Burnt pistons aybody?
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Freshman User
Joined: Nov 2002
Posts: 46
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From: Las Vegas US
Burnt pistons aybody?
So, I have found that I have burnt a piston, number 8. My bronco has only has 94K on it and I'm not sure why it would burn a piston. I don't drive it hard at all because they suck gas enough as it is. My brother incidentily has the same truck (90' EB/w302) and he burnt one two, but his happened because his distributer came loose and the timing moved. I have kept up maintence, and I'm sure that at least the base timing was correct. Know I have to overhaul it because it damaged the cylinder wall too. But I need to find out WHY it happened so I don't do this twice. I've heard Truck 302's were common for this but why? I've been through several mustangs with the HO motor when I was a young punk and pushed them to the limit all the time, and never burnt a piston. Anyone else burn a piston?
Hotshot
Joined: Oct 2002
Posts: 18,488
Likes: 22
From: The Big, Oregon
Burnt pistons aybody?
This is VERY common on these engines, as the #'s 7 and 8 fire sequentially. If the wires for these two touch, then they will cross fire, and the spark for #7 will hit #8 a few degrees too soon. The fix for this is to route #8 at the top of the looms, and #7 at the bottom. There isn't a cross fire problem on any other cylinders that I am aware of.
Jared
Jared
Postmaster
Joined: Jun 2001
Posts: 2,809
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From: Loveland, CO.
Burnt pistons aybody?
On mine, the factory wire looms were cracked, so when they put the wires on, they cable tied them all together! As far as I know, it has been this way for over 50,000 miles. The truck runs fine. Maybe because they used OEM wires as replacements and they didn't cross fire. Who knows. But just as a precaution, after reading this I bought some wire separators and put them on, and cut the cable ties that were holding the wires together.
Junior User
Joined: Jan 2002
Posts: 53
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From: MI
Burnt pistons aybody?
Happened to me. I bought the truck with around 179,000 miles on it I had it for about 2 or 3 months and burnt my #8. My buddy had replaced the wire's and zip tied them together(7-8)I heard the pinging, but could'nt find the problem until it was too late. After replacing the motor and hearing pinging again(cross firing)I did a search on this site and found out about the 7-8 plug wires. I seperated them and solved the problem. Thanks to who's ever post I read when I did the search, saved the new motor! 
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