L78 Jetting and Spark Plug Reading
Rebuilt L78 running very hot even with correct timing and advance so I re-jetted the Holley from #70 to #73 and running hot problem went away. The question is how long do you have to run the engine before you can see changes to the spark plugs so that you can tell if the jetting is right?
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Re: L78 Jetting and Spark Plug Reading
With todays gasolines, I am afraid you will not live long enough to see much change.Dick Whittington -
Re: L78 Jetting and Spark Plug Reading
Dale, at your elevation you should be jetted about right - I run #72 front and #76 rear at 500' elevation. I run NGK Iridium GR5IX gapped at .035. Used to run Champion RN14YC gapped at .035 before I switched to NGK's in all my vehicles. Of course if you are chasing the blue ribbon you will need AC's. If you can find an open mile or so of road close to where you can pull the plugs after two or three hard pulls thru all 4 gears up to 5800-6000 shut down after last run and read the plugs. I have found that is the best way, if you make one or two runs and lug it back home or to your shop your reading may not be true. With a fresh motor you may wish to wait till you have 500 miles or more then change the oil and check valve lash ( I run .024 intake and .026 exhaust hot at idle) 'for you go hammering on it!Comment
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Re: L78 Jetting and Spark Plug Reading
Thanks for the help. This is fresh frame off so I only have 300 miles on it mostly shake down mileage working out the kinks. I will wait for the 500 mile mark or more before hammering on it.Comment
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