I had my l98 apart for some porting work and on reassembly i lapped my valves and the seats looked prettu good but after a hpur of having the heads sitting upside down with the combustion chambers filled with water a very small amount is getting through,how much should i be worried?or should i diassemble them and get the seats ground thanks

 

Were the heads assembled, meaning were the valve springs holding the valves tightly against the seats, or were the valves just resting against the seats? Also, did you coat the seats with any type of oil before setting the heads up with the water?


Unless your valve guides are in perfect shape, no machine shop is just going to grind the seats without reconditioning/replacing the guides. At that point, you're in for a complete valve job.

 

yeah i had the heads fully assembled seals and springs,i did not oil the seats but i oiled the stems

 

With the springs in place, they should seal completely. Actually just finger pressure should be enough to seal them. I assume you got every bit of valve grinding compound removed. We coated the seats with cam lube prior to assembly, because some sets of heads were put on the shelf, and who knows how long they would sit there. When I worked at the machine shop, we tested them using vacuum.
If the water leaked through with the springs installed, then that ain't good enough.
Correct it now before you have to do the job twice.

 

yeah i cleaned everything beat i could before assembly,was a trial fit to see if i had them sealed i lapped them and it looked to be seating ok but i guess not good enough,gping to disassemble and take to machine shop thanks for the reply

 

When doing a valve job - new guides, ground seats, ground valves, you would know beforehand if you got it right by dropping the valve in its guide (oiled stem) and if it was right, the valve would bounce off of the seat a few times.

 

I will keep that in mind thanks

 

Curious, when you removed the valves did any come out tight, or have to be "unscrewed"? If so there was most likely a burr at the valve tip where the rocker arm rides. Valve locks can also raise burrs at the keeper grooves. Any burrs should have been removed prior to removing the valves. If you didn't, then you put grooves in your valve guides.


You're welcome and good luck.