So as some of you may be aware I ended up running a VG30DE in my car with a pair of turbos strapped to it. Inevitably the high compression took its toll and we lost compression. This is when I realised what was there, rather than a turbo block. Anyways that's by the by. It's a late spec unit with 10Y heads. What am I doing with it I hear you ask? Well I'm currently dissecting it to work out what exactly went wrong and wether its rebuildable. So today i had an hour spare, I stripped the front down and pulled the heads.

 

 

 

 

It would appear at least one piston isn't central in the bore. I haven't actually pulled the Pistons and rods yet. Need to get them some clean storage. I'm assuming the rod is bent. Clearance one side is 0.5mm the other side is 0.09mm anyone know what the piston to wall clearance should be? The bores look very clean, no scratches etc, the original hone is still viewable. Same situation on cyl 2 and 4. The rest are even.

Edited March 1, 20169 yr by Stephen

So I finished stripping the block today. Still got to fully inspect the rods but they arnt visibly bent. The rods and Pistons will be replaced in any event. Cylinder 4 the low compression one pretty much fell out. Number six required some encouragement. Crank looks great as do the cylinder walls. The next step really is to clean the block down and take some measurements to check the deck, piston round and size and crank.

The big end crank bearing show some marking on two, not sure if this is normal wear? Appears uneven.

I did notice it appears two bolts are missing from the oil pump...should there have been bolts in here?

Another point I need clarification on, I take it the valves stamped 30 are NA valves and TT valves would have 40? Following suit with other things like heads, Pistons etc?

Hi Stephen, Is piston from cylinder 4 the same size as the other ones?

Could they have changed it at some point and just used one to hand being the wrong size?

Only a thought....

It's not a silly suggestion mate. I get the feeling this engine has been rebuilt before. The Pistons are graded, I suppose it's possible the wrong grade was fitted. Il have to clean the deck and see what's stamped and what it's supposed to be. I have a mate that has the tools to check it all out and has offered to do the machining if I want him to. Currently though this just an exercise in seeing how ****ed it is. Ideally I'd like to send it to Jim and go all out. No rush.

It's not a silly suggestion mate. I get the feeling this engine has been rebuilt before. The Pistons are graded, I suppose it's possible the wrong grade was fitted. Il have to clean the deck and see what's stamped and what it's supposed to be. I have a mate that has the tools to check it all out and has offered to do the machining if I want him to. Currently though this just an exercise in seeing how ****ed it is. Ideally I'd like to send it to Jim and go all out. No rush.

Hope it is something silly like that and everything else is good...... you deserve some luck for a change....

As you said.... No rush.... take your time and do it right.... I rush and look where that has got me...... lol

Worse comes to worse Russ the block will be over bored and forged Pistons fitted. Which would happen anyway if it goes to Jimmer.

Had a bit of help from some of the American guys. So Page 51 outlines a range of 0.21-0.40 for the top ring my gap is 0.05 as verified by the process outlined. So worn. However the FSM states 1.0mm max gap so not excessive.

http://www.300zx-twinturbo.com/cgi-b...st=em&slide=51

Whilst I'm waiting to borrow the equipment to check the crank and bores etc I've recorded the piston grades and rod bearings. I've also stripped the Pistons off the rods.

Cyl Piston grade Rod bearing

1 2 1

All cylinders and bearing are the same grade as each other. I haven't had time to check the crank ones yet.

Just to clarify am I correct in the understanding that if wear is within tolerance and should I wish to replace the 30P Pistons with 30P1 replacements, I would require a set of 30p1 Pistons of grade 2 and a set of rod bearings grade 1? I like to be clear with these things.