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Posted by Mike Hernke [63.151.218.18] on Monday, August 09, 2010 at 09:52:53 :
I am working on a flat head in a 1937 dodge (I think it is a 218) and it runs good at idle but when loaded in back fires through the carb. I have tried timing it is currently at +5 at idle and +20 when revved up (no vacuum advance) but I have tried -10 to +10 static with no change. I tried the carb off my old 230 which always ran great just in case. Then checked compression which was a little low at 118 but was consistant in each cylinder. I then decided maybe a valve was too tight and not closing so I checked valve lash which is .014 across the board (mostly cold). I also looked at the valve springs and there is no obvious problem there. Lastly I finally decided to check the vacuum readings which I had avoided because there were no easy test ports and I had to come up with some adapters. On the newer of two gauges I tried I had a pretty bad fluctuation between 10-17 in-hg. The manual I had available says 18-21 is acceptable and that a large fluctuation idicates worn valves. I tried adjusting the idle mixture but it had almost no effect on the vacuum. So the question does this sound like worn out valves or seats? could the cam timing be off one tooth? The engine does not smoke and has a reasonable smooth idle would it be worth doing a just a vavle job or is it time for a full rebuild?
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