suggest a decent performance dual plane intake be selected,and port matched, and you certainly don,t need to spend a fortune
something like this easily improves flow if matched up correctly
We decided to use my 84 as the mule because of the hood clearance concerns. 82 Vettes are roomier in the engine compartment.

YOU MAY WANT TO READ THRU THESE LINKs ... ration.htm ... ancing.htm ... ration.htm News.html ... olish.html







this may interest you

THE HEADS ON THE 1984 cross fire corvettes are pathetic also

Heads: Iron, casting number 462624
Chamber Volume: 76cc
Intake Valve size: 1.94"
Exhaust Valve size: 1.50"
Intake Port Volume: 158cc
Flow Numbers:







viewtopic.php?f=52&t=5364&p=16066&hilit=head+flow+numbers#p16066 ... 5/A-P1.htm






if you have a cross fire 1984 corvette with dual throttle body injection your dealing with what is eventually a very restrictive set of heads fed by an extremely restrictive intake on an engine thats designed to operate at under 4000rpm, that makes a factory rated power curve under 220 hp.

your original cross fire throttle body injection intake was and is VERY RESTRICTIVE, there are far better intake manifolds, cylinder heads and cams available, to upgrade a cross fire corvette. , for both upgrading the TBI or swapping to a carburetor fueled engine

READ A FEW LINKS, and sub links, it should take you a few hours to read most of the related info but it could save you weeks of work and a good deal of ca$h






renegade intake
mild cam
better heads
roller rockers
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Ive had several cross fire owners driving the 1984 corvettes ask about upgrading to the TPI as it flows a bit better and makes even better power than the crossfire engine, and the real question , that instantly brings up is why would any sane person going thru the trouble time and expense to upgrade from a totally restrictive cross fire system to a new EFI system select a stock TPI when theres several much better options
really you have two valid options, you can either upgrade the current intake, with a custom, or renegade intake, which is basically a parts swap, that will increase the engines ability to breath with a much less restrictive intake design, but one that allows you to keep the stock throttle body's and computer controls, sensors, etc.
keep in mind before you make any changes step back mentally and ask yourself what your real goal and budgets are and if you can reasonably expect to reach that goal with your budget and skill level, a bit of research can save you a great deal of wasted time and cash. If you take the time to do a bit of research youll find that you have several options, and starting with the basic 1984 sbc engine MIGHT NOT be the best choice if you want more than about 350-375 hp

crossfire1.jpg ... olish.html
keep in mind , if your starting with a stock cross fire 350 corvette engine, your only starting with a stock 205 hp/290 ft lbs of torque... one of the first questions most guys who own a cross fire engine ask is whats the best cam upgrade, well obviously the answer is dependent on several factors like what if any other mods are to be done to the engine, but if your corvettes essentially to remain basically stock other than the cam swap upgrade Ive had very good results with the CRANE 114122 for cars with an automatic transmission (usually worth about 22-25 rear wheel hp with zero bad habits) or the CRANE 114132 with cars having a manual trans.(usually worth about 30-35 rear wheel hp with zero bad habits) and in either case 1.6:1 roller rockers seem to add additional responsiveness, but obviously clearances in the valve train must be verified and if necessary corrected


82crossfire.gif ... 3230_1.pdf


or get something noticeably better , but to take advantage of that youll also want better cylinder heads cam upgrade and headers, with a low restriction exhaust.



if you want to perk up a cross fire corvette porting the stock cross fire intake and a cam swap helps
but replacing a stock restrictive intake to a converted SY1 or SMOKEY RAM INTAKE, or the new renegade is a HUGE improvement in air flow!

Still think you should look into the SY1 Edelbrock intake(pictured above), there is only so far you can go with the CFI intake


IF your thinking you can port the stock intake and heads......Ive got some advice gained thru experience

don,t get the idea I'm against the x-fire system,design, it has potential,
I'm just against throwing money down a rat hole!
one option....selecting the aftermarket cross-ram bases matched to a correctly matched cam, better heads and a low restriction exhaust with decent headers can make a huge improvement.
but the stock intake, heads and cam are KILLING your potential power


Ive been playing at the hp wars for years,your stock heads,intake, displacement and compression ratio and cam are killing performance. the cross fire intake is the worst offender as it only flow about 170cfm-190cfm
swapping to a EDELBROCK SY1 OR OFFY CROSS-RAM INTAKE with CUSTOM LID removes that restriction


custom lid SY1

compare the ports, the SY1 flows about 270cfm

IF its to retain the stock auto transmission and rear gear ratio,
<b>"A MODIFIED EDELBROCK SY1 WITH CUSTOM TOP MATCHED TO 190CC AFR HEADS, or BRODIX IK HEADS, or TRICKFLOW 195 cc HEADS, CRANE 114142 CAM -- AND add a 383 high compression engine kit"
but if youve got a MANUAL TRANSMISSION, and a 3.54:1-3.73:1 rear gear, you can step up too a significantly more aggressive cam like a crower 00320, if your willing to put up with a lopey idle and adjusting flat tappet lifters occasionally, but you WILL NEED TO HAVE EITHER SWAPPED TO A CARBURETOR(S) OR DRASTICALLY RE-PROGRAMED THE COMPUTER CONTROLS ON THE EFI if you've retained the TB injection, and naturally swapping to carburators requires a different fuel supply and pressure regulator, ... &x=35&y=12

