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My engine saga continues....but worse


nbristow01
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Well today after a good night sleep I go out to do a good visual inspection on the head and motor. Head looks great. But if you guys rememebr I was getting only 120 compression in cylinder 3. And it was taking about 8 turns to do it vs 4 on the others. Well look at the pics of cyl 3. at the 2 oclock position you can see a flat spot on the piston where it meets the cyl wall. You can look down that slot and actually see the first ring!!!!

The defect is in the piston and not the cylinder. Clylinder wall looks smooth all the way up. The reflection on the cylinder wall makes it look like its the wall but it is not

I have no idea how that happened or what can cause an issue like that.

So I am ordering 1mm over pistons tomorrow. Same 9.5s. Have a spare block so it goes to a DIFFERENT machine shop that has been refered to me.

Guess I will be headed to Eureka Springs with a newer motor

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man I do not know. i did not see it when I put the head on. Man it is so obvious I am wondering if it happened after the motor was built?

I am starting a new motor from ground up this week. Taking it to a machine shop that is highly recommended. Having a REAl engine builder build the short block for me.

What a whoopin this has been

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did you buy those pistons new ? Where you taking it ?

Have not ordered new pistons yet. Guess I will be tomorrow. Brad has a machine shop he has used for years next to Boardwalk Lambo. I am taking it there

Paul man I need an engine hoist. Anyway you can bring your down south?

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I have no idea how that happened or what can cause an issue like that.

Dropped on the floor at the shop?

Of course you didn't notice it when you were exited putting together your shiny new engine. Pretty easy to not see flaws in that situation.

Tommy

Interesting you say that Tommy. When I saw it that was the first thought that popped in my head. looks just liek it was dropped and pinged that edge pretty good. And you may be right, in the excitement it could have been missed by me

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I think you lost part of a ring. The other thought when they installed the new pistons is they did not check the bore totally. I have seen machine shops do one bore measurement and draw from that. Should be 5 or 6 mesurments on each cylinder. The old pistons can wear funny leaving gaps allowing the new piston to have contact with the cylinder. Also allowing a ring to break. Do yourself a favor and have the block measured by a competent machine shop before you order pistons. BTW cam overlap is not really an issue on these cars. It is an issue on V8's and cars with a lotta valves. There is a ton of stuff on the internet.....Also if only #3 is worn you can sleeve it.....

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I happy you found the source of your problem, but like you, not so happy it turned out to be something terminal.

I wasn't convinced it was valvetrain related, based on what you were reporting. Though I must say most offering valves/timing as a possibility were spot on in their logic. It's just not the usual cause.

If rebuilding, consider having the builder dial-in the engine with new static timing marks and use an adjustable cam sprocket to account for the different cam, but also skimming of the block and head.

When you skim these, you effectively close the distance between the crank and the cam, and this will alter your timing by a degree or two. The adjustable cam sprocket allows you to restore the original timing, or set different mechanical timing to maximize performance.

Cheers!

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I happy you found the source of your problem, but like you, not so happy it turned out to be something terminal.

I wasn't convinced it was valvetrain related, based on what you were reporting. Though I must say most offering valves/timing as a possibility were spot on in their logic. It's just not the usual cause.

If rebuilding, consider having the builder dial-in the engine with new static timing marks and use an adjustable cam sprocket to account for the different cam, but also skimming of the block and head.

When you skim these, you effectively close the distance between the crank and the cam, and this will alter your timing by a degree or two. The adjustable cam sprocket allows you to restore the original timing, or set different mechanical timing to maximize performance.

Cheers!

Thanks man. I know people got very frustrated at me when I was trying to explain the issues I was having. Now they know why it was so difficult to pinpoint. Was not just a black and white issue

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I noticed from the image, first there is no scuffing on the cylinder wall. Generally you see scuffing with tune up related piston failure, be it too lean, over boost, too much compression ect, all result in detonation and piston damage. Heat is the culprit with detonation and is tell-tailed in piston expansion and the resulting scuff marks. It surely looks to be damage prior to assembly and covered up with an anti oil fouling plug "shield" installed to keep the cylinder running.

I thought those plug shields had long disappeared from the used car lots long ago along with sawdust in the rear-end. I would assume the machinist must have re-cut or filled the top ring land so they could use the piston.

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Nick -

I suggest this time around you start a project blog and record everything in one place. This way, everyone here can watch (and maybe learn) from your engine failure.

Seeing that piston break - maybe one or more rings were installed upside down?? Did you vary the load on the engine during break-in to help seat the rings? Did you keep the engine revs. to a reasonable level during this period? I'm wondering what your machine shop comes up with regarding this failure.

Jim

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Have you thouight about contacting IE abourt purchasing one replacemnt piston and new rings four all four. If the other three pistons are relatively new, it might save you a few bucks if that is a concern.

Earl

74 02 Lux

02 M Roadster

72 Volo 1800ES

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