Measuring Valve to Piston clearence

v8alex · Post by **v8alex** » Thu Mar 08, 2007 10:12 pm

I'm thinking of checking piston to valve clearance to be sure my home rebuild is OK. The block has had a minimal deck, but I don't know how much the heads have been skimmed. When all assembled and the lifters primed with oil, I can turn the engine over by hand no probs and do not detect any impedence. Lifter preload set at 16 thou.

I'm thinking about using some plasticine on a piston on each bank, bolting it all up and turning the engine to check for marks, but really don't know what the clearance should be and how thick a piece of plasticine I should use.

I'm using 9.75:1 CR pistons and a composite gasket and a DJE 220 cam.

Alex

Post by **katanaman** » Thu Mar 08, 2007 11:48 pm

I always go on 80 thou inlet clearance and 100 thou exhaust. If you do this with head gaskets you will have to torque it fully down or your measurements wont be accurate. Best way to measure is with a dial gauge and soft springs, its also not a good idea to use hydraulic lifters as they will still compress without oil pressure behind them. Either make a dummy lifter or use a solid mechanical lifter. The main danger area is between 15 deg and 5 deg BTDC and 5 deg and 15 deg ATDC on the compression stroke. Do more than one pot as well just in case they aren't all the same, all of them would be best.

Post by **Coops** » Fri Mar 09, 2007 1:46 pm

I know this sounds a bit heath robbinson,
but is there any way you can make a cutter and use an old head as a guide and use a drill to spin the cutter to put the valve pockets in the pistons while still fitted in engine?????

minorv8 · Post by **minorv8** » Fri Mar 09, 2007 1:54 pm

Thats what I did with mine. I used Rover intake to cut ex valve pockets and a Chevy 1,7" intake valve to cut intake pockets. Crude but it worked. When I checked for clearance I did not have the gasket fitted. Actually, my old had marks on the pistons that they had just touched each other (9,75 pistons 0,040" down the bore at TDC, tin gasket and RS Typhoon cam)

Post by **Coops** » Fri Mar 09, 2007 2:16 pm

cheers mate,
you still got them cutters about that i may borrow????

kiwicar · Post by **kiwicar** » Fri Mar 09, 2007 2:26 pm

Hi Tony
I can let you have a couple of chevy 1.65" inlet valves if it is of any help (I can let you have a couple of exhausts to go with them if you want)

Mike

Post by **Coops** » Fri Mar 09, 2007 2:38 pm

Hi Mike,
that would be cool mate,
Will have to put an edge on them for cutting though, so they will be ruined then mate,
That ok???

kiwicar · Post by **kiwicar** » Fri Mar 09, 2007 2:45 pm

Hi Tony
no problem I won't need them back, they are from a head that I am no longer planning to use (they would need changing anyway), what do you need, two of each (inlet and exhaust)? PM me your address and I'll get them in the post to you on Saturday.
Best regards
Mike

Post by **Coops** » Fri Mar 09, 2007 11:47 pm

cheers Mike,

minorv8, you got any pics of the cutters you made????