Supercharged blown small block build help!

[The yob]

Hi There

Im after abit of advise, Im just in the process of building a Blown injected small block chevy, Im after some advise on what compression pistons to use? I hear many different things, I was thinking about 8.5-1 ? Having never ran a methanol blown motor im new and on a steep learning curve! Im using a standard stroke with standard size rods (5.7) the blocks +30 with standard deck height, Any advise would be highly appreciated, also any advise on running a blown methanol injected beast would also be very welcome.

Many thanks

Mat

[rev-erend]

I would have though one of the American web sites would give loads of advice in this area.

This one is also useful :

http://www.ten-tenths.com/forum/forumdisplay.php?f...

Edited by rev-erend on Monday 15th October 17:05

[stevieturbo]

Elaborate ?

Methanol as the sole fuel, or methanol injected ?

What sort of cam ?

What type/size of blower ?

And how much boost or power do you hope to achieve ?

[The yob]

Well here is my spec

Bore 355 - (4030)
Stroke - 3.48"
Rod size - 5.7"
Standard Deck 9.000
Heads - GM - 23 degree - Intake port volume 169cc
exhaust port volume 65.5cc
valve size-int - 2.02"
Valve size ex - 1.60"
6-71 Blower
Methonal fuel injected
Blower roller custom roller cam

Any advise appreciated

[The yob]

oops.....very high boots 28-30psi

[GavinPearson]

Trooper2 might be able to offer some advice, but for what it is worth I would look at the following sites - Summit Racing, Edelbrock, Detroit Speed Shop & Jegs. That would get you an answer with 90% reliability.

TBH I think 8.5:1 is very much on the high side, if you want to run a lot of boost you need to be looking at closer to 7:1 to avoid the engine detonating to oblivion. Running methanol or ethanol will allow you to run a slightly higher CR, but against that you have the inherent deficiencies of the combustion chamber shape, dizzy ignition etc.

If in doubt, be conservative, blow ups are expensive.

[stevieturbo]

I wouldnt even run as low as 7.0:1 if I was using 95RON fuel !!!!


On most modern builds, 10 psi isnt too difficult to handle on regular pump fuel, even with 10.0:1 CR or a tad higher.

With methanol, that would be a doddle. I defo wouldnt go any lower than a 9.something.

[350Matt]

Thing is he's quoting 28-30psi of boost not 10psi

But you're right 7:1 is too low, really depends on the cam duration more than anything

Matt

[The yob]

Thanks for the replys, After talking to alot of people im going to be aiming for about 10-1, All i have to do now is find pistons that are up to the job! Ive been looking at JE ,but i think i might be struggling to get off the shelf blower pistons of this sort of comp!

[stevieturbo]

He is also using straight methanol.....( and a blower Im not convinced will ever make 30psi )

The link I gave above, showed a twin turbo motor, on methanol, 10.0:1 CR, and it was pushing 44psi, no intercooler.

Just get a set of custom pistons made. They arent that expensive these days.