tbanzer

Currently getting ready to install a "custom cam" that I had speced and Im concerned by looking at the lift and duration numbers. The build is as follows. 540ci 8:1 compression afr 325 cnc chamber heads. Gil exhaust manifolds, and going to be Vortech supercharged, looking for around 800hp. The Camshaft numbers are: 243/249 duration and .662/.646 lift hydraulic roller. Both the duration and lift numbers seem excessive and Im concerned with valve train life and possible reversion. When I voiced my concerns I was told this was a mild Camshaft by who supplied the cam and components. Any help would be appreciated.

Budman II

iTrader: (1)

I'm not an expert by any means, but I believe the positive pressure from a supercharger can help alleviate reversion in some cases. What is the LSA? The cam card should list the valve opening and closing events. That will tell the real story.

ICDEDPPL

iTrader: (1)

There`s no positive pressure at idle from the blower. What rpm you wanna run? Personally Id want a cam with more duration. Small boat, you don`t need some stump puller. With Manifolds reversion shouldnt be an issue with that cam

HaxbySpeed

With an efficient centrifugal SC, that is certainly more cam then you need to make 800hp, but not crazy. It will likely make great power with those cubes and cylinder head. The downside to running more duration then you need is idle, in and out of gear, docking, etc. becomes a little more difficult to tune. The downside to running more lift then you need is valvetrain longevity and maintenance. There are many variables, but often times due to the way the boost comes on with a centrifugal, you're better off running a little less cam, and a bit more boost. This will bring the boost in earlier in the rpm range for better acceleration, and you can make your peak hp number at a lower rpm. This will give you a better cruise speed, and less cycles on your valvetrain. Those manifolds aren't the best for reversion resistance because of the big short runners and large "collector" opening before the riser. Careful idle tuning can make a world of difference to help fight reversion, specifically when it comes to timing.

HaxbySpeed

Valid points as well. It really depends on the application.

tbanzer

6000 rpm red line, lobe separation 114 deg.

GPM

In my opinion, not that it matters, that's a small cam in a 540, on a 114 should idle fine.

Panther

It's not too far off from a 139651 with less exhaust duration and a little less lift and they work well in 540's from what I've seen. 800hp shouldn't be hard. I don't think it's excessive either. The blower also helps to mellow the idle a bit from my experiences.

Panther

Is this an blow-thru deal or efi?

GPM

We had pretty good luck with a 256/264 @.050 and a Procharger, seemed to like the 112 better than the114. The 14 was lazy on the bottom.