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240Z Aftermarket Itm Pistons Issues


redzedsled

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Hello,

 

My engine builder has just informed me that after mounting my pistons, ITM brand, item number RY2516-030, they are protruding above the deck of the block. The top of the P30 block was decked with about 5-7 thou removed, so that is not the problem.

 

They measured the piston height to the old ones that came out before mounting (a slight difference of 5 thou) and after mounting them on the rod bolts and into the cylinder, they protrude about 30 thou above the block,

 

Does any one have a theory as to why this would happen.

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Is the crank offset ground or from a different engine to give more stroke?

 

Are the same rods used?

 

Are the correct sized rod and main bearings used?

 

The crank was from the original engine to my knowledge. The original connecting rods were used and were not replaced.

 

They did remove 10 thou off the crank, and thus inserted the Clevite Undersized Rod and Main bearings if that tells you anything.

 

I have read that some of the stroker engine guys use two head gaskets instead of one, but there has to be another answer.

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Hello,

 

My engine builder has just informed me that after mounting my pistons, ITM brand, item number RY2516-030, they are protruding above the deck of the block. The top of the P30 block was decked with about 5-7 thou removed, so that is not the problem.

 

They measured the piston height to the old ones that came out before mounting (a slight difference of 5 thou) and after mounting them on the rod bolts and into the cylinder, they protrude about 30 thou above the block,

 

Does any one have a theory as to why this would happen.

Which is old and which is ITM?  You don't really say which is which.

 

There's much written about L28's and piston pop-up of about .022" but I can't find much on L24's.  BRAAP measured a bunch of L28's with flat-tops.  Post #19.

 

http://forums.hybridz.org/topic/58127-best-way-to-achieve-piston-to-head-clearance/

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Which is old and which is ITM?  You don't really say which is which.

 

There's much written about L28's and piston pop-up of about .022" but I can't find much on L24's.  BRAAP measured a bunch of L28's with flat-tops.  Post #19.

 

http://forums.hybridz.org/topic/58127-best-way-to-achieve-piston-to-head-clearance/

 

The ITM pistons were ever so slightly taller when they were both placed on the same wrist pin together for measurement.

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Sounds right to me. You should be fine.

5-7 thousands-couldn't be more specific than that?

Now this is where the HG really gets important. What's the crushed thickness of your selected HG?

 

Hi Steve,

 

I think I am going to go with the FelPro gasket, not sure of thickness.

 

I think I might need a head gasket between my left and right lobes of my brain!

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The ITM pistons were ever so slightly taller when they were both placed on the same wrist pin together for measurement.

That is ever so much clearer.  Kidding.  Kind of.  Seriously, you need numbers.

 

Really though, your engine builder should be familiar with this and know how to deal with it if he's experienced with the engines.  Nissan pistons are all essentially the same except for flat-top versus dished.  Did he say it was a problem or just mention it in passing?

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That is ever so much clearer.  Kidding.  Kind of.  Seriously, you need numbers.

 

Really though, your engine builder should be familiar with this and know how to deal with it if he's experienced with the engines.  Nissan pistons are all essentially the same except for flat-top versus dished.  Did he say it was a problem or just mention it in passing?

 

No, he was disenchanted and frustrated, with no answer except to machine the top of the pistons. Not something that should be done in my mind.

 

I have seen a few threads where the piston and valves were on a collision course, it can't be good.

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No, he was right pissed off and frustrated, with no answer except to machine the top of the pistons. Not something that should be done in my mind.

 

I have seen a few threads where the piston and valves were on a collision course, it can't be good.

Disturbing.  Their web catalog of services says that they work on 81-83 L28's, which all have a pop-up of ~.020".  He shouldn't have been surprised and should have compared to the old pistons right away.  Not really clear what the problem is.  If the new ITM's are just a hair off the old, what's to be right pissed off about?

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OMG-don't let him machine those pistons.

That's what i ran on my L24(deck height), and was fine. It's a bit tight with a 1.25mm HG, but that's probably what the Felpro is.

Like stated, most of these engines run about 22 thou deck height(what I have read from numerous posts). Then you shaved off 5-7 thou off the deck, so there you are with about .019 piston the head clearance.

The only way to know is to measure. I bought two felpro HG's just for that reason. I am going to find out exactly the crushed height of the felpro.

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Disturbing.  Their web catalog of services says that they work on 81-83 L28's, which all have a pop-up of ~.020".  He shouldn't have been surprised and should have compared to the old pistons right away.  Not really clear what the problem is.  If the new ITM's are just a hair off the old, what's to be right pissed off about?

 

Agreed! He did say that the difference of 7 thou was no big deal either, but why the difference once installed?

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