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Tech Talk => Engine Mechanical / Electrical => Topic started by: MerikaRogers on July 27, 2017, 08:10:58 PM

Title: Engine pop at 4500
Post by: MerikaRogers on July 27, 2017, 08:10:58 PM
Been goin crazy. Ive checked total timing at 32. All rockers moving equally. Float level correct. Swapped distributor still pops at close to 5000 sometimes out carb and sometimes out exahust.

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Title: Re: Engine pop at 4500
Post by: 69kona on July 27, 2017, 08:49:39 PM
Msd box ?


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Title: Re: Engine pop at 4500
Post by: MerikaRogers on July 27, 2017, 09:03:08 PM
Msd box ?


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No box. Hei. Fires rite up. Idles smooth. Only when rpm is around 4500 it will pop

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Title: Re: Engine pop at 4500
Post by: MerikaRogers on July 27, 2017, 09:03:52 PM
Feel like I'm missing something

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Title: Re: Engine pop at 4500
Post by: bobjthomson on July 27, 2017, 09:26:17 PM
What set up are u running ? Single carb ? Tunnel ram ? Need more info


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Title: Re: Engine pop at 4500
Post by: mash on it on July 28, 2017, 05:05:46 AM
Fire it up, in the dark and look for leaky plug wires.

A cracked porcelain on a plug will cause this too.

A lobe going flat will do the same, hopefully the former and not the latter.

Dan'l
Title: Re: Engine pop at 4500
Post by: MerikaRogers on July 28, 2017, 05:07:01 AM
Single carb. 750 Holley. Basically stock 454. Put my buddies carb on it yesterday and same thing happened. So it's gotta be ignition?

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Title: Re: Engine pop at 4500
Post by: MerikaRogers on July 28, 2017, 05:09:24 AM
Ya I been meaning to do that maybe tonight ill fire it up and check for a light show

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Title: Re: Engine pop at 4500
Post by: 69kona on July 28, 2017, 06:05:12 AM
Try and take a video when it's poping ..
and post it ... could be a fuel pump problem not pushing enough volume


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Title: Re: Engine pop at 4500
Post by: MerikaRogers on July 28, 2017, 09:12:43 AM
Try and take a video when it's poping ..
and post it ... could be a fuel pump problem not pushing enough volume


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It's a mechanical pump and bowls are full. Can that happen at high rpm?

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Title: Re: Engine pop at 4500
Post by: 86caribbean on July 28, 2017, 09:33:18 AM
If you have an open in a plug wire or a cracked spark plug you would be having a miss all the time. If your only having this in the higher rpm range, it could be a possibility that your valve springs are getting weak or even have a broken one, check them all very closely, maybe it’s time to change them, springs only have so long of a life, heat and duty cycles will cause the coils to weaken.
Title: Re: Engine pop at 4500
Post by: MerikaRogers on July 28, 2017, 10:03:01 AM
If you have an open in a plug wire or a cracked spark plug you would be having a miss all the time. If your only having this in the higher rpm range, it could be a possibility that your valve springs are getting weak or even have a broken one, check them all very closely, maybe it’s time to change them, springs only have so long of a life, heat and duty cycles will cause the coils to weaken.
Never thought about springs. Makes a lot of sense to me. That's prob the issue

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Title: Re: Engine pop at 4500
Post by: BlueBayouRacing on July 29, 2017, 12:05:11 PM
If you have an open in a plug wire or a cracked spark plug you would be having a miss all the time. If your only having this in the higher rpm range, it could be a possibility that your valve springs are getting weak or even have a broken one, check them all very closely, maybe it’s time to change them, springs only have so long of a life, heat and duty cycles will cause the coils to weaken.

X2
Title: Re: Engine pop at 4500
Post by: GT Jets on July 29, 2017, 12:23:09 PM
When you changed the distributor, did you use the same cap and rotor?

How is the power wired to the distributor? Is there a relay? Or are you running straight from the ignition switch?

Voltage drop will do what you are saying, not enough spark to keep stuff lit.

Grab an inexpensive fog light relay and wire it to the distributor at the engine using the ignition wire from the switch to energize the relay and run a wire from the battery (or solenoid for the starter or other hot source) with a 12 gauge wire and the other side of the relay to the distributor....


GT
Title: Re: Engine pop at 4500
Post by: MerikaRogers on July 29, 2017, 04:09:38 PM
When you changed the distributor, did you use the same cap and rotor?

How is the power wired to the distributor? Is there a relay? Or are you running straight from the ignition switch?

Voltage drop will do what you are saying, not enough spark to keep stuff lit.

Grab an inexpensive fog light relay and wire it to the distributor at the engine using the ignition wire from the switch to energize the relay and run a wire from the battery (or solenoid for the starter or other hot source) with a 12 gauge wire and the other side of the relay to the distributor....


GT
Different cap n rotor. I took the vacuum secondary off and found the port gummed up. On the lake now and running good. Only thing is right before wot it pops but wide open runs perfect

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Title: Re: Engine pop at 4500
Post by: GT Jets on July 29, 2017, 06:09:11 PM
Different cap n rotor. I took the vacuum secondary off and found the port gummed up. On the lake now and running good. Only thing is right before wot it pops but wide open runs perfect

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Vacuum secondary? Gummed up with what?

GT
Title: Re: Engine pop at 4500
Post by: MerikaRogers on July 31, 2017, 07:48:07 AM
Vacuum secondary? Gummed up with what?

GT
Not sure what it was. Piece of plastic or something.

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