E: Engine Nip up Comet

Nulli Secundus

Well Known and Active Forum User
VOC Member
VOC Forum Moderator
You are doing the right thing I think. I would just like to say that whilst the bore looks OK with regards to damage from the partial seizure it does look very black. I have never stripped the top end of an engine down and found that amount of black impregnation. Could graphite grease been used on assembly?
 

Tony Wilkinson

Well Known and Active Forum User
Non-VOC Member
You are doing the right thing I think. I would just like to say that whilst the bore looks OK with regards to damage from the partial seizure it does look very black. I have never stripped the top end of an engine down and found that amount of black impregnation. Could graphite grease been used on assembly?
Probably just my poor photo. The liner does look fine.
 

Bill Thomas

Well Known and Active Forum User
VOC Member
I have never had or seen a GM piston , But I have been told they are not the best, They are Round !!.
Cheers Bill.
 

oexing

Well Known and Active Forum User
VOC Member
Big question, is the bore still round when pushed into the crank case ?? The piston seizure marks are strangely diametrical not really at centerline positions but sideways so guess there is more to that than just a classic nip up. 6 thou clearance should be way more than enough to not get any seizure. But then my guess there is really a big geometric flaw in one of the components when fitted. Get good micrometers for measuring in various places to find out.

Vic
 

oexing

Well Known and Active Forum User
VOC Member
Yeah, but only two of them -so somehow I do not follow this argument , suspecting some other flaws . . . .

Vic
 

Black Flash

Well Known and Active Forum User
VOC Member
Tony
For safe of mind in inspect the ends of both top rings carefully. If one or both of the rings shows shows bright polished dots at the ring gap ends your rings are too tight and need gaping.
You can check this without removing the rings.

Only a few minutes to check one more possible cause.
Cheers Bernd
 
Top