Another Cam Question

[VD CRUISER]

Dennis Moore,
I have a 21' Howard, V-drive with a 547 ci Chevy,(4.250 stroke x 4.530 bore ). I have 8.2 to 1 comp. with Canfield alum. heads,1071 mooneyham blower with 2 1050 holleys,( 10 psi boost ), and Lightning headers. I use a turbo 400 and run 48 % over drive in the Casale. I am currently using a flat tappet Clay Smith cam with .640 advertised lift. The RPM's are 6200-6400 with a 11 3/4 dia x 16 pitch Menkens 2 blade prop. Do you think a roller cam would be worth the investment and if so what would be your recommendation?

[Dennis Moore]

That is a tough question, I would think that a dual pattern camshaft with about 240 degrees intake duration and ONLY A LITTLE more exhaust duration (about 246 degrees exhaust duration) would work the best. Not a single pattern camshaft like you probably have with the Clay Smith.
I would also go with a wide lobe separation angle (114 degrees). I would also guess that the Clay Smith camshaft is much tighter (as much as 110 or even 108).
Just for practicality I wouldn't use more lift than you have now. Higher lifts requires stiffer valve springs that are hard on roller lifters. A big engine/blower combo like you have doesn't need a lot of valve lift to make power.
This may be controversial but I really like the solid roller lifters with the horizontal link. The link doesn't ride up and down with the lifter like a vertical link lifter. This makes the lifter much lighter, something important to be able to keep valve spring tension a little lighter.
Adding all of this up I would recommend that you have Comp Cams grind you a camshaft using the new Xtreme Energy Street Roller camshaft lobes. Intake lobe # 4874 has 242 degrees of intake duration @ .050 and the Exhaust lobe # 4875 has 248 degrees of exhaust duration @ .050 Have them grind it with 114 degrees of Lobe Separation Angle and the intake lobe centerline advanced 4 degrees.
I think that Comp Cams would agree with me on these specs. They might not like the lifter recommendation and probably want to sell you new valve springs. Listen to their recomendations very carefully, they know their stuff!
Hope this helps!
Sincerely
Dennis Moore

[058]

I'm not Dennis Moore but I think I can answer your question. If you do alot of idling or low rpm such as dealing with no wake zones, 5 mph areas or low speed cruising do not use a solid roller cam. Low rpms are hard on the cams and rollers, there has been other posts regarding this subject...see "Roller cam wear" post

[VD CRUISER]

058, don't have to contend with to many 5 mph zones, but we can use lower gears in the turbo 400 when needed.
Huffpower, looking for more topend. Of course this will mean more RPM unless we up the overdrive, already at 48%. I was using a 3 blade SS Menkens for everyday use and two different 2 blades for speed, 12 x 16 and 11 3/4 x 16. I don't want to turn too many more rpm's, so if we can get it to go 6600-6700 I will consider changing the gears. It does pretty good now, but most people think a roller cam will make more power, and I don't mind a rough idle or adjusting the lifters. This is just a fun boat, but this time of year here, as atmospheric conditions get better, the racing picks up and I have some Jets and Outboards to contend with. It radared at 109 mph last year in ideal conditions, but naturally I want to go faster.
Dennis, thanks for the reply.

[cole89]

A solid roller should work OK. I have one my Cole and it will idle all day long. My cam is a Comp Cam street roller with a 610 lift & 110 L/C. You could use the wider lobe center with your blower. The main deal with the solid roller is maintaining the valve spring pressure. I'm my running spring pressure around 250 @ 2.030.
Your V-drive ratio sounds like a bit much to me.