cam for my new motor

[502procharger]

I am looking for cam suggestions for my new 540 BBC. I am running the cmi headers that come on a 500hp and I want to put the correct cam in to prevent reversion. I am running 9:1 comp. And a procharger. Ported rec port gm hp heads, dart intake, je pistons, Manley rods, etc. all good internals and I would hate to ruin a new motor b/c I put to big of a cam in. hydraulic roller.
Please HELP!

[Dave F]

I've had several notions of a 540 with a Pro Charger stage 4 kit...Lucky you!
Anyway, with a Mark 4 style block, I've always thought I'd use a Crane 139651. 244/256 114 .632/.632
This cam has 22* of overlap but with CMI's you should be ok.
If you want to stay on the conservative side, or the Pro Charger isn't atleast a stage 3 then you might want to go with 139741. 234/242 112 .610/.632. That cam has 14* of overlap. I KNOW you wont have any reversion with that one.
DAVE

[blowngas]

502procharger:
I am looking for cam suggestions for my new 540 BBC. I am running the cmi headers that come on a 500hp and I want to put the correct cam in to prevent reversion. I am running 9:1 comp. And a procharger. Ported rec port gm hp heads, dart intake, je pistons, Manley rods, etc. all good internals and I would hate to ruin a new motor b/c I put to big of a cam in. hydraulic roller.
Please HELP!whatever cam you decide on, be sure that the existing valve springs will handel the increased lift---best to buy correct springs along with new cam----

[502procharger]

i will most def. put the right springs in with the cam. how much hp am i loosing going with the more conservitive cam (14 deg over lap) my block is a gen VI does that make a diff.?
[ September 24, 2002, 03:53 PM: Message edited by: 502procharger ]

[blowngas]

502procharger:
i will most def. put the right springs in with the cam. how much hp am i loosing going with the more conservitive cam (14 deg over lap) my block is a gen VI does that make a diff.?degrees of crankshaft rotation are the same on all motors---hard to say what h.p. loss would be if any between the cams---not knowing what your intent is with reguard to the type of boating you plan on doing, I would favor the the lessor of the two cams in reguards to duration, although I would go more on the lift if it were mine---most everyone cruises around 3000 to 4500 rpm depending on their setups,and the lessor duration would give you more punch at a lower rpm than the higher duration stick --and usually limit the top end to around 6500 to 7200---again, depending on their setup, and how good the guy is that puts it all together---I think the gen 6 block has the tall lifter bores so make sure the lifters are for that block--the bearing journal sizes are the same as mk 4&5---be sure and check the rocker geometry to make sure the valves don't bind and the rockers and valve keepers don't hit---use a flashlight and watch the rocker tip as you rotate the crank thru a valve cycle---do not hesitate discussing your plans with a cam manufacturer of your preference---they can usually make the right choice---best of luck

[Infomaniac]

502procharger:
i will most def. put the right springs in with the cam. how much hp am i loosing going with the more conservitive cam (14 deg over lap) my block is a gen VI does that make a diff.?This is a stern drive boat? If so do not worry about HP. Pick a cam that makes good torque. Low end and mid range. Chances are your engine will never see the RPM's necessary to make big HP. Look at the RPM range of whatever cam you choose very carefully. Never install a cam that peaks power at an RPM that your engine will never see. 112 or 114 lobe sep. and very short duration. It will not sound cool at idle, but will perform very well for you. wink
Dennis Moore has recently recommended a cam exactly like I have been recommending for quite some time on this board.

[Dave F]

You need to realize your own goal. If economy is what you're after, (ya, I know, why put on a blower if you're looking for economy?) the smaller cam would help because as I've said before, you pick your cam primarily on the rpm range for which you want to operate.
Remember, there's only 3 ways to make hp:
RPM
compression
cubic inches
So, on the 540 that I've built (on paper) and saved I also compared those two cams.
To give you some small details of my build up:
Static 8.5:1
8# boost
with the 234/242 approx numbers:
HP= 851 @ 5-5200
T= 1036 @ 3500
the 244/256
HP= 922 @ 5500
T= 1036 @ 4000
So as you can see it depends where you want to operate.
If you like to cruise above 3500 rpm and have a WOT of 5500-6000 rpm then the larger cam is for you. This cam is more for top end speed. Remember, there's a possible price for that, LONGEVITY.
If you like to cruise between 3-3500 and have a WOT of 5-5500 then the smaller one is better.
Now, for the fact that it's a Gen 6, they do make specific cams for those blocks that are close.
Again these will be Crane hydraulic, as that's my personal choice. You can choose the cam manufacturer of your choice of course.
Cam number 168741 236/244 112 .610/.632
I had this cam in my 502, with a pair of CMI's and had no problems with reversion. (16* overlap)
The next size up would be a 168771 240/248 114 .621/.632
In the comment section of the book it reads, "...marine perf. for 540+ engines..."
Using the same engine as above the numbers are:
HP= 887 @ 5-5200
T= 1031 @ 4000
Hope this helps
DAVE

[FASTERDAMITT]

Another suggestion is to consider what kind of idle you want. I personaly don't like my idle more than 900rpm. With the cams your mentioning I think you will be putting a lot of load on your drive when put in gear. What do you guys idle at? I run a 224-236 on 112 ProCharger stage2.

[Dave F]

All those cams I mention'd will idle between 800-900, and in gear between 6-700 rpm.
when I had the 236/244 112 in a 502 it idled right at 800, no sweat.
DAVE

[paradigm shift]

I ran a 139651 crane hyd roller in a 540 1071 Blower. CMI exhaust with standard tails and Teague switchable mufflers. The 450s and no reversion. Type of tail pipes you run and how much water also effect reversion a little. I also ran a big heavy flywheel and it idled better than I had hoped. A roots type blower will help mellow a bigger cam more than that procharger will also in my opinion. If your worried about idle and not running the high RPM numbers I would go with the smaller cam you would probably be happier. Nothing worse than a cam to big and problems idling with an I/O. You can always change a cam and or pulleys to make a little more power if you want. I run a Bravo on a 29' deep vee. Wife drives it no problem. :)