BTW Ill save you the math, you'll need to get the 10:1 cpr flat top piston 383 kit for the street, and the 74cc combustion chambers AFR 190cc HEADS with L98 spark plug angles if you intend to run high test gas you find everywhere (some is lousy quality) and get the head gasket as close to .018-.022 as you can for correct quench
fyi DD-2000 and EA pro both guess at OVER a 115 hp improvement at the rear wheels, having done this type mod in the past Im reasonably sure that's UNDERESTIMATED for those listed changes

383 rebuild kit $1000]
crane cam/lifters $150
AFR heads $1200
SY1 with custom lid $500-$600
DOING YOUR OWN WORK>>>>>PRICELESS! :thumbs: :thumbs:


Part numbers are 5893 base,

5903 for the dual-four top,

5902 for the linkage.


MORE USEFUL INFO ... ration.htm ... ancing.htm

unless your rich or hopelessly masochistic get a SY1 or OFFY BASE

the sy1 flows close to 270cfm out of the box, a cfi flows 170-190cfm (DEPENDS ON WHICH PORT (STOCK) and theres not enough room to port without cutting/welding (EXPENSIVE AND TIME CONSUMING AND EASILY SCREWED UP)



If you intend to build a SBC with a corvette cross fire engine as a starting point,
we certainly have a good deal of related info you can use.

carefully reading the threads and links will be very helpful.
as youll see the web site is set up to teach and answer questions and if you have anything , youve learned that might help other members ,please post the tips, pictures and info.

theres a great deal that can be done, but I'm forced to point out that the Stock cylinder heads and intake are killing the engines potential, and obviously both your budget and skills might limit or increase your options, upgrading the intake and heads and cam will be key to good results, obviously a low restriction exhaust and headers and possibly a increase in compression and displacement sure helps


this is the port work necessary to get them to flow even as pitifully as a TPI
for those guys that suggest swapping to a LT1-4 and MPFI on your 1984 crossfire...
just so your not confused, or under the wrong impression, the offanhauser intake base significantly out flows even a ported LT4 intake,doesn,t require re-plumbing the coolant flow like on the LT4 intake,(remember the LT1 and LT4 have no place to install a radiator hose or distributor in stock form),the offy, will function with minimal rewiring,and has a wider effective power band ONCE ITS CORRECTLY MODIFIED with the correct dual TB top or if you just use the dual 4 barrel top plate and a couple 650cfm carbs like many guys use, plus if its correctly done the engine appears to remain stock too the average casual inspection as you can still use the stock air cleaner assembly with the custom TB top, but the windshield wiper motor needs to be replaced with a smaller version for clearance issues

one of the most restrictive components on the x-fire is the less than ideal #624 casting cylinder heads, one factor that gets discussed a great deal is the difference in port size or port CCs, the sad truth is that Id bet 90% of the discussions are just guys repeating stuff they have heard with zero real idea what they are talking about.
while theres generally some relation of port cross sectional area to the listed port CCs its NOT a direct linear relationship, and its the cross sectional area,shape, length and surface finish not the port CCs that matter to the air flow., and if the exhaust system can,t effectively scavenge the cylinders or the intake can,t supply the flow, or the cam duration and lift don,t match the intended port flow rates performance will suffer

The first thing I hear is usually some guy suggesting vortec heads, as an example its been my experience that standard vortecs become a restriction above about 4500rpm compared to several options, and are not the best selection if your trying to exceed 430hp, (vortecs also require an intake and rockers and valve covers that match) the BRODIX,AFR and TRICKFLOW heads in the 180cc-200cc range matched to a decent cam and a better intake can produce a huge boost over a stock x-fire

you don,t build an engine combo by selecting just heads, first and then matching the other components to that head flow rates, you select a hp/torque/rpm power band as a goal and then select the necessary components to slightly exceed that hp/torque/rpm power bands requirements knowing all parts NEVER work at 100% of the potential when matched in a combo.

TBI Fueling Introduction:

Second only to the stock TBI ECM, the stock TBI fuel delivery system leaves a lot to be desired. Starting at the tank the fuel pump is a turbine pump. Quiet and long lasting, but weak fuel delivery. The fuel pressure regulator is set for approximately 12 psi (30 psi on '94 & '95 BBC trucks). With a service range of 9 to 13 psi being considered good. This equates to a 17% to 20% change in injector flow rate over the service range. Then the stock injectors are just large enough for the engine they were on top of.

