7000 rpm pop in high gear

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camaroman9 · #1 Post by **camaroman9** » Sat Sep 19, 2009 12:44 pm

so, i have a problem with my setup on my car. i need some opinions on how to fix it. on my old tuneup, it was way too fat and ran fine for 1/8 mile. for some reason though, when i ran 1/4 mile it would pop at 7000 in high gear. we thought it was the tuneup, so we downsized the fuel jet and got the tuneup pretty much dialed in now. the car still does the same thing . it does fine for 1/8 mile, but whenever i make 1/4 mile passes, itll pop at 7000. some people i have talked to think that my carb is too small. its a 750 holley with a proform main body. i thought the distributor could've been causing it, but i just rebuilt it 2 weeks ago. any help is appreciated.

Chevyfireball · #2 Post by **Chevyfireball** » Sun Sep 20, 2009 6:56 am

Need some details on the motor.

camaroman9 · #3 Post by **camaroman9** » Sun Sep 20, 2009 11:48 am

388 cubic inches, 11.2:1 compression ratio, custom ground ultradyne roller cam, ported dart pro 1 platinum 215's, ported vic jr intake with a cold fusion plate setup. msd 6al igniton box with pro billet distributor.

supernova · #4 Post by **supernova** » Sun Sep 20, 2009 3:56 pm

How much nitrous are you trying to use? What fuel set up do you have?

The carb isn't too small. I ran a 750 for yrs. on a 385 sb. I'm thinking it's more ignition related. A 6al box may not be enough for the nitrous or is breaking down the spark because the box is old. How does it runn with out nitrous?

ytnova · #5 Post by **ytnova** » Sun Sep 20, 2009 4:43 pm

How old are the valve springs? What chip is in the msd? Have you tried a different chip or even ohm'ed it and checked against the known values?

camaroman9 · #6 Post by **camaroman9** » Sun Sep 20, 2009 5:01 pm

supernova wrote:How much nitrous are you trying to use? What fuel set up do you have?

The carb isn't too small. I ran a 750 for yrs. on a 385 sb. I'm thinking it's more ignition related. A 6al box may not be enough for the nitrous or is breaking down the spark because the box is old. How does it runn with out nitrous?

I'm using a .092 n20 jet, .083 fuel@5.75 psi for the nitrous tuneup. The box is pretty old, but the car runs fine on the motor. The fuel system is a bg400 pump, -10an feed, 2 port log with holley regulators and an aeromotive a2000 to regulate the bypass which is -8an.

ytnova wrote:How old are the valve springs? What chip is in the msd? Have you tried a different chip or even ohm'ed it and checked against the known values?

The motor was brand new in spring of 2008. It has not been apart since then. It has an 8000 chip in the rev limiter, i have not ohm'ed it to check the resistance.

#7 Post by **John_Heard** » Sun Sep 20, 2009 7:52 pm

Have you tried tightening up the plug gap? Did it get better or no change?

Pegasus · #8 Post by **Pegasus** » Sun Sep 20, 2009 8:00 pm

I think the problem is in your tow truck.

A good looking tow truck with a

rear plate.

I hope you get it fixed and come back to ORP in Oct.

gmracing355 · #9 Post by **gmracing355** » Mon Sep 21, 2009 1:40 am

I had a popping problem in my car and a friend mentioned the msd rpm chip so I pulled it out and the popping problem is gone.
Greg

vegaracer · #10 Post by **vegaracer** » Mon Sep 21, 2009 6:38 am

I had a popping problem to and my tank vent hose wasn't big enough.

camaroman9 · #11 Post by **camaroman9** » Mon Sep 21, 2009 9:26 am

John_Heard wrote:Have you tried tightening up the plug gap? Did it get better or no change?

we tightened it up from .033 to .031 with no noticeable difference.

camaroman9 · #12 Post by **camaroman9** » Mon Sep 21, 2009 9:30 am

Pegasus wrote:I think the problem is in your tow truck.
A good looking tow truck with a rear plate.

no way don, that helps my truck climb hills better with the trailer behind it. besides, i dont think that has anything to do with the car running wierd. lol

I hope you get it fixed and come back to ORP in Oct.

#13 Post by **John_Heard** » Mon Sep 21, 2009 9:49 am

camaroman9 wrote:
John_Heard wrote:Have you tried tightening up the plug gap? Did it get better or no change?
we tightened it up from .033 to .031 with no noticeable difference.

So one the 1/4 mile it's doing this after the 2-3 shift and when you're at the top end right? It doesn't do it when you are at 7000 ish on the 1-2 or 2-3 right? If it's valve springs it ought to do it even 1/8th mile if you're turning it that tight also. Running 1/4 mile and doing it at the top, I wonder if you're dealing with a lot of bottle pressure drop for some reason and it's going fat? Or some other kind of air / fuel issue going on.

camaroman9 · #14 Post by **camaroman9** » Mon Sep 21, 2009 10:05 am

correct. it doesnt do it in 1st or 2nd, only in high gear at 7000-7100. we pulled the plugs after it did that friday night and looked at them. they looked fine to sam and i.

#15 Post by **John_Heard** » Mon Sep 21, 2009 10:18 am

What was the deal with the black crap in the bottles and lines? Did that get resolved? Do you have any filters in the solenoids that might have gotten plugged up with that stuff?

7000 rpm pop in high gear

7000 rpm pop in high gear

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