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zildjian4life218 03-17-2010 07:11 PM

TPI with Turbo
I have a stock TPI setup from a 305 out of a 86 camaro. I have been wanting to do a turbo build for a couple years now but I want to run fuel injection. What do you guys think about the GM TPI intake used under boost.

The engine will be a hyd roller 350ci sbc vortec block. Alum heads maybe 180cc 2.02 by 1.6. I have a forged crank from a vortec block. I also have a set of scat i-beam rods, just need pistons. I will send the cam from the vortec block to my cam guy to see if he can regrind it for a turbo build. Anyone use this intake with turbos and have success? The engine will have a 6000rpm redline. Im hoping for 400-450hp on 8psi and a track tune that will have around 12-15 psi hopefully around 525hp. Im also gonna be running megasquirt III. Will be fully sequential and will also have coil on plug conversion. I have been debating buying some h-beams and bumping up my power goals by 75-100hp. Just want to get the induction figured out before I start putting the short block together. Thanks in advance everyone!!!!

ap72 03-18-2010 07:09 AM

If you're going to run the stock TPI system there is no need for 180cc runners, your intake will be the choke point with any decent set of stock heads. YOu're going to want to use forged pistons, DO NOT use a reground hydraulic roller, when you grind it it looses the surface hardness, Vortec engines never had forged cranks, coil on plug at this level is a wasted expense, but if it floats your boat...

The intake is your biggest restriction.

zildjian4life218 03-18-2010 07:25 AM

I will def reconsider the intake and cam. I am 100% sure the crank is forged. My machinist is 100% sure the crank is forged. The number on the crank is 14088532 which according to the book I have says its forged. It also has no casting marks on it. It came out of an 880 block that was in a big bread van.

Will changing the throttle body help or will the intake still be a major choke point? I have also seen hi-flo runners but between the two of them thats gonna be about $700. I have always like the look of the edelbrock pro-flo XT. Maybe ill look into that.

I thought when they reground cams they had to put them through a heat treating process to harden the surface.

ap72 03-18-2010 07:37 AM

should the cam be heat treated- yes, do they? most often time NO. If they did the cost would be the same as a new cam.

I wasn't aware of the Vortec engines receiving forged cranks, but that is a forged crank casting number. I learned something.

A common swap for TPI folks is either a Holley Short Ram intake OR a converted LT1 intake. Either would probably be better match for your goals.

zildjian4life218 03-18-2010 07:51 AM

Alright I will call my cam guy sometime in the next week and see if he heat treats them. If he doesn't I will just get a new one made.

Now what do you say for the pro-flo XT vs. the holley stealth ram or the lt1 intake.

ap72 03-18-2010 08:17 AM

If cost isn't a factor I'd go with the ProFlow XT, if it is a factor, which I'm guessing from the list of your parts then an LT1 intake is the cheapest route. If it came down to it I'd but a real camshaft and use the LT1 intake over a regrind and the ProFlow intake.

454C10 03-18-2010 08:19 AM

you can use the stock cam for a low boost turbo (less than 15 psi). The amount of overlap the turbo can handle depends greatly on the turbine selection. A low rpm boost turbine can't handle any overlap.

set compression at 8:1 for 8 psi of boost.

In theory, a 245hp/330 ftlb tpi 350 with 7.5 psi of boost should make 50% more power (368hp/495ftlbs).

8 psi should make 378hp/510 ftlbs
10 psi should make 412hp/554 ftlbs
12 psi should make 445hp/597 ftlbs
15 psi should make 490hp/660 ftlbs

yes, the tpi intake is restrictive, but boost will change that. However, better to use a regular intake design that is modified to hold injectors.

if you plan to run more than 10 psi of boost then use 7.5:1 cr.

proper compressor and turbine selection is critical.

A couple of first generation 300zx turbos (T3, 1984 to 89) would work well to 12 psi of boost on a 350. Use a good bar and plate intercooler.

zildjian4life218 03-18-2010 08:25 AM

what about twin turbos off of the ford thunderbird? I have heard they work well on twin turbo sbc.

ap72 03-18-2010 08:30 AM

it depends what you want. the thunderbird turbos will be all done by 5000 RPM, BUT they will spool fast.

I'm kind of getting the feeling you have champagne tastes and a chocolate milk budget though...

A good custom cam is going to be required to get whatever random mix of swap meet parts you pick up to work together. Any used turbo is not going to be optimal for your setup, just do the best you can though and since your power levels are fairly modest you should be able to make it. Don't cheap out on injectors, a starved turbo engine is a BAD thing.

zildjian4life218 03-18-2010 08:47 AM

What other stock turbos will work well? Im not going to garret and spending 1800-2400 for two new turbos I will buy used stock ones. I will end up putting some cam in it. It won't be a huge cam but it will be an improvement over stock. I just want to throw my ideas out and have you guys help me shape them into something do able. I might for my first turbo build keep my power goals around 500hp. I have no need for some 600+hp build right now. the main reason I am going with a turbo setup is due to the increase in VE. I am sure I could build a 383 like everyone else and get the same power goals.

ap72 03-18-2010 08:51 AM

look at the "big 16G" turbos. Two of those should match you pretty well.

zildjian4life218 03-18-2010 08:57 AM


Originally Posted by ap72
look at the "big 16G" turbos. Two of those should match you pretty well.

Is that a TD05?

ap72 03-18-2010 09:04 AM

yea, pretty widely available too.

454C10 03-18-2010 09:32 AM

those t-bird turbos are setup for a 2.3 liter. so 2 would be good for a 4.6 liter. a little small. but they will make boost quickly. max out about 8 psi and 5,000 rpms.

the 300zx first generation turbos have t3's and are setup for a 3 liter. I see lots of them at junk yards. 50.00 each.

zildjian4life218 03-18-2010 09:37 AM


Originally Posted by 454C10
those t-bird turbos are setup for a 2.3 liter. so 2 would be good for a 4.6 liter. a little small. but they will make boost quickly. max out about 8 psi and 5,000 rpms.

the 300zx first generation turbos have t3's and are setup for a 3 liter. I see lots of them at junk yards. 50.00 each.

For the past 2 years scavenging through my local u-pull i have never come across a 300zx. Only turbo cars I come across are saabs or vw which are almost always T25. I will def start looking for some of those 300zx turbos. they seem much better for my power goals. If you come across a pair at your local u-pull can u PM me and maybe we could work something out. Ebay only shows those chinese made "aftermarket" turbos.

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