Before I make some calls tomorrow, I thought I'd throw this out to the Group; What should be the minimun clearance between the intake valve edge and the valve relief on the piston?? Now this is an aluminum rodded motor. I put the clay in, the clearance between valve and piston top is no problem, but the clay in the valve relief was pretty thin...no piston showing thru, but pretty thin. Anyone with an answer, thanks for the info. Gary G.
That sounds right for the intake (.100"), with .120" for exhaust...at least, for iron heads. Not sure how much extra should be added for alum. heads....extra .020" maybe??o No:
I appreciate the Input, but the clearance you guys mentioned is almost 1/8 (.125) of an inch, .100. This sounds good for valve "face" to top of piston, which is what I have, it's the valve reliefs that I think I have to make a little bigger. Gary G.
Any signs? You've had the motor on the dyno haven't you? Any sign of contact? I would think you need about .050" on the Lifter galley side of the piston to allow clearance for piston rock and about .030" on the sides. I don't have any problem with my motor and those clearances but that doesn't mean its the absolute rule. It was just my educated guess that I felt comfortable with. :grin: My pistons weren't cut right for Stg3's so I had to open the up a little. Good luck!:TU:
when cutting valve relieves the general rule would be to measure the dia. of valve plus .100 extra. meaning the valve would be 2.100 plus .100 making the cutting tool 2.200 witch would give you .050 per side of valve clearance.
OK, yes the motor ran on the dyno, and after taking it apart to figure out the oil press. problem, I noticed a slight amount of contact in the Intake valve relief. I trimmed the reliefs out with a really small drum sander, but just not quite enough. I talked to TA Mike today, he said .030 to .050 would be a minimum amount. So Rick, you got it down, I think there was a misunderstanding regarding what size valve I was going to run,I have the big valve, 2.260 and the reliefs just weren't cut like "rogersperf" had mentioned. Oh well more work for me, out comes the pistons...again...The things we do to go fast..... Thanks again for the input. Gary G.
Take em'Out? You don't have to take them out to fix those reliefs. just make a tarp to go over the engine and mask off the valve relief that your working on. Clean as you go and you'll have no problems. Figure out what you need on one piston then take a compass and transfer it to the rest of the pistons. Unless you would feel better taking them out and sending them off to get done on a machine. I've just learned in all the work I've done that the more work I could do myself the faster it got done and the less things got screwed up. Did you find your oiling problem? Your running a solid flat tappet cam aren't you?
On my SBO with almost 16 to 1 compression I run .070 on the intake and 120 on the exhust. The intake valve you can get away with .050 to .060.
OK Group, I got the valve relief "issue" all done, .070 on the intake, i didn't measure the exhaust, but it's at least double the size of the intake clearance. Short block is back together, heads are back on, one side rocker arms and valves adjusted, now if I could only find the hardware for the other rocker shaft!!!! Good thing TA has them in stock, I have a funny feeling that my 5yr. old daughter thought that they would be better off buried in the mud, I'll never know...........Rick, the oil problem, the guy who redid my crankshaft thought that some "dirt" went thru the motor, that, and the "loose" clearances, probably was the problem, "dirt", I cleaned all parts that I put on the short block, yes, I'm running a flat tappet cam, It's big, but I don't think that it is so big that it would put the lifter in a position to bleed off a large amount of pressure. I had Peterson go thru the pump, I plan on running it with a drill, pumping oil into a bucket, to flush it prior to final installation. I'm going to run the motor on a run stand before I put it in the car, just to make sure I have Oil pressure, I'm also going to run a thicker oil, 10w 40 or 20 50. Should have it ready to run very soon, also have to finish the run stand. Gary Giessen
Gary, be very careful if running heavier weight oil as you may be replacing both the cam gear and distributor gear regularly due to the excessive loads placed on them--especially during a cold start-up. Something to consider.
THick oil? With that peterson pump you shouldn't need to run over 10w-40. The 20w-50 won't hurt anything but on cooler days make sure to warm it up a little before making a pass. With a flat tappet cam you wont have any oiling issues due to lift like a roller. Since you run the quarter mile stuff, you might look into restricting the oil flow to the roller rockers since they are a needle roller design and don't need much oil. They will almost get enough oil off splash from the lifters. Keep as much oil in that pan as you can. If you check around alot a serios race motors restrict oil to the upper half of the motor. Hows that fuel system looking? Is it all ready for the spray?
