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Engine Diagnosis

General engine tech -- Drag Racing to Circle Track

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chevyfreak
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Re: Engine Diagnosis

Post by chevyfreak »

Maybe try a different plug brand.
I have always had problems with ngk.
Some bad from the start others a little while after some use.
These days i use bosch , delco or autolite. Way less issues.

Also thinking fuel pressure creep, had a 4.5psi mech pump that pushed 8psi when hot, and had a regulator on a electric system that did the same.


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xanadu
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Re: Engine Diagnosis

Post by xanadu »

Run fine on dyno but not in car. Possibly old / contaminated / stale fuel in tank? Check for good earths as in from Battery to chassis, Engine to chassis etc.
You did state 13.4V to HEI, Has that been checked with engine running?
Also, was an alternator used on the engine dyno? What alternator is being used in the vehicle?
Is it OK?
1980RS
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Re: Engine Diagnosis

Post by 1980RS »

chevyfreak wrote: Sat May 14, 2022 12:28 am Maybe try a different plug brand.
I have always had problems with ngk.
Some bad from the start others a little while after some use.
These days i use bosch , delco or autolite. Way less issues.

Also thinking fuel pressure creep, had a 4.5psi mech pump that pushed 8psi when hot, and had a regulator on a electric system that did the same.


Chevyfreak.
Last set of AC Delco's I got misfired like a SOB, put the old ones and problem was gone. That what you get when the plugs are made in china. I also had fuel pressure creep on my race car with every regulator then I switched to an Arrowmotive regulator. Steady 6 psi now.
econo racer
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Re: Engine Diagnosis

Post by econo racer »

There are bad plugs coming up every where. Fakes are bad news. I would try a new set of Autolites.
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Re: Engine Diagnosis

Post by Tom68 »

1980RS wrote: Sat May 14, 2022 5:14 pm

Last set of AC Delco's I got misfired like a SOB, put the old ones and problem was gone. That what you get when the plugs are made in china. I also had fuel pressure creep on my race car with every regulator then I switched to an Arrowmotive regulator. Steady 6 psi now.
Had that with a set of champions in the 80's, Methanol 350, new plugs, fire it up drops a cylinder, put the old NGK back in drops another cylinder, by the third one spotlessly clean Champions in the bin, new set of NGK's, no problem.

That was with points ignition and the old yellow Accel monster coil.
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Re: Engine Diagnosis

Post by skinny z »

It used to be that a guy could depend on new parts working as advertised.
These days we come across plenty of products from a wide range of manufacturers that simply don't work out of the box (and this is from an industrial maintenance point of view including automotive).
Against all of my training, it's turned me into a parts swapper rather than a diagnostician. It irks me to no end.

Following along to see what the problem actually is.

Good luck.
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Re: Engine Diagnosis

Post by mag2555 »

Don’t rule out inadequate gauge wire feeding the HEI system enough current.
As temps go up so does a wires resistance and when things are at room temps it may be right on the edge of doing what should be done.

Other then the wallet. It never hurts go one gauge up in wire size then what’s needed!

Also any customer made crimp connections that may be part of the HEI system could be poor and making for the same inadequate levels of current flow when hot.
You can cut a man's tongue from his mouth, but that does not mean he’s a liar, it just shows that you fear the truth he might speak about you!
skinny z
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Re: Engine Diagnosis

Post by skinny z »

mag2555 wrote: Sat May 14, 2022 6:52 pm Don’t rule out inadequate gauge wire feeding the HEI system enough current.
As temps go up so does a wires resistance and when things are at room temps it may be right on the edge of doing what should be done.

Other then the wallet. It never hurts go one gauge up in wire size then what’s needed!

Also any customer made crimp connections that may be part of the HEI system could be poor and making for the same inadequate levels of current flow when hot.
Very valid points made here.
Wiring is my business and at the risk of offending anyone, I'm known around these parts as the crimp nazi.
Do it right and with the proper tools. (please don't say solder).
Last edited by skinny z on Sat May 14, 2022 8:08 pm, edited 1 time in total.
Kevin
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Re: Engine Diagnosis

Post by HQM383 »

What are the heads on this engine? Or is it the correct plug reach for the heads?
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Re: Engine Diagnosis

Post by vortecpro »

HQM383 wrote: Sat May 14, 2022 7:28 pm What are the heads on this engine? Or is it the correct plug reach for the heads?
It has GM oval port 781. I appreciate everyones help!
Racing a NA NHRA stocker should be mandatory before any posting.
xanadu
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Re: Engine Diagnosis

Post by xanadu »

Another thing to consider. Altitude where engine now resides. Could see that the plugs have a recessed tip. Picture of plug doesn’t show earth strap / timing.
chevyfreak
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Re: Engine Diagnosis

Post by chevyfreak »

1980RS wrote: Sat May 14, 2022 5:14 pm
Last set of AC Delco's I got misfired like a SOB, put the old ones and problem was gone. That what you get when the plugs are made in china. I also had fuel pressure creep on my race car with every regulator then I switched to an Arrowmotive regulator. Steady 6 psi now.
I hear ya. I did note way less issues, had some delco and autolite dropping out here and there but alot less than ngk.
I have a theory that the ngk are handled roughly at the main warehouses locally or in transport or dropped at the parts counter, etc. Just my thinking.

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Re: Engine Diagnosis

Post by Firedome8 »

Plug to cold ? Using high lead content fuel? Timming retarded?
Just thinking
A good test is worth a thousand opinions.
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Re: Engine Diagnosis

Post by vortecpro »

xanadu wrote: Sun May 15, 2022 4:31 am Another thing to consider. Altitude where engine now resides. Could see that the plugs have a recessed tip. Picture of plug doesn’t show earth strap / timing.
5800 feet elevation
Racing a NA NHRA stocker should be mandatory before any posting.
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Re: Engine Diagnosis

Post by fabr »

skinny z wrote: Sat May 14, 2022 7:12 pm
mag2555 wrote: Sat May 14, 2022 6:52 pm Don’t rule out inadequate gauge wire feeding the HEI system enough current.
As temps go up so does a wires resistance and when things are at room temps it may be right on the edge of doing what should be done.

Other then the wallet. It never hurts go one gauge up in wire size then what’s needed!

Also any customer made crimp connections that may be part of the HEI system could be poor and making for the same inadequate levels of current flow when hot.
Very valid points made here.
Wiring is my business and at the risk of offending anyone, I'm known around these parts as the crimp nazi.
Do it right and with the proper tools. (please don't say solder).
You are soooooo correct!!
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