View Full Version : Update to BB compression issues
HTRDMX55
07-18-2007, 08:29 PM
Well first off all intake pushrods bent on both heads. Pulled off heads and all intake valves were hitting pistons. Two bent valves and stuck open thus proving the no compression theory. So at first i thought maybe the deck height is to low on the heads i bought. Some one else suggested valves were too tight or the timing is way off. Could it be that the cam is off. I swore i adjusted the valves correctly three times. Dont know if i should get valves fixed and try again or buy new heads.
Adam's 55 Chevy
07-20-2007, 03:08 PM
If it's all cylinders buy 2 valves and set them up again. Check installed height's. Piston height & cam lift. Was the head gasket too thin? If you can get it right on one cylinder you should be able to get it right on 8.
z28orshoot
07-22-2007, 12:29 PM
make sure of the timing chain. quick reference is dot to dot. but check the crankshaft keyway. it should be in the 2 oclock position. not straightup.
what is the cam installed at? how big are the piston domes, how far in the hole is the piston and what size heads/chambers are they?how muck have ben milled off?
MonzaRacer
07-25-2007, 07:51 PM
Are you talking a big block chevy? If so you need to notch your pistons.
BBC needs 0.080-0.090 at max lift ( Ill go over my lifty spec by at least 0.010 to be safe, on the intakes and 0.100 on the exhaust.
I believe its Powerhouser that makes a valve shaped "cutter valve" you slip it in place of the valves, (first you use modeling clay and measure with a dial indicator at max liftand piston at tdc how much valve claerance you need. The cutter has a sleeve that you lock down after measureing clearances, you slip the needed change amount of feelier guages under the lock sleeve and the valve guide, then you simply install the heads (i do this less the head gasket), hook up an electric drill and and push down till the cutter hits the stop sleeve and remove the heads, vacuum the negine and clean up well, then Ill break all the sharp edges of the piston dome with a piece of emery cloth or 320 wet/dry sand paper. And then you wont kiss valves.
Also if you have aftermarket heads the valve angles may have been modified by the designer/manufacturer for better flow from stock angles.
Good Luck
Lee Abel
AFTERMARKET PERFORMANCE
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