496 flat-lines at 5200 rpm - Page 3

**427L88** · Jul 6th, 10, 2:50 PM

Yeah, its not the size of the cam here, that's for sure.

Keep it basic baby, what Gary said. to wit, I know I'm not getting WOT with my 3X2 setup since I've redone a few things, but I don't need 1125 cfm to feed a 427 anyhow. 80% works.

You need all of 850cfm, and primaries only would keep RPM at around 5000. With only the center carb connected on the 427, it would only run up to 4000 rpm or so, driven under load, so 5000 seems right freewheelin'.

I hope for your sake its something so basic and simple.

The rev-a-bility is what kept me away from a HR. 427s make all ther snot in the 6000+ rpm range. Means beehives and travel restricted lifters. Nothing box stock about it.

Dave Birdwell · Jul 6th, 10, 5:59 PM

There aint no point in talkin, 'cause nobody's listenin......

chevster · Jul 7th, 10, 12:06 AM

OK, so In order, the possible causes:
Valve springs (float)
Fuel - (Holley mech 170gph, lw pushrod, 8an line to carb, 3/8 from tank,btw)
Distributor (HEI)
Carb
Ignition timing?
Tach (lol)

**SWHEATON** · Jul 7th, 10, 12:41 AM

Quote:

Originally Posted by kettbo View Post

242/248*@ .05 .646/.653" lift 110* LSA /106* ICL
while not a 'big' cam for a 496, it should get the job done....look at the springs and fuel before the cam. Vortecpro runs a smaller cam in his engines and make power above 5200. Look at his posts last week

Like you say his cam can still get it done but making power to a little lower rpm of maybe 5,800 or so in his 500 cid bbc after he gets the valve springs squared away and or fuel delivery issues corrected too ,could collectively 2-3 issues reducing his top end power rpm.

And to me 5,800rpm or so is plenty of rpm for street 500 cid bbc to be turning that will keep it safe for many yrs of foot to the floor tire shreading fun/LOL!!!!!

But remember Mark does extensive head porting and who knows what else that can also have an affect on where power will drop off with a slightly milder cam he may be running vs if the motor in this post doesnt have the same extensive head porting and or other perf mods etc Mark does that can maybe extend top end power making rpm a bit like in Marks motors.

I dont think his cam is the complete issue here but i still feel it's part of the problem not maing the 6,500rpm goal is all i am saying. But his cam is a good street cam for a 500cid bbc thats for sure. The original poster stated in his inital post that he expected his basically 500 cid bbc to power thru 6,500 rpm with a 280 deg adv dur cam which i dont feel is generally up the task of making good power it thru 6,500 rpm before noticeably dropping off on power esp in 500 cubes which is what my point is.

His other lower top end rpm related problems could be v - springs too weak & or fuel delivery issues too reducing top end rpm some.

But i would be surprised to see an everyday perf 500 cid bbc pulling strong thru the 6,500 rpms (this poster stated he was expecting his combo to do) before showing signs of and or noticeably dropping off on power with a fairly mild 280 deg advertised dur cam in 500 cubes i just don't see happening.

Pulling strong with his 280 deg adv dur cam to 6,500 rpm in a 396-402 or maybe even a 427 could likely be done with right combo. But it's not as easily done in a considerably larger 500 cubed bbc unless someone like Mark Jones builds it with his bag of majic perf goodies/head porting mods ,thats a different story. And as we all know Mark's motors weather they be a mild perf lvl build or a higher perf lvl build in BBC or SBC form they all perform very well esp when considering whats in them and the cost ,thats for sure !!!!!!!!

Scott

chevster · Jul 24th, 10, 1:18 PM

UPDATE:
Dropped in my billet msd distr., my 6al box, and blaster coil..
Now I am glad i have a rev limiter.

Looks like my problem was mostly the ignition setup. Wheew glad thats over.
Thanks for the help all.

mr · Jul 24th, 10, 1:58 PM

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