Hey guys, since my 383 just died I am pushing up the time table on my twin turbocharged SBC project for my little V8 280z.

The basic foundation will be a seasoned early '70's 350, bored 0.040", 4 bolt main, studded on mains and heads. I'll prob block fill it half way. I will be using a decent set of heads, 200-220cc runners, unknown at this time which brand or material (hopefully aluminum). The turbos will likely be T3/T4 hybrids with a .63 A/R (still playing with compressor maps).

Anyway, I will very likely be ordering my crank soon, but wondered what you guys thought would be the better engine size for this project. It will be a SCAT 4340 forged piece in either 3.48, 3.50, or 3.75" strokes. Either way I will be running SCAT H-Beam rods in 5.7" length (bushed).

Normally I wouldn't be asking because I always run stroker 383's. But this time is different because of the forced induction, plus the RPM range will be much higher.

If everything goes to plan, the car will have a 12 point cage, weigh 2500-2800 lbs (without me), run a low 10 second E.T., run on 26/10.5/15" slicks, with 3.69:1 rear gear. Plus there will be alittle converter slip on the top end (prob a Coan, Trans-Specialities, or ATI converter).

So, for the sake of arguement, lets say the motor will shifted at 6500-7000 RPM and be buzzing around 7500 RPM when going through the traps. The HP goal is 550 to the rear wheels.

I have been led to believe that strokers don't like to be rev'd like that on a regular basis. So if that's true, would I be better off going with a 3.48/3.50" stroke?

Thanks guys!!

EDIT: Hey guys, I am already set in certain ways I am building this motor. Please do not suggest any changes like aftermarket engine block, crank/rod brand, or other ways for force induction. Thanks for understanding.

Will a .040 over block handle that much cylinder pressure without flexing the walls? I know many people carve .060 out of those blocks, but it always scared me.

Originally posted by Schurkey:
Will a .040 over block handle that much cylinder pressure without flexing the walls? I know many people carve .060 out of those blocks, but it always scared me. Machine shop says I should be fine if I stay under 14.7 psi and that's with no block fill. I don't plan on more than 7-8 for street driving and maybe 10-11 for the strip w/C-16 race gas and alky injection.

I don't know if he's wrong, but he's never steered me wrong before.

What happens at 14.8psi? ;)

Just build a 377 de-stroker. 350 crank + 400 block + main bearing spacers = high revs safely.
Here is Speed-O-Motive's (http://www.speedomotive.com/chevy_400_destroked_to_377_cid.htm) 377 combo. 502 Hp @ 6500 rpm normally aspirated.

14.7 psi = 1 atmoshpere (or 1 bar if ya into metrics)

Originally posted by three85stroker:
Just build a 377 de-stroker. 350 crank + 400 block + main bearing spacers = high revs safely.
Here is Speed-O-Motive's (http://www.speedomotive.com/chevy_400_destroked_to_377_cid.htm) 377 combo. 502 Hp @ 6500 rpm normally aspirated. Thanks for the input, but I already have the block prepped and its a 350 or 383 at this point with two little snail thingys.

mmmmmmmm snails! tasty.

is this engine strictly for drag racing?

I know nothing of turbo motors but a smaller stroke is definately more rev friendly on parts. Piston speed and rod bearing speed will be reduced.

Originally posted by wrc:
is this engine strictly for drag racing? Yes and no. It will see most of its life a quarter mile at a time.

But it will see 40 mile cruises on Friday night's too.

With twin blowers, you do not need to go to a 383. Turning the boost up by a small amount will have the same effect. The block you are using will not support the power that you will easily attain. I gaurantee you that it will split itself in two through the cam tunnel. You need an aftermarket block, or a bowtie. 14psi on a 350 is over 700HP.

what transmission?

"lets say the motor will shifted at 6500-7000 RPM and be buzzing around 7500 RPM when going through the traps."

why do you say that? shift points are usually chosen based on the motor not the other way around.

Im officially jealous.....i would love nothing more than to do somthing like this with my 350!!!BUT i do think i would save that 350 block for somthing else also. With the money youll have invested in the turbos and the 4340 parts it would be a gamble on if the block was going to hold up.

Originally posted by wrc:
what transmission?

