I got a slight ping.
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New User
Joined: Feb 2008
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From: in the garage frig
I got a slight ping.
Hi all I am new around hear. Been reading a while but not finding the help I need.
I have a 78 F-250 with a 351m from a 79. I bought all the parts from tmeyerinc to turn it into a 400 using stock heads. Very mild cam, holley 670 truck avenger carb.
I got it together and in the process of breaking it in I found it ping in third and four under load. I had stock plugs in it, went to a range cooler and it helped. Checked my timing and put it at the factory 6 degs bftdc and thaat help. 'was at about 8 or 9. I talked to holley and they told me to go up in jet size that that carb needed a little tweak to run well on a 410. ' .040 overbore'
I went from a 68 jet to a 70 no difference. Should I back the timing of more?
I am running 87 octane gas witch i want to stay with. I have been told that I can run that gas with under 9.5 to 1 com. And Ideas?????
Thanks
Bubba
I have a 78 F-250 with a 351m from a 79. I bought all the parts from tmeyerinc to turn it into a 400 using stock heads. Very mild cam, holley 670 truck avenger carb.
I got it together and in the process of breaking it in I found it ping in third and four under load. I had stock plugs in it, went to a range cooler and it helped. Checked my timing and put it at the factory 6 degs bftdc and thaat help. 'was at about 8 or 9. I talked to holley and they told me to go up in jet size that that carb needed a little tweak to run well on a 410. ' .040 overbore'
I went from a 68 jet to a 70 no difference. Should I back the timing of more?
I am running 87 octane gas witch i want to stay with. I have been told that I can run that gas with under 9.5 to 1 com. And Ideas?????
Thanks
Bubba
Posting Guru
Joined: Jul 2007
Posts: 1,355
Likes: 1
what about bigger jets, try also 91 octane... if you are using tims 0 deck with a 40 overbore and shaved some how your heads, yo should be around 9.8 to 1 and with the open chambers, you will ping with anything under 91 octane...
besides 6 btc is really retarded....
besides 6 btc is really retarded....
Posting Guru
Joined: Jul 2007
Posts: 1,355
Likes: 1
did you polich well your cumbustioon chambers? a dirty one could make your engine ping, you should´ve checked you chambers cc also, I dont know what else could be causing it, but the only solution would be trying a blend from 87 octane and 91 to see if it stops....
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MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
What distributor are you running? If you are running the stock one then that is your problem - the stock distributor on a '78 will be set up for EGR. Engines with EGR are set up with a steeper timing curve to provide more advance at part-throttle. If you take the EGR away and leave the distributor untouched then you will get pinging. One way to fix this is to replace the standard vacuum advance with an adjustable vacuum advance; then you can adjust the timing curve with an allen wrench.
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Postmaster
Joined: Aug 2001
Posts: 4,270
Likes: 5
From: Delaware
You need to change the springs in the distributor to slow the mechanical advance, if you do not have EGR. The springs in the '71 distributor are the correct springs. Crane sells a kit with an adjustable vacuum advance and several different springs. You need stronger springs, you are getting full mechanical advance at too low RPM.
Postmaster
Joined: Aug 2001
Posts: 4,270
Likes: 5
From: Delaware
The Crane kit is: Crane Cams 99607-1
It's available at Summit Racing (www.summitracing.com).
Here is a link to the instruction sheet.
http://static.summitracing.com/globa...s/crn-271e.pdf
It's available at Summit Racing (www.summitracing.com).
Here is a link to the instruction sheet.
http://static.summitracing.com/globa...s/crn-271e.pdf
Last edited by danlee; Feb 13, 2008 at 08:51 PM.
Thread Starter
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New User
Joined: Feb 2008
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From: in the garage frig
As a test I disconected the vacume line to the avance and plugged it. Went for a drive and all pinging was gone. Got the advance kit and installed it without using new springs. reset the timing and it runs great now.
Thanks for the help.
Bubba
Thanks for the help.
Bubba