Limits to the TPI intake system

the subject kinda says it all. I'll be building an engine soon for my 88 camaro and Im trying to find out what sort of induction system would be best and most cost efficient. i'd REALLY like to use the TPI system, but ive been researching the stealthram intake, super ram and mini ram for the last couple of days. these systems go for anywhere from 2200-3800 dollars. this, to me, is absolutely insane. my question is, what can the stock TPI give me from the factory, and what if i ported and polished it? including the runner? I dont see how it could possibly be worth the money to buy those systems when their air flow specs are hardly any better.
just so you know, i'll be using a 350 and will be expecting to run it up to about 6 grand MAX, naturally aspirated, expecting roughly 420-450 hp

thanks for the help guys! i really appreciate it!

To be honest, I don't think you'll see your goals with the factory TPI. The stock TPI was designed to feed a 305, and it is one of the best truck intakes ever made. What you're looking at for $2200-$3800 dollars is a 500-600 dollar intake and a $1600 dollar digital EFI computer. As far as the stealth ram goes, you can find the manifold under Holley PN 7540 (or 7540P for polished) and the fuel rails with adjustable regulator should be PN 534-186. You can use a stock GM computer with a custom burned chip to control the thing.

I have heard good things about the Stealth Ram. One drawback tho. You cannot pass emmissions without and EGR and the HSR does not have it. If you have to pass emmissions, get an Accel Superram.

The stock TPI has a runner that is 17" inches long. This makes good port velocity to fill the cylinders at low rpm (this is why they make so much torque). But at high rpm it is a restriction. The stock TPI intake is pretty well "done" by 4200 RPM on a 350. It will make some power above that, but you are losing alot of HP at that point as well. I suspect you'll make more power with the Stealth Ram, but if you must have EGR the SuperRam is a huge improvement.

My thoughts.

Actually the runners are closer to 19" long to the intake valve seat, and most of the restriction is just the runner diameter and base intake runner diameters. And stock is good for around 4800rpms, modified..upwards of 5400 rpms...
And contrary to popular belief, the TPI was deigned for the Corvette 350 and NOT the 305. GM engineers raided the Vette parts bins to rush the TPI Camaro into production in '85.

I'd either get some large-tube runners and an Edlebrock base intake, modifying the plenum; or a Holley Stealth Ram $296 and fuel rail $199.

I'm modiying my TPI by porting the plenum and base while buying some large tube runners. And I'm building a 400-420HP 350, 24# inj + Prom, 52mm T/B, stock ported heads-Street-Flo valves and ZZ4 cam/springs, headers, 2500 stall, 3.73 rears.

wait. i can get a holly stealth ram intake for 296 bucks? and what's the fuel rail for? is it required in order to fit under the intake?
in this particular part of Va. there are no emmisions tests. Im sure it'll come around some time, but for right now if you've got a cat in your exhaust, that's enough to pass the test. it can even be gutted, as long as it's on there.
so the stock TPI system has unusually long intake runners? and that's what causes the air flow problems at high rpms?
how does the holly stealth ram help? what's better for performance, the stealthram or the super ram? how much could i get each for? how much does it cost to have a chip burned? I've been told there's a guy at Ethyl corp. who custom burns chips and i've got a guy on the inside of that company so maybe i could ask for a favor and get it done cheaper.
I've got a stock TPI intake system on an engine I designed on desktop dyno 2000 that puts out... 422 hp i think it was and 433 ft/lbs of torque. is that considered good for the TPI?
any tips you guys could give me on this tpi build up would be great
im also having a hard time trying to find a rebuild kit with new rods/pistons in it for the TPI system. i can hardly find a TPI rebuild kit itself. i dont know why.

thanks SO much you guys!

How about going here (http://www.stealthram.com/)?

thanks for the link. ill read over it in a second. Can I get some follow up posts from 97WS6 and 90rocz? it seems like you two were heading in the exact direction of what i needed.

On my dyno program I put a "tunnel ram" intake on the engine instead of the TPI system and the hp jumped from 422 up to 483 using the same cam and everything and there was also a huge increase in high end and overall torque. is the Stealth Ram intake considered a "tunnel ram?" what exactly is a tunnel ram intake? thanks guys!!

the holley stealth ram is sorta like a tunnel ram...a tunnel ram sits up real high and allows more air and fuel to go into the combustion chamber (correct?)

go and and click on the 1 that says "view product"...it will show u what a tunnel ram looks like
http://www.jegs.com/cgi-bin/ncommerce3/ProductDisplay?prrfnbr=2345&prmenbr=361

hope that helps

Originally posted by 90rocz

And contrary to popular belief, the TPI was deigned for the Corvette 350 and NOT the 305. GM engineers raided the Vette parts bins to rush the TPI Camaro into production in '85.