From all of this, it is obvious that GM never put a TBI unit on anything but a low performance engine. The largest GM TBI unit was provided on the BBC 7.4l trucks. This is a 2-bbl unit with 2" bores.

Even though in stock form TBI setups were never used on a performance engine, it doesn't mean that they can't be used on a high performance engine.

All is Not Lost:

There are several ways to increase the flow capacity of the TBI unit and the injectors. The TBI units can be bored out larger for more airflow. Two 2-bbl units may be placed on a dual-quad intake manifold. Holley and Accel make 4-bbl TBI units. For additional fuel larger injectors and/or high fuel pressure can be used.

The first thing to do is to start with a decent estimation of engine horsepower. For the best results be reasonable in this estimate. From this we calculate the required fuel for that horsepower. Then work toward the required injector flow rating. Selecting the injector and fuel pressure that delivers the required amount of fuel as the final step.

Calculating Fuel Requirements:

You knew there had to be some math. Can either use your Windows calculator or open a spreadsheet, then follow along.

An important parameter in engine performance is known as Brake Specific Fuel Consumption (BSFC). It is the pounds of fuel required to generate one (1) crankshaft HP for one hour. The lower the number the more efficient the engine. Engines using gasoline with forced induction (turbo/supercharger) run between .55 and .60 BSFC. That is it takes between .55 and .60 pounds of fuel to generate one horsepower for one hour. An engine with moderate compression ratio and so-so heads the BSFC will be about .50. An engine with higher compression ratio and a decent chamber runs about .45 BSFC. With ultra high performance engines running .35 BSFC and lower. If you have the engine dyno'd (not the car) the BSFC can be measured.

For your basic high performance street engine with decent heads a value of .45 is typical. Let's say that the engine is making 400 HP peak. How much injector is required?

First calculate the amount of fuel required to produce 400 HP at a BSFC of .45:

400 * .45 = 180 pounds of fuel per hour (#/hr).
Then factor in a maximum of 85% duty cycle for the injectors:

180 / .85 = 212 #/hr
The duty cycle of the injector is the ratio of on time to the available time. Note that this is not the best method. The available 'off' time is really tied to RPM, not a duty cycle. With the injector firing synchronized to spark plug firings, the available time is less as the RPM increases.

OK, now we know that the engine requires 212 pounds of fuel per hour to produce the rated 400 HP. To do this with two injectors each needs to provide half that amount.

212 / 2 = 106 #/hr per injector.
As of writing this there are no 106 #/hr TBI injectors available. However, by using BBC 81 #/hr injectors and increasing the fuel pressure the 106 #/hr delivery can be achieved. To calculate the required fuel pressure we will use the square of the ratio of the injector flow rates (the 13 is the stock fuel pressure in psi for the rated 81 #/hr):

SQ(106 / 81) * 13 = 22.3 psi (To do this with the Windows calc put it into scientific mode: View->Scientific. Then use the x^2 function for SQ).
By using two 81 #/hr injectors at 22.3 psi they will provide 106 pounds of fuel per hour per injector. This is enough for the 400 HP. And by running the fuel pressure above 18 psi it is a perfect candidate for a Vacuum Referenced Fuel Pressure Regulator (VRFPR). See further along for information on the VRFPR.

Fuel Delivery

So now how do we get 22.3 psi of fuel pressure. First thing is to install a high pressure pump. Second is to install an external FPR or modify the stock one.

For a fuel pump be careful to not purchase the biggest baddest pump there is. High pressure pumps move a lot of fuel at 43 psi (port fuel pressures). And deliver even more fuel at 22.5 psi. The TBI unit, regulator, and return fuel line need to pass back to the tank any fuel that isn't used by the engine. A pump that is too large can cause the fuel pressure to increase above the set point.

Vacuum Referenced Fuel Pressure Regulator (VRFPR):

Once the fuel pressure is over 18 psi a decent upgrade is to use a fuel pressure regulator (FPR) that is referenced to the intake manifold vacuum. This vacuum referenced fuel pressure regulator (VRFPR) changes the fuel pressure as the engine load changes. A higher engine load equates to a higher fuel pressure along with a higher injector flow rate. And with a lower engine load a lower fuel pressure along with the lower injector flow rate. This not only makes tuning easier, the engine also runs better.

To take advantage of a VRFPR you need to use an ECM that is set up to handle the varying injector flow rate. Both the EBL Classic and EBL Flash have the required calibration parameters for this.

Note that an external port style bypass FPR can be used for a TBI setup. Normally a TBI setup runs a consistent fuel pressure. To do this with an external regulator leave the vacuum port open to the air. To use the regulator as a VRFPR connect the vacuum port to intake manifold vacuum. If using a port on the TBI unit for manifold vacuum double check that it is manifold vacuum and not 'ported' vacuum.

A note about MPFI FPR's when connected to manifold vacuum. This has the actual fuel pressure changing with manifold vacuum. However, it is done to provide a consistent fuel pressure across the injector. With the spray end of the injector exposed to manifold vacuum, the fuel pressure needs to change in order to have the same fuel pressure differential between the inlet and outlet of the injector.

