# Timing Help on 455 Pontiac



## Goatman455 (May 29, 2009)

Just curious on what the best options for timing would be on an HEI 455 with high compression (10.25:1). I use NOS octane booster, but sometimes even 8.5 starts detonating on a hot day with I believe vacuum advance (not positive though).

Also, the secondaries seem to be opening improperly, can anyone help with this?


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## Rukee (Feb 8, 2007)

You want to run as much timing as possable without pinging or hard starting hot.
As far as the secondaries go, the choke must be fully open before the secondaries will work so maybe check the choke adjustment and be sure it is comming fully off when the engine is warm.


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## geeteeohguy (Feb 2, 2008)

Also, inaudible pinging is pretty common...it may be pinging without you knowing it. Rukee is right, run as much initial timing as you can, but it sounds like you need to back it off 2 to 4 degrees. Or, find a way to make your engine run cooler on a hot day. I was never able to get my '67 400 with automatic to keep from pinging (10.75 compression) so I changed the heads (now at 9.2 compression) . That fixed the problem, at the cost of some HP. Try different octane boosters, too. Some work better than others. I've used TEL130 in the past for off road stuff, and it worked for me.


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## Goatman455 (May 29, 2009)

It looks like the choke is open, how far should it be open? Any more info is appreciated. I know the choke isn't staying closed completely because I have had that happen before.


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## Rukee (Feb 8, 2007)

Goatman455 said:


> It looks like the choke is open, how far should it be open? Any more info is appreciated. I know the choke isn't staying closed completely because I have had that happen before.


It needs to be completely open, all the way can't open any further open, straight up and down open. :cheers


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