Heads & Pistons

Message

Alex Wendorf · #1 Post by **Alex Wendorf** » Mon Apr 07, 2008 9:43 pm

hI, hOW MUCH CLEARANCE IS NEEDED FROM TOP OF PISTON TO TOP OF HEAD? i HAVE ASSEMBLED MY ENGINE, BUT NOTICE A KNOCK(RAP) AT 2000RPM. AFTER USING SOME SOLDER INSERTED IN SPARK PLUG HOLE AND TURNING ENGINE TO COMPRESS SOLDER i GET .045 CLEARANCE, COULD THIS CAUSE RAP? tHANKS, ALEX 8)

Cliff Murray · #2 Post by **Cliff Murray** » Tue Apr 08, 2008 7:08 am

Here are a few rambling thoughts.... .045 inch should be enough clearance but measuring at one point may or may not be accurate. It is possible for the piston to rock a little and therefore measure larger than it really is. If you are using 22 degree heads with 30 degree pistons you need about 4 X .010 gaskets to get clearance but the engine will not run well due to poor combustion. When the chambers are machined to 30 degrees, one .010 gasket usually works. Having a tight squish is very good for combustion. Worn or poorly machined rods can cause noises. Worn pistons and wrist pins likewise. Also, I assume that you have good timing gears and have run the engine with no belt and considered the fuel pump? Sorry for your troubles.

Mark Jung · #3 Post by **Mark Jung** » Tue Apr 08, 2008 11:02 am

Alex, Cliff gave you some good information. Can you give us some history on your engine? What engine do you have? Was the engine rebuild a complete rebuild? Did you do the work? How much time has passed since the rebuild and when the noise (rap) started? What parts were changed or added in the rebuild? These answers will help on finding out what the noise might be.