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post #1 of 7 (permalink) Old 09-23-2017, 01:23 PM Thread Starter
 
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My 1968 Gto original 400 engine pings at part throttle. I replaced the points style distributor ( original distributor long gone by previous owner) with an HEI dizzy. I have 12 volts at the dizzy and replaced springs in th HEI with the gold springs as suggested by Lars,the initial timing set to 10 degrees,vacuum advance disconnected and plugged off.The total initial and mechanical timing is 36 degrees but on a road test I had pinging at part throttle,disconnected vacuum advance and plugged it off,took another road test still pinging but not as much.NEED HELP!!!! Allen
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post #2 of 7 (permalink) Old 09-23-2017, 09:37 PM
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Back it off to 34 and see how it runs.
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post #3 of 7 (permalink) Old 09-30-2017, 08:30 AM
 
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Two questions. Any mods to the engine? What octane fuel are you using?
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post #4 of 7 (permalink) Old 09-30-2017, 12:36 PM
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Originally Posted by RRconductor76 View Post
My 1968 Gto original 400 engine pings at part throttle.
That could be your problem right there. The word "original". If your engine is in good condition and making good compression with those iron heads it could be just making too much cylinder pressure for the fuel you're using. Run the highest octane you can find, and if that doesn't solve the problem then you'll have to start backing the timing down from that (probably optimal for power) 36-degrees total. Running heavier springs on the advance mechanism to slow down the rate at which the advance comes in might also help.

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post #5 of 7 (permalink) Old 10-05-2017, 10:20 AM Thread Starter
 
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Thanks for all the advice guys.I have it running like a scalded dog now.I went up one heavier (stronger ) spring and that did the trick.Thanks
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post #6 of 7 (permalink) Old 10-05-2017, 08:14 PM
 
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Now go and get you a B26 Vacumn can and one of Lars vac correctors,.....put those on and hook it to full manifold vac...

You will keep all your current strength and get better idle cooling, better throttle response, better gas mileage and smoother overall operation with a light pedal......

With vac advance you will have 46 to 48 degrees advance at light throttle cruise......perfect on today's gas,..and idle timing at 20 BTDC with vac and base together...

Try it.....best $25 you will ever spend on your car....
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post #7 of 7 (permalink) Old 10-06-2017, 08:15 AM
 
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Sorry, correction,...you now have an HEI, even easier.....scratch the B26 and Lars corrector....

Get a Standard Motor Parts VC 302......SMP VC 302....Standard Motor parts makes them all.......rock auto has them at that description

NAPA has it as a VC 1703.....Oreilly as a BWD V482....

That will give you 10 degrees of Vac advance.....spec is starts at..3 to 6 hg......5 degrees Dist ( which is 10 at crank) all in by 7 to 9 Hg

Use full manifold vac
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  Pontiac GTO Forum > The 1964-1974 Pontiac Tempest, Lemans & GTO > 1964-1974 Tempest, LeMans & GTO Engine Tuning and High Performance

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