Don McCormick (Dandy_don)
Junior Member
Username: Dandy_don
Post Number: 81
Registered: 2-2002
| | Posted on Wednesday, July 16, 2003 - 9:38 pm: | |
Hi, I need some advice. I am engaged in a 308 engine rebuild project with a respected engine tuner/builder. The engine is a Euro dry sump 308 and will be fitted with P6 cams, 3 ring Daytona pistons and has ported and polished heads. Should be good for about 280-300 HP which sounds reasonable depending on tune/timing etc. The 3 ring Daytona pistons bump the compression ratio to about 9.7 to 1. The builder has asked me whether or not I would like him to shave the heads a small amount and bump the compression ratio to about 10.5-6 or so. He is concerned that the engine will ping on 91-92 octane but really believes that the added compression will put the engine solidly over the 300HP mark. Very cool, but not if the only gas I can run is avgas with octane of 100 or so. One of our number has offered his opinions on the matter off line but has suggested that I post the issue on this forum for some help. Specifically I am interested in the following:
Is there any downside to shaving the heads to raise the compression ratio? ie the timing belt tensioning system or other similar issues. Clearly this is a non reversible modification.
It seems clear that bumping the comp ratio to 10.5 to 1 will be a good thing with P6 cams (more power and broader band) but will I need to run higher octanes (avgas) with that ratio? and will the engine be streetable/driveable?
I really would like to tap the vast breadth of experience here on the board without the differing opinions degenerating into a brawl so I do ask for some civility here. I just want your best thoughts. It is crystal clear to me that I haven't any of the necessary experience to make an informed decision and I feel the need for some discourse on the matter before coming to that decision. Thanx in advance for your thoughtful opinions on this matter. Don |