tweaking the l98 for a bit more hp

[grumpyvette]

just hit continue at the top of each link for more useful info

Keep in mind even the factory 502 cubic inch big block used the stock L98 TPI throttle body size and made 500 horse power

yes a 58mm can potentially increase hp if your engines highly modified and your still using a stock 48mm throttle body, but its hardly a big restriction, and your probably going to gain more with other mods

http://www.wallaceracing.com/chokepoint.php
If you calculate the point where dual 48mm throttle bores become a significant restriction to flow on a 383 SBC
youll find you need to spin it to well over 10,000rpm

http://www.corvettemagazine.com/2000/ma ... /l98p1.asp

http://www.corvettemagazine.com/2000/ma ... l981p1.asp

http://www.corvettemagazine.com/2000/ma ... l982p1.asp

http://www.corvettemagazine.com/1999/se ... /l98p1.asp

http://www.corvettemagazine.com/2002/ap ... ance-1.asp

http://www.compcams.com/Community/Artic ... 1737510521

vaguely related builds

http://www.vetteweb.com/tech/vemp_0607_ ... index.html

http://www.superchevy.com/technical/eng ... index.html

http://airflowresearch.com/articles/article031/A-P1.htm

http://www.summitracing.com/parts/EDL-3817

swapping to VORTEC HEADS AND ADDING A 383 stroker kit can do wonders for your cars power curve

http://www.summitracing.com/search/Prod ... toview=SKU

http://www.summitracing.com/parts/SUM-151124/

summit sells a VORTEC TPI BASE, to convert your current TPI intake to the vortec HEADS

IF your goal is to have a significant increase in torque, to match the stock rear gearing, and keep the basic low rpm torque and response of the stock tpi and don,t mind the engine nosing over on power as it runs out of air flow at about 4700rpm

build the 383 add the vortec heads and a decent cam, like a crane 114132, keep the cpr down in the 9.0-9.4:1 range so you can run pump gas, get the quench in the .038-.044 range and enjoy smoking the tires

you'll have a very noticeable gain from the increased displacement and better head flow, and have a great combo for cruising and daily driving, far to many guys get fixated on the potential peak hp numbers , that the bigger heads, and larger cams can produce at the cost of lost low rpm power,rather than the much more useful low and mid rpm torque curve that makes the car fun to drive on the street
you could easily gain 70-80 hp OR MORE thru those mods (heads,intake,cam, stroker kit)
verify the quench and compression ratio, when you add the 383 kit, keeping in mind vortec heads have small combustion chambers that may require dished pistons and limited valve lift due to valve train clearances
http://www.summitracing.com/parts/CRN-114132/

(the crane 114132 cam should clear easily) and add the cam with new flat tappet lifters or if its a roller engine get a mild roller cam, swap to the vortec tpi intake base, the rest is fairly strait forward since you have a vortec engine your starting with, but keep in mind the damper and flywheel/flex plate balance used on the 383 must match the crank balance, so verify internal or external balance on the crank, and remember your current flex plate and harmonic balancer may not work on a 383 depending on your other component choices



hp is great for bragging but an instantly responsive engine with a great deal of low and mid range torque is a lot more fun on the street

 

[grumpyvette]

when you start out thinking your going to modify a TPI, engine ,youll want to keep in mind the stock TPI l98 engine factory heads flow less than 210cfm with a mild port clean up and about 200cfm in as installed form, the TPI intake itself effectively restricts flow above about 4500rpm the cam has a duration and lift that basically restricts power above 5000rpm, the stock 350 displacement and fairly low compression ratio doesn,t help and the rear gearing is usually in the 2.87:1-3.07:1 range, the original L98 engines made less than 260hp at the rear wheels, the factory exhaust is not designed to flow any where near the required flow rates to support over 400 horse power so with that in mind your going to need to make major changes
now that doesn,t mean its hopeless but it does indicate the need for rethinking the combo and parts selection and realizing that the whole power curve and all the air and fuel flow rates MUST BE INCREASED,IF YOUR INTENDING TO INCREASE THE POWER PRODUCED, now depending on the compression ratio, cam selected converter stall speed and rear gear ratio, a larger 383-421 displacement SBC certainly could be configured to use a slightly larger port size than the AFR195cc, but that head is a very good match to the FIRST intakes basic power range and I certainly would not go swapping them If I currently had those heads and a FIRST TPI intake as the basic start points building a 383- 421 CID SBC engine.
a 3000rpm stall converter a 9.8:1-10.2:1 cpr 383- 421 sbc and a CRANE 119661 hydraulic roller cam, 1.6:1 rockers , headers , low restriction mufflers 32-36 lb injectors should produce a very effective torque monster and a 3.36:1-3.73:1 rear gear sure won,t hurt

