Lost Compression in cyl 7&8 Mystery Solved!

[Crackerjack17]

Well, It's been a while since I lost compression in cylinders 7 & 8. The car has been sitting for months waiting on the new shortblock, parts, etc. I finally got the energy to start taking it all apart. It's a lot of work by yourself. lol

(for those who don't know, 13k miles on the car, 9k of which procharged. I did not baby it. Lots of roll races to near 160mph.)

Here are the results of the teardown...

Cylinders 7 & 8 on the right, which is drivers side near firewall.

And the answer is... When I first pulled the piston out, I could barely see the cracks, then I pried the broken pieces out.

Both pistons broke in the same exact spot. And that side is at the top of the motor. All the rings are intact and solid.

New Shortblock going in. Brand new block, Manley I beams, Manley forged pistons, Boss 302 Crank, ARP everything.

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[Ponderthis]

Ahhh...Those Coated Manley pistons look sick!

 

[z06psi]

Nice. Keep up the motivation. I do all of my work myself as well. Sometimes it's tough but hang int there!


Built not bought!

 

[FLYIN4D]

Crackerjack,

How did the cylinder bores, cyl head chambers, crank journals, rods and bearings look on those two holes? Damn that almost looks like you were throwing nitrous at it - those pistons saw some detnation/rattled in those holes. New shortblock setup for boost I'm sure. Nice work.

 

[z06psi]

Who was the tuner BTW?

 

[Reds197]

What fuel and boost?

 

[kcc0521]

Pretty certain he was on 93 Octane with P1sc stage two kit.

 

[F1scamp]

Piston rings butted from getting hot. They are pretty tight from the factory, along with the bearing clearances. Detonation didn't do that.

Are your cam lobes blue or is that an illusion?

 

[JC500]

So it looks like a cherry picker and you can pull the engine out from top . I thought you only could drop it out from bottom with car o. Lift . Good work

 

[Jay159866]

Well, It's been a while since I lost compression in cylinders 7 & 8. The car has been sitting for months waiting on the new shortblock, parts, etc. I finally got the energy to start taking it all apart. It's a lot of work by yourself. lol

(for those who don't know, 13k miles on the car, 9k of which procharged. I did not baby it. Lots of roll races to near 160mph.)

Here are the results of the teardown...

Great choice on the setup. Who built the shortblock?

 

[kcc0521]

Piston rings butted from getting hot. They are pretty tight from the factory, along with the bearing clearances. Detonation didn't do that.

Are your cam lobes blue or is that an illusion?

What failed on the one in your car? Did you keep the shortblock?

 

[F1scamp]

What failed on the one in your car? Did you keep the shortblock?

Two connecting rod bearings spun. Welded themselves to the crank. Gave the shortblock back to ford for the core. Cheaper to buy a shortblock then to machine and repair the old one.

 

[Crackerjack17]

Crackerjack,

How did the cylinder bores, cyl head chambers, crank journals, rods and bearings look on those two holes? Damn that almost looks like you were throwing nitrous at it - those pistons saw some detnation/rattled in those holes. New shortblock setup for boost I'm sure. Nice work.

The crank and rod bearings look perfect. They are super smooth. That little mark in this bearing picture is a light scuff mark and you cannot feel it. All the cylinders have those vertical scratch marks, you can't feel them. I'll have to take some pictures of the cylinder heads, but they look perfect too. I had to pry those pieces out of the pistons. Engine ran fine and was very smooth, but had a lot of blowby and compression was down.

 

[Crackerjack17]

It was lund tuned, logs were perfect, 93 octane. Hitting up to 11-13 psi at 7500 rpm. Most time though it was 10-11 psi.

 

[Crackerjack17]

Piston rings butted from getting hot. They are pretty tight from the factory, along with the bearing clearances. Detonation didn't do that.

Are your cam lobes blue or is that an illusion?

Must be an illusion. Cam lobes have regular wear. Super smooth.

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