just wondering what some advantages are for the different combos of bores and srtokes. generally, with a turbo motor you want to keep the stroke a little smaller, but then again LPE is a fine example of making 427cid crank the boost to their advertised 1000hp on their test car. ?? thanks

 

This has been the subject of many debates. It has to do with how well the cid matches the turbocharger.

If max hp at any boost level is the goal, then:

260 - 331 cid needs a T-76, and will make 1100 hp
350 - 383 cid needs a T-91, and will make 1500 hp
400 - 427 cid needs a T-96 or bigger, and will make over 1700 hp

Of course, all of these are at 25+ psi boost.

If you're talking pump gas, then you need max power at <16 psi. For that, larger cid is better because it will make more power/psi boost, assuming the exhaust side of the turbo isn't a big restriction. With the larger motors, something like a TV8101 should be considered. It's a T6 frame turbo (huge exhaust side), but only 74 mm compressor. The compressor will support 1000 hp and the turbine will not cause excessive backpressure behind 427 cid.

Mike

 

i was thinking of the 427with the t-76gts with that .96 ar...not a good idea?? definately more of a pump gasser

 

Mike has summed it up pretty well. How much hp do you want to make and how much do you want to spend? Cost increases almost exponentially with hp (for the same basic engine architecture). A big part of this is the supporting components to make the power (fuel system, valvetrain, igntion/engine management) as well as the components necessary to handle the hp (chassis, drivetrain, etc.) besides the basic motor (short block, heads, etc.) itself. Reliability issues and maintainence also go up rapidly as hp increases.

When you start considering things like a 427ci small short block built for boost, right away you are in very big buck territory. And the shortblock maybe represents 25% of what will eventually be needed.

Rich

 

Yes, a T-76 will not be capable of more than about 15 psi on a 427. The downside is that it's going to impose 40 psi of backpressure in order to get there, making a poor exhaust/intake pressure ratio. With this ratio, you won't reach 1100 hp, probably more like 900 or less.

Mike

 

If your dead set on a 427ci, then go with a T88...

 

completely tossing ideas. i prefer to stay single turbo. I'd like to be able to make 800-900rwhp when needed, and a more convervative tune for pump gas. as far as components to match and hold power, that wont be a problem. This is going to be one of those 3 year buildups...lol 9" with 3.23's and pobably a g-force t-56. cost is an factor, but I do understand how much it will cost. okay. if you don't prefer a 427, what other combos would be great for a turbo?

 

My setup I am building consists of a HPE 383ci with AFR210's and a custom true header kit with a GT42-76 T6 1.15 A/r. This setup should support 1000fwhp (850-900rwhp) @ 18-20psi.

 

A 350 cid engine has been proven to 990 rwhp with a T-76 at 22 psi boost. Turn it down to 15 psi for pump gas and it should still be in the 700 rwhp range.

 

real quick, thats a big turbo. i like the t6 frame, especially its monster a/r and exhaust outlet. thanks guys. I'd really like to slap a kit on my lt1, but it would require me to limit myself to 10 psi street and 14-15 race gas. probably 10psi all the time would be nice. if i did this, i'd have to buy another kit for ls1 cars....that gets expensive....then again, i could reuse the intercooler, turbo and various other things.

 

If you want the 427cid I would definetly go with an 88mm. If you want to use a 76mm then something like a 383cid would be a better match. Although I have a buddy with a 402cid engine using a 76mm and it made 660rwh at
15psi on pump gas. Then made 720rwh at 18psi on pump gas with the help of some methenal. These numbers were achieved with a very conservative tune (22 degrees timing and a 10.7 afr). Could have made 800rwh with a couple more pulls. The 76mm with make great numbers, although his is going to upgrade to the 88mm pretty soon.

 

i kinda like the idea realquick had on the 427. what is a good size turbo for a 358lt1 with 9:1 compression? I was going to just use the t-76gts and keep it for the ls1 build, but if I'm going with something on the t-6 frame work, i wont want to use that on the 10psi street lt1.

 

PT76GTS

 

Anything from a T70-T76 would be fine for 358ci. The one Mike mentioned will yield the most power at an given psi...stick to the T4 housing with that small a cubic inch.

 

yeah i can't efficiently go over a t4 with a small cube, low psi street app. lag shouldn't be much a problem on the t-76gts should it? at least not on 10psi and 358cid.??