installing pistons got some questions

[chevyCowboy]

So im finnaly going to stuff the new pistons into there new homes tomorrow.
i have some questions
where are the ring gaps supposed to line up at?
what is the spec on the ring gaps?

i need to also check the rod bearing cleances with plastigauge, is this done after all the pistons are installed or should it be done as they are put in? will it seems to me that it will be hard to check them with all the pistons installed and unlubed wont beable to turn the crank???? help? im confused on this

any other important info that you fellas with more experince than me can offer would be greatly appreciated.

thanks guys

 

[redshift96]

Might as well check them in pairs on each rod journal on the bench. That way if anything needs attention, you won't have to pull rods and remove the crank to do it.

You will have to rotate the crank in order to attach all the rod caps though, so one certainly *could* do it as the rods are installed if your confidence is high that all is right.

I recommend the former.

Oh, and best to check the mains clearances with plastigage first. Getting the rear and middle main caps off while the rods are installed isn't extra fun.

 

[3500GMC]

So im finnaly going to stuff the new pistons into there new homes tomorrow.
i have some questions
where are the ring gaps supposed to line up at?
what is the spec on the ring gaps?

i need to also check the rod bearing cleances with plastigauge, is this done after all the pistons are installed or should it be done as they are put in? will it seems to me that it will be hard to check them with all the pistons installed and unlubed wont beable to turn the crank???? help? im confused on this

any other important info that you fellas with more experince than me can offer would be greatly appreciated.

thanks guys

This thread will help. Originally posted by our dear Missy Good Wrench. http://www.thetruckstop.us/forum/showthread.php?t=11375&page=2

Post #22 for ring orientation.

No lube with plastigauge. Dry, do not spin. Measure.

All the best...

 

[SmithvilleD]

Top comp ring end gap = 0.010 to 0.020"
2nd comp ring = 0.030 to 0.040"
oil ring = 0.010 to 0.020"

Anybody else have an opinion on trying to plastigage rod bearing oil clearances on the bench?

I've never tried that and would wonder if doing it that way could/would allow the possibility of seeing clearance taper from the rods not being positively held/located at their other end by the piston in its bore.

We typically measure journal OD's & bearing ID's (w/ caps properly torque'd) & calculated what oil clearances will be. So plastigage during assembly is basically a last chance/final check for errors/mistakes.

That said, I get the mains plastigaged first. After your satisfied the main's clearances are right, then lightly lube the mains & install the caps. Only lightly tighten the main that includes the thrust (fore/aft motion limiter) bearing. Then tap the crank forward/back with a deadblow hammer. This ensures the top & bottom halves of the thrust bearing are aligned so they'll equally share the thrust load. Then torque all mains & see/feel how freely the crank spins. If you feel anything except free/easy spin, you know something's not right.

 

[chevyCowboy]

the crank and mains where put in last weekend and all the above mentioned advice was used, thanks for the replys guys hopefully every thing turns out good

 

[chevyCowboy]

well i got all the ring gaps checked and the rings on the pistons only to unwrap the new rod bearings and find that one has a nasty nick in it so ill have to contact engine tech monday and see what they will do about it. kinda bummed was really hopeing to have this ready to put heads on today. oh well got other stuff to do still i guess

 

[btfarm]

Anybody else have an opinion on trying to plastigage rod bearing oil clearances on the bench?
I've never tried that and would wonder if doing it that way could/would allow the possibility of seeing clearance taper from the rods not being positively held/located at their other end by the piston in its bore.

Agreed. Always check rod bearings as installed for that very reason.