Thread: inline six woes
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Old July 26th, 2014, 01:23 AM
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Default Re: inline six woes

Quote:
Originally Posted by Pops View Post
Thanks Doug!
Your input is valued. As much evil as we find on the internet, its also an amazingly wonderful asset. I have gotten more information through guys like yourself than anyone else. Never need to apologize. I am still learning what to call things, and, sometimes I don't explain myself well enough.
I have two vibrations going on:
--One is sitting at light and engine is not silky smooth and therefore I feel and hear vibration transfer through cab. My mirror shimmies until I give it a little gas. This is part of the tuning I have been working on. Might add, its more of a vibration than rough running. (May easily be part of valve problem your are referring to.) To be honest, somedays the truck seems to run and smell a little differently. I sometimes want to blame my concerns on a watered down batch of gas, and/or the personality of the Rocheseter. I've also had times where a slightly richer setting helps with vibration.

--The second vibration feels like wheels out of balance between 10 and 35 mph. Whether going up in speed or coming down in speed. It just started doing this in the last month. My first inclination was tie rod components or ball joints as they are older and have deteriorated grease cups. It could be tire belts? But, yesterday I felt a clunk in rear on take off. This just started. Man at parts store said he would bet on u-joints.

Regarding the carburetor, I have a Model B if pictures tell the difference. I don't have a tag (remanufactured) but it does say BC on back side. I believe the "C" represents auto choke though mine is manual. I'm going to check fuel pressure soon as I have read that too much pressure will cause flooding; even leaking. My gasket at float bowl is always moist.

Better stop here or this will become a book - lol.
Have a great day.
I also appreciate the help and education I get on this forum from the experienced folks posting here and hope to pay a little back now and then with some small things I have ran across trying to keep old beaters running on the cheap!-LOL!

Low volume flooding can cause exactly what you are describing, Pops. At idle small amounts of extra fuel will cause the rough idle but soon as more gas is required it will smooth out. The top bowl gasket will stay damp while idling quite often but may actually dry out off idle. The damp gasket is because the fuel bowl is too full possibly from a high float level or a damaged or worn out needle or seat or a float that doesn't float well anymore. If you have the mechanical fuel pump I really doubt it is over pressuring the needle, seat and pressure from the float unless there are the above described damage or wear.
There could also be debris stuck in the seat holding the needle open.
You probably know that the Model B is a dual float carb. They are great carbs and will last forever. I've got a couple and the only reason I went with the Model M is to get the "kick down" type manual choke. my B's require a throttle cable to keep the idle fast while opening the choke. I drive my '55 in pretty cold weather and like the high idle no choke warmup.

The clunk you described definitely sounds like a u-joint, and a bad one can cause vibrations at different speeds and load conditions.

Your carb may be one of these.

DAC
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Doug Crawford
Rapid City, SD

1970 GMC K5 Jimmy Mom drove 30 years
1972 GMC C2500 owned since 1979
1955 GMC 100 driver-project
2006 GMC Yukon Denali---wife's truck

Hope to have a '60 GMC Suburban again someday
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