"lets say the motor will shifted at 6500-7000 RPM and be buzzing around 7500 RPM when going through the traps."

why do you say that? shift points are usually chosen based on the motor not the other way around. TH400.

If you are asking about just about the RPM. Shift points aside, if the motor is running through the traps at 130+ then the RPM will be damn near 7500.

drop it down 100 cubs do a 283 and 8k is cake tongue.gif

Originally posted by three85stroker:
Just build a 377 de-stroker. 350 crank + 400 block + main bearing spacers = high revs safely.
Here is Speed-O-Motive's (http://www.speedomotive.com/chevy_400_destroked_to_377_cid.htm) 377 combo. 502 Hp @ 6500 rpm normally aspirated. Well as my luck may have it, I have just scored a virgin 1974 400 2 bolt block. I looks like it might clean up at 0.020" overbore. Regardless I am having it drilled/tapped for splayed billet steel caps. Then of course line bored/honed. I might still block fill at least half the block.

Cable, have you talked to the GN guys and other people running turbo'd drag cars? I read a while back that turbo's don't tend to like being spun real high. Then again 7500 might not be considered real high either. Just a thought that popped into my mind.

Other than that the extra bore of the 400 block would help unshroud the valves a bit, theoretically at least. And you'd still have only 350ci w/ the short stroke deal which would help with not making way too much power and splitting the block.

I always thought drilling a 400 for the extra main bolts would weaken the main webbing more than the extra bolts can offset with clamping force? Or do the special main caps negate the weakening main webs?

Just a bunch of Q's that popped into my head. Not questioning what you're doing, just asking if you'd talked to your machine shop about these things.

Hmmm I see we have a doubting gearhead here. Here's a link to guys who push the limits of factory blocks. Ya, I know they're FORDS, but they are also all Windsor blocks which are tough little buggers. Forced induction places a completely different load on the motor. It will not be the crank or the rods that fail first, it will be the block...... You will not need to spin this motor to make big power, in fact the turbos will like a taller gear to push against.

http://www.turbomustangs.com/techarticles/stockblock.htm

Originally posted by Slowpoke70:
Cable, have you talked to the GN guys and other people running turbo'd drag cars? I read a while back that turbo's don't tend to like being spun real high. Then again 7500 might not be considered real high either. Just a thought that popped into my mind.

Other than that the extra bore of the 400 block would help unshroud the valves a bit, theoretically at least. And you'd still have only 350ci w/ the short stroke deal which would help with not making way too much power and splitting the block.

I always thought drilling a 400 for the extra main bolts would weaken the main webbing more than the extra bolts can offset with clamping force? Or do the special main caps negate the weakening main webs?

Just a bunch of Q's that popped into my head. Not questioning what you're doing, just asking if you'd talked to your machine shop about these things. Hey Enrique, no problem about Q's. It lets me know I've covered all the bases.

According to Turbonetics (sp?) as long as the turbo was built for the RPM its no problem.

From what I've been taught, its not a good idea to have a factory 4 bolt 400 for any type of racing or load. I guess there isn't enough material for the outer bolts to secure to.

But having the outer bolts splayed (22 degrees) places the bolts in an area between the cylinders where there is more meat to hold on to.

At least that's my understanding.

theres really no reason to spin that motor that high unless your trying to make 4 digit HP. If you just have to spin it that high you better rethink your turbo selection and go with something bigger, alot bigger. Those little T3 turbine housing are going to be a major restriction at 7500rpm. A couple of days ago one of my friends/customer made 652rwhp@19lbs/boost with a 358ci at 5200 rpm. Not bad for a low rpm motor huh?

TJC is right, turbomustangs.com is the best turbo website Ive seen. spend some time there, you'll be glad you did

Originally posted by turbodave:
theres really no reason to spin that motor that high unless your trying to make 4 digit HP. If you just have to spin it that high you better rethink your turbo selection and go with something bigger, alot bigger. Those little T3 turbine housing are going to be a major restriction at 7500rpm. A couple of days ago one of my friends/customer made 652rwhp@19lbs/boost with a 358ci at 5200 rpm. Not bad for a low rpm motor huh? I don't want to spin the motor that high, its just with a TH400, 3.69 gears, 26" tall tires, and having a 130 mph trap speed will produce a high RPM at the end. Plus I a limited to the changes I can make to lower the trap RPM.

