compression increase?

[crf311]

How much improvement could I expect from a increase of compression from 7.9 to about 9.0? The reason I ask is because I purchased a gen 5 454 truck motor for a real good price. The guy helping with my motor advised me to go ahead and changed the pistons now while I have it out the boat. We are changing the heads from the small peanut port to the larger rect. ports and also changing the cam. With the mods and cam change he feels we can get about 450 hp easy. Thanks

[oldbuck40]

im running a 40 over flat top with a stroker crank with the heads milled 40 getting about 10-1 comp and looking right 500hp

[Nucking futs]

im running a 40 over flat top with a stroker crank with the heads milled 40 getting about 10-1 comp and looking right 500hp
What are the cc's on your heads? Open or Closed chamber.
Tim

[TIMINATOR]

CF; about 8-10 hp. REALISTICALLY, or 1/2 mph in a jet. Had customers go from open/flattop to closed/flattop, and seen nothing. It seems that the guys who got gains made other changes at the same time. TIMINATOR

[QuickJet]

How much improvement could I expect from a increase of compression from 7.9 to about 9.0? The reason I ask is because I purchased a gen 5 454 truck motor for a real good price. The guy helping with my motor advised me to go ahead and changed the pistons now while I have it out the boat. We are changing the heads from the small peanut port to the larger rect. ports and also changing the cam. With the mods and cam change he feels we can get about 450 hp easy. Thanks
What heads are you going to run? I know you said rec ports however I hope you know that production GM Gen 4 heads will not seal on Gen 5 blocks. If you are going aftermarket then make sure that they are compatable with both such as those offered by Edelbrock, brodix, AFR ETC. Chevrolet also offers an over the counter head aluminum head. 990 or 188 heads will NOT work.
Also if your only shooting for 450 hp you'd more than likely pic up power and speed by going to an Oval port head. The rec head (especially with such low compression) might not have the velocity you need @ the lower RPM's while at the same time your pump might keep you out of the RPM your heads need to really pull the power.
Just a thought.

[crf311]

Thanks for all the input. It looks like I am going to up the compression to about 9.5. Along with the gen 5 rect heads and cam we are shooting for 450hp. We will do a dyno run so I'll let you'll know.