(1) With this combination would it be worth the time to have a custom cam made for my application? Will I see that much of gain in HP?
(2) I was thinking, when you check for valve to piston clearance with a hydraulic roller cam, what do you use for a lifter. I always used a solid hydraulic to push the pushrod and valve?
(3) Any other suggestions would be great.

Stroked 496 MarkIV
9:5: Compression Ratio
Edelbrock Marine Heads, Oval , 110CC
Imco Exhaust
RPM AirGap Intake
Barry Grant 750DP
Currently Comp Cam Extreme Marine 270
224/234 @.050 and .550 lift

I only want to spin this setup to 5,300 RPMS Max

Jim,

I have several Hydraulic roller (and non-roller) lifters that I have modified for this purpose. I take the lifter apart and stack it full of little washers until I can just barely get the snap ring back in. That way you can check pushrod length at the same time. Solid roller lifters are usually a different hieght and use different length pushrods.

Hope this helps,

Bill Koustenis
Advanced Automotive Machine
Waldorf Md

Call up Crane and get a 525HP Mercury cam.It runs good in alot of combos.They make the cams for Mercury

There are a lot of posts here that will go into this in more detail but the condensed version is that the 731 and other older grinds have upwards of 10* more duration on the exhaust than the intake. This was done to compensate for the relatively poor flowing exhaust ports(compared to the intake ports) of the stock GM heads. The newer heads have much more efficient exhaust ports and do not need that much additional duration. I have heard many reccomendations in the 4* -6* range. Too much exhaust duration on these newer heads actually will cost you HP. For this reason I had my cams custom ground by Cam Motion based on my flow bench #'s for my dart heads. These cams were not any more expensive and they do a great job. Hope that helps.

JC's choice is the choice I would make for max power on a 496. That cam is a Crane 741 on a 114 LSA. Don't go with the myth that says that 8* of split is going to lose HP on modern heads. No matter how well the heads flow, you still need the cam to get the air into and out of them. Your drawback to making HP is the parts that you have. The heads don't flow that much. The cam that you have is very close to the 731 Crane, which is where I would probably suggest that you stay based on the parts that you have now. You will see an increase in HP at higher RPMs, but you have stated that you don't want to turn above 5300, which is limiting you. The last 496 (with a 741 in it) I saw dyno numbers for made 611HP @ 5500, and 645 @ 6000, with a Tq peak at 5000 RPM of 588. This was with ported Brodiz heads flowing near 400 cfm @ .600 lift, which is way way more than your heads flow. Just giving an example of the 741 cam HP potential

The 731 has a lot more lift than what he has and is only one size smaller than 741.
The 731 is .587/.610 226/236 on a 112 lobe sep
The 741 is .610/.632 236/244 on a 112 lobe sep

The 731 will probably make more usable power in the rpm ranges you'll be in 98% of the time. The 741 will probably make more power above 5500rpms. I would get with OSO member rmbuilder and see what he recommends with your heads.

Thanks all. I am trying to contract Bob M. about a custom cam and the $$$ difference it would cost.

Which is why I said that the current cam is "very close" to what he has now. I don't believe that with the heads he has, and the RPM that he wants to run, that changing cams is going to have much if any effect on his HP/top speed.

If the Edelbrocks are untouch when it come to porting they are around a 70% IE ratio. You're looking for a cam with 10 degree split at .50" and about a 14 degree at seat.

RMbuilder will take care of you.

Cam/brain selection is very important. If you really want a good recommendation on a cam with your combination, then at least one person I would consider is to consult RMbuilder's expertise (Bob Madara) of Marine Kinetics and you will be happy!