Pistons

[pugwash]

Just starting to get towards building my RV8 and need some pistons

the engine i have is a 4.9 with a 95.2mm bore and a 86.4mm stroke. The heads I have are CC'd at 32 (i beleive) across the 8 and haven't been skimmed, neither has the block been decked (i don't beleive). Now assuming that i am going to run Comp Gaskets how do i work out the specs of the pistons so that i end up with a CR of 10.5:1?

is there an easy formula?

(fyi block is an early block that has had a cross bolt kit put on but still has the old journal size on it!)

Whats the difference between Forged, Cast and Hypereuretic (if that's how it's spelt). Which is best for a lazy 4x4?

who makes em? what information will i need to provide which i haven't got above? If i found some chevy or buick pistons at the right "spec" could i use those?

finally i think i understand notching- but how does it affect the CR?

[V8CAMEL]

Just starting to get towards building my RV8 and need some pistons

the engine i have is a 4.9 with a 95.2mm bore and a 86.4mm stroke. The heads I have are CC'd at 32 (i beleive) across the 8 and haven't been skimmed, neither has the block been decked (i don't beleive). Now assuming that i am going to run Comp Gaskets how do i work out the specs of the pistons so that i end up with a CR of 10.5:1?

is there an easy formula?

(fyi block is an early block that has had a cross bolt kit put on but still has the old journal size on it!)

Whats the difference between Forged, Cast and Hypereuretic (if that's how it's spelt). Which is best for a lazy 4x4?

who makes em? what information will i need to provide which i haven't got above? If i found some chevy or buick pistons at the right "spec" could i use those?

finally i think i understand notching- but how does it affect the CR?

have a chat with steve lund

[Hybrid_From_Hell]

I can help you some part of the way

Whats the difference between Forged, Cast and Hypereuretic (if that's how it's spelt). Which is best for a lazy 4x4?

K

Most people will argue Cast Pistons are far inferior to forged, and thats why cast is cheaper

while its true that Forged have a much stronger molecular structure than cast, so they say then that Forged must be best for anything thats going to be heavily tweaked, - qulaity does come into it big time

std cast pistons rpm limit for is 5000 max for real relaibilty, but qulaity (Omega) cast pistons can go to 7000 all day long(ish)

Also, don't forget forged will really rattle - as they often have greater bore clearance / skirt etc and it will drive you nuts on a road V8, hence why Omega are good as lower cost cost option but 100% good - being ultra high quality

Omega (can get from JE) are either flat top with or without valve cut outs dependant on if your going high lift cam, normally 10.5 :1 rating, if you wnat higher compressins you can get domed pistons - Mahle do them.

Other comps often sold are 11:1 or 12:1 (too high IMHO). Also a tin gasket is thinner than a composite head gasket, which means you should bear this in mind, can't remeber the amounts

I think Real Steel do ROSS stuff, good quality or go seriously barking mad and use Jahns pistons in the land of "hell yeah" (usa) and have whatever you wnat made to order ! Cosworth also do them, as do Venolia B)

Having the whole assemble dynamically balanced is key, people often forget this, its essential the higher the BHP output and the revs your looking at, use someone who specialises in V8s and V12s etc

HTH

Nige