On a TBI setup the injector spray end (outlet) is basically open to the air and is not exposed to manifold vacuum. So by vacuum referencing the FPR the actual fuel flow of the injector is changed. We take advantage of this trait when using increased fuel pressure and a VRFPR on a TBI setup.

Back to our calculating fuel requirements 400 HP engine example, use a 2-bbl BBC TBI unit with the 75 or 81 #/hr injectors. Then use a VRFPR set at 23 psi (26 psi for the 75 #/hr) with the vacuum line off. This setup will easily support 400 HP with good driveability.

Injector & TBI Unit Information

GM produced TBI units in both 1-bbl and 2-bbl configurations. Single 1-bbl units were used on 4 cylinder engines. Dual 1-bbl units were used on the Corvette and Camaro Crossfire injection setups.

In the 2-bbl TBI series the popular units are found in three sizes:

  • 2.8l and 3.1l engines:
    • have 1-3/8" bores and flow about ?? CFM
  • 4.3l, 5.0l, and 5.7l engines:
    • have 1-11/16" bores and flow about 490 CFM
  • 7.4l engines:
    • have 2" bores and flow about 645 CFM
The flow ratings are approximate and are at 1.5" Hg. This is the same pressure that 4-bbl carburetors are rated at.

For injectors they come in various flow rates. The common injectors that are found in the above TBI units are:
  • 2.8l and 3.1l engines: 33 #/hr
  • 4.3l engine: 45 #/hr (note: some units have different flow rate injectors. This is done to help with fuel distribution.)
  • 5.0l engine: 55 #/hr
  • 5.7l engine: 61, 65, & 68 #/hr
  • 7.4l engine: 46*, 75 & 81 #/hr.
*Just watch for the '94 - '95 BBC truck units as the injectors only flow 46 #/hr at 13 psi. Which is 74 #/hr at the 30 psi these TBI units use. On the up side they come with a 30 psi FPR. The down side is that the injectors are small.
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not knocking or praising this product
just looking forward to testing one
and yes Im only too familiar with the delays and problems of producing components on more than a custom,one of basis,
for at least a year Ive heard rumors that the RENEGADE x-fire intakes will be available shortly and they have a PRE-BUY deal going, but It seems like its always taking a little longer ...........I was wondering if any ones seen any progress or knows whats REALLY going on here , when products are ACTUALLY going to be delivered
these might be a really nice intake, but until I have one to test & tune its just pie in the sky
so I was hoping you guys have the strait scoop

Dynamic Crossfire Solutions






the OEM crossfire heads for 1984 are casting number 462624 76cc heads
462624 chevy head flow numbers
(these are the heads that came on the 1984 corvettes)
just a bit of info on those stock #624 head flow rates

The 624 is a light weight version of the 882 head.,. The 624 is one of the worst that GM produced and not intended for high performance use.

every time I hear that MYTH,
( that starts out with, BUT THE 1984 MAKES GOBS OF TORQUE) I want to point out a few facts

right from Chevy (1984 vette)
Net HP @ RPM 205 @ 5200
Net Torque @ RPM 290 @ 2800
Comp. Ratio 9.0:1

The new RENEGADE intake ALONE on a stock crossfire engine, with its factory intake, replaced, with the newer renegade intake, produces 32 hp and 16 lbs/ft of torque at the rear wheels over the stock crossfire intake, adding better flowing heads like the AFR or BRODIX , profiler or TRICKFLOW heads,

below a mildly ported OEM cross fire intake with its restricted runner design
manifold7.jpg ... toview=sku ... -23-degree
in the 195cc-210cc range and a decent cam like a CRANE 114132 (btw thats a good street cam for the basic crossfire engine but with a 3.73:1 rear gear, and a higher stall converter speed it can use a bit more cam than that also, easily boosts that result, add a 3.73:1 rear gear ratio and a 3200 stall converter if its an automatic transmission and it will preform like a totally different car, ID expect more like 60-70hp and 60 more ft lbs at an absolute minimum PLUS with all those component changes, depending on the components used, a more radical hydraulic roller cam in a 10:1 compression 383 could certainly boost results much higher doubling your horse power from stock is certainly obtainable as a goal

