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mikep · 06-03-2002, 09:08 PM

Thats the first time Iv'e heard of anyone remark about too little compression with a 383. Generally guys complain about too much compression even with flattops and 76 cc heads your getting into the high 9's compression wise. I'm not sure if theres commonly availabe dished pistons and if its not a d cup design then quench goes to hell in a hurry. That, the long stroke to bore ratio and the rod to cam clearance issue is why I'm not completely sold on the 383 even if its with an internally balanced steel Scat crank and 5.7 inch rods. Ideally for street use with decent heads with at least 200 cc port size I'd want .500-.520" of gross lift and 236 to 242 degrees duration on tight lobe centers for a 383 using a nominal 10:1 compression. Much less duration than that isnt going to fill the cylinders to their potential and much more than that would be sacrificing too much bottom end without real gains on the top end as hydraulic cams are going to run out of steam at 7000 or so no matter what you do. Ive never seen a hydraulic lifter that didnt pump up at around 7G and nothing gets into my stomach like the sensation of floating valves.

BTW MikeB

Thats too much cam for 3.08 gears in a truck.

06-03-2002, 09:08 PM	#10
mikep Used to have a truck Join Date: May 2002 Location: port orchard WA Posts: 1,552	Thats the first time Iv'e heard of anyone remark about too little compression with a 383. Generally guys complain about too much compression even with flattops and 76 cc heads your getting into the high 9's compression wise. I'm not sure if theres commonly availabe dished pistons and if its not a d cup design then quench goes to hell in a hurry. That, the long stroke to bore ratio and the rod to cam clearance issue is why I'm not completely sold on the 383 even if its with an internally balanced steel Scat crank and 5.7 inch rods. Ideally for street use with decent heads with at least 200 cc port size I'd want .500-.520" of gross lift and 236 to 242 degrees duration on tight lobe centers for a 383 using a nominal 10:1 compression. Much less duration than that isnt going to fill the cylinders to their potential and much more than that would be sacrificing too much bottom end without real gains on the top end as hydraulic cams are going to run out of steam at 7000 or so no matter what you do. Ive never seen a hydraulic lifter that didnt pump up at around 7G and nothing gets into my stomach like the sensation of floating valves. BTW MikeB Thats too much cam for 3.08 gears in a truck. __________________ No truck :-( Last edited by mikep; 06-03-2002 at 10:02 PM.