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Bad Coyote piston. Why?

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25
23
Exp. Type
Autocross
Exp. Level
20+ Years
Maryland
Ive been lurking for here for a while. I’ve learned a lot as I build my 1st Autocrossers only Mustang.
I know you all have a lot of combined knowledge on Coyote destruction 😁. Can anyone tell me what may have caused mine? That’s #8 piston, and valves. Pictures taken with articulating bore scope. Did the piston melt? Spark plug was fouled black. I did a leak test and air only went into the crankcase. All other cylinders are about 180 compression and plugs look ok.

Some specs: Haltech R5, NA engine. Stock crate 1st gen Coyote engine with headers and gen3 intake.

Some history: I bought the engine used from a good track day friend. I knew its history and it was well cared for. Plugs looked good when I bought it and it ran OK. I ran a few Tours and a Pro and it seemed fine. I do know the exhaust cams were not advancing during this time. I sorted out the exhaust cam issues and took it to the dyno to retune. Catch can was smoking lightly during warm up. Smoke increased on each dyno run, till I called it quits on the 4th runs. Smoke was pouring out at that point.
Any ideas on how I can figure out what caused it so I don’t make the same mistake again?

PS: My fix is likely a Gen 3 short block, with my Gen 1 parts bolted onto it.

see pics , Valve picture is is at the BDC after TDC compression stoke.BadPiston 8.jpegBadPistonII 8.jpegCyl 8 Valves.jpeg
 
6,674
8,774
FWIW there's some evil, magical BS going on with #8 cylinder. A car we service was a Boss 302 with under 10K miles, it lunched #8 on a track day. Bret just bought a Boss 302 with ( no lie) 7, seven, just 7.. miles on it. It ate #8 on its first track day. Our fuel guy had his Boss eat #8 on his car several years ago. I cannot give you a legit answer but whatever reason, these cars eat "8 at even the mildest of tunes.. and sometimes they just do it out of spite. It's always #8.
I know that's not a good answer, but at least you are in good company. Rebuilt or reman engines don't seem to have this issue. I wish I could be more help.
 
25
23
Exp. Type
Autocross
Exp. Level
20+ Years
Maryland
Well, that does not inspire confidence. Does this magical 8 meltdown happen with the Gen 3 short blocks? A gen 3 might get me to Nationals, rebuilding my block ends my season. I have no spare engine.
 
6,674
8,774
Well, that does not inspire confidence. Does this magical 8 meltdown happen with the Gen 3 short blocks? A gen 3 might get me to Nationals, rebuilding my block ends my season. I have no spare engine.
Not sure, but I would tune conservatively, add plenty of cooling, even an oil cooler.
There has been a lot of theories, but nothing concrete on this, injector issue? Some kind of deal with all the Is and Os not happy in the program, I'm sorry I just don't know.
 
25
23
Exp. Type
Autocross
Exp. Level
20+ Years
Maryland
I’m getting my google-fu dialed in. Lots of stuff on early 1st gen #8 meltdowns. Something about #8 not getting cooled well (MMR mod for fix), coupled with an aggressive timing tune and maybe a flakey knock delection = #8 failure. Dunno if any of this applies to the gen 3 block.
 
6,674
8,774
I’m getting my google-fu dialed in. Lots of stuff on early 1st gen #8 meltdowns. Something about #8 not getting cooled well (MMR mod for fix), coupled with an aggressive timing tune and maybe a flakey knock delection = #8 failure. Dunno if any of this applies to the gen 3 block.
Link to that plz
 
532
504
Exp. Type
HPDE
Exp. Level
Under 3 Years
MD
Link to that plz
 
6,674
8,774

OK, so according to my sources that is a great mod for those cars
 

captdistraction

GrumpyRacer
1,961
1,710
Phoenix, Az
all good, was curious if I was mistaken since I'm setting up a couple motors and the time would be now to run one of those kits.

In the past I ran the HCM from MMR on a motor, but I didn't seem to notice any difference in cooling - that said it wasn't properly instrumented testing . I get the idea and #8 is the most hot hole, but almost better to invest the money in the cooling system as a whole.
 
532
504
Exp. Type
HPDE
Exp. Level
Under 3 Years
MD
Pump 93 octane
then that would be the reason for low compression in 8. Or at least a reason. Unfortunately I’m in the process of rebuilding my engine because of low compression in #8. It is the fate a few of us have face because of running pump gas at the track. Best to use is race fuel or e85. Shaun at AED warned me years ago. Kinda forgot and now paying the price.
 
25
23
Exp. Type
Autocross
Exp. Level
20+ Years
Maryland
It is the fate a few of us have face because of running pump gas at the track. Best to use is race fuel or e85.
The previous owner ran it on pump gas on track days and never had a problem. That being said, I am looking at switching it over to E85. I have a duel in tank pump set up right now and I’m trying to find small enough fuel pumps that can handle E85. I believe I have 260s in it right now and I don’t think they handle 85.
don’t ask me why I have dual intake pump set up. The previous owner of the set up put in dual pumps. Pretty sure I don’t need them for an NA motor, but they’re there and the fuel hat is very nice so I wanna keep it.
 
25
23
Exp. Type
Autocross
Exp. Level
20+ Years
Maryland
I’d like todo the cooling head mod , but if I use the bolt hole on the back of the heads to bolt down the cooling hose, I have no place to ground my Holly smart coils. I don’t know why Ford did not put more bolt holes in the back of these heads. Maybe I can figure out how to bolt down one of the flanges with a stud and use the top part the ground the coils.
 

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