Ken dropped by late this morning and we started going through my new old truck. All valves except one intake were about 3-5 thousandths loose. (Using Nate's hot adjust method). All plugs looked good. Gaps varied from 0.027" through 0.035". Set them all to 0.032". Plugs are AC 43 type, pretty cold. When they need changing I'll put in the specified AC 44 type plugs. Tried to set timing according to the maintenance manual (350 RPM), but no luck. Timing stayed too far retarded even with distributor turned max counter clockwise. The BB was just starting to show in the window with the distributor turned max CCW. Maintenance manual DOES NOT SAY to remove and plug vacuum advance line, so I assume that timing is supposed to be set with vacuum advance operating. Then I noticed that the vacuum advance did not seem to be working. I connected a Mighty Vac to the vacuum line where it leaves the carb. Could not pull a vacuum on the advance unit. Looks to have a bad diaphram. Anyone have a source for a vacuum advance unit for a '52 228. NAPA, O'Reilley's and Rock Auto did not shown one. Is the GMC distributor the same as a Chevy distributor? Chevs of the 40s vacuum advance http://www.chevsofthe40s.com/detail/6003/Chevrolet_Vacuum_Advance_Bracket_With_Timing_Mark_90_To.html for 39-55 trucks. Cylinders 1-3 and 6 compression was about 125 pounds. 4 was around 115 pounds. 5 was only around 85 pounds. Oil shots into 4 & 5 made little/no difference. Will eventually need to look into this, but for now I just want to enjoy my new old truck. Then we went to Strack's and ate BBQ. Thanks again Ken. Couldn't have done it without you.
Check this... By gum, are you in luck, Bill! I bought one with my disc set because of the same problem. My new one snaps right back as per Nate's suggestion. After I pulled the distributor, put the new one on and found out I had the same damn problem, it was then that I realized when I *first* pulled the distributor for engine cleaning, paint and all, when I put the distributor in, I didn't realize the front of the vacuum advance collar was riding high and therefore binding its movement.. Loosing the bolt that pegs it to the block and gently tapping the collar (towards the radiator side) drew the front down and lo and behold, distributor snappage! In short, make sure the color is flush with the block before spending $$$. If yours IS toast, guess what I can send you? A perfectly good original! Let me know~ 83-274 (1937-62) Vacuum Advance - 6 Cylinder 37-62 $29.95
Well, I tried to pull a vacuum on it and no vacuum occurred. I was at the carb end of the line, so it it possible the leak is somewhere in the line, not the diaphram. I didn't have the necessary fitting to connect the Mighty Vac directly to the vacuum advance unit on the distributor. I'll pick up the fitting tomorrow AM and try again. I see that part number is 83-274 (1937-62) Vacuum Advance - 6 Cylinder 37-62 $29.95 is from our host Classic Parts. Their listing does not specifically say that it fits both Chevy AND GMC, but I looked at LMC's web site and it does say fits both.
Try this, Bill. Go out and grab right below the distributor cap and twist the distributor counterclockwise. It should move without much effort that direction. Then let go. The distributor should snap right back. If it doesn't, check to see if the front of the mounting plate is stuck up higher than the back. All the grit and grime on the shaft can bind it if it's been sitting "idle" for a while. When I tried this with my old one, it didn't even think of "snapping back". But when I put my new one on, it didn't either. That's when I discovered how much of a difference a LITTLE makes! Once I checked my old one, I was embarrassed to see it worked as nicely as my new one. Details, details~ It's yours if you want to give it a go!
BTW, Bill, you might want to reread my earlier post. The part inside the ( )'s might help that make more sense. (I hope.)
Got it~ I'm thinking an F4 tornado would have a hard time sucking enough air to get a buttoned down vacuum advance to advance. So, would you like for me to send you my old one? It's probably fine. Otherwise, it'll just hang around here collecting dust. Let me know.
I'll pass on your old one Zig, but thanks for verifying that Chevy and GMC parts are the same. I'll order a new one from our host before the weekend is up if I can't find a reference to a NAPA or O'Reilley's part number.
The guys over on the OldGMCTrucks forum straightened me out. Turns out I was loosening the locking bolt for the "octane selector", not the main clamp for the distributor. I'll try again in the morning when Ken isn't around to screw up my thought process.
I had to buy from the host to get correct part I too had problems with my Vacuum Advance and ordered from my local trusted NAPA dealer. He toiled over the catalogs and finally found the correct part. He is the owner, very experienced and 99.9% is spot on. However, when the part arrived, it looked nothing like what was on the truck. I suppose it could have still worked, but I had not the time nor money to waste, so I sent it back and ordered from our host. The part arrived, looked just like the one on the truck, and the CP catalog and worked as expected.
I will be curious as to what you find! This is something that I have been meaning to look into on my truck, but just haven't. It would be nice to verify that it all is working well. I just don't know... Thanks Bill
L O N G Motor Progress ! Sounds good ! . I'm far from my shop manuals , does it really say 350 RPM tickover ? . I ask because that's really slow and below 500 RPM the dissy's flyweights tend to snap in and out a bit , causing erratic idle timing . Once you get it up and running , drive it a bit and do a hot compression test , don't forget to prop the throttle wide open and crank until the gauge's needle stops rising.... FWIW , adding a Pertronics " Ignitor " points replacement to your original dizzy will wake up that L O N G Motor more than you can imagine ~ ty it , you'll like it ! .
Nate: Yes, 350, but only for setting timing. Book says mechanical (centrifugal) advanve starts at 400 so they have you take idle down below that to set timing, then increase back to 450 for normal operation. One more thing... I commented above that the procedure for setting timing DID NOT SAY to disconnect the vacuum advance. I know that is normally done, but find it unusual the the factory book did not say to. Is that just one of those things the book just assumes you know to do? Or is the timing actually set with the vacuum attached? In my case (blown diaphram in the advance unit) it wouldn't have made any difference. Maybe the vacuum connection in my carb (Carter YF) is ported, so you would not need to disconnect it. Comments PLEASE! 2nd one more thing.... Adjusting idle mixture screw seems to have very little effect on the idle quality. I can crank it in or out more than 1.5 turns with no noticable change. -Bill
Oops ~ Sorry Bill ; You're correct : the vacuum signal to the dizzy is ported , always & so @ idle there should be NO vacuum signal but the *instant* you open the throttle , there MUST be a vacuum signal . If the idle mixture screw makes 0 difference , there's either a vacuum leak or the carby has crud in it ~ engine idling try removing the screw ~ just as it backs all the way out and falls into your hand , the engine should momentarily gain speed then load up on excess fuel and stall out . DON'T loose the idle mixture screw spring ! . If you can remove the mixture screw without stalling , get a Foo-Foo can of engine starting fluid (Ether , remember carby cleaner is DEADLY STUFF ~ DO NOT USE IT !!) and put a plastic snorkel into it's nozzle , you may have to swap the spray head , and spray Ether into the open mixture port as the engine idles , as fast as you can adjust it to idle ~ expect the engine to die but that oughta clear it out ~ if not , stop the engine and hold the throttle well open as you spray into the open idle mixture port , WEAR SAFTEY GLASSES and peer down the venturi , you should be able to see a thin stream of Ether come squirting out the idle port once it's clean . I hope this is helpful ? . Back to work to - morrow so expect slow(ish) replies .
