any sbc guru's out there?
 

Same post just new title:rolleyes:

I am currently rebuilding a Merc. 300 Tempest. I noticed that when turning the engine over by hand the intake valve does not start to open until the piston is almost @ the bottom of the cylinder on the intake stroke, and does not fully close until almost TDC on the compression stroke, is it supposed to be that way??
It didnt seem right to me but I'm no expert.

I am alomst posotive that I have the timing chain and sprokets installed correctly, and to my knowledge the engines were completely stock and I am using exact replacement parts.
Any suggestions or ideas?

Sounds like you're rotating the engine backwards. Is that a reverse rotation engine? If not maybe you have a reverse rotation cam in it.

Bob

The problem with...
 

The Tempest was an automotive L-82 short block with stock heads.
The camshaft was big for a marine engine. Be sure and install a modern camshaft for best performance or the only way you will get any performance out of the engine is to run it at 5,500 rpm and higher.
Sincerely
Dennis Moore

Sounds like you are looking at the exhaust valve, not the intake valve. If not, and if everything is the correct rotation, the cam must be out of time.

BT :cool:

The only question you have to ask yourself is where are the timing marks on the timing chain? Are they set correctly? There are 2 ways to set up the chain:
1--- Set the dot on the cam gear to 6 o'clock postion, then set crank gear to 12 o'clock. Put the chain on. Then drop the distributor in at # 6 cylinder.

2--- Set both the crank and cam gears at 12 o' clock. Put the chain on. Then drop the distributor at #1 cylinder.