Checking Piston to Valve Clearance?
Thread Starter
Safety Car
Joined: Sep 2003
Posts: 3,558
Likes: 2
From: Cape Coral FL
Checking Piston to Valve Clearance?
Well, I am about to embark on my h/c swap - as soon as I get my AFR's... 4-5 weeks... = (2 mos.) 
I'm having the heads milled .015 and using a .228/.228 @.588/.588 112LSA + 2 cam. Stock thickness head gaskets. I was going to pull the motor to do some internal work and checking P/V would have been easier then. I just found a way to support the engine from above while removing the crossmember, so I think I will do my work that way. I want to check P/V clearance. The way I know is to install low pressure springs on the head and put clay on the piston and turn it over by hand. I also suppose I could do the valve drop method. I was also thinking I may be able to use a borescope through the sparkplug hole. Is there a way to avoid disassembling the valves on my nice new heads to install low pressure springs so I don't collapse a lifter and get false clearance readings?
I'm having the heads milled .015 and using a .228/.228 @.588/.588 112LSA + 2 cam. Stock thickness head gaskets. I was going to pull the motor to do some internal work and checking P/V would have been easier then. I just found a way to support the engine from above while removing the crossmember, so I think I will do my work that way. I want to check P/V clearance. The way I know is to install low pressure springs on the head and put clay on the piston and turn it over by hand. I also suppose I could do the valve drop method. I was also thinking I may be able to use a borescope through the sparkplug hole. Is there a way to avoid disassembling the valves on my nice new heads to install low pressure springs so I don't collapse a lifter and get false clearance readings?
Burning Brakes
Joined: Sep 2001
Posts: 1,173
Likes: 1
From: Aguila AZ
It is impossible to get reliable P-V clearance data using a hydraulic lifter. Light springs just make matters worse. I have modified a stock hydraulic lifter to eliminate the internal spring which is the source of the measurement error. With the proper thickness spacer under the plunger it becomes a 'solid' lifter for checking purposes only. You may also need to scribe an air path in the side of the plunger to allow air to bleed off under the plunger. With the test lifter(s) in place, temporarily reinstall the head and valve train on the valve. Adjust to zero lash with the lifter on the cam base circle. Use light springs. With the engine near TDC you can roll the crank back and forth until minimum P-V clearance is established. Pushing down on the valve and measuring the valve to rocker clearance will be your P-V clearance at that point. You can save disassembly time if you make up two test lifters and install one on the intake and one on the exhaust. Once the head and valve train are properly installed, you can check both I and E in one set-up. Hope this helps.
Shirl
SDRE
Shirl
SDRE
Safety Car
Joined: Mar 2002
Posts: 4,928
Likes: 1
Cruise-In V Veteran
St. Jude Donor '09
If you have a couple extra lifters you can make solids by filling the lifter chamber with auto-curing resin. The internal spring and hydraulic pressure will push/hold the Pushrod receptor in place and the excess flows out thru the oil hole. Any methacrylate or ethacrylate resin will work. I think the acrylic they use for fake fingernails is meth or ethacrylate. Dental/Denture Labs have lots of methacrylate. FWIW.
joel
joel
Thread Starter
Safety Car
Joined: Sep 2003
Posts: 3,558
Likes: 2
From: Cape Coral FL
I purchased a new set of Comp 850's to go with the install. So I can take a couple of the old lifters and drill out the side hole and fill them with epoxy. I also bought a set of stock head gaskets. Can I use these after torqueing the heads on and off 4 times? My gut says yes because there are no heat cycles involved, but does anyone have some experience on this?
Thread Starter
Safety Car
Joined: Sep 2003
Posts: 3,558
Likes: 2
From: Cape Coral FL
Originally Posted by ArKay99
I also bought a set of stock head gaskets. Can I use these after torqueing the heads on and off 4 times? My gut says yes because there are no heat cycles involved, but does anyone have some experience on this?
Safety Car
Joined: Mar 2002
Posts: 4,928
Likes: 1
Cruise-In V Veteran
St. Jude Donor '09
I have the ARP head studs.
You don't need to be so exact as to need the head gasket and torque wrench. Just snug up the head without the gasket - don't tighten. If you find .030" clearance on the intake and the gasket is .056", crushed at final torque, then you have .086" clearance. The crushed gasket thicknesses are available but I don't remember the them. Hope this helps some.
You don't need to be so exact as to need the head gasket and torque wrench. Just snug up the head without the gasket - don't tighten. If you find .030" clearance on the intake and the gasket is .056", crushed at final torque, then you have .086" clearance. The crushed gasket thicknesses are available but I don't remember the them. Hope this helps some.
