Degsy Posted December 30, 2008 Share Posted December 30, 2008 What about points, condenser, plug leads and have you checked the distributor cap,they are a poor design especially the carbon brush being a fixed item as opposed to the replaceable type and I would definitely have the carb set by a tuning specialist, I'm lucky as a garage owning friend is a whizz on carbs.Other thing, have you ever cleaned the valve in the pipe which runs from the oil filling tube to just below the carb,won't affect the running too much but if it's blocked will cause pressure in the block which will contribute to the oil seal problems which most if not all GMC's suffer from. Quote Link to comment Share on other sites More sharing options...
Richard Farrant Posted December 30, 2008 Share Posted December 30, 2008 What about points, condenser, plug leads and have you checked the distributor cap,they are a poor design especially the carbon brush being a fixed item as opposed to the replaceable type and I would definitely have the carb set by a tuning specialist, added to that, check valve clearances............and although it would not appear to be related, check for any dragging brakes. Quote Link to comment Share on other sites More sharing options...
Degsy Posted December 30, 2008 Share Posted December 30, 2008 added to that, check valve clearances............and although it would not appear to be related, check for any dragging brakes. I was wondering where you were:???, good points though Richard, I should have remembered those:embarrassed::tup:: Quote Link to comment Share on other sites More sharing options...
R Cubed Posted December 31, 2008 Author Share Posted December 31, 2008 (edited) What about points, condenser, plug leads and have you checked the distributor cap, they are a poor design especially the carbon brush being a fixed item as opposed to the replaceable type Points new ok and gapped right. Condenser good, clean, Insulation tested as per Clive, knew this years ago. Plug leads in good condition, no spark tracking in the dark so can assume ok. distributor cap clean, oil free, no cracks, carbon bump ok tight and not worn, same for rotor arm. I would definitely have the carb set by a tuning specialist, I'm lucky as a garage owning friend is a whizz on carbs. This has crossed my mind, on the to do list. have you ever cleaned the valve in the pipe which runs from the oil filling tube to just below the carb, not on oil filler :??? do you mean the one from the top of the rocker cover to just below carb ? thought it was just a pipe will check. Something else to put on the to do list. Something which has also sprung to mind, does any of the GMC owners out there know if these engines are prone to wearing cam lobes down !!!! How much lift should there be at the valves between open and closed ??? Come on check those manuals for me.... R. F. <quote> added to that, check valve clearances............and although it would not appear to be related, check for any dragging brakes. Valve clearence done as per TM manual Brakes all good never drag, regularly checked and greased. Edited December 31, 2008 by R Cubed Quote Link to comment Share on other sites More sharing options...
Degsy Posted December 31, 2008 Share Posted December 31, 2008 Yes you are quite right about the pipe, typing without putting brain in gear,:embarrassed: it is mentioned in the TM as an item that requires servicing. The valve is at the manifold end and basically consists of a small ball and a spring working against a restrictor,the spring is prone to breakage and the valve to blocking with crud. IIRC it is taper threaded but its best to use ptfe tape when reassembling. Quote Link to comment Share on other sites More sharing options...
42 chevy Posted January 5, 2009 Share Posted January 5, 2009 Getting back on topic here, AC Delco 44 were the original plugs that were installed, They are still available thru ebay US. John Gott Quote Link to comment Share on other sites More sharing options...
ashley Posted January 5, 2009 Share Posted January 5, 2009 Getting back on topic here, AC Delco 44 were the original plugs that were installed, They are still available thru ebay US. John Gott If no luck, try and find someone in to older Vauxhalls or Bedford's (owner clubs) i know champion do an equivalent but they were rubbish in my old Bedford van. Ashley Quote Link to comment Share on other sites More sharing options...
Degsy Posted January 5, 2009 Share Posted January 5, 2009 Getting back on topic here, AC Delco 44 were the original plugs that were installed, They are still available thru ebay US. John Gott Tried 'em once......didn't like 'em:nono::-D Quote Link to comment Share on other sites More sharing options...
N.O.S. Posted January 6, 2009 Share Posted January 6, 2009 :idea: Is it reasonable to conclude that NGK plugs seem to suit the operation of restored jimmies (i.e. bumblimg about and not carrying too much weight) better than most others? :??? I can certainly say that since using the hotter NGK plugs I have had no oiling up trouble - they stay remarkably clean. Quote Link to comment Share on other sites More sharing options...
Degsy Posted January 6, 2009 Share Posted January 6, 2009 :idea: Is it reasonable to conclude that NGK plugs seem to suit the operation of restored jimmies (i.e. bumblimg about and not carrying too much weight) better than most others? :??? I can certainly say that since using the hotter NGK plugs I have had no oiling up trouble - they stay remarkably clean. Exactly what I've experienced, wouldn't use anything else. Quote Link to comment Share on other sites More sharing options...
Richard Farrant Posted January 6, 2009 Share Posted January 6, 2009 I can certainly say that since using the hotter NGK plugs I have had no oiling up trouble - they stay remarkably clean. Spark Plug technology has progressed a long way since the 1940's, if those AC 44 plugs are old stock or not of a modern type then NGK will give better performance. I think NGK were the first to use a copper core, others followed, this and other features, gave a wider heat range, giving better performance. Sometimes an old engine oils plugs so you go for a hotter grade, next number up, etc., with these modern plugs the heat ranges tend to overlap adjacent grades. In my Bedford, I use Champion J8C, which is a copper core, denoted by the C suffix. They have been in there for years and still good. Quote Link to comment Share on other sites More sharing options...
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