ok lets keep this rather basic, on a $3000 budget Id go this route, now obviously you could make a bit more horsepower with higher dollar parts but I think a combo like this should provide decent value, in increased responsiveness and acceleration, over the stock engines power level for the money spent.
the stock engines make a bit over 205 hp
many 1984 cross fire corvette owners will brag about the low rpm massive torque the original cross fire engines have, but the truth is that the intake manifold, cylinder heads cam and even the original throttle body's and the fuel pump that supply those throttle body's are all nothing short of pathetically restrictive compared, to whats currently available and rather easily acquired and can be used to upgrade the original engines meager power level to something that's far more robust and effective.
keep in mind you don,t need to start converting the engine to some totally different high rpm small block that spins at 7000 plus rpm, the original concept of the cross fire intake design with its long runner design was and is to maximize the low and mid rpm torque, but in the last 31 years a great deal of improvements in component design and new parts have become available, the renegade intake design is specifically matched to that lower rpm power band, but to take full advantage if the increased flow rated a slightly longer duration cam, much better heads (but keeping a rather effective 175cc-195cc port size) and swapping to a 3.54:1 or 3.73:1 rear gear to move the whole power band up about 800 rpm-1200 rpm higher and extend its upper rpm effective reach about 1000 rpm, from the original 4000 rpm-4500 rpm too, the now available 5000 rpm-5500 rpm ,while still maintaining and even increasing the available torque and instant responsiveness of the original design is not only easily accomplished but can produce rather amazing results, but you will need to look at the concept as a combination of matched parts that are well designed to work together,each boosting the other components effect on the wholes NOT the random swapping in a few better performing individual components.
the change in cylinder heads,intake, cam, rockers and the rear gear ratio that allows the car to maximize it higher torque and horse power potential will be very noticeable in the drives seat, the heads and cam, intake and gearing all maximize that 2000 rpm-5000 rpm that will be used the vast majority of the time on a street driven corvette.
A combo like this will produce a nice boost in performance, but before you ask, no you can,t mix & match or only install part of the combo, it won,t work to near its full potential unless all the parts are correctly installed and the cars engine adjusted and tuned to take full advantage of the increased air flow,and higher effective average useful rpm band

the renegade intake is a good value
$544.99 ea.
, its worth about 30 hp over the pathetic o.e.m cross fire manifold
your stock cylinder heads are very restrictive

$843.00(easily 35-40 hp if used with the cam and intake)


the crane 114132 cam is the largest Ive found that works reasonably well with the basic OEM THROTTLE BODY INJECTION (also worth about 20-30 hp)

$34.97 timing set, yours is without doubt in need of replacing

1.6:1 ratio ROLLER ROCKERS
$237.99 (almost required to maximize the head flow and worth 12-15 hp in reduced friction and increased lift at the valve)
your up to about $1900 at this point, youll need another $80-$100 in sealants and gaskets, you may be able to reuse the push rods but check the rocker geometry
spend the rest on a DANA 3.73:1 rear gear ratio and its install cost
the combination of these parts will produce what your looking for, a noticeable increase in performance, if you don,t get ALL the parts it won,t work nearly as effectively




the milder cam (cranes 114122) is easier to tune and will still give you a noticeable boost in performance, of about 20-25 hp, over the stock cam, but its also not going to give as much power over about 4500rpm as the slightly longer duration version (crane 114132)
the scorpion 1.65:1 ratio rockers, or the 1.6:1 Jegs rockers have almost no effect on the idle characteristics , as they don,t do much to the duration or LCA. just increased valve lift and on these mild cams that extra lift helps



the forged steel rockers generally clear in most application if the short nuts are used





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drop back to the basics of fuel spark timing , valve timing and compression

1) whats the compression NOW and check MORE than just cylinder #1

2) verify TDC

3) verify your getting fuel pressure

4) learn how to adjust valves

5) learn how to degree in a cam

6) timing ... sIndex.htm
geekinavette posted this

"First things first...retrieve the ECM code(s). This can be done with a simple paper clip or by purchasing a OBD1 (On Board Diagnostics, 1st generation) code scanner. To use a paper clip, just use it to jumper pins A and B of the ALDL connector (mounted under the dash to the right of the steering column). Turn the ignition on (do not start!) with the ALDL jumper installed, and the CEL (Check Engine Light) will flash stored codes. The first code will always be 12 (no Distributor Reference Pulse...or in other words the engine is not running). To display a code 12 the CEL will flash once (1), then pause, then flash twice (2), then a longer pause, then repeat this process two more times (every stored code is presented three times). After the last code 12 is presented, it will pause a little longer and display any other codes that are stored in the same manner.

Some definitions...

Throttle Body Injection
As ex-x-fire mentioned...a "wet flow" system, which means that fuel AND air flow through the intake manifold (as opposed to a port injection system which injects fuel directly at the cylinder, so only air flows through the intake manifold). The crossfire system uses two Throttle Bodies, each feeding opposing sides of the engine (thus the term "crossfire"). Some TBI systems use a single "dual barrel" throttle body, with two bores and two injectors, but all within one housing. Many consider TBI to be somewhat of a "hybrid" system between a carburetor and modern port fuel injection systems.

Electronic Control Module
Also referred to often as the "computer"...which is really what it is, albeit a very slow one.

MAP sensor:
(intake) Manifold Absolute Pressure...reported to the ECM in Kpa (and being a physics professor you already understand the significance of the word "absolute" here. Yes it is just a basic absolute pressure transducer). Manifold pressure is directly proportional to engine load.