From page 123 of John Lingenfelter on Modifying Small Block Chevy Engines:

"An interesting aside to this story is that there is no difference in size between the 305 and 350 TPI factory manifolds. This is because the TPI was originally designed to increase the 305's torque, since misguided GM planners at design time had dropped the 350 from future Chevrolet plans! Thankfully, Chevy discovered that performance wasn't dead and quickly rushed the 350 back into production plans. Unfortunately, Chevy was forced to use the 305 TPI manifold since no other performance manifold existed. This explains why the stock 350 TPI engine tends to give up around 4800 RPM as opposed to a higher RPM point, because the intake was originally designed for an engine 45 cubic inches smaller!"

Originally posted by CamaroStylin
is the Stealth Ram intake considered a "tunnel ram?" what exactly is a tunnel ram intake? thanks guys!!

Exactly what it's considered. Tunnel Ram for EFI. Tunnel ram is just an intake with an open space in the middle. The inside kind of looks like a tunnel, so much open room. A carb tunnel ram intake is the same concept, really tall and lots of area inside. I think at least.

thanks for all this info guys! and thanks a LOT for the link to that Stealth Ram info site. i read most of it and it looks like the total cost of converting would be just under 700 dollars and would give me a 61hp increase at the flywheel. my new question though is this:
earlier it was said that the stealthram could be used with just the intake and the fuel rail in combination with a custom burned chip. this conversion parts list doesnt say anything about modifying the computer. can i use the stock computer? is there a place on the stealthram that will hold the "manifold density" sensor or whatever it is that was used from 90-92? do i need a new intake manifold with this or will it easily swap with the TPI intake and runners?
seems like every little bit of info leads to 5 new questions, huh?
I ordered that book by John Lingenfelter off amazon.com on the 16th but unfortunately it hasnt come in yet. it's latest delivery expectation is on the 2nd. hopefully there will be enough knowledge in there to help me answer some of these questions

keep the info comming guys! it's the little comments and suggestions that make the biggest difference

The Stealth Ram should be able to run in SD mode. It will use all the standard sensors from a TPI. When it comes to a custom chip, you will retain the factor computer, but you will pull the actual chip inside the computer and replace it with the custom unit. While changing the chip isn't completely necessary for the manifold to work, you won't see the full potential of the new parts without the custom programming. :)

You might also want to check out the TPI Swappers Guide, it's another book with alot of ideas for TPI guys.

The stock computer is just a dumb box. When you put the right chip in, it takes readings from the inputs and does processing. You will have to burn the chip in the ECM to make it work well.

How about ordering the book from Lingenfelters themselves. I did and was lucky enough to order it before his demise so he autographed it for me.

I thought the HSR was the complete thing and you would not have to reuse your old manifold

The HSR is a complete manifold and the only thing you reuse are your sensors (well, maybe your injectors too). Oh, and you have to reuse your TB I believe, unless you get a big shiny billet one from Holley. :)

Find a TB that is the best priced. I would not reuse the stock one but either Holley or say Accel.

so it's agreed that the HSR can be installed with nothing more than buying the intake and the fuel rail? the stock TPI intake manifold will work fine?

what sort of computer work actually needs to be done. i dont quite understand what that does for the system.

Originally posted by CamaroStylin
so it's agreed that the HSR can be installed with nothing more than buying the intake and the fuel rail? the stock TPI intake manifold will work fine?

what sort of computer work actually needs to be done. i dont quite understand what that does for the system.

I believe it has it's own manifold that comes with.

You would need to take the EPROM out to have it reprogrammed for optimum performence.

i understand that it comes with an intake manifold, because the whole kit itself is designed to completely cover the intake system of the engine (except the heads), but if I'm converting an engine that's already got a TPI system on it, I think I can use the TPI intake manifold. that's what it sounds like anyway. is that right everyone?

no you cannot reuse the stock TPI intake with the HSR. the HSR is a plenum and base. if you have TPI now, you'll reuse your injectors, sensors, TB, wiring harness. you'll be replacing the plenum, runners, and base with the HSR. you must use a smal lcap distributor. so, if your car is 85-86, you'll need to get a distributor also. and thanks for visiting my site. www.stealthram.com feel free to sign up and ask your questions there also.

Nope. The Stealth Ram uses an old tunnel ram base [which is why it doesn't pass emissions] and a bolt on plenum at the top.

You must remove the entire TPI intake - runners, plenum, and base.

it won't pass a visual inspection. but mike davis passed maryland emmisions with it.

