High Comp Motor on Pump Gas

[85montemj]

What do I have to do get my 10.1 compression 406 to run on pump gas? It was originally a short track motor run on 113 octane. Now it pings constantly during mid and light load conditions. Never at high rpms.
I've done everything to stop it, or at least I thought so.

 

[85montemj]

 

[Bonnewagon]

The easy and most beneficial way is to swap heads for some low compression units. Other than that there are special cams that can restrict the intake volume thus lowering combustion pressure, adjustable timing modules that retard timing some use a detonation sensor, but this is really counter-productive. It just makes a lot more sense to lower the compression ratio so the motor can use what it has and live on the cat-piss gas we are paying through the butt for.

 

[pontiacgp]

the problem your going to have is the engine was not built to run at low rpm...it was balanced and built to run at 6000 or above. Plus a 10.1 compression engine should be able to run on 93 octane. Have you looked at the timing chain to make sure it's not stretched and the crank gear is not running an advanced degree? And it could be your running it too lean building up the temp in the combustion chanbers

 

[jimmyp618]

x2 with pontiacgp. My big block buick in my elco is 11.8:1 and does fine on 93. Full msd with 32 deg overall timing.

 

[CHRIS.O]

Agreed, 10:1 is not too high for pump gas. Do you know anything about the internals of your engine? Do you know what the quench was when it was put together?

 

[jcbannis]

just keep in mind running it with low octane could cause detonation

 

[85montemj]

A guy on another post said to advance it to 18 degrees advance at idle. I tried that but it wanted to die when in gear at idle. So i have it at probably about 14 now. I honestly wish i knew about the internal, my dad said he thinks theyre flat tops, but he doesnt remember. Is there anything that could go bad if the engine sat too long? It was moth balled for about 18 years but ran great before it was taken out. And i just put and Edelbrock 750 on it. So i would imagine its not too lean. I did the idle mixture adjustment according to the manual.

 

[pontiacgp]

if an engine is stored for 18 years I would have torn it down to check it out and at least change all the seals and gaskets and lube everything before it's started...

you can't set the timing until you know what the crank timing gear is set at

 

[chevy2480]

I am going to bet seeing how it was a short track motor. That they set the the timing gears up advanced i would pull timing cover and check it. If advanced change it back to stock configuration. Also keep in mind if its a true 406 with a 5.7 or 6.0 rod if they didnt use a base circle cam. They may have advanced to avoid connecting rod to cam contact.