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-   -   looses power (https://classracer.com/classforum/showthread.php?t=55410)

Frank Castros 10-26-2014 08:01 AM
Re: looses power
 
Quote:
Originally Posted by Myron Piatek (Post 450916)
If I may.....Try breathing through a straw (small carb), then try breathing through the cardboard spool out of a paper towel roll (big carb). You can only take in so much air in so much time through a small hole. The restriction doesn't allow you (or the engine) to breathe enough volume quickly enough to satisfy the needs. (High rpm or you running.)

Thanks Myron,

I agree about lower shifts points, but I still suspect the Super Victor intake manifold is the wrong choice, and going to test a Victor which is designed for lower rpm applications.

Myron Piatek 10-26-2014 08:46 AM
Re: looses power
 
Just trying to help with my perspective, and hoping Mr. Mulry doesn't mind me cutting in.

The manifold change appears to be a very good idea also. I've heard of several people disappointed with the small block version of the SV as well, noting the larger plenum volume and recommended rpm range.

Bob Mulry 10-26-2014 03:04 PM
Re: looses power
 
Quote:
Originally Posted by Myron Piatek (Post 450921)
Just trying to help with my perspective, and hoping Mr. Mulry doesn't mind me cutting in.

The manifold change appears to be a very good idea also. I've heard of several people disappointed with the small block version of the SV as well, noting the larger plenum volume and recommended rpm range.
Be my guest.....

You broke it down better than I did.........

Take care,
Bob



PS:

But on the other hand, a large plenum and a small runner can fool the engine into thinking that it has a larger carb..

There are a lot of ways to fool an engine..........

Chris Hill 10-26-2014 08:02 PM
Re: looses power
 
Quote:
Originally Posted by Frank Castros (Post 450867)
GT/HA '66 Plymouth Belvedere, 426 Street Wedge, 3,675 lbs.
2.77 first gear ratio, 4.89 rear gear, shifting @ 6,500 rpm, 7,500 rpm at the finish line.
1.44 60', 4.35 @ 330, 10.80 @ 122.00 mph.

Problem is it runs out of steam at the top of the first gear.

Running an Edelbrock Super Victor with a Carter AFB 585 cfm, fresh Product Engineering 9500 Fuel Pump and 4 port regulator.

What do you guys think?
Everything seems ok. 1-2 shift sooner.

Don't go to 4.56 and 2.45 low gear. It won't leave starting line at all.

HTMtrSprt 10-26-2014 11:10 PM
Re: looses power
 
I would agree that a large runner and plenum wouldn't cause a lack of power. Sprint cup restrictor plate motors (similar to the big motor, small carb setup) actually make power using the biggest runner size they can cut into the manifold casting. More likely a fuel delivery issue if it only occurs in low gear as that is when there is the highest 'G' loading on the fuel system.

Glenn Briglio 10-27-2014 12:17 PM
Re: looses power
 
Frank , has this combo been on an engine dyno? All the guessing and possibilities are answered.

Frank Castros 10-27-2014 07:29 PM
Re: looses power
 
Thanks Glenn,

This is not my car, but a friends who is not a Class Racer member and cannot post here. It was my idea to post because he's is frustrated and I knew you guys could help.

I know the engine has been dyno tested, but not flogged and I'm not familiar with the data.

Because of the small carburetor I think the Super Victor intake is too much, and he's going to try the smaller Victor at the track.

The fuel delivery theory has been adequately addressed, and I agree the 2.77 low gear and 4.89 rear are correct for the combination, also shifting at 6,000 seems to make sense.

Thanks to everyone for the thoughts, but if there are more ideas, I'm all ears.

He's only looking to go 10.40s or 50s.

69Cobra 10-27-2014 07:58 PM
Re: looses power
 
1320/122=10.819 It sounds like he's right on target with the power he's making.

Pvt Parts 10-27-2014 08:59 PM
Re: looses power
 
Quote:
Originally Posted by 69Cobra (Post 451062)
1320/122=10.819 It sounds like he's right on target with the power he's making.
There's always more!

69Cobra 10-27-2014 10:01 PM
Re: looses power
 
Quote:
Originally Posted by Pvt Parts (Post 451070)
There's always more!
Yes. But there's not 3 or 4 tenths more with the same hp to run 122mph.

Just curious does anybody have good data on what it takes hp wise to pick up 1 tenth at this level?


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