If they stick a tailpipe sniffer, you will be fine. If they look for the EGR, you are screwed. Stick on a EGR on it with double sided tape and hope no one notices. :D :D

mrr23, your site is awesome. the parts list only tells you to get the intake system and the fuel rail. does the "intake" for 299 come with the runners and plentum and all that stuff?

ok have you seen the pic of the HSR? it's right there on the site. the runners are part of the base.
this is what you get for $299.00 just not polished http://holley.com/HiOctn/ProdLine/Products/AMS/AMSM/f7540P.html

oh i see, the intake manifold is part of the base... gotcha. thanks bud! have you done this conversion yourself?

yes. i own www.stealthram.com the costs associated with the swap on the main page is what it cost me to do the swap. the dyno results off the main page is from my motor.

anybody know where in the rpm range the L98 spends most of it's time of residence on the drag strip?
i went to your site, mrr23, and i looked at the dyno graph for that camaro that shows the difference between the tpi and hsr intake and I'm questioning it's ability to help the engine at low RPM. it looks like it hurts it just as much in the low end as it does in the top end

ok if you are refering my graph, you didn't read it all. look at the a/f graph. just by swapping the intakes, the a/f went way lean. there was no tuning to the HSR at all. if i spent time doing PROM tuning there would've been more gain. you spend all your time above 3000 rpm when racing. shifting at 5200, my tach would drop to 3100ish. i gained .1 in the quarter just by swapping the intakes. with tuning there would be more. look at the whole picture. i drive this car everyday. you don't notice the 30 lbs-ft of tq. my 60ft dropped by .1 but i gained .1 in the quarter. with the 150 n2o i gained .3 over the TPI setup. plus you have to remember that TPI set up is a fully siamesed SLP runners and edelbrock intake.

with the TPI, i shifted at 4800. with the HSR, i now shift at 5200. and the only reason why i shift there is because the zz4 craps out right there.

ok, so i've got a desktop dyno setup now that uses a tunnel ram intake and has a peak hp of 501 @ 6500 i think
just because that seems a little high, we'll say I'm expecting 450hp. with 450hp what could i do to the suspension to land me in the 12.5 range? I noticed from your conversation that you spend a lot of time track tuning and running, so i figured you'd be the best to ask.
there's a guy that my auto instructor knows who took an 80s mustang 5.0 (not that great of a car) and didnt do any engine mods, but he did suspension work for the track and the car ran 12.5 all day long with that stock engine, tranny and rear end in it. I wanna know how i can get my piece of that pie :)

ask around on the stealthram board also. i currently run a 12.13 @ 112. here's my personal site www.fl-thirdgen.org/mrr23 documents everything i've done to my car. click the suspension page to see all i've put on. also when you use the desktop dyno, set the induction airflow to say 670 @ 3.0hg (48mm TB) our TB is really a 2 barrel carb per say. not a 4 barrel. only two throttle blades. it'll bring the numbers to something more realistic. the 383 i'm putting together right now says about 466 hp.

i made those changes to the dyno program and now it's pumpin out 464 @ 6000 rpms

are you sure it's only 650? that sounds pretty freakin low. Chances are i'll be using the Holley Stealthram and a larger TB (maybe a 52. i doubt i'd go as large as 58 unless it would really help a lot)
you think that counts for anything?

over at thirden.org i got a these numbers from someone there.

Stock Throttle Body 48mm 670
Stock with Airfoil 709
AS&M 52mm 750

i suggest not going above 52mm unless you are going to boost (super or turbo) it. even though mike davis runs a 58mm on his 355 and runs 11.83. i'll be using a 52mm holley when i put my 383 in next month.

ok, and just so i know, what does the @1.5 inHg or @3.0 inHg mean and how does that relate to the performance of the engine?

when you go to select what type of induction you'll notice 2 barrel carbs are measured at 3.0 of mercury (Hg). 4 barrels are measured at 1.5Hg. even though it says 4 barrel or FI it's wrong. that's why it shows such higher numbers.

i've found in desktop dyno you need to make some adjustments to get accurate predictions

cam timing - seat-to-seat timings give more accurate numbers than 0.050"

exhaust - if you have small-tube headers, enter "factory manifolds", if you have large-tube headers, enter "small-tube and mufflers"

intake manifold - if you want to predict HSR or Miniram output, select "Single-plane"

good-luck

edit: a factory 48 mm TB might flow 670 cfm on a flowbench. once attached to a TPI intake flow drops to around 540 cfm. I imagine you'd see the same flow on a HSR manifold.

why is it that desktop dyno has all these little things that arnt completely accurate? like the exhuast selection and what not?

even with all these things bringing down the numbers it's still listing 462hp and 439 torque. it's got 330 torque at 2000 rpms for gods sake. even those numbers, although they dont match up to what i had hoped for, are still worth working torward given that it would only cost about 2500 dollars for the build.
would you all agree?