predetonation trouble!!!!
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Freshman User
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predetonation trouble!!!!
i have a 78 f150 with a 400 in it. about 6 weeks ago this ping showed up. it is not at idle but is there at all other speeds. have set timing back to around 6 degrees and have unhooked my vacuum advance. when warm i have around 20 hg steady at the intake. have put on an hei dist on it but it ran fine for a couple of months then it went south. motor does have some wear on it not sure of the miles. i have ok oil pressure and have changed the rod/main bearings to rule that out. i am running 93 octane. no one seems to be able to help. can my carb cause this? its a edel 1405. need new ideas as i have been trying everthing. please offer any help you can!!! thank you so very much!!!
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Freshman User
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i have no egr, at idle nothing but it shows up after it warms up at light throttle and louder driving at about 50 mph. can there be something wrong with the pick up coil on my hei dist? or maybe the module inside there?
Postmaster
Joined: Aug 2001
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From: Delaware
I could be a lean mixture in cruise mode. Check your metering rods & primary jets. Try to go one stage rich. The edelbrock website will give you the info that you need.
It may be too much timing advance too soon. You should check your total advance and at what RPM it occurs. I don't know what advance curve those HEI dists are set for. The stock advance curve is too soon for a motor with no EGR. I think that you are the second person, that reported a similar problem and he also had an HEI dist.
It may be too much timing advance too soon. You should check your total advance and at what RPM it occurs. I don't know what advance curve those HEI dists are set for. The stock advance curve is too soon for a motor with no EGR. I think that you are the second person, that reported a similar problem and he also had an HEI dist.
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Joined: Aug 2003
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From: near pittsburgh pa
Originally Posted by 78oldsmokey
it also seems to get loudest when i let off of the gas pedal around 50 mph?
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sorry, i ment when i get on it the ping is not as noticable but when i am up to speed and i let off trying to maintain a certian speed it gets alot louder. i changed the timing chain and gears less than 4 months ago.
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i do not know if i still have 20hg driving down the road, i guess i could rig up a gauge to put in the cab if its important?
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Elder User
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From: near pittsburgh pa
I was wondering on the vac reading for timing chain wear. Truck sitting an at idle reading is good enough and I see you said chain was replaced.
I would really look at your timing curve. Not sure on the carb, as danlee said, check out their website
I would really look at your timing curve. Not sure on the carb, as danlee said, check out their website
Postmaster
Joined: Aug 2001
Posts: 4,270
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From: Delaware
Originally Posted by 78oldsmokey
sorry, i ment when i get on it the ping is not as noticable but when i am up to speed and i let off trying to maintain a certian speed it gets alot louder. i changed the timing chain and gears less than 4 months ago.
Who is the manufacturer of your HEI dist?
See if you can get the timing advance specs from them.
Posting Legend
Joined: Sep 2001
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