496 flat-lines at 5200 rpm - Page 3 - Chevelle Tech
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post #31 of 42 (permalink) Old Jul 6th, 10, 2:50 PM
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Gene
 
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Re: 496 flat-lines at 5200 rpm

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.

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Last edited by 427L88; Jul 6th, 10 at 3:12 PM.
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post #32 of 42 (permalink) Old Jul 6th, 10, 5:59 PM
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Re: 496 flat-lines at 5200 rpm

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

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post #33 of 42 (permalink) Old Jul 7th, 10, 12:06 AM Thread Starter
Nash
 
Join Date: Feb 2010
Location: Michigan
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Re: 496 flat-lines at 5200 rpm

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)
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post #34 of 42 (permalink) Old Jul 7th, 10, 12:41 AM
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Re: 496 flat-lines at 5200 rpm

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

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Last edited by SWHEATON; Jul 7th, 10 at 1:01 AM.
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post #35 of 42 (permalink) Old Jul 24th, 10, 1:18 PM Thread Starter
Nash
 
Join Date: Feb 2010
Location: Michigan
Posts: 26
Re: 496 flat-lines at 5200 rpm

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.
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post #36 of 42 (permalink) Old Jul 24th, 10, 1:58 PM
mr
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Re: 496 flat-lines at 5200 rpm

Quote:
Originally Posted by chevster View Post
Having some trouble with my 496 bbc not wanting to spin over about 5200 rpm.

In first gear itll go to about 5400, second only 5200, and third bearly hits 5k ..

Specs:
xr280r cam, solid roller
10.2 cr
Air gap
Oval port heads, opened up
850 mighty demon
Stock hei ignition (for now)
170 gph holley mech fuel pump
regulator sitting at 7.5 psi always.
Turbo 400 rmvb
3.08 gear (for now).

Seems like its running out of fuel? maybe ign? This motor zips up to 5000 so quick and really pulls till it just stops.
Quote:
Originally Posted by chevster View Post
I did not expect to make tons of power with my 496 past 6000 rpm, with my cam (242/248* dur @.05, .646/.653" lift).
But I am in fact expecting to achieve more than 5400 rpm in gear.

I'm simply asking for a starting point to find the culprit, If I was made of money I would upgrade the fuel and ignition as to eliminate any chances of losing power.
Quote:
Originally Posted by chevster View Post
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 ...
How high will it rev now ???.... I'm curious ......

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post #37 of 42 (permalink) Old Jul 24th, 10, 3:07 PM
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Re: 496 flat-lines at 5200 rpm

Quote:
Originally Posted by chevster View Post
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.
Did closing up the spark plug gaps lead you to do that?
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post #38 of 42 (permalink) Old Jul 24th, 10, 11:19 PM
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Jim
 
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Re: 496 flat-lines at 5200 rpm

Quote:
Originally Posted by chevster View Post
Having some trouble with my 496 bbc not wanting to spin over about 5200 rpm. In first gear itll go to about 5400, second only 5200, and third bearly hits 5k. I built this motor to spin to nearly 6500 and i need to know where to look for a cause.
Specs:
xr280r cam, solid roller
10.2 cr
Air gap
Oval port heads, opened up
850 mighty demon
Stock hei ignition (for now)
170 gph holley mech fuel pump
regulator sitting at 7.5 psi always.
Turbo 400 rmvb
3.08 gear (for now)
Its in a 4900 lbs truck.

Seems like its running out of fuel? maybe ign? maybe gearing? Cam??
This motor zips up to 5000 so quick and really pulls till it just stops. Not sputtering, no back-firing, just wont go anymore. Where should i look first?
Thanks for reading

I have built allot of "factory" cubic inch motors but that cam seems too small to get much more out of that big ole motor....I bet it is a stump pulling SOB before it max-s out!

jim
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post #39 of 42 (permalink) Old Jul 26th, 10, 3:28 PM
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Mike
 
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Re: 496 flat-lines at 5200 rpm

Quote:
Originally Posted by Tom Mobley View Post
yeppers. This is outright garbage on the part of CC and this is not the first time it's come up here either. Stuff like this is why I hate that crappy company and all their crappy products.
Just curious...what is the difference between this post and vendor bashing?

Mike

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post #40 of 42 (permalink) Old Jul 26th, 10, 3:34 PM
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Rich
 
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Re: 496 flat-lines at 5200 rpm

Quote:
Originally Posted by 69bu View Post
I have a Comp billet solid roller cam that I like very nice.....what ever happened to no vendor bashing?
I asked that question a while back and got no response...

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post #41 of 42 (permalink) Old Jul 27th, 10, 12:15 PM
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Re: 496 flat-lines at 5200 rpm

I guess moderators can bash at will.

Mike

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post #42 of 42 (permalink) Old Jul 27th, 10, 11:24 PM Thread Starter
Nash
 
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Re: 496 flat-lines at 5200 rpm

Quote:
Originally Posted by mr View Post
How high will it rev now ???.... I'm curious ......
It will easily rev to my limiter (6 grand) and i'm sure even past that. But as some have pointed out, it makes most of it's power below 5800 rpm.
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