If you were building a motor for a turbo, say t-70 12-15 psi mostly pump gas, would you do a 355 or 383 and why. I ask because me and a friend are having an argumant about what would be best for my car including cost .ie is going to a 383 worth the extra cost over a 355.
-Mark

 

If you build an all forged motor, then the only real difference in cost would be the extra machine work to clearance the block for the crank and rods. Just about everything else would cost the same.

Personally, I'm building a 383 for my turbo project, and it will be using a 70 something series turbo for street/strip duty.

 

Yes, unless your trying to go <8:1 compression or so then you might as well go with a 383.

 

AFR makes a 76cc head for the LT1, and Trickflow has their 64cc heads. You should be able to get just about any desired compression ratio you want now.

But you're right, using those heads will up the cost considerably.

 

I've been contemplating this myself. Basically for me the labor for assembling the motor and clearancing if I go the 383 route would be free as the guy who'd be building it owes me for some work on his website. The thing is, from what I've read a given size turbo/blower will make less boost on a 383 vs a 355. The other thing is I will likely have to use the ported LT1 heads on the car now to be able to afford the turbo kit, so a 355 may be neccessary to be able to get the comp ratio down to ~8.7 - 9:1

-Tony

 

I'm going with a 355 with stock crank and rods to save money. I'm using an SRP forged piston at ~9:1 and using ARP main studs and rod bolts for extra insurance. The stock rods are fairly strong. It's the crank that I'm worried about. If it breaks I'll build a 396 next year.

From a performance standpoint a 383 makes more sense, since the extra stroke creates a higher exhaust gas velocity and helps spool a big turbo quicker, even with a small port head. You may see less boost, but you'll make more power.

-Chris

 

I only plan on going w/ ported LT1 heads/intake. So would a 383 be more streetable? And how much sooner would the 383 spool a t-70 than a 355? If any one knows it would be appreciated.
Thanks
-Mark

 

The 383 builds more low-end power so it all depends on your usage. The turbo builds with RPM's so the 383 would make more sense in a daily driver plus you'll see less wear...

 

I went thru this thought process when I was building mine. Problem I ran into was getting the compression low enough with the stock (LT4) chambers, and a long enough rod to make the 383 work. The shortest rod I wanted was a 5.7, but preferred a 6. But off the shelf pistons for a 6 wouldn't get the compression low enough.

And then after running the twins on the stock 350 and discovering how much low end torque it makes, the need for the 383 was gone! I can't hook what I had with the stock motor, so a 383 would be even worse. Plus the gears available for my rear are limited, so I have to go to a taller tire to keep the rpm livable (stock motor with a Hot Cam I was spinning over 6500 )

You just have to decide what you want out of it, and what your budget can afford!

 

Not really true. A turbo builds boost exponentially. A centrifugal blower builds boost linearly like you're describing. For most applications a properly sized street turbo will make boost quickly off idle and make max boost by the middle of the powerband.

-Chris