Throttle Position Sensor.
Nothing more than a potentiometer between a fixed 5V and ground with the wiper lead reporting a voltage to the ECM that is directly proportional to throttle position. The adjustment of this is important so that the ECM can detect idle as well as WOT (Wide Open Throttle) conditions (as well as other conditions, but these two are important). The TPS mounts to the driver's side TBI unit, actuated by a lever connected to the throttle shaft.

Coolant Temperature Sensor
A simple thermistor used to provide engine temperature information to the ECM. (not to be confused with the temp gauge sending unit...yes they do the same thing but these are two separate sensors).

Idle Air Control.
This is a stepper motor mounted to each throttle body with a tapered cone plug attached to a lead screw. There is an air passage that bypasses the throttle bore (kidney-shaped hole on the top of the throttle body base), the IAC motor will extend or retract this "plug" to control how much air is allowed to bypass the throttle bore. This is used to control idle speed mostly, and is also used as a "stall saver" device.

O2 Sensor:
Just that...a device that measures oxygen content in the exhaust stream, used by the ECM (in addition to other sensors, like MAP, CTS...etc) to control fuel flow to the engine.

Electronic Spark Control/Electronic Spark Timing. Modern-day equivalents of the old vacuum operated spark advance.

Fuel Pressure Regulator
In contrast to a carburetor, fuel injection controls fuel delivery by pulse-width modulating a solenoid inside the fuel injector. How much fuel is delivered is determined by how long the solenoid is engaged in combination with fuel pressure. Obviously higher fuel pressure will deliver more fuel for a given pulse width. You can see here why fuel pressure is very critical in any fuel injection system. When checking fuel pressure it is very important to not only check pressure at idle, but under engine load also. The crossfire system is a serial plumbed system...fuel flows through the first throttle body (passenger's side), then to the second throttle body which contains the fuel pressure regulator. The stock injectors are rated at slightly different flow rates to compensate for the small amount of pressure drop between the two injectors (inherent in any series system), so if the injectors are removed for any reason it is important that they be replaced in the original locations.

The term "dual plumbing" probably was referring to the fact that the crossfire system uses two independent throttle bodies...each with its own fuel feed/return as well as IAC valve (where as the "dual barrel" setup just has one fuel feed and IAC valve). However as with most dual plumbed systems, it is NOT a parallel plumbed system.

There's no mystery to it...all of the laws of physics apply. I would not go the route of just buying stuff and replacing it...all that does is waste money and you won't really learn anything, and likely you won't fix anything either. There are items that wear out that manuals and "normal" repairs aren't going to cover. However with that said...a Factory Service Manual is an invaluable tool.

Again...get those ECM codes! You have to start there.

Some other nuances specific to the crossfire system...

As mention in the previous post...fuel pressure! The stock '82 and '84 fuel pumps are notorious for falling short under heavy engine loads...they just can't deliver enough flow to maintain the required 13-14psi of fuel pressure. (yes the FSM states 10-13, but there's enough experience out there that will agree that 13-14 is really what is needed). A common "upgrade" is to swap the stock pump with one for a TPI (Tuned Port Injection) '85-'89 or so Vette. The TPI system requires more pressure, so the pumps are inherently designed to deliver more flow so as to maintain correct pressure. You will not effect pressure by upgrading to a higher flow pump, the Fuel Pressure Regulator takes care of that.

Throttle Body Balance! Being independent throttle bodies, they MUST be balanced! One item that tends to wear out and severely upset this balance is the throttle shaft bores. You can do a quick check by just feeling how much movement there is of the throttle shaft within the throttle shaft bores. This "play" allows the throttle plates to move around, and it takes very little of this movement to upset the balance between the two throttle bodies.

Vacuum Leaks! The intake plenum "lid" is notorious for developing vacuum leaks...not to mention old and cracked vacuum lines.

These are probably the most common ailments of the crossfire system that effect driveability and reliability.

Once again though...before any of this stuff is addressed...

RETRIEVE THOSE ECM CODES! (yes it is important enough to yell) "
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a few useful wiring, and related diagrams for the 1984 crossfire corvette













this should be the 82 crossfire wiring diagram.. you might want to print it...


grounds are at B6, B12, B13, A15 shows as a ground... i wonder.

you will also want to print this one..



on the far right of this image blow.. is the EGR control valve.. note the ground wires for the fuel injection system are attached to the bolt next to it...

there are more ground wires stashed around the car.. and ALL ARE IMPORTANT to be cleaned..

here is a list of data stream from the 84/89 models. the 82 won't show this many...


lastly... the coolant temp sensors that are screwed into the FRONT of the intake manifold.. NOT in the heads are horrible.. replace with an SU102 from autozone or wells.. they come with a pigtail also for 3 bucks more than just the sensor.. the only difference is the type of connector... Ask for it by part number.. as they will try to sell them to you individually.. for double the money.. hmm..

lastly... take off the distributer cap... expose the coil.. also .. examine it for signs of high voltage leaks from the sides...

