Cam upgrade 741 or 651
 

Anyone running the crane hyd roller 139651 cam ? Its the next step from the 741 grind . I have a pair of 496 ( 1/4 stroke ) mark4 block 454's currently running a very conservative 731 grind .Engines have dynoed @ 785 hp ( 5 psi ) after intercoolers .Static compression 9 to 1 . I have them out for overhaul and considering running a more aggressive profile cam . www.cranecams.com is the 651 to much for these engines ? I run K/E's dry ... so reversion shouldn't be a factor .
I know the 741 will be a improvement over the 731 ... but have been leaning towards the slightly more aggressive 651 grind.

What do you guys think ?

I think your heads won't flow enough to support much more than the 741 and will hold you back from the higher lift cams. You might consider a longer duration cam or even get your cams reground to compliment your heads and setup. Bob Madra of marine kinetics would be a great source for info on your specific setup and if regrind is an option. Have a nice day and good luck with your project. Let us know what you decide to do. :kiss:

Thanks Dave . Regrinding my cams is not an option . I want an off the shelf stick . My heads have surprised the experts there one of a kind for sure . 290 Edelbrock Oval port matched to the rectangular blower intakes. Only way to see is to flow em on the bench . Then again ... how important is the port size when were talking a 496 inch engine ? We can speculate all day ... on cams ... just wanted to throw it out there to see if anybody has run this cam and what were the results ? Franks buddy had the 651's in this N/A 502's with iron heads ... 9 to 1 comp ... they really woke them up ... he did turn them to 6000 rpm .

I don't think your changes to the heads would impact your flow numbers of the heads unless you did more to them then the pics showed. I also am not familiar with the edelbrock oval port flow numbers so I can't say for sure. I am familiar with the rect port edelbrock heads flow numbers and they are about done at .600 of lift if memory serves me. So just make sure your heads can support the 651 and I think you have a winner. I am just concerned they cannot. Franks example was with a guy running iron rectangle I think.

741 cam
 

I put together a 548" motor for my street car. Used a 731 cam first and it was too mild. Replaced it with a 741 and it really woke up the motor,it would pull about 500 rpm higher than the 731.

i have them in my 548 in motors in my cat,i love them,i have 8.71s with innercooler,made 950 at 6500 with 8 lbs boost,i used the isky tool room springs,set at 185 seat pressure.im not sure how it will work with your oval port setup.give it a try,you might be pleasantly suprised.:coolcowboy:

i forgot to mention,i have dart 320 heads that have a mild port job.

IMO, the 651 has way too much duration for a 496ci. You would have to spin it at least 6000rpms to make power. I think the 741 would be a better choice.

741 is the same cam in a 525 correct?

Dyno Sheet for Bob's motor with blower. Sorry for the quality. Couldn't find originall sheet.
Peak torque - 773 @ 4500
Peak Hp - 785 @ 5800


http://i448.photobucket.com/albums/q...20motor202.jpg

The 651 works well in a 540 blower motor. I think its a little big for a 496. The 741 ground on 114 lsa would be my choice.

That nice numbers for a 496 stroker with a 250 blower :drink:

Not sure I would do more cam at this point. I'd slap a larger blower like a 420 b&m, slow the blower down, and maybe run it to 6lbs of boost. Probably pick up a bit of power, and the blower will live longer.

I'd imagine on that setup, the 250 blower at 5lbs intercooled, is probably overdriven quite a bit. Guessing you are still running the 250 blower overdriven quite a bit based on those massive torque numbers from 3000rpm and up. :drink:

Mild Thunder,
Right now its a 489, Bored .030 over. Bob is going .060 over which will make it a 496. I think thats his reason for the bigger cam.

I doubt the extra 7ci will matter much. If anything, maybe gain a tad of airflow from the larger bore unshrouding the valves a bit more.

The 741 is 114lsa cam, where i think the 731 is 112lsa. The 114 might make a little more cylinder pressure. I suppose if the engine is torn down already, go for it. I assumed it was together already.

Im sure the 741 will keep pulling past 6000. Use some good lifters and maybe some stud girdles! Keep us posted on the results!

...

139741 grind is the cam I'll try then . I wanted to try a dual carb set up this time ... hoping for better distribution of fuel. The 250 single set up have a tendency to leanout the forward cylinders . B&M had a plate that move the carb about 1.5 inches forward to correct the problem. I found a set of new /old stock dual quad adapters from Holley so why not give it a try.
The reason for the bore to 4.310 is a cylinder with some pitting that I couldn't hone out last June when I repaired the port engine ( head gasket ... burn't #6 pistion ) to save the boating season I decided to run it as is . It ran fine but was pushing oil out the dip stick after a hard run . After 4 seasons on these short blocks its time to freshen them up .

Always looking for more ... Thanks for the help everyone !

The 525EFI cam is 741 that is ground on a 114 lob sep instead of the standard 112 lob sep.
http://www.summitracing.com/parts/CRN-168741/

Good choice on the 741, think about doing the 7/4 swap while at it. Also I liked Mike280s idea on the 1.8s for the exhaust valves. Add shaft mount rockers and you should get a nice pop.

Being that your my running buddy should I still be looking for a set of peanut ports ?:grinser010:

with his current cyl heads,i agree,the 741 would be better,but if he goes with a better set of heads,even though the motor is small,the 651 will make more hp,but at a higher rpm,and when he gets ready to go with a bigger blower[as everyone who has a b&m eventually does]he will see even more gain.

thanks griff, that's what i thought, and mine also has the firing order switched... which wouldnt apply to the 496 as it already has it.