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Breaking up around 4K #2697544
09/14/19 04:38 PM
09/14/19 04:38 PM
Joined: Aug 2012
Posts: 58
WV
WV Runner Offline OP
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WV Runner  Offline OP
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WV
Took the car to a local show today, went to hope on interstate to leave and I romped it, got to about 4K and it fell on its face and started popping/backfire out of exhaust. Lifted and was fine, roll back into it and same once again at about 4K. At this moment I think electrical, I have a new msd 6al box, and new msd pro billet dist with mechanical advance. I removed the ballast resister with the new msd stuff. For a coil it’s an Accel super coil 140001, it’s about about 7 years old and use to run it with old stock ignition stuff. At the moment I’m thinking coil? This is a new issue, had the car at the track last month at the nats and was running great up 5,500 rpms. Any advice?

Re: Breaking up around 4K [Re: WV Runner] #2697549
09/14/19 04:57 PM
09/14/19 04:57 PM
Joined: Jan 2003
Posts: 30,747
Grand Prairie,Texas
stumpy Offline
I Win
stumpy  Offline
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Grand Prairie,Texas
Did you do the ignition changes after racing at the Nats? Also how's your fuel supply?

Re: Breaking up around 4K [Re: stumpy] #2697550
09/14/19 05:02 PM
09/14/19 05:02 PM
Joined: Aug 2012
Posts: 58
WV
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WV
All the ignition changes was made this spring when I put the motor in. Haven’t touched anything since. Fuel supply is a Holley blue pump with 3/8 fuel lines and running 7psi

Re: Breaking up around 4K [Re: WV Runner] #2697554
09/14/19 05:13 PM
09/14/19 05:13 PM
Joined: Jan 2003
Posts: 28,541
Hamtramck, PA
Alaskan_TA Offline
Fluffy Balladeer
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Fluffy Balladeer

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Posts: 28,541
Hamtramck, PA
That happened to me yesterday.

My alternator failed, so when the battery drained, not enough power to keep it running.

Check your voltage just in case it is a similar issue.

Re: Breaking up around 4K [Re: Alaskan_TA] #2697577
09/14/19 06:32 PM
09/14/19 06:32 PM
Joined: Nov 2003
Posts: 35,544
Lincoln Nebraska
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RapidRobert Offline
Circle Track
RapidRobert  Offline
Circle Track
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Posts: 35,544
Lincoln Nebraska
MSD issue I am thinking, what specifically, not sure. I would check the dist for a start. EDIT on second thought check the plugs/plug wires.

Last edited by RapidRobert; 09/14/19 06:44 PM.

live every 24 hour block of time like it's your last day on earth
Re: Breaking up around 4K [Re: RapidRobert] #2698196
09/16/19 06:42 PM
09/16/19 06:42 PM
Joined: Aug 2012
Posts: 58
WV
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Charging system is good, I swapped coils and went for a ride tonight, seemed better first hit but wasn’t right, didnt pop but felt week. Tried again a few minutes later, yes car was a little warmer and it was back to how Saturday. Wires aren’t burnt, will pull plugs tomorrow. Thinking maybe box is acting up once gets hot?

Re: Breaking up around 4K [Re: WV Runner] #2698239
09/16/19 09:08 PM
09/16/19 09:08 PM
Joined: Jan 2003
Posts: 1,495
PA
7
70Duster Offline
pro stock
70Duster  Offline
pro stock
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Posts: 1,495
PA
"Thinking maybe box is acting up once gets hot?"

That's what I'd suspect based on the results of your last post.

Re: Breaking up around 4K [Re: 70Duster] #2698249
09/16/19 09:43 PM
09/16/19 09:43 PM
Joined: Aug 2012
Posts: 58
WV
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I’m I correct in thinking it’s electrical and possibly the box? Or could this possibly be something going bad in the motor/ heads?

Re: Breaking up around 4K [Re: WV Runner] #2698261
09/16/19 10:10 PM
09/16/19 10:10 PM
Joined: Mar 2003
Posts: 17,715
Fresno, CA
Jim_Lusk Online content
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Jim_Lusk  Online Content
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Fresno, CA
I wouldn't think mechanical. Last time we had a motor that wouldn't rev it was a direct result of messing around with the metering rods in an Edelbrock 750. Ran fine to 4k and wouldn't rev beyond that. Voltage and ground to the MSD is critical. Anything less than 10v and it will not operate properly. We've had one MSD failure and it was a hard no start.