take a bright flashlight and check the sides of the pickup coil for signs of broken magnets in the stack.. the thermal soaking these get under the corvette hoods is tremendous.. if you have to pull the distributor.. please preset the crank so the rotor is pointing in the proper direction and the reluctor tips and the pick up coil tips line up perfectly without going past and needing to turn the crank backwards... then look at the timing marks.. where do they line up.. this can save a LOT of time... as they are a PAIN to get the distributer out and in.. and dead stick timing it works great...

sorry if i have bombarded you with info... i went to GM training school on feedback carbs and these throttle body fuel injection and also port fuel injection systems..

if you get in trouble.. check your private message...
Post Reply

Posts: 122
Joined: 03/13
Posted: 05/19/13 06:11 PM

these images are for the 84 models. but are almost identical to the 82 models.. 82 models used an earlier computer than the 84s did..



su102 coolant temp sensor kit


this is probably an 84.. i don't think the battery is in this location.. i usually work on C4 versions.. not the slightly earlier 82 crossfire versions...

please look at all the ground connections that you have... and they ALL GO TO DIFFERENT circuits.. they all have to be intact...


if your thinking of buying a renegade intake upgrade here is a damn impressive limited time sale

Read more:

the symptoms sound like a defective sensor or fuel pump or fuel pump relay, but read through the links it will prove useful.
as is true with many questions here theres a few related threads that may hold the answer your looking for in the links and sub links





87vette81big said:
I was around on old Corvette Forum when we had factory C4 EFI tuning bashes.
Dave Dahlgren was the most experienced & knowledgeable around.
He taught me.

When GM EFI cars are at WOT, the O2 sensor is bypassed, taken out of the ECM input parameter.
The ECM commands a Super Rich 10.0:1 air to fuel ratio for 2- 5 seconds. This is done so the factory catalytic converter is quenched cooled immediate. Important on C3 & C4 Corvettes with Fiberglass floor pan so it does not catch on fire.
After the quench time cool time down the air fuel ratio is brought to around 12.5 :1 WOT.
Not 14.7 :1 as you would assume.
Can only be checked with a wide band O2 sensor gauge or on a chassis dyno with a tailpipe inferred sensor sniffer.
But it does happen this way at WOT.
Why your not experiencing engine knock at WOT.

Also make sure the Harmonic balancer outer inertia ring has not moved or slipped.
1982-1991 Corvettes had the same 6-1/4 " inch OD balancer.
If it has moved any, you will never be able to set base ignition timing correct on your Crossfire C3.
Went through that this past fall with a Fellow DC members C4 1985 TPI Vette. Road trip to Kentucky. Brought a new Napa Harmonic balancer with me just in case.
It did fail & spin 120 degrees.
Covered on Grumpys Performance forum my adventure.
Rubber dry rots out with time. All bound to fail eventual with hard driving.

The original GM Top End Cleaner that came in Steel Oil Can was the best Decarbonizer I ever used in the past Marc.
You would Open the hood & Remove air cleaner(s).
Rev engine to 2,500-3,000 rpms. Pour cleaner in slow over 30 seconds.
If you missed pouring still sucked in.
Last 1/3 of can you dumped in Fast. It would flood stall the engine.
Shut ignition key off & wait 15 minutes.
Restart with foot on the floor gas pedal.
Once engine catches & takes off ease off gas & let idle.
The GM Mechanics next to You , The Boss man Service Writer ran for cover, Even Dealership owner dissapeared.
3 minutes later Smoke gone.
Test drive. Throttle response better. 9 out 10 times spark preigntion gone.You cleaned backside of Intake valves spotless. Combustion chambers, piston dome crowns. Freed up Top Piston Fire Ring too & correct backclearance back. Shit carbon non existant.
Be a Great way to get rid of Al Gore & his Piss Ant EPA Bastards today.

The GM Top End Cleaner sure did a superb job of decarbonizing an engine.
We used it on high mileage late model EFI Engines too.
On a 4 BBL engine with a Q Jet, I would look in afterwards using, Flashlight shining, seen spotless Intake floor and Forward intake runners.
Maybe your Local GM Dealership still has a few cans of GM Top End cleaner around in the storeroom. Have to ask them .
It was a special mix concoction of light Aromic petrolium based solvents.
Funny brown tan liquid poured out of can. Had its own unique smell.
Viscosity thinner than water.
Was not MEK Acetone based. I know that putrid smell.
GM Hired the best Mobil Oil Engineers in the past to solve tough problems.
Where GM EOS Came from. I know that guy. Around 80 now.
All the Good stuff has gone away or forgotten.

Seafoam does a pretty good job. No where near as good as that Old GM NOS TOP END ENGINE CLEANER.

