Reply to "COBRA JET: Unleashing The Performance Capabilities Of 351 Cleveland Engines With Open Chamber 4V Heads (Q Code)"

The cylinder walls are too thin for anything greater than about 8.0:1 dynamic compression; i.e. fuel compatible with 91 octane pump gas (US & Canada) or 95 octane pump gas (Europe & Australia). An engine operating at 8.0:1 dynamic compression on 91 octane fuel, operated at wide open throttle is pushing the limits of the cylinder walls. So build the engine based on that limitation, no matter how high the octane of the pump gas which is available to you.

The amount of static compression the engine can use is dependent upon when the intake valve closes. A "bigger" cam can usually use more static compression. An engine can use about 11.0:1 static if the intake valve closes at 76 degrees ABDC.

Also be aware that raising compression is a situation of diminishing returns. Less horsepower is gained going from 10:1 to 11:1, than was gained going from 9:1 to 10:1. This is because the engine has to work harder to compress the fuel/air higher.

Finally, in my experience, open chamber heads are no more prone to detonation than quench heads.

Technically a solid roller tappet cam will make the biggest horsepower, but I'm a bit reluctant to recommend it. There are no rev-kits available for the 351C, and without a rev-kit the roller tappets take quite a beating due to the lash clearance. I can explain what I would do to operate a solid tappet roller cam ... if you wish. But the hydraulic roller tappet cam is a better bet for engine longevity because there is no lash clearance. A Cleveland for the street needs lots of lift but conservative duration to keep the overlap at or less than 60 degrees.

Here's what I consider the biggest "street cam"
(i.e. the valve events bump up against all of my valve event limits)

286°/290° duration at 0.006
232°/236° duration at 0.050 (approximately)
Lift will be limited by the valve spring.
The spring I've been recommending has a max lift of 0.630 inch.
114° LSA, 60° overlap
index the cam +1° (113° ICL)
This cam can use 10.8:1 static compression

That's a pretty bitchen cam. Too big for me at my age.