-I can't fit larger than a 26" tall tires in the fenders

-There is ZERO aftermarket for Nissan gear sets and there is no other gear sets available for my R230 vlsd from Nissan.

-An overdrive tranny like a 2004r will cost $2000+ w/o converter to be built to withstand the HP/TQ

-A Gear-Vendors unit will not fit under the car

Cable,
I would suggest Aluminim rods and pinning the main caps.
since your looking for suggestions

change the rear end then.How long do you think that nissan rear end will last anyway with 800lbs of torque

Originally posted by turbodave:
change the gears thenYou edited your post, but I already stated:

Originally posted by bluerebl:
-There is ZERO aftermarket for Nissan gear sets and there is no other gear sets available for my R230 vlsd from Nissan.

Originally posted by turbodave:
change the rear end then.How long do you think that nissan rear end will last anyway with 800lbs of torque At least a 1000, its from a Nissan Skyline. I can show you a number of videos of them running 8 second ET's with the stock pumpkin. The ring gear is 9" alone. Its a viscous limited slip, no side or spider gears, just a ring and pinion.

The CV's and axles are custom Moser pieces.

Trust me when I say, the rear is the last thing I am worried about.

I think he means swap the entire diff......

Originally posted by TJC:
I think he means swap the entire diff...... TurboDave asked how long do I think the Nissan rear will hold to 800TQ.

Maybe that's what he meant, but that's not an option. I am keeping the IRS, the stock suspension, and the stock look. Even the turbo's will all be under the stock, flat hood.

Anyone can swap in a 9" Ford and huge tires, I wanna see how fast I can go on a 10" tire and IRS.

your right then, your options are limited. build the motor to RPM, put on the biggest wastegates that money can buy to keep you boost low.
What about using a medium frame single turbo, you got room for that?

Originally posted by turbodave:
your right then, your options are limited. build the motor to RPM, put on the biggest wastegates that money can buy to keep you boost low.
What about using a medium frame single turbo, you got room for that? Maybe. I'll have to place it in front of the motor, run an electric water pump, lower mount alternator, etc.

It is do-able, but alot more hassle (and money).

The biggest hurdle is routing the exhaust back under the car. With two turbos in the same position as your car, the exits (downpipes) are easy to route.

If I were to run a single turbo, I'd need a GT-40 or GT-42.

yeah, the crossover is always a pita. turbos like mine would be alot easier to size for your rpm and hp goals than T4/3's. plus they're alot easier to upgrade should you want more in the future. but you would need room for the wastegates and downpipes too.

By the way, the 350, 4 bolt, is for sale if anyone is interested.

Just picked it up from the machine shop today.

Chevrolet 350 small block, factory 4 bolt mains. Early '70's casting, '010' casting number, high nickel, high tin content markings, Hi-Perf markings.

Its been hot tanked, mag'd, bored 0.040 over, 0.010 decked, line honed, and honed with a torque plate.

I have $250 into it without the cost of the block itself (worth at least $100-150). I have the receipt for the machine work.

I need the money, $250 obo.

http://www.chevelles.com/showroom/bluerebl/4boltblock.jpg

I think JE offers a piston for use with your 3.5 crank and also 6.125 rods.

As a simple rule you want to keep the mean piston speed under 4000 FPM on stock components. With forged crank, high strength rods, light pistons, and full floating pins you can push that up. How much?...maybe 5000 FPM. A 350(040) at 7500 RPM = 4350 FPM. A 383 at 7500 = 4688 FPM. How about a 350 with a 283 crank? AKA 302 at 8000 = 4000 FPM!

An occasional drag motor will last longer at higher piston speeds than a street motor. Also, longer rods help are a help on high-reving motors.

Staying under 7500 rpm with forged pistons and those rods should be no problem with it living at that boost.

At 15 lbs of boost you will just have to not detonate and limit your boost to that.

Which way are you going to limit revs and boost? You should be able to get by with the equivalent of 115-118 octane/alcohol/water probably just good racing gas at 1 bar.

Are you running an intercooler?

Not sure I'd fill the block if I were driving this on the street. You're going to have heat problems anyway even if it's just external radiation under the hood from the turbos.

I'd do what I could with keeping the mains where they're supposed to be.

Are you going to o-ring your heads or is that necessary at 14-15 lbs?

Interesting project and should be very fast.