[BrandX]

Ok, if i have a 30 over 455 with a 4.250 stroke, 6.8 rod, o decked with a 56cc cylinder head and a .039 gasket.....Whats my compression? Ross flat tops 2 valve relief.............


Now same motor combo, but lets try to get it to 10 to 1......How much dish and head gasket would i need to get it down there? And would it be reliable for a blower application?

[Ron H]

http://wallaceracing.com/Calculators.htm
From this calculator you can figure things up.
It's showing 14.40 with 6.6 cc valve reliefs and 466.8 CI

I have read here that the best goal for boosted application is 8.1 CR so you will probably need to change the heads or have the chambers opened up if possible. 10 to 1 will still be quite high. But I do not know that for sure. Someone else will probably confirm that.

[Mr. P-Body]

Brandx,

We have 30 CC dished Ross "blower" pistons with a 66 CC chamber, making right at 9:1. in our 475. A 36 CC piston (including reliefs), .060" thick head gasket would get you right where you want to be. SCE makes head gaskets in various thicknesses up to .100". With the blower, O-ring the block and use the SCE. You will be very happy.

Jim

[cgeise]

with a 4.5 stroke and 67 cc heads - we had to go with a 32 cc dish and - leave it .100 down the hole - with a .040 gasket

[Brian Baker]

8:1 or lower with gas, even race gas. 10:1-12:1 with alcohol. You can go higher with alcohol but I wouldn't recomend it as your tuneup would need to be dead nuts on.

[screamingchief]

Agree with a blower app,leave the pistons down in the hole somewhat,and target the CR with the head gasket thickness and piston dish as mentioned above.

Your not worried much about quench with a boost application,so dont sweat that stuff,leaving the pistons down in the hole some is much easier on the head gaskets from what some smart fellas have told me.

Example,4.180" bore,4.250" stroke,56 CC heads,-.040" deck height,.050" compressed head gaskets,and 30cc dish nets 9.997:1 CR.

[BrandX]

sweet, so what you are saying is that leaving the pistons in the hole is a better idea....Ok, i have some serious thinking to do. If i were to do it, it would be a 871 and on alcky. Nitrous has been good to me, but i have always wanted a blower. Gotta count the pennies and see if its feasable......The RIGHT thing to do would be to use the blower money to buy a good block................I dont know why its so hard for me to pull the trigger on the block. With the blower, i could piece it together and it wouldnt hurt so bad over time........I better sleep on this deal. Thanks alot for the input fellas.

[Brian Baker]

Spend the money on an IA-2 block first...then hunt down the blower. No need to purchase new, there's a huge market out there on used blowers.

[BrandX]

yeah, you are right.....its just a heavy chunk of change man.