What's an acceptable compression reading for a 68 200 cu in 6 cyl ? As far as I know the engine has never been rebuilt and God only knows how many miles it has on it. Thanks...

 

Here's a good thread on Fordsix explaining how to do it and what you should look for in results

 

Need to buy air compressor to hold valves closed when replacing valve stem seals. From the numbers in this post it looks like a compressor with a maximum of 115 psi might not be enough???

 

here's another trick I once read about. BUT i have never tried it, so it would be great if someone could chime in:
remove spark plug and shove a rope into the bore. keep a good bit sticking out so it cannot fall in. When the cylinder is filled with rope the valve obviously cannot go down.

That even a good idea? in my opinion there's no guarantee that the airpressure will keep the valve up there. the slightest leak and it'll fall

 

BTW: i'd measure first before I'd install anything. otherwise you'll never know what improved

 

Well the rope isn't there to pressurize the cylinder, just to hold the valve closed by giving the valve no room to open. You'd have to put the piston and TDC, then put the rope in.

I haven't tried it either

 

Actually, the idea behind the rope is to have the piston down in the bore some. Feed in some rope and raise the piston. This pushes the rope against the valves with a little bit of pressure. I have heard of this being done but never had a need to try it. It sounds good in theory. May want to use a nylon rope(or cord) or something that won't fray easily. Like clothes line?...but a lot smaller?

As for compression...don't know if you found your answer to that yet, but worry more about all cylinders being close together. Like witthin 5% of each other. I would expect for an older motor to still see in the neighborhood of 120lbs.

 

What's the best way to get the piston at TDC - just turn the fan? Also, how do you tell when the piston is at TDC?

 

I've tried turning the engine with the fan before and sometimes the belt slips and it just feels like I'm putting a lot of strain on the fan and/or the water pump. I'd use a breaker bar on the nut on the crank pulley.

 

The easiest way to turn is with a socket on the crank pulley. If you stuff something in the hole, you won't get to TDC. Just high enough to contact the valves.