I am going to put some heads on my 575SCI and would like to raise the compression. Can anyone tell me the combustion chamber size on the stock heads? Also, what does it have on it for rocker arms? I have never had a valve cover off. Thanks

118 cc and Crane gold rockers

What he said ^^^^^^^
They are just GM Rect port heads.

Why not just increase the boost with a smaller top pulley????
Stock boost is only 4.5# and you could easily go to 6-7#.

Agreed ^^^^^ Don't bump compression, bump the boost. Much safer in long run. Add a chiller, smaller pulley and flash ecu and wake them up !!!!!

I don't think you have lots of options for getting compression up, without changing pistons. Which I wouldn't do unless needed.

If heads stock heads are in good shape, I'd run them. I'd take the 2000-2500 bucks you'd spend on heads, and use it towards a roller cam upgrade, send the blower to DPME and have him go thru it, and work his magic on it. He can make the blower more efficient. I wouldn't have a problem running 7lbs without a chiller on that setup.

+1 I am in the process of doing just that. I have 3.5 pulleys which I expect to be at 6 lbs.

Does anyone know how much boost (non chiller) is made from the 3.25 and 3" pulleys?

Does anyone know how much boost (non chiller) is made from the 3.25 and 3" pulleys?[/QUOTE]

Around 7 Psi and you have to run a shorter belt it will smoke the stock belt. Not really any more power than 3.5. I have some extra belts left over if anyone needs them. I repowered last year with 600SCI's
Gates 2 -K10040 New and 1-K10040 used blower belts and new 1) 57-80775 PS,WP,Alt,etc. serpentine If you run any pully smaller than 3.5 use Gates K100535HD This was from my experience with the set of 575SCI's that powered my Spectre for several years.

FYI, in the other 575 Thread, a member replaced his 256 blowers with 8-71 kits in his 40FT outlaw. half pound more boost, and picked up around 5mph.

Around 7 Psi and you have to run a shorter belt it will smoke the stock belt. Not really any more power than 3.5. I have some extra belts left over if anyone needs them.
Gates 2 -K10040 New and 1-K10040 used blower belts and new 1) 57-80775 PS,WP,Alt,etc. serpentine If you run any pully smaller than 3.5 use Gates K100535HD This was from my experience with the set of 575SCI's that powered my Spectre for several years.[/QUOTE]

What do you want for the lot of belts?

[QUOTE=4bround 7 Psi and you have to run a shorter What do you want for the lot of belts?[/QUOTE]

3/ 575 SCI Super Charger Belts Merc# 57-817113 Bam Price Each $179.70
2 are new 1 is used.

1/ circulating water pump belt. Merc # 57-807755 4

New Bam Price Each $86.12

How about $150 + the ride for all of them? The used one has about a 1/4" piece missing out of it but it will get you home no problem. PM your info and I will send them to you and you can pay me after you take a look at them. If you do not want them you can send them back to me.