ported crossfire 383

Frankinvette84 · Mar 5, 2014

I want to put this engine under a ported crossfire manifold with stock ECM. What should I expect
http://www.tristarengines.com/catalog/h ... heads.html

I really don't want to go to a carb and I want to keep the originality of the crossfire

grumpyvette · Mar 5, 2014

the engine you linked too, will be a decent replacement for the stock engine but the stock crossfire intake is highly restrictive to flow until extensively ported and the option #1 cam should be selected as its the only option that might work with the TB cross fire injection with minimal mods and tuning.
the formula for horsepower is torque x rpm divided by 5252=hp
I doubt even once ported that the STOCK intake will support over about 4000rpm without becoming restrictive, given that Ill assume youll add decent headers, that will most likely result in a combo with a bit more power than the stock engine had but Id expect less than the full 375 listed hp.
personally ID buy the RENEGADE INTAKE (LINK)
http://www.crossfireinjection.net/
the stock 1984 cross fire cylinder heads are pathetically restrictive
more info
just a bit of info on those stock #624 head flow rates

.......intake....exhaust
.100..44..........41cfm
.200..101..........82cfm
.300.155..........125cfm
.400..182..........137cfm
.500..196..........140cfm
http://www.crossfireinjection.net/renegade.htm
CROSSFIRE

if I wanted to keep the original dual throttle body set up as its got more potential with less work than the ported L83 intake
best matched to a manual transmission.
the basic cross ram intake design has a lot going for it, its very compact and efficient.
where the chevy crossfire intake design fails is the port size runner length and the cylinder heads were all designed to maximize off idle torque with almost no concern for power potential once the rpm range exceeded 4000 rpm,
(exactly where the typical offanhauser cross ram intake just starts to shine in its power curve, with its much larger and more efficient intake design)
crossfire , (notice the much smaller runner size , less than 1/2 the cross sectional volume of the offy)

OFFANHAUSER BELOW

below the offy intake (below UPPER, the CROSSFIRE with its MUCH SMALLER RUNNERS LOWER)

http://garage.grumpysperformance.com/index.php?threads/the-cross-ram-intake.623/#post-53061

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.
we can sure help you make a lot fewer mistakes and help select good matched parts.
http://www.technovelocity.com/chevyhack ... olish.html

viewtopic.php?f=32&t=102&p=143&hilit=1984+crossfire#p143

viewtopic.php?f=32&t=640

viewtopic.php?f=32&t=303&p=986&hilit=1984+crossfire#p986

Strictly Attitude · Mar 6, 2014

looks like a cheap crate engine with a nice set of heads strapped on to it.

grumpyvette · Mar 6, 2014

If you want a high flow intake you can, locate a used OFFY, modify the OFFANHAUSER CROSS RAM TO FIT, as it has even bigger ports that easily support 500hp, but its not a direct bolt on swap

OFFY BELOW

https://www.corvettemods.com/C3-C4-...ke-Manifold--Crossfire-Injection_p_14318.html

http://garage.grumpysperformance.com/index.php?threads/ported-crossfire-383.10240/#post-41065

http://garage.grumpysperformance.com/index.php?threads/got-a-cross-fire-corvette.640/#post-25767

http://www.hotrod.com/articles/cross-ram-manifold/

http://www.technovelocity.com/chevyhackers/tech_articles/port_polish/port_polish.html
porting the original cross fire intakes basically wasted effort

http://www.ecklerscorvette.com/corv...24816-1-_-NA&gclid=CMbDzc74l8gCFQ6DaQodtFIGxw

there is a RENEGADE intake designed as a replacement for the OEM cross fire 1984 corvettes thats easily worth an additional 30 hp , or more
Dynamic Crossfire Solutions
http://www.crossfireinjection.net/
http://www.crossfireinjection.net/

WELL THE DYNO RESULTS ARE IN
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, If your intent is to significantly boost the cross fire engines power curve (and who doesn,t) keep in mind the stock twin throttle body injectors can support about 250hp if you turn the fuel pressure up to about 15 psi, but above that power level, your going to need to swap to higher flow rate injectors to keep up with the increased air flow and fuel demands

below a mildly ported OEM cross fire intake with its restricted runner design

http://www.airflowresearch.com/index.php?cPath=24_29
http://www.summitracing.com/parts/bro-1021001/overview/
http://www.trickflow.com/partdetail.asp ... toview=sku
http://www.profilerperformance.com/raci ... -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

