For my just over 500 cube, fuel injected twin turbo, would there be much difference between the 315, 335 & 357 AFR CNC Ported heads? It's probably going to have around 800 rwhp and will be only street driven.

For my just over 500 cube, fuel injected twin turbo, would there be much difference between the 305, 335 & 357 AFR CNC Ported heads? It's probably going to have around 800 rwhp and will be only street driven.
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I would say the 305 with the CNC chamber or the 315 for a full CNC.
I don't know much about turbos but I would think you want a head that is efficient off boost too??

If you email me I may be able to help you with the heads, I have pretty fair pricing on them. ;)

Is there a disadvantage in going with the 335 or 357 comparred to a 315?

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Velocity, and it will want more RPM to make up that velocity. Off boost, the 315's with the tulip exhaust valve option are very hard to beat. The 25 degree tulip exhaust valve helps the flow numbers very nicely for only an extra 50 bucks.

I, too can get very good pricing on them.

Is there a disadvantage in going with the 335 or 357 comparred to a 315?

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Yep ;)
The smaller head will be much more responsive at lower RPM,s
Normally aspirated it will make peak power about 6200 to 7000 on a 500" engine depending on cam & intake & will have killer torque down low.
The air speed (velocity) through the head will be higher which is a good thing to a point.
The bigger head is more suited to either a larger engine or one that you intend to run to a higher RPM.

Far as I know you want to select the head for a blown deal pretty much as you would for a normally aspirated one but as I said I don't know much about turbos so this is just my limited opinion.

a turbo engine has the same principles as naturally aspirated engine. you want the most flow for the most hp having a bigger intake runner on the head will not effect "low end tq" it is all about the turbo and the setup not the head size you need a excelent exaust port and headers matche in the right sixe to keep the exaust velocity up!!!!! the turbo is not going to be effected by intake size as much as it will be on the exaust flow and cam grind. go with the 357's or 335's you will need it especially with that many cubes+twins. you will well excede 800rwhp if the set up is done correctly, i would sugest further reasearch into turbos and therorys before you cont' it is a little harder than most people think.

most importanly.....have fun!!!!

a turbo engine has the same principles as naturally aspirated engine. you want the most flow for the most hp having a bigger intake runner on the head will not effect "low end tq" it is all about the turbo and the setup not the head size you need a excelent exaust port and headers matche in the right sixe to keep the exaust velocity up!!!!! the turbo is not going to be effected by intake size as much as it will be on the exaust flow and cam grind. go with the 357's or 335's you will need it especially with that many cubes+twins. you will well excede 800rwhp if the set up is done correctly, i would sugest further reasearch into turbos and therorys before you cont' it is a little harder than most people think.

most importanly.....have fun!!!! We have a local here that has a big single turbo and it has so much power that he has a constant struggle getting it to hook up. When it does it carries the drivers side front wheel about 3-500' at a height of about 4-6". These things on any engine the size of yours is a real powerhouse. Todd's makes about 2000 H.P. and no telling how much torque. Hooking it and keeping the boost at a manageable level will be the problem. You might want a smaller engine or get with a knowledgable turbo manufacturer for recommendations of every engine component your thinking about using.