L98 performance help needed!
 

I have a 90 model L98 shortblock(rollercam) with Dart Pro aluminum heads(200cc intake runners, 64cc chamber with angle plugs,2.02 and 1.6 valves), with throttle body injection(454SS truck throttle body) on a 84 vette. I was wondering if switching over to tpi would increase the hp, and fuel economy. It feels slower with the dart heads compared to the stock aluminum heads. I was thinking that multiport injection would make up for the bigger heads that I added. Maybe I made a mistake by putting too big of a head...so I am trying to make the best of things. I do know with tpi, the pulling stops at about 5k....which is fine. Im looking to complete my engine package making more low to midrange power, with decent mileage. SO what do you think will a stock tpi setup help me, or should I go with something like the miniram from tpis? What about the cam.....I wouldnt mind changing the cam too but again I dont wanna hurt my mileage! Any suggestions guys on how I can make the best of my setup?


[Modified by MrCrowley, 6:57 PM 12/9/2003]

Re: L98 performance help needed! (MrCrowley)
 

A miniram would be a better choice, the heads are too big for the motor and their huge ports are killing your low-end.

You would be better off by either going to another intake, or by adding rear gear and stall converter to the tranny if its an automatic.

Re: L98 performance help needed! (MrCrowley)
 

Gear & Converter !! No tuning problems !! :iagree:

Re: L98 performance help needed! (MrCrowley)
 

The TPI intake will surely help with low end torque but I'm not sure about those heads. With 200cc runners and 64cc chambers they may be a bit much for your setup. I think a set of used #113 heads pocket ported would do better.

I bought a used TPI setup from a Forum member for $100 for the purpose of porting.

For a cam, try a nice flat tapped cam unit combined with 1.7:1 RRs to gain more lift without stressing the cam.

Re: L98 performance help needed! (MrCrowley)
 

for this only one question remains what cam do you have now? and what are your rear gears like?

Yes 220cc is probably too big of a head depending...

Yes Tpi would "calm" it down quite a bite, but since all that high velocity flow is going to stop in the large port your performance will be not as good.

The preferred solution is of course to stroke you motor to a 408 ci, then your head will be torque-y.

have a nice day

Re: L98 performance help needed! (ZD1)
 

The heads have 200cc intake runners. The cam I have is also the stock roller cam for a 90 model L98. I was figuring since the heads were kinda big, that the throttle body was killing the low end. The gas and air has to flow threw the intake and the heads to get to the combustion chamber. So I then figured a tpi setup would be better cause it would inject the fuel right at the head giving it less top end from flowing through the intake. The car also has a 6 speed, and I have 1.6 roller rockers. Any other suggestiongs?

Re: L98 performance help needed! (MrCrowley)
 

Its not the intake thats hurting the low-end, its the heads.

Go ahead and change the cam too, cuz youre wasting the potential of those heads.

Re: L98 performance help needed! (vader86)
 

you gotta remember that stock truck tbi intake is made to produce torque (pulling power). that said, i would keep you heads. they are too good and to much of an investment to change out. i would change to a miniram and a cam in the 220@.050 (maybe a little bit smaller, but you will miss out on the top end) duration range with a wider lsa ~114. the duration will give you the opening time you need for those heads while the wider lsa will keep the cam relatively tame and it will still get decent gas mileage.

just my thoughts

Re: L98 performance help needed! (clemsonvette)
 

What about that same cam, but on a tpi setup? I think that would work well. What are your thoughts?

Re: L98 performance help needed! (MrCrowley)
 

a tpi setup is going to really limit your rpms. your 200cc heads are gonna want to rev past the 5000 rpms that the tpi can support. if you are dead-set on using tpi, i would sell those heads and get a set of 113's and pocket port them. for a cam i would suggest either a comp cams compu cam that is designed for tpi (higher torque) or the lingenfelter 219 (lots of people here use them with super rams).

Re: L98 performance help needed! (clemsonvette)
 

Well Im definately not pulling the heads off. So I guess I will be in the market for a miniram setup.