2g Piston Valve Reliefs

[aspekt9]

Alright, I'm blueprinting out my motor before I start assembling things. Let me throw out some quick numbers:

Head:

Top Left: 5.155"
Bottom Left: 5.155"

Top Right: 5.164"
Bottom Right: 5.164"

Block will be shaved to about .008", I plan on running an MLS head gasket. So we figure ~ .048 total removed, I would need to run a pretty thick HG to restore the proper height.

I purchased adjustable cam gears because without a doubt I'm going to need to adjust the timing because of how much was shaved off the head... Now, I'm shooting for a quench of about .040 while keeping valve to piston clearance within spec. In order to do this I will inevitably need to run a thicker head gasket, the only thing is I still have to measure piston to deck height so I can determine what headgasket thickness I need.

I'm running 2g pistons and the issue is will the valve reliefs cut in the pistons be deep enough to allow me to keep the valve to piston clearance in spec or will I need to get them cut deeper? I could solve the problem by purchasing a thicker HG but I don't want to go over the .060 quench area... Does anyone have any experience with this or can tell me if the 2g piston valve reliefs are cut generously?

 

[BogusSVO]

your piston to valve clearance will depend on wht cams you run.

so what is the net lift of your cams? or are you running stockers?

on the 1g 6 bolt engines, with the 1g internals, the piston to deck clearace is about .003 in the bore

so by milling your block .008, you should be appox .005 out of the block.
I would ask them to try to mill just .003 or less, so the HG is just shined (I can cut .0005 a pass if I choose too)

next is your head, you are thin and on a tilt (from the numbers posted) by .009
also you are very thin, new thickness is 5.200 and AREA min thickness spec is 5.185
(the mitsu manual allows for a COMBINED total .008 from the head and block)
so your head is .045 on the left and .036 under on the right.
and .030 and .021 min thick spec as it is..
(your measurements also tell me that whomever milled the head at some point there level is out of wack...)

as far as your head gasket goes, with the quench values you want, and my "guess" where your piston will end up out of the block..
a .060 compressed thickness HG should give you a .055 quench
this will also restore head thickness by appox +.015 ,assuming that a OE HG has a compressed thickness of .040 (most factory composite HG are about .039-.041 compressed)

as far as the valve to piston clearace goes, you should perfore a "dry build" and clay the valve reliefs and measure the compressed thickness of the clay ( I would use an old HG in the dry build)
You will ned some "dummy" wrist pins for the dry build too, this is incase you do need to have the valve reliefs fly cut

you should want about .040 piston to valve clearance on the intake side and .060 on the exhaust. This is just a general rule of thumb

good thing you will have adjustable cam gears, they will be needed to dial in the cams back to the OE installed specs.

 

[aspekt9]

your piston to valve clearance will depend on wht cams you run.

so what is the net lift of your cams? or are you running stockers?

on the 1g 6 bolt engines, with the 1g internals, the piston to deck clearace is about .003 in the bore

so by milling your block .008, you should be appox .005 out of the block.
I would ask them to try to mill just .003 or less, so the HG is just shined (I can cut .0005 a pass if I choose too)

next is your head, you are thin and on a tilt (from the numbers posted) by .009
also you are very thin, new thickness is 5.200 and AREA min thickness spec is 5.185
(the mitsu manual allows for a COMBINED total .008 from the head and block)
so your head is .045 on the left and .036 under on the right.
and .030 and .021 min thick spec as it is..
(your measurements also tell me that whomever milled the head at some point there level is out of wack...)

as far as your head gasket goes, with the quench values you want, and my "guess" where your piston will end up out of the block..
a .060 compressed thickness HG should give you a .055 quench
this will also restore head thickness by appox +.015 ,assuming that a OE HG has a compressed thickness of .040 (most factory composite HG are about .039-.041 compressed)

as far as the valve to piston clearace goes, you should perfore a "dry build" and clay the valve reliefs and measure the compressed thickness of the clay ( I would use an old HG in the dry build)
You will ned some "dummy" wrist pins for the dry build too, this is incase you do need to have the valve reliefs fly cut

you should want about .040 piston to valve clearance on the intake side and .060 on the exhaust. This is just a general rule of thumb

good thing you will have adjustable cam gears, they will be needed to dial in the cams back to the OE installed specs.

Thanks for responding BogusSVO, you always have detailed technical answers and know what you're talking about, I appreciate it. I'm waiting on the cam card, I'll be running the Delta H272s, so I'm not 100% sure on the total lift, I'll see if my machinist can get away with .003 or less milled. I was definitely planning on claying the pistons, could I do this without a HG and then just add the compressed HG thickness to the clearances I measure? Would that ruin the surfaces of the head and deck? Should I clay two valves at a time or is it okay to do all the valves at the same time? I figure I should do all of them because the head is tilted so the clearances are going to be a little different from one end to the other. Also, could you elaborate on the dummy wrist pins being needed for a dry build? Thanks

 

[BogusSVO]

Thanks for responding BogusSVO, you always have detailed technical answers and know what you're talking about, I appreciate it. I'm waiting on the cam card, I'll be running the Delta H272s, so I'm not 100% sure on the total lift, I'll see if my machinist can get away with .003 or less milled. I was definitely planning on claying the pistons, could I do this without a HG and then just add the compressed HG thickness to the clearances I measure? Would that ruin the surfaces of the head and deck? Should I clay two valves at a time or is it okay to do all the valves at the same time? I figure I should do all of them because the head is tilted so the clearances are going to be a little different from one end to the other. Also, could you elaborate on the dummy wrist pins being needed for a dry build? Thanks

with the 272 yes you will have more lift than the stockers, the cam card will give you the info needed.

yes, you can clay all 4 at the same time

get a old or cheapo composite gasket, with out the gasket, as thin as your head is, you may not get the engine to roll over by hand to compress the clay

with out the gasket, it is risky, but you may scratch the new mill the surfaces.

the piston/rod combo you are running is a press fit wrist pin, chances are if the pistons have to come off to be fly cut, the pistions will be damaged by the act of pressing them off,

Dummy wrist pins are a simple thing to have, take your old wrist pins (the 2g) in your case, and buff/sand the entire wrist pin till it barely slips into the rod

next take the rods you are going to use, and the new pistons, and the dummy wrist pins and assemble the rod/piston combo and do your checking
MAKE SURE TO INSTALL THE NEW WRIST PINS FOR THE FINAL BUILD!!
at the most, it may throw off your clearace by .001-.002

I would number the rod and piston, so they will go back in the same hole for the final build

**TECH TIP**
#1) when claying the pistons, wipe the valve head with oil/wd-40 to keep the clay from sticking

#2) install the oil scraper rings for the dry build, so the piston will not rock in the bore

 

[aspekt9]

Now should I be claying everything with the head torqued, timed and the cams dialed in with the adjustable gears before I take measurements?

The issue with the pistons is I bought them as a combo from DSM Graveyard, the rods are already attached with the wristpin. If I do need to get them flycut is there anyway it can be done with the rods still attached?

Also, what is the stock piston to valve clearance on a 1g?

 

[BogusSVO]

Now should I be claying everything with the head torqued, timed and the cams dialed in with the adjustable gears before I take measurements?

The issue with the pistons is I bought them as a combo from DSM Graveyard, the rods are already attached with the wristpin. If I do need to get them flycut is there anyway it can be done with the rods still attached?

Also, what is the stock piston to valve clearance on a 1g?

yes you will clay the pistons with the cams and time set, just as it would be if installed and running

well as far as the pistons go.... I hope you will not need to fly cut them, I do not know of a way to do it with the rods on.

I do not know what the factory piston to valve clearance is.