1988IROC-Z28

Hey I'm new to this site, but not new to TGO AND IROCZONE. Any how I just had to throw my 2 cents in, as I'm a 3rd gen owner of a modified 383 TPI naturally asperated. My goal which I believe to be obtainable is related to the link below.

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

And I don't care what those doubters say about TPI'S. I had a 94' Z28 LT1 with some bolt on's. It ran the best of 13.4 at the track. My 88' ROC pulls a lot harder and for a longer time than my 94' did. I don't know what my ROC will do yet, as I haven't taken it to the track. Hopfully in 2010 it will happen.

ayers1967

Take it easy , I don't think it's a big secret!

texas97z

There are alternative's to the stealth ram or an aftermarket TPI base. On the base one of the biggest flow restriction is in the middle of the port in between where the runners bolt on, and where the intake meets the head.If you are willing to spend $50 at harbor freight(if you don't have this stuff already) then you can greatly improve the flow of your stock intake manifold with patience. Buy a long shaft die grinder(electric)$40 and a set of cutting bits and not the dremel tool ones(about $10). The one that I use most often is shapped like a football. And you will need a golf ball too.

If you take the golf ball and drop it in the runner side of the intake manifold, it will not go past the middle. There is a pinch right there where the air gets bottle necked and then opens up again on the other side as the port goes to the cylinder head.

Aluminnum is soft so it does not take much to open this up. Just make sure the base is secure and will not move cause you need both hands on the grinder. A good idea would be to stick the grinder in there OFF and get a feel for where the pinch is, you do not want to be randomly grinding away as the walls at the pinch aren't supper thick and you can go through them. Keep a steady circular pace and do a little at a time. Drop the golf ball in and see if it gets past the middle. If it does, on to the next one. If not, take a little more out. If you go through in a spot, I have heard of people using a two part epoxy to seal the hole and it works fine. Like JB weld, but there is probably a better alternative.

I just posted on another thread about the LT4 hot cam the rest of the stuff I did to my TPI. But another intake alternative if you don't want to mess with porting out your base,runners,and plennum would be the lt1 intake conversion. I have seen dyno results from this and it is impressive, but you will spend more than $50 for that one. Gotta buy the inake, modify fuel rails, remote thermostat housing,etc. I think the website for the guy who started that one is www.lt1intake.com .

Still cheaper than a mini or stealthram and a big power boost/upper RPM breathing capabilities. Hope that helps,

Josh

1988IROC-Z28

That is what I did to my Edelbrock intake base, runners, and plenum. And as I said before its amazing the power my ROC makes through the gears from a stop, or a roll.

bmillington

The TPI intake ported with trick flows heads was funner to drive with the low end torque than my stealth ram with same heads and more HP. If your not racing the stock TPI intake ported is what I would recommend.

1988IROC-Z28

I also had my Edelbrock Performer heads ported, re-valved, and springed. The guy who did it said very proudly I might add. That they have better flow than the aftermarket AFR heads!

Z28SORR

After rereading this old post I see that no one has actually done this using the "STOCK" TPIS. Even the article in Super Chevy had, IMO, I would NOT use the TPI on a 383ci motor. I think you would be losing to much potential.

1988IROC-Z28

My goal is to keep the original GM TPI design, but make it better. I believe I have accomplished this and more. The 383 engine is known for low torque, as well as the TPI. But since I modified the top end of my TPI I'll lose some of that torque. Thats were the 383 I believe has made for the loss. I use to have a 94' Z-28 LT1 with some bolt ons. I got to run the car at the track doing a best of 13.4 in quarter mile. I've beaten on the Z-28 many times, and it held its own well. But the difference between my IROC and and the Z-28 is like night and day. My wife use to drive the Z-28 comfortably, but shes very intimated by power of the IROC, and she says there's alot more power than the Z-28 ever had. I could not agree with her more, the IROC is a monster!

Z28SORR

Well I've fallen into the trap of not realizing you highjacked the thread.
I was refering to the original poster who said he wanted 350hp. And it doesn't appear so!

As far as your 383 goes, I still don't think I would use the TPI setup. You say it's a monster but you haven't taken it to the track. Also I would think it should be faster then your LT1 as you have 33 more cubes and a lighter car. I've never seen anything that says letting and engine "breath" hurts the low end torque!!
Just generally speaking I'm inclined to think that the increase in torque has more to do with the 33 extra cubes and less to do with the .25 extra stroke!
Anyway the article is impressive with 534 lbs-ft out of a small block.

dhirocz

Tuned ports are alot better engines than most people think. However I always see constant mistakes made in reference to them by people who honestly dont know any better. To make a long story short, they are a tuned torque intake, not an untuned carb intake; the approach and mindset when selecting parts and modifying (porting) them is completely different than your typical small block build.

They can make some wicked torque for a small block. If you dive in, keep in mind that peak torque, not HP, is your goal. HP is a fictional number based on torque anyway(describes how well an engine can work and is based on torque @ RPM whereas torque is an actual measurement), so if you increase the torque, the HP increases accordingly.

There are many formulas and principles to know when modifying a tuned port intake that simply do not apply to most other intakes out there. I've said this on TGO plenty of times, and have proven it over and over, though the mainstream seems to not care.

Most people go wrong when they apply ideas for making HP to an engine that is supposed to make torque. Completely different animal when it comes to intakes and heads.

And yes, the torque advantage comes from the stroke of a 383, not the cubes. It's kind of like using a longer prybar... the only problem is when you start adding cubes, you start pushing the ideal CSA and runner length that are tuned to a particular RPM away from one another, weakening or killing the tuning effect entirely. Larger cubes from a tuned port require an intake with runner length and CSA to match far before cfm. TPI engines don't require much as far as that goes, so 300cfm heads on a tuned port are overkill, even at 383+ci.

Marc 85Z28

No way in hell are you getting 170cc Performer heads to even remotely compare with the AFR stuff - I don't care who ports them. If he got them in the 240-250cfm range he would be doing very well!

dragginS10

There are many formulas and principles to know when modifying a tuned port intake that simply do not apply to most other intakes out there.

Do you have a link with some of this information? After reading this it looks ill be happy with a ported stock intake. thanks alot for all the info

gtadude

you asked if you can get 300-350hp with the stock tpi intake and i say yes you can and more. i have just over 400hp with my set up.

stock tpi intake upper, lower & runners
58mm throtle body
36lb injectors
aluminum vette heads 10088113 castings fully ported
custom cam hydr roller=(this is the key to it all)
1.5 roller rockers
flat top pistons 350 rotating assembly .040 over
1-3/4 tube 3" collector ceramic coated
deep pan with windage tray and scraper
custom ecm prom also

this works awesome i know this i surprised alot of ls1 cars that have work done to them

Marc 85Z28

Do you have dyno results to prove this? I'll go ahead and say that you don't, and that you're guessing. If you do happen to get this combo on a dyno, don't go in expecting 400HP+.

gtadude

this show me your inexpirence in engine building and cars PERIOD... i dont race dynos or flow benches, the only numbers that matter are on the track. i be willing to bet you never even built a tpi engine or one that was worth a dam. i dont see any engine specs posted by you or any help....so please me a river