Timing for h comp engns w unleaded gas

[SCO]

I have a 73 135 hp v4. Considering that we all use unleaded and these engines were designed for unleaded, what numbers should these engines be timed for? My service manual specifies 5 degrees advance at idle(I presume idle in the water in gear at 650 rpm) and 4300 to 4600 rpm in gear at 22 degrees advance. Thanks

 

[Dhadley]

Re: Timing for h comp engns w unleaded gas

Those are good numbers, dont worry too much about the idle setting. I would recommend checking the wot timing at 5800 rpm.<br /><br />Good luck!

 

[kglinz]

Re: Timing for h comp engns w unleaded gas

Actually the big problem running unleaded fuel in older engines had to do with valves and valve guides in 4 stroke engines. Not having the lead meant less lube on the valve stems.

 

[FlyBoyMark]

Re: Timing for h comp engns w unleaded gas

Lead was the original antiknock compound..lubricity for valves was jus a side benifit...

 

[SCO]

Re: Timing for h comp engns w unleaded gas

I've heard both ideas. Seems leaded effectively did the same as raising octane to prevent knocking, but the octane was not raised( 87 octane in those days too I think). Forktail, you ought to know the answer on this one. We need a chemist to satisfy the curiosity. What Dhadley says can be considered as gospel.

 

[kglinz]

Re: Timing for h comp engns w unleaded gas

Here's Chevron's bulletin on this.... Chevron Technical Bulletin