BadDog

Just picked up my HP 500 from the machine shop. New pistons, rods and head service. I asked that he dial the C/R to 9.0 The calculation from CC'ing the heads and measuring piston height showed that it came in at 8.67 to 1.

How much HP was left on the table with the lower compression ration? Is it enough to worry about or should I just be happy I don't have to pay for 89 fuel and have a bit less chance of detonation? It is not too late to pop the heads off and have him take a little off or use a thinner head gasket.

BadDog

Anyone have Desktop Dyno they could run this through? Picking up a 1/4 point should be easy with a head gasket change but is it worth it?

jeff1000man

Depends on the camshaft, head work, exhaust etc.

If nothing was changed except the CR, then I doubt you changed the power by much.

BadDog

Fresh built HP 500, no cam change. Lightning Headers.

US1 Fountain

No Mo Blo?

jeff1000man

I don't remember what the CR of the stock engine was, but I thought it was less than 9.

US1 Fountain

8.75 comes to mind

BadDog

It was 8.75 per book so I am a tad below that. Might just give me a margin of safety but I hate leaving power behind.

Jerry,
No Mo Blo, sitting on the bench looking for a new home. The blower just got to be too much maintenance with heads, oil changes, blower rebuilds insurance etc. Looking to be a bit more reliable and less trouble as I plan to move into a different boat soon.

B&M 250 with cam and Nickerson Carb for sale if anyone wants a quick 625 HP.

jeff1000man

You should have just had him bump it up to 9.5 +-. Still pretty safe at that range.

Griff

You won't notice a difference from stock. I'd guess maybe 10-15hp if you bumped it to 9.0.