I just bought this 51 Plymouth wit a slant 6.
It has 3 angle valve job on head. rv cam. Offenhouser intake with holley 4 bbl. And headers.
Now the previous owner ran it on 87 octane, i am currently and its just fine. No pinging etc. What would you recommend? Also what should timing be set at?

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51 Plymouth Cambridge with / 6

There are lots of threads here on engine timing. It sounds like you have a sweet set up. I would just fiddle with the timing until you find the best performance. Look for Aggressive Ted's thread on his timing curve. If you are just driving this to shows, don't worry about it too much if it runs OK.

In general, base timing of anything between 5 and 10 BTDC will work OK. They say look for the highest vacuum reading, but that is perhaps over simplified. If it pings under light load, then either move it back slightly or play with the vacuum advance so it drops timing out sooner as vacuum goes down under part throttle. . You will need to know more to figure out which for sure.

Sam

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The easy answer; Check & make note of where base timing is set- confirm that the vacuum advance works, then leave everything alone. If it ain't broke, don't fix it.

The harder (more involved) answer; use a "dial-back" type timing light or a timing tape on the balancer & determine the curve of your mechanical & vacuum advances. Confirm TDC mark accuracy. Set initial advance for best idle quality & light throttle performance. Adjust carburetor idle & mixture as needed. Modify & adjust the advance curves (& vac pod) as needed to prevent detonation at part / heavy throttle. Keep notes on every adjustment & the effects that it had.

You can get more out of your engine, but you'll have to put a fair bit more into it.

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63 Valiant Wagon
225 - 4 bbl

Well after. Talking to the guy that built the car. And since it starts and idles smooth in all temps,I'm going to leave it all alone for the time being. Maybe just replace the ignition box and ballast since I have new ones. ( keep old for just in case)

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51 Plymouth Cambridge with / 6