Street and strip 70 gto turbo build
 

I could use advice on a turbo build I am starting. My brother and I built a draw through and a blow through street turbo charging system 20 years ago in a car while in college. Ran it for several years, but eventually removed the system because the car was needed as a daily driver and we had a difficult time keeping it together. I want to do another system, with modern tech, in a Pontiac 70 gto tribute.

Goals: Work the car deep into the 9s, stock looking car, tire 10.5x28.5. All steel car with a fiberglass front end, no frills but full interior, glass, roll cage, etc. Fi system that is e85 compatible. I would like to start with some parts that I have, no 96 ported d port heads, ra 4 ports, heads flow 270s intake and 200s exh. The block I would like to use is a 1960 389 adapted to a turbo 400. I have girdle designed made to help hold the lowly 500557 blocks together for 500 hp stroker setups. I want to make it expandable into a cage girdle, and want to test it in this car, in this block. Really not interested in a aftermarket block at least not at first. I could stroke the engine, but do I need too? Have a solid roller cam and rev kit for the cam/engine, 290/290 252/252 112LSA .55/.55 lift solid roller. I would like to start with that cam. Probably use a torquer 2 intake, The car has a 4000 stall, turbo 400. Right now it has 4.88 gears set up for the 1/8 mile, I will change that as needed.

Questions: efi system best for boost and dual fuels e85 and pump gas.

Cid: Any need for more cubes than 400? Am I better off with more cubes and less boost to spool the turbos up faster?

Given the head flow, cam and about 400 cid, 9 compression, suggestions for turbos or turbo. Right now I would like to do twin turbos to limit lag, some of the racing the car will see is using a pro tree.
Thanks, Jay

I would probably use a different intake?
The 400 CID isn't bad, but maybe a 428 or so setup?
(aftermarket 4" stroke crank)
The stroke would still be able to handle the higher RPM's and more cubes doesn't hurt?


:)

Thanks for the reply. I am hoping to fit everything under the stock hood. I have a small pattern warrior intake right now. It is a little tall, might work, open to suggestions. Jay

Good luck with it! I recommend tall gears and tight converter..... Torker 2 is very similar to my intake.. can't see the issue ? Good rods and pistons, correctly gapped rings with a hardened top ring .. balanced rotating, ARP studs on heads and main caps. I'd give that cam a try.

Look into Borg Warners lineup .. S366's ?

http://www.forcedinductions.com/productsborgwarner.htm

Kris

What you have is good as far as the 389 with stock stroke and heads. Dont play around with the cam though. Have one done for boost. Call Tim at bullet if you want a great guy to design you one..

E-85 or pump gas with efi will work fine . For 9's you will be more then fine with a blow threw though..

A 389 is more then enough for what you're doing . By the time you have 15 psi running through it the motor will be acting like its a 778ci and you will not be better off with less boost and more cubes for spooling . It doesn't work that way..

As for what turbos to use for twins , Id have to say somthing between a set of 62's and 68's. I have a 6870 from precision. Each turbo can make 1100 hp times that by 2 .. lol..

Definitely less gear, turbo cars like 3.55-3.90

Similar sort of budget set up to mine, '59 389 block with mains girdle, 4.00" crank, twin MasterPower T70 turbos, 96 heads home ported, cam was a mild flat tappet 250@.050", .600 lift, TH400, on the footbrake ran 8.90@163 with a too tight converter and 3.55 gears. Around 960 hp at 18psi boost.

Intake?
EFI correct?


:confused:

I had not looked and rings yet. Are there rings in paticular that work better for boost?

I have head studs and main studs.

Looking into the turbo options. So far Garrett, Borgwarner, Precision and Masterpower.

Is it worth looking into a big single turbo?

The build does look close your build taft2. To move up too a forged or billet crank instead of the arma steel, it problably makes sense to go 4”. How far will the arma steel 3.75 go under boost? Is your cam a solid ft? What lsa?

I would gladly have Tim do a boost cam for the motor. I know I have some expensive surprises coming though. Plus I have $$! several projects going on at the same time. Trying to spread our resources around the best we can. Cam is just sitting there on the self....But if the cam will be a complete dud, this is a lot of work for a dud.

Gears I will have to change, 3.5 to 3.9 sound better, maybe I will actually drive it and keep up with traffic.
Jay

Yes, efi. Not necessarily MPFI, but I have not ruled anything out yet there.

Yes sorry, solid flat tappet, 114 lsa, turbo grind from Comp Cams. There are not many 3.75" forged cranks being made-just Ohio cranks I think. We are going to use a 3.75" crank on my sons single turbo combo, less side load on the factory block with a short stroke crank.

My short block will be 9.5" deck IA-2 Block, 4.310" bore, 3.5" stroke (3" mains), proper short rods for that deck height most likely 6.125" BB Chevy Rods, Pistons will be purchased and made by CP Pistons to the compression height needed for .005" deck height, based on the final block height after making sure everything is square and parallel.

So my point is I REALLY LIKE SHORTER STROKE CRANKS WITH BOOST.

Tom V.

That being said and the lack of good 3.75" stroke Forged Cranks (all the ones I have inspected, I passed on).
Marty Palbykin got the only other really good 3.75" stroke crank I know of. RA-IV SD forged steel Kellogg crankshaft I had.

That probably settles the stroke question. I will likely get the 3.75 forged from Ohio Cshaft.

We have a Econo mod 360 cid International Harvester 460 pulling tractor project we are working on, we have been looking for a 3.5 Pontiac crank?????

Thanks
Jay

Most of the Quicker Street Outlaw cars seem to be BIGGER CI engines in the over 500 CI range.....probably 4” stroke or more.


GTO George

This engine will not be competitive with the power adder street outlaw classes. But hopefully it gets the boosted engine and chassis sorted out. After that maybe I will consider stepping it up with an AI-2 and better heads.
Jay

Just throwing out different options that may work better even on the street!


GTO George

Was not my intent to sell your thoughts short George, I absolutely appreciate your thoughts. Jay

Tom, the Ohio 3.75" forged cranks are not very good then? We need the shorter 3.75" for my sons combo as we already have a new set of BME ali rods with Pontiac size big ends, and we're trying to keep the displacement down to 400 for the big single turbo combo. The Ohio seems to be the only one out there.
Sorry for the hijack Jay.

No problem Taff2, hijack it when ever you want.

Not saying that you could not find a better 3.75" stroke Ohio Crank out there today.

Going by the testing I did on cranks some years ago for Bob and Frank and the BOP Guys.

The stuff I tested was not in the same class as the better SCAT CRANKS.
If SCAT made a 3.75 crank it would probably be a good one.

Tom V.