Kool88vette

Will upgrading your runners, porting the plenum and keeping the stock base increase HP? I always thought that the plenum was the choke point. I read in Lingenfelter's book that the plenum was made for a 305 and is not adequate. I also read that the long stock runner length is good for torque but will not let a L98 rev past 4800 RPMs. I think the base was intended for a L98 and should not be too restrictive on a stock 350. Correct me if I'm wrong. I know that the stock base will not outflow a Bigmouth or an Accel but is it OK for a stock L98? Will the stock base perform OK on a slightly modified L98 or is it a choke point?

Vic'89

You need to replace all 3 to get the maximun benifit.

Vic

Aggravated4life

Its always gonna be the choke point,and the TPI itself,the whole thing,was designed for a 305 through and through;GM decided last minute to use on the 5.7 and it worked,just didnt make higher peak HP like other 350s did in the past.

The TPI is a long runner length system..shorten the runner length and the peak power moves up higher.Its problem is its too long,that is to make peak HP,like say,an LT1 intake makes.

John A. Marker

I thought you had the SR. , all three are restrictive.

Sending you a email with bolt on comparison for performance

John

Kool88vette

I have the Super Ram. I still have the stock base. I picked up 4 tenths with this setup and 1.6 RRs. I was told that the stock base was OK and a high performance base manifold was not needed until I changed my heads and cam. I think the stock base flows at 195 cfm. I may change it later. My next mod will be 3.54 gears. If I get the AFR Eliminators, I'll change the base then. I'm not sure what I should do. I just checked Vader's website and I read about Accel's base manifold on their website. Accel claims 15 HP over the stock manifold. If I'm reading Vader's info correctly when Vic89 put the Accel base on his stock L98 he ran a little slower. Now I'm more confused. This is from Vader's site:

Results from Vic89s car:
Track Times
Bone Stock -> 13.87@98.60 MPH (60 degs , 2.0 60')
With Crank Pulley -> 13.74@99.56 MPH (60 degs , 2.0 60')
With DR's, TB Bypass , K&N , Air Foil , Cut Lid
-> 13.34@102.20 MPH (40 degs,1.85 60' )
With Air Pump Elim , 12" GM Convertor , Ported MAF ,160 stat
-> 13.16@102.04 (65 degs , 1.76 60')
With TPIS catback ->12.85 @104.90 (45 degs , 1.74 60')
With Accel lower Manifold ->12.96 @105.18 (45 degs, 1.79 60')
With AS&M runners ->12.81 @107.09 (65 degs, 1.73 60')
With Hooker headers he made 271rwhp and 345rwtq

Vic maybe you can shed some light on this. I don't want to spend $539.00 plus shipping and see no improvement.
PS Great times Vic.

BADDUCK

I think I would put that money in a cam that will complement the SR and forget the intake for now. That's a lot of money and time for minimal gains on stock heads.

vader86

Vic's times were slower initially, but then he got them back down as I recall, ask him.


Yes you need to replace the base, its very restrictive.

cv67

The intake will only flow as much air as the most restrictive (size) part will flow. Go bigger with all of it or (IMO) go straight to a miniram.

JAKE

I feel many misunderstand the restrictive nature of the stock TPI setup. Often I've seen posts saying the engine won't "rev" beyond such and such.

It'll "rev" to redline and over, engine just won't make any power above 4500/4800 range. In other words, you nail the throttle and the R's start climbing, but when they reach 4500/4800 they don't just stop there and refuse to go any higher. They'll keep climbing.

I've used Diacom to log some top end runs and Diacom reported 6300 as the max RPM the TPI engine reached. I believe that's as high as it can log or as high as the ECM can report.

I siamesed the ports on my stock base when I was running one. I used a SawZall with a metal cutting blade and removed the dividing walls between two side-by-side ports. I went in as far in as the blade would reach. That move increased the area that any one cylinder could feed from.

Thirdgen.org has a lot of pics on how to do it, on all three - base, runnders and plenum. First person I saw do it was a guy with the screen name 'MadMax'.

Hope this helps.

Jake

Kool88vette

Thanks for all the info. I think I'll stick with plan A. I will do the gears next and start saving for new AFR eliminators. I will change the base or port it at the same time. After that I will be looking for a mild cam, maybe a 211.

the blur

but the low end torque is just amazing.
My TPI is always such a blast to drive around town.
For a daily driver, the TPI is great.

hippy

So is my Miniram. Pretty nice to lay waste to the tires at 15 mph up til 6,000 rpms.

Kool88vette

That why I want the 3.54s. I really think my 2.73s are great on the freeway and for MPGs. But from 0 to 60 it's slow. That's where I drive about 95% of the time.

Red Tornado

tonite i just throttled it to 120 mph several times out on RT 83 highway. i guarantee you i wasn't slow from 0 on up.

wayne lowry

The stock base sucks

Vic'89

I agree 100% ! The TPI is great on the street.

Vic

Red Tornado

stock sucks, period

CentralCoaster

The stock base is the worst part of the intake, followed by the runners, then the plenum, then the throttle body, which is the last part of the intake you'd ever replace.

(Notice I didn't mention the Eckler smooth power coupler in that statement. )

black85

What were your results? Noticeable? I was thinking of doing this. Couldn't find info easily on 3rdgen.

cv67