I was trying to get the cam swap finished today and ran into a problem. I was putting on the roller rockers and went to spin the engine over to do the last few and it wouldnt rotate the whole way around. Seems to me that the valves are hitting the pistons.
Here is what I have:
Stock 289 bottom end rebuilt ~20k ago. Flat-tops w/ small reliefs
Comp Cams XE274H (.520 int/.523 ext)
Comp Cams double roller timing set
'70 351 Heads w/ 1.94/1.60 valves (CC'd @60)
Felpro "performance" head gaskets
TFS pushrods (6.950")
When I first put the cam in and used my adjustable pushrods to determine the proper length I had clearance issues. To remedy this I used the -4* keyway on the timing set. Problems solved I thought. Can being off by 1 tooth on the cam sprocket cause this? When I tightened the rockers just to the point all slack was gone I was good. When I took it down the additional 3/4 turn (is this correct?) the issues began.
When I picked the cam I forgot to take into account that the heads have larger chevy valves in them. I would image this is the sources of my problem. With as much trouble as the headers caused me going on I have pretty much decided that I would rather swap cams than take the heads back off. If I find that my timing chain is correct I am thinking of stepping down to the XE268H or XE262H (.509/.512, .493/.500 respectively)
What is the best and/or easiest way to get past this? Any help would be greatly appreciated.
Here is what I have:
Stock 289 bottom end rebuilt ~20k ago. Flat-tops w/ small reliefs
Comp Cams XE274H (.520 int/.523 ext)
Comp Cams double roller timing set
'70 351 Heads w/ 1.94/1.60 valves (CC'd @60)
Felpro "performance" head gaskets
TFS pushrods (6.950")
When I first put the cam in and used my adjustable pushrods to determine the proper length I had clearance issues. To remedy this I used the -4* keyway on the timing set. Problems solved I thought. Can being off by 1 tooth on the cam sprocket cause this? When I tightened the rockers just to the point all slack was gone I was good. When I took it down the additional 3/4 turn (is this correct?) the issues began.
When I picked the cam I forgot to take into account that the heads have larger chevy valves in them. I would image this is the sources of my problem. With as much trouble as the headers caused me going on I have pretty much decided that I would rather swap cams than take the heads back off. If I find that my timing chain is correct I am thinking of stepping down to the XE268H or XE262H (.509/.512, .493/.500 respectively)
What is the best and/or easiest way to get past this? Any help would be greatly appreciated.