Valve clearance from head

trainguy

trainguy

Well-known member
Have built a 59 engine with 45/16x41/8 b&s Isky max1 stock heads.valves hit head upon assy.fly cut the valve chambers and checked with playdough.upon starting engine and reving engine I think I hear the valves striking the head:mad:My question ,how much clearance should there be between valve and the head? :confused:Thanks Phil
 
You simply need "clearance". That can be as little as .020. Did you check piston clearance?
 
Mick said .050, Jwl said .020, both are right, but i would go with the .050, that is the usual minimun advised clearance, gives a margine of safty, with the cost of engine repairs go with the larger clearance
 
Could it just be lifters or fuel pump rod clicking? It can be hard to pin-point the exact location of these noises.
 
Don't laugh, but I would not use "Playdough". It has too much recoil in it. It's dough, not clay. There is a difference, and I would not trust your measurments. Repeat your measurements with either clay or aluminum foil balls and grease.
As to the clearence above the valves, I would consider what your going to do with the engine and the RPMs your going to turn. Also the aggressiveness of your cam and the appropriate spring pressures. An aggressive cam with stock springs, I'd go .050". With heavier spring pressures, .020". Your choice
 
I have always heard .050 valve to head clearance. Usually most people check it by sitting the head on the block without a gasket, if it clears without the gasket it should be ok. Something does not seem right, stock heads with large combustion chambers and a mild cam should not have a clearance problem.

My Dad has a Isky Max 1 in his '32 Roadster, it does not lope at all so it does not loose too much power on the low end like a big duration cam does, it pulls really hard for a little flatty.
 
50 thou is ok...also keep in mind the valve angles. if you plunge straight in the head the clearance may be too tite at the top....
 
Set the heads up with a 5 degree angle, bore the pockets so you have at least .050 over the top edge of the valves. I also inlarge the back wall close to the head gasket to make more room for the air/fuel get up over the top of the valve. With stock 59AB heads and a Max-1 cam I'd be more worried about the pistons lower edge hitting the heads, if the heads have been milled any. Depending on the brand of pistons your useing and if the crank grinder might have stroked a little longer when he went to 4-1/8 stroke, the pistons might be hitting the heads. Something to worry about. Walt
 
I put the heads on the block loose with no head gasket, turn the engine over carefully and make sure nothing is hitting, the gasket takes up .050" or more, depending... Karl
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I initally checked it by turning the engine without nuts and a head gasket and the heads lifted,I then put a gasket and the did not move,I then milled the pockets about .050,and checked with playdough and had about .030-.060 clearence.Maybe the noise is somthing else.:rolleyes:
 
Are you sure when you turned it over looking for clearance that it was indeed the valves touching and not the pistons? Did you observe the valve timing position when the heads lifted. and it was not a TDC condition.
 
I installed flat top pistons[ross] the pistons did not extend above the deck I used "big bore" [3 3/8 max] head gasket.I did see any reason to ceck further.Phil
 
The valves should clear then. Try running it with the belts off and the fuel pump rod out and listen for the same noise. Keep us posted. Run it until the carb runs dry.
 
I did not tell the guy to set up at .020, or .050, or any specific clearance. I am simply pointing out the fact that even a minimal clearance eliminates the valve contact as a source of his reported noise and to look elsewhere.
 
I have been having low oil pressure problems,turned out to be missing the plug in the front main oil gallery.I installed the plug and the noise vanished.Oil pressure is now 30# idle 50# run was 5#-25#Thanks for all the support,looks like the problem is gone .The engine sounds great:D:D:D.Phil
 
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