40 V8 compression change all cylinders same time

Was the dye all on one side or did you have low spots around the seat ?
If they used the guide with a 11/32 pilot and it wobbles around you don´t get a consistent cut...you have the cutter/stone shatter around badly.
 
For all that are interested here is where my situation is. When I started this I thought 3 days and it will be done. It has taken 3 months to get where I am now. To make a long story short I had a friend come by on Memorial Day that has flathead engine experience. The valve base in the engine measures 1.5 inches. We measured the valve seat in the block and found it also to be 1.5 inches. We took a 30 degree stone and ground all the seats to narrow them down to 1.4 inches. Lapped the new stainless steel valves and the lap line was about 1/16 inch wide in the middle of all the valves base. Put the engine back together and did an air pressure leak down test. Compression was 60 to 80 lbs. on the cylinders. Put a 6 volt battery in the car and did a compression test with the starter. Same readings of 60 to 80 lbs. on each cylinder. Really discouraged at this point. Prayed about it and decided we had nothing to lose by putting in a 12 volt battery and doing a compression check off the starter. Turned the engine over with the 12 volt battery and we got 120 lbs. of compression on each cylinder. Now what? Why is this happening? Went and talked to an older worker at a local machine shop. Told him the measurements on the valve seats, told him what the valves looked like after lapping, the compression readings for all the ways we checked the compression. He told us he had been in this same situation before and could not explain it. He told us if everything looks good put it together and drive it. So, we put it together not knowing anything else to improve the situation. Got the engine together and hit the starter with the 6 volt battery. Engine started up and sound very good. Ran it until it got up to normal temperature and shut the engine off. Hit the starter again and the engine started instantly. Car has more power than it did, starts better than it did, and runs cooler than it did. I have been driving it as the weather permits with improving performance from the engine each time I drive it. Cannot explain the difference in the compression checks mentioned, but it is greatly improved over what I had when I started. Starts, runs, and drives with ease. I am going to drive it for a few more weeks before I even think of doing another compression check. What do you think about all this?
 
well by golly that is good news. odd that readings between 6 and 12 volts should change, more cranking rpm "should" have nothing to do with it. you spin the motor over 3 times when checking your compression gauge? at any rate, happy motoring, and i would do a couple quick oil changes to be sure of getting the valve grinding crud out. best wishes, skip
 
When you took the 6 volt compression check, did you block the throttle open and let it cycle through at least 4 compression cycles on each cylinder?
 
Maybe I missed it, but I didn't see anywhere that you did the compression checks with a warm engine. Perhaps all the checks were with a cold engine except for the final check while warm? I'm thinking warm vs cold would give very different readings.
 
ford38v8 said:
Maybe I missed it, but I didn't see anywhere that you did the compression checks with a warm engine. Perhaps all the checks were with a cold engine except for the final check while warm? I'm thinking warm vs cold would give very different readings.
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All compression checks I did were cold engine. Great deal of work to put all the engine back together to do a warm engine check not knowing if the problem was corrected.
 
120 lbs compression with a cold engine before the rings are seated? Even on 12 volts, I don't think you have anything to worry about.
 
First, well done. You now have a proper valve job. As for the compression discrepancy, a slow cranking engine gives more time during the test for the air in the cyl to leak past the ring end gaps and the relatively dry cylinder walls you may have had at the time of the tests. My tired '41 flathead checked at 70# with a 6V battery and now checks at 105# on 12V. My guess is you're going to be just fine now that the compression isn't being pushed past the poorly sealing intake valves and into the manifold. That situation makes for a very poor running engine. Well Done!


Terry
 
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