Brian R.
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step back and consider what your goal might be and your budget, then ask yourself if you want the corvette to run better while you maintain the basic original cross ram dual throttle body induction?
or are you more concerned with getting the corvette to run considerably better and far less concerned with maintaining the original look in the engines intake design?

we are all forced to work on limited budgets, but if your going to maximize a cross fire engine combo...
the most restrictive components are the stock intake cylinder heads, exhaust system, and cam
Id suggest you replace the intake with that renegade, intake and I do at least some port and runner clean-up port work,

Id suggest you call AFR and brodix about cylinder heads in the 180cc-200cc range
the key to good power is in good heads maximizing the mid rpm air flow and a cam that will match the intake and head flow characteristics, you might also consider a 383 stroker assembly to maximize low speed torque.
(its a very cost effective way to boost torque and hp an easy extra 40 ft lbs and 45 hp in most cases)
Id suggest getting the static compression near 10:1
Id strongly suggest you replace the exhaust system with a 3" and (X) pipe design with low flow restriction mufflers

and add full length headers


keep in mind that a properly designed exhaust system and headers goes a very long way towards increasing the efficiency of the intake manifold and head flow , and remember that the better the heads and the more effective the exhaust scavenging the less duration the cam used will require!
Id suggest a mild hydraulic roller cam and use of quality roller 1.6:1 ratio rockers
Id be looking for something in the 215-220 duration on the intake at .050 lift, call and get suggestions from crane, crower, erson, etc.
the basic intake design and port config of that renegade intake design will limit the engines power band to near 2000 rpm-6000 rpm so a longer duration cam will mostly reduce lower rpm torque
Id suggest a 3.73 rear gear ratio
Id suggest a 2400 rpm stall converter
these two drive train mods maximize the cars ability to use the power produced

carefully reading through
these links and sub links will help
ITS GOING to be well worth the time and effort
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Upgrading a Cross-Ram Manifold
Written by Ed Taylor on December 11, 2013


Building a Twin Four-Barrel EFI Manifold for the Street

Those who follow such things will tell you that the best designs not only perform well, but that they just flat look good too. There are certain designs that will always be timeless, like the near-perfect form of a P-51 Mustang warbird or the shape of a 1955 Chevy taillight. Such a case could be made for the cross-ram manifold. The idea was simple enough. It’s really nothing more than a horizontal tunnel ram. There are plenty of early examples of the tunnel ram. The Chrysler-bred Ramchargers designed a crude but effective tunnel ram out of lengths of rubber hoses fitted to a large box on top of which was bolted a couple of carburetors.

But it wasn’t until the mid-1960s when that idea finally caught hold. In 1966, Trans-Am took off and suddenly short stroke 302ci small-block Chevys were in need of eight barrels worth of air and fuel. But these little motors also needed torque to pull them off the corners and that demanded intake manifold runner length. The current eight-barrel intake manifolds lacked runner length, so an enterprising engineer, probably in the employ of General Motors, created the cross-ram manifold. All he did was lay the runners down across the top of the manifold so that the added length didn’t pop through the hood. With that elegant solution, generations of hot rodders were entranced with the idea.

That lust for an exotic eight-barrel induction has never really gone away. Combine this with a better understanding of engine tuning and the effects of a pair of big carburetors on a small displacement engine and we have circled back to resurrect an old-yet-new Offenhauser manifold on our 1955 Gasser project. (As luck would have it an Offy manifold base (PN 5893), a manifold top (PN 5903), and the appropriate linkage kit (PN 5902) were waiting for us on a back shelf. You can still order these part numbers from Offy but they may be on back order.) Form demands that we not place a mundane single four-barrel on such an aggressive nose-high Gasser so the cross ram seemed a natural, if for no other reason than Gassers never came with such an animal. But function demands that beyond killer looks our eight-barrel adventure must also work. So that became our quest and the not-small effort that ensued.

Watch Heat Kills Power—The How and Why
Street Rodder Editor Brian Brennan wanted one of Offenhauser’s cross rams to put on top of his retro 327 small-block being installed in the 1955. Ironically, among the dusty piles of tooling in Offy’s backroom were the exact pieces necessary to produce one of these discontinued manifolds. The die was, ahem, cast and the result is what you see here. But that was just the beginning. Most rodders would be content to add a couple of early Holley four-barrels or perhaps even a pair of early Carter carburetors, but while this is a classic retro ride, there aren’t any rules that we had to follow the norm. The best way to add a little 21st century flash was to integrate a pair of electronic throttle bodies using FAST’s EZ-EFI system. Usually the FAST system is designed to operate with just one four-barrel throttle body, but FAST offers a system with a piggyback harness to connect to the second slave throttle body with injectors only. This adds a wire harnesses to the top of the manifold but that was relatively easy to disguise to maintain the look of a typical 1960s Gasser induction. We added a retro-looking fuel line and some slick throttle linkage pieces and we were in business. Follow along as we chronicle the crossover of a 1960s manifold into a current piece of fuel injection technology. Don’t forget to stay tuned for the buildup of our Retro-Tech 327, which will grace the pages of this magazine in the next couple of months. We will once again be combining both old and new technology in our 327 Gasser motor. Who says you can’t teach an old dog a few new tricks?


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