Strictly Attitude · Mar 6, 2014

grumpyvette said:
If you want a high flow intake you can, locate a used OFFY, modify the OFFANHAUSER CROSS RAM TO FIT, as it has even bigger ports that easily support 500hp, but its not a direct bolt on swap

That is sexy

Frankinvette84 · Mar 6, 2014

I just found 2 cracks on(one on each side) of my orig.L83 block. I had just finished an entire interior update and my paint is a good 9 out of 10 so I don't mind putting around $4000. into having a pretty much brand new 30 year old corvette . NOW for this investment I was hoping to get acceleration close to a newer vette (late c5). I'd hate to go backwards in tech. by going carberated but I think that's my easiest and most economical way if cant make my crossfire perform. If I went to Offy. or Sy1 how much fabbing is required . My goal was to do engine between now and summer... drive and enjoy car ... then next winter do the trans and maybe dana44 swap. I'm into this 1984 for the long haul. I've had for over a decade and hope to be driving it a couple more (at least

) so I wanna have fun doing it...Thanks

Frankinvette84 · Mar 6, 2014

Checked out OFFY', looks like it wont fit under the hood. Has anyone modified a stock air cleaner so it will sit on top of a carb but still looks like the crossfire is under it. "tricky ". and is there any way to keep the mpg and miles to empty gauge operating ? then there's that TC.switch thing. AHHH P**P. Now I remember why I didn't want to go to a carb. Ideas please. Help. the weather is going to get nice sooner or later and I need my Vette.

Strictly Attitude · Mar 7, 2014

so you have a set budget of $4000 is that a max or is there a little play in ther? Your current block is cracked from what I got? I think you have the right idea with the crate engine.

just an idea for your budget
you will need to buy a balancer and use your othe components
http://www.summitracing.com/parts/mll-b ... /overview/

Frankinvette84 · Mar 7, 2014

That was the original engine I was looking at. Then I saw the Tristar one had dart heads and a better cam selection. I'm just looking for the best engine I can put under a highly ported crossfire manifold and I know I'm pushing the limit but I would ilke to get to the low 13 -to high 12 second 1/4 mile range. I know there are folks here who have similar things. I'm just trying to gat as much info as I can before choosing a new motor....I wanna go FAST

philly · Mar 8, 2014

Frankinvette84 said:
That was the original engine I was looking at. Then I saw the Tristar one had dart heads and a better cam selection. I'm just looking for the best engine I can put under a highly ported crossfire manifold and I know I'm pushing the limit but I would ilke to get to the low 13 -to high 12 second 1/4 mile range. I know there are folks here who have similar things. I'm just trying to gat as much info as I can before choosing a new motor....I wanna go FAST

is there any real reason you wanna run the crossfire? it wouldnt be much to get a used lt1 intake and use it there and pick up GOBS of untapped power... the modification process used to be posted up on www.lt1intake.com but apparently the website is down

Frankinvette84 · Mar 9, 2014

I would like to keep it as stock looking as orig. besides I already have the crossfire(making it less expensive then Lt1) and would like to keep my mpg and dist until empty gauge in the center of my dash. BUT the LT1 idea seem cool. im' trying not to use a carb just seems like going backwards. Thanks

87vette81big · Mar 9, 2014

I think the Renegade intake is overpriced .
Much better can be had for less.
Offy cross Ram.
Smokey Yunick Signature Cross Ram.