heres DD2000 softwares wild guess keep in mind the stock trans shifts at about 5200rpm so past that in the rpm range is meaningless, and the car will shift at its hp peak and fall into or very near its torque peak with a 3.54:1-3.73:1 rear gear

keep in mind this software dyno above shows the results of a cam thats not nearly large enough in lift and duration to maximize the engines power potential, but without changes from the stock components to a 3200rpm stall converter, a 3.73:1 rear gear ratio, better headers, better intake and heads a larger cam like a crower 00471, or crane 119661 ETC, that could easily boost total power won,t work correctly, engine components need to be selected as a MATCHING SET, designed to operate at a pre-planed power,rpm and air flow level.
you may find reading through these links of interest
viewtopic.php?f=32&t=430

viewtopic.php?f=69&t=3814

viewtopic.php?f=52&t=5078

viewtopic.php?f=44&t=38

viewtopic.php?f=50&t=428

partly clogged injectors, or injectors running at over 80% duty cycle tend to reduce power and increase emissions

intake runner stack length changes, and to some extent cam timing can be used to tune the torque peaks, but cross sectional area of the runners and head ports will dictate a great deal of the air flow speed and where the restriction to flow occurs

READ THRU THESE LINKS

http://www.trickflow.com/articles/dynod ... _heads.asp

viewtopic.php?f=44&t=38

http://www.rustpuppy.org/chp/goodwrench5-1.html

viewtopic.php?f=52&t=5078

viewtopic.php?f=52&t=181

viewtopic.php?f=52&t=3802

viewtopic.php?f=52&t=322

viewtopic.php?f=52&t=333

viewtopic.php?f=69&t=3814

Hi guys, I am looking at purchasing the 508HP Blueprint Engines 400 Long Block. This engine comes with Blueprint aluminum heads which have a 220cc intake port and a 64cc combustion chamber which puts compression at 10.3:1

I have a new set of AFR 195 Eliminator heads with a 65cc combustion chamber. Below are the flow numbers for the blueprint heads that come on the motor vs my AFR 195's.

The AFR's seem to outflow the blueprint heads by a fair bit and use a smaller intake runner. Given this information if everything else was left the same do you think I would make a lot more power with the AFR heads?

Cam Specs for the Engine
Cam Specs:

Cam Type: Roller
.555 Intake .576 Exhaust
236 Intake / 242 Exhaust duration
@ .050 - 110° lobe separation
With 1.6 Roller Rockers



Intake

Intake Runner Volume (cc): 220cc
Intake Port Location: Standard
Intake Valves Included: Yes
Intake Valve Diameter (in): 2.08 in.
CFM Port Flow Average @ 28"
.100" - 76
.200" - 137
.300" - 189
.400" - 228
.500" - 254
.600" - 258


Exhaust

Runner Volume (cc): CNC- 65cc
Exhaust Valve Diameter (in): 1.600 in.
Exhaust Valves Included: Yes
Port Shape: Square-Port
Exhaust Port Location: Standard
CFM Port Flow Average @ 28"
.100" - 112
.200" - 155
.300" - 186
.400" - 203
.500" - 208
.600" - 216

(NOTICE THE SPECS ARE SIMILAR TO CROWERS 00471)