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 Pinging at part throttle
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rrconductor
Two Feathers

USA
59 Posts

Posted - 22 Sep 2017 :  09:37:33 AM  Show Profile  Reply with Quote
I have a 1968 Gto with the original stock 400 with 10.75 to 1 cr. I have replaced the distributor with an HEI (original dual vacuum dizzy replaced with another points style dizzy before I purchased the car). I have rewired the HEI and have 12 volts at dizzy.My initial timing is set to 10 degrees,vacuum canister disconnected and getting pinging at part throttle. I changed springs in the distributor to the gold ones.Need help!Allen

tjs44
Cochise

USA
422 Posts

Posted - 22 Sep 2017 :  09:42:32 AM  Show Profile  Reply with Quote
do a pumping compression test.If over 175-180 your in race gas mode.Tom
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Blued and Painted
Chief PONTIAC

USA
3415 Posts

Posted - 22 Sep 2017 :  1:13:35 PM  Show Profile  Reply with Quote
The vacuum and mechanicle abvance may need to be limited. Does it ping with vacuum disconnected and plugged. Initial + mechanicle should be around 32 degrees. Then vac advance limited to 8 to 10 degrees. These are generic settings for a hi compression engine.
Use highest available octane fuel.


Bull Nose Formula/ 461/ Q-Jet/
TH400/ 3.08 8.5 / R44TS.
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rrconductor
Two Feathers

USA
59 Posts

Posted - 23 Sep 2017 :  1:27:16 PM  Show Profile  Reply with Quote
Using 93 octane fuel,Ithe vacuum advance is disconnected and plugged off,I am thinking maybe to much mechanical timing.I have installed the gold springs as Lars suggested but not sure where to go next.
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phil400
Cochise

Canada
458 Posts

Posted - 26 Sep 2017 :  11:58:45 AM  Show Profile  Reply with Quote
The gold springs are the lightest springs, did you try running stockist heavy springs to bring the timing I later?

78T/A 4-SPEED Marty blue 400/milled 6x-4's/268H,comp roller tip rockers/ performer Q-jet/RA manifolds 2.25" exhaust with x-pipe/ mine since '99 3rd & final owner as long as I'm alive
"sometimes I do what I want to do,rest of the time I do what I have to"
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Blued and Painted
Chief PONTIAC

USA
3415 Posts

Posted - 27 Sep 2017 :  10:28:42 AM  Show Profile  Reply with Quote
Agree. Try a heavy spring.


Bull Nose Formula/ 461/ Q-Jet/
TH400/ 3.08 8.5 / R44TS.
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