Re: Breaking up around 4K [Re: Jim_Lusk] #2698669
09/18/19 08:36 AM
09/18/19 08:36 AM
Joined: Aug 2012
Posts: 58
WV
WV Runner Offline OP
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WV
My msd has good power and ground, battery for both

Re: Breaking up around 4K [Re: WV Runner] #2698688
09/18/19 09:41 AM
09/18/19 09:41 AM
Joined: Feb 2014
Posts: 888
central il.
S
second 70 Offline
super stock
second 70  Offline
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central il.
Might try unhooking the tach. Myself and others have had this problem. Easy test take off one wire and see if goes away.

Re: Breaking up around 4K [Re: second 70] #2698710
09/18/19 11:06 AM
09/18/19 11:06 AM
Joined: Aug 2009
Posts: 902
Ohio
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jlatessa Offline
super stock
jlatessa  Offline
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Posts: 902
Ohio
Had a similar problem on a car a long time ago, after chasing my tail for a while I found the center Carbon
contact, (this was the spring loaded one on a Prestolite cap) had disintegrated...problem solved.

An easy check, Joe

Last edited by jlatessa; 09/18/19 11:07 AM.
Re: Breaking up around 4K [Re: jlatessa] #2698767
09/18/19 06:17 PM
09/18/19 06:17 PM
Joined: Jan 2003
Posts: 5,880
North Dakota
6PakBee Offline
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North Dakota
Just a curiosity question, does the problem change with load? 4K at standstill, at part throttle, at full throttle?


Wife says too many cars, liquidation coming soon......
Re: Breaking up around 4K [Re: 6PakBee] #2698812
09/18/19 09:53 PM
09/18/19 09:53 PM
Joined: Aug 2012
Posts: 58
WV
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Originally Posted by 6PakBee
Just a curiosity question, does the problem change with load? 4K at standstill, at part throttle, at full throttle?



At stand still nothing, part and full throttle it happens

Re: Breaking up around 4K [Re: WV Runner] #2698941
09/19/19 10:27 AM
09/19/19 10:27 AM
Joined: Jan 2003
Posts: 1,308
Windsor, ON, Canada
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Diplomat360 Offline
pro stock
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Windsor, ON, Canada
Had something similar to this, the difference being that at about 5k the motor would just about nearly back down to idle RPM (this was at the track, so literally 2 secs after shifting to 2nd gear). As it turned out my fuel system was the problem, or specifically the filter I had placed in front of the Carter mechanical fuel pump.

It worked fine having been installed that way for about 3 seasons, this was NOT the correct installation though. The minute I removed that filter I had my fuel pressure back up and no issues.

I suspect that in my case maybe the pump diaphram just wore down enough that it could no longer overcome the pressure obstruction in the line which the filter element presented.

Anyways, it was weird, work the day before just fine, then all of a sudden it "gave up the ghost"...LOL!

Re: Breaking up around 4K [Re: Diplomat360] #2699173
09/20/19 09:19 AM
09/20/19 09:19 AM
Joined: Sep 2003
Posts: 12,318
north of coder
moparx Offline
"Butt Crack Bob"
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Posts: 12,318
north of coder
years ago, i had a guy come around with a new ford pickup that had this issue, but this engine would only go to around 3500 or so.
the problem turned out to be a plugged muffler.
he had taken off the factory exhaust at the cat, then used a pipe to smash the guts out of the cat. then, he replaced the factory exhaust with a cat back system.
well, it just so happened he only got the big pieces out of the cat. over time, the cat shed enough pieces that were not rodded out back to the cheap turbo muffler, causing it to plug up.
the point being, [and you don't have a cat] could your muffler[s] be coming apart internally, and the baffles blocking the exhaust ?
GM products were notorious [around here, anyway] for plugged cats causing the symptom you have.
please let us know what the cause turns out to be.
beer


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