Posted by Tim Holloway [69.54.28.229] on Sunday, October 18, 2015 at 21:06:35 :
Hi All,
My M37 engine runs really well. Until you show it a hill and then it really loses power. I have always just figured that this was normal until the recent West Virginia Road Rally. While travelling in a line of like powered and geared trucks, we would get to a hill and the trucks in front of me would all pull away from me and thye ones behind me would no doubt be cursing me!
Matt from VPW was at the Rally and drove my truck and agreed that it was lacking power on the hills. He suggested timing it to 4 degrees and to play with the carb, and to try to get 17 inches of vacuum on a gauge. He also suggested that it might be the governer.
Yesterday I re-timed it, advancing it to 4 degrees and took it for a test drive. There is a hill near my house that I can just barely make it over in 4th. No difference. I brought it back into the shop (out of the snow no less) and installed a rebuilt carb that I had bought several years back as a backup. I pulled the top cover off first and it looked brand new inside. I installed it and started it up. It idled, and then stumbled upon accelleration. I tried the idle mixture screw with no change. Took it for a test drive and barely made it a couple hundred yards down the road. I could only keep it running with the choke on. I limped it back to the shop and sprayed carb cleaner around the carb looking for a vacuum leak but didnt find anything. Took the rebuilt carb back off and then took my old carb apart and blew out all of the passages etc. Reinstalled it and took it for another run and I was right back to where I had started.
Now, I am wondering if the valve timing might be off a tooth? Short of pulling the front cover off, how would you test that? This truck will do 55 on a (long) flat road, never overheats and like I said, runs great. I did a full tune up this spring with no real difference in performance noticed.
Any input is appreciated.
Thanks,
Tim
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