Push rod trouble for my 80"
Road Master
Joined: Jan 2008
Posts: 1,187
Likes: 8
From: Montgomery, AL
This has always messed with me also. Compression vs. exhaust?? But I know now dropping the distributor in on the wrong stroke she will not run on a SBC. It always causes flame shows out the carb. It just baffles me on the adjusting on the valves though with the tdc exhaust or compression? This is probably the reason I've never swapped my cam.
Outstanding HDF Member
Joined: Nov 2013
Posts: 2,358
Likes: 34
If I read the FSM and everything here right if you line up the timing mark on the pinion and cam gear and breather gear you can't be off. There is no 180 degrees to be off its TDC on the pinion every time around.
Road Master
Joined: Jan 2008
Posts: 1,187
Likes: 8
From: Montgomery, AL
Right on the tdc but on what stroke compression or exhaust. The only way I know is putting my finger over spark plug hole.
KP you are right about timing, but TDC is two times on a 4 stroke engine, 1 compression and 1 exhaust. When installing pushrods (solids) you need to be on compression(both valves closed) this is the cam base circle everyone talks about. If you drop the rods in place and tie the covers up so you can see, rotate the engine until the rods are at their lowest point for that cylinder, then do your tightening sequence. My thought is vnilla tightened his boxes with the cam in the (valves open...exhaust position).
Outstanding HDF Member
Joined: Jul 2013
Posts: 2,874
Likes: 36
From: Houston, TX
Guys, I really think the OP is trying to do both cylinders at one time and it doesn't work that way. He either needs to learn what the compression stroke feels like on the particular cylinder he's working on when watching the pushrods when they're in the tubes sitting on the lifters, and rotating the back wheel in high gear, or stick a straw in the cylinder through the spark plug hole and watch it. OP, once you have determined that you are on the base circle of the cam, the compression stroke for that particular cylinder, and the pushrods are at their lowest point, and if the rockers were on the valves would be "closed", THEN you can bolt the rocker box on and bleed down the lifters. You'll have to wait 5 minutes or so for the lifters to bleed down so you can rotate the push rods, THEN you can turn the motor over and go on to the next cylinder. It doesn't matter which cylinder you start on, but you CAN NOT do BOTH at the same time.
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