grumpyvette · Mar 9, 2014

he following are different static compression ratios (SCR) with a 3.48" stroke and different camshaft intake closing points @ 0.050" tappet lift on Keith Black's dynamic compression ratio calculator. The calculator, starting at 8.25:1 SCR. The dynamic compression ratio (DCR) has been kept at just over 8.0:1, a figure that is acceptable for use with today's pump gas with a little cushion:

watch the video, and like I stated many times,
its the combo of the engines,
compression,
displacement ,
cam timing
and the exhaust scavenging ,
and the intake manifold design,
NOT the intake port cross sectional area,
that are the most critical factors, in the engines lower rpm and mid rpm torque.
but for damn sure an intake runner port can be small enough to noticeably restrict upper mid range and peak power significantly,
For 5 decades I've heard endlessly about how installing larger free flowing cylinder heads would devastate the engines ability to make any low or mid rpm torque.
especially when Id suggest using a set of smaller 300cc-320cc, aluminum,rectangle port heads on a 496 BBC, or 200 cc-210cc heads on a 406 sbc, I was asked to build
yet on every engine I've ever had built or had some guy ask me to look at, to see why it ran a great deal less impressively than he expected it too,
they brought into my shop its was very obvious (at least to me) that it was the combo of low compression, too little displacement, with too much cam duration ,
a restrictive exhaust or some guy who was trying to save money and continuing to use a stock stall speed torque converter, or retain a badly mis-matched 2.87:1-3.08:1 rear gear ratio,
with an engine that he miss matched components by slapping a large carburetor , and a single plane intake on,an engine that will rarely exceed 6000 rpm, that was the major reason.
if you want an engine combo to run your first step is to logically match the list of components you,ll use to the application,
and that requires you stop, engage the brain and think things through carefully,
and the most common way to screw up the process is to over cam a low compression engine,
have a restrictive exhaust or mis-match the drive train gearing to the engines power band.

Static CR....Intake closing point @ 0.050"....Dynamic CR.
8.25........10* ABDC......8.010........................................................................................................
8.50........20............8.012........................................................................................................
8.75........27............8.022........................................................................................................
9.00........33............8.018........................................................................................................
9.25........37............8.061........................................................................................................
9.50........42............8.029........................................................................................................
9.75........46............8.016........................................................................................................
10.00.......49............8.038........................................................................................................
10.25.......52............8.043........................................................................................................
10.50.......55............8.029........................................................................................................
10.75.......57............8.069........................................................................................................
11.00.......60............8.022........................................................................................................
11.25.......62............8.038........................................................................................................
11.50.......64............8.042........................................................................................................
11.75.......66............8.035........................................................................................................
12.00.......68............8.017........................................................................................................

87vette81big · Mar 9, 2014

grumpyvette said:
in my experience the offy can be made to fit and function well on a 383 in a c4 corvette, with two 500 cfm carbs and produces good hp

I seen a Smokey Yunick Signature Cross Ram on a SBC 377 .
Installed in a Base 1970 -1/2 Firebird Espirit.
Joliet , IL area about 2007.
Car was Race Cammed. Flat Tappet Mushroom lifters.
About 260 @.050".
.575 " lift
Car sounded great @7,000 RPM.
Pair of Holley 600 cfm carbs.
Sticks in my mind Grumpy.
I would not hesitate to use an Offenhauser Crossram.

I purchased a Vintage Offy Intake for my Olds 425.
Port Cross section & pinch point not bad.
Price was right & no corrosion damage.

philly · Mar 9, 2014

Frankinvette84 said:
I would like to keep it as stock looking as orig. besides I already have the crossfire(making it less expensive then Lt1) and would like to keep my mpg and dist until empty gauge in the center of my dash. BUT the LT1 idea seem cool. im' trying not to use a carb just seems like going backwards. Thanks

i understand, its just with the big cid motor its something like an olympic athlete having to perform while breathing thru a coffee stirrer

Frankinvette84 · Mar 9, 2014

I understand I'm not going to get full potential out of engine, I'm just hoping to get to run as well as I can with the crossfire if that's in the high 12's low 13's I may leave it for a while. I've heard this can be done by porting and adding bigger injectors(65-90gph) to "trick" the ecm into behaving. and if I don't like what it is I can change the induction system to something that will make the engine perform and fit under the hood. Has anyone herd of modifying the stock air filter housing(that lines up with vents in hood) to accommodate a carb. I would think I could do it by cutting the bottom out and replace it with a piece of sheet metal.

Strictly Attitude · Mar 11, 2014

http://www.competitionproducts.com/Long ... ucts/1225/

Look around here they at least let you know exactly what your getting

ported crossfire 383

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