Which setup would tolerate the most boost, a Forged 355, or a Forged 383 for a Turbocharched application? I'm currently engine shopping and am deciding what to do with the block.

 

Give it a half-fill.

 

Doesnt the half fill screw with the knock sensor any?

 

reallt either depending how they are built alot of factor involved

 

If both are built properly, I don't know that one is superior to the other as far as handling max boost. If it were me, I'd go with the 383. Generally it would create more torque in the lower RPM's which will help fight against any turbo lag you might get down low. Just my opinion.

 

I like over square engines.....but thats just me...never really been a fan of 383s ....but I do love me a 377

 

I would go with the 383 because it would generate more torque. The 383 will take more boost because of the larger displacement.

 

 

You can combat that on the 383 by running a shorter (think 5.7") rod or having a custom piston built. That's what we're doing with my in progress motor right now, a Lunati Sledgehammer 3.75 crank with Lunati Pro-Mod 6" rods and full custom JE Blower pistons.

 

What?

-Chris

 

How about saying it like this:

"A properly setup 383 will (should) have a high volumetric efficiency making more use of the boost being provided."

 

What size turbo do you have?

A smaller engine will make more power on a moderate sized turbo. As an example, I had a GT-42 I was planning to run on a 383 until I spoke to enough turbo gurus to convince me the turbo would make around 100hp MORE on a 355.

If you have an 88mm or bigger thumper, the 383 might be better. Then again, a turbo that big is going to make more power than you can use on a street car. Having a larger motor that brings on the boost at lower rpm just makes the traction problem worse.

 

I would go with a 355. The pistons will be stronger (able to take more boost) and the motor will rev better than a 383. A 383 is good for N/A due to the increased stroke. But, with forced induction, the increased 1/4" stroke becomes much less of a factor. And you don't have to worry about clearance issues with the crank.

The 383, being a bigger displacement than the 355, will take more flow, Q, than a 355. At the same boost level, let's say 10 psi, you will flow more air into the 383 than the 355. From that, theoretically the 383 will make more power. But if you really boost a 355, like 20 psi, that will make more than enough power. The bigger 383 may run better on pump gas due to it's increased displacement. The 355 on high boost will like race gas. Something to consider.

 

There will be no appreciable difference. The limit on boost in a street car is gasoline octane. At some point, even with water injection, intercooling, etc. detonation will be a problem and will limit the boost you can use. Exactly how much boost depends on a number of factors. Using race gas, you start to run into issues related to the mechanical strength of the components. Once you get to extremely high boost/power levels, keeping the heads on the block becomes an issue and this will not be different between a 355 and a 383. One aspect of engine architecture that relates to extremely high power levels is cylinder thickness. High hp = high cylinder pressures and these can be sufficient to distort the bore or even split a sylinder. As both the 355 and the 383 are 30 over, cylinder thickness is the same.

So, the Cliff Notes version is that there is no difference.

Rich