mikemids Posted June 9, 2013 Share Posted June 9, 2013 After replacing a damaged valve in my Morris C8, i'm having trouble with it running? I am guessing its more to do with the timing than anything else as I obviously had the distributor off etc.. I have gapped the new valve, and checked the others, although it ran like a dream prior to the one breaking.. I marked the distributor up prior to removal , and have refitted it back to the same place, the Morris starts up like a dream, first turn etc, it ticks over nicely, and revs really well, the problem I am finding is when I road test it... as soon as get up the gears into 4th and 5th it starts to pop through the air filter and I just cant get any speed, 20mph max, I have rotated the distributor either way and tried it, but this doesn't seem to make any difference? Turning it more one way increases the idling speed but creates more bangs back through the air filter, turning it the other way reduces the back firing but I have less power when driving? I have had new points, condenser, dist cap etc.. As I say it ran superb before the valve issue so I cant see anything other than timing? Any suggestions would be really appreciated! Quote Link to comment Share on other sites More sharing options...
paulbrook Posted June 9, 2013 Share Posted June 9, 2013 Pretend you didnt do anything and start (again) from scratch. Assume nothing (eg "its a new distributor cap so it can't be that...."). Check all the fuel stuff first up to and including valve timing. Make sure they all close too. Things to look for include a lazy pump (the seal around any sediment bowl is a classic failure), blocked jets, water or muck in the carb, leaky joints. Then do the same with the electricals; clearances, terminals, fit, leads, plugs static timing. What were the circumstances of the valve failure? Did it jump or was it pushed? This may give us a clue. Quote Link to comment Share on other sites More sharing options...
mikemids Posted June 9, 2013 Author Share Posted June 9, 2013 Pretend you didnt do anything and start (again) from scratch. Assume nothing (eg "its a new distributor cap so it can't be that...."). Check all the fuel stuff first up to and including valve timing. Make sure they all close too. Things to look for include a lazy pump (the seal around any sediment bowl is a classic failure), blocked jets, water or muck in the carb, leaky joints. Then do the same with the electricals; clearances, terminals, fit, leads, plugs static timing. What were the circumstances of the valve failure? Did it jump or was it pushed? This may give us a clue. Not sure what caused the valve failure, I was travelling to an event a couple of years ago and one just broke? Ok I will look at everything from scratch again which is mildly irritating as I have double checked everything but I guess I need to do so thoroughly... I had hoped the loss of power and backfiring at higher speeds and under pressure would have been a clear sign of something recognisable... WISHFULL thinking I guess.. Thanks. Quote Link to comment Share on other sites More sharing options...
cosrec Posted June 9, 2013 Share Posted June 9, 2013 you got plug leads 0n right Quote Link to comment Share on other sites More sharing options...
mikemids Posted June 9, 2013 Author Share Posted June 9, 2013 you got plug leads 0n right As far as I am aware but will double check, you mean correct firing order? Quote Link to comment Share on other sites More sharing options...
Richard Farrant Posted June 9, 2013 Share Posted June 9, 2013 ... as soon as get up the gears into 4th and 5th it starts to pop through the air filter and I just cant get any speed, 20mph max, I have rotated the distributor either way and tried it, but this doesn't seem to make any difference? Turning it more one way increases the idling speed but creates more bangs back through the air filter, turning it the other way reduces the back firing but I have less power when driving? I have had new points, condenser, dist cap etc.. As I say it ran superb before the valve issue so I cant see anything other than timing? Any suggestions would be really appreciated! Hi Mike, Did you check the cylinder head face for bowing when you took it off? If not, then I would not mind betting this is due to a warped cylinder head and when tightened back down it will not pull it straight, and the popping through the air filter is due to a compression leak between two cylinders. If you have a compression gauge, check the cylinders and my guess is no's 2 and 3 will be lower than the other two and equal to each other. Seen this many times before and only recently had to deal with one. The answer if bowed is to take the head to a machine shop to have its refaced. regards, Richard Quote Link to comment Share on other sites More sharing options...
paulbrook Posted June 9, 2013 Share Posted June 9, 2013 Not sure what caused the valve failure, I was travelling to an event a couple of years ago and one just broke? Ok I will look at everything from scratch again which is mildly irritating as I have double checked everything but I guess I need to do so thoroughly... I had hoped the loss of power and backfiring at higher speeds and under pressure would have been a clear sign of something recognisable... WISHFULL thinking I guess.. Thanks. Irritating definitely - there is little worse than a fault whos cause is unclear. The compression test Richard suggests is a damm fine idea - I did a Tilly with a crack between the cylinders (see tales from a big shed), but unlike your comments about a quick start and smooth tickover the Tilly was seriously lumpy at any speed. Frustratingly though the compression tests at cranking speed were all on the money, it was only when it was actually running did the cracks (there were two in a wedge shape) open and cause chaos. If the valve went a while ago then I assume that the engine has been stood idle for the same length of time - and all sorts of simple things can happen. Could I clarify that when you say backfire you are talking about banging out of the exhaust (normally very retarded timing or a stuck exhaust valve or two) rather than popping back through the carb (very weak mixture, over advanced timing, plug leads on wrong (although i doubt it would run smooth at tickover in this condition) or crossover where a spark from one lead jumps over to another (cracked distributor cap or duff and leaking leads))? As an aside I have had tons of trouble from recent purchases of so called new items - particularly spark plugs. I did a 28hp non-running bedford recently that had all new ignition components - and it only ran when I put all the old stuff back on! So if you have spares of anything, including rotor arms, swap them out one at a time and give it a go. Quote Link to comment Share on other sites More sharing options...
mikemids Posted June 9, 2013 Author Share Posted June 9, 2013 Hi Mike,Did you check the cylinder head face for bowing when you took it off? If not, then I would not mind betting this is due to a warped cylinder head and when tightened back down it will not pull it straight, and the popping through the air filter is due to a compression leak between two cylinders. If you have a compression gauge, check the cylinders and my guess is no's 2 and 3 will be lower than the other two and equal to each other. Seen this many times before and only recently had to deal with one. The answer if bowed is to take the head to a machine shop to have its refaced. regards, Richard Hi, no I didn't check this, must admit I didn't know it could happen? I don't have a compression gauge but will happily buy one to test this, but I presume I need one with the same thread size as the plugs? Quote Link to comment Share on other sites More sharing options...
mikemids Posted June 9, 2013 Author Share Posted June 9, 2013 Irritating definitely - there is little worse than a fault whos cause is unclear. The compression test Richard suggests is a damm fine idea - I did a Tilly with a crack between the cylinders (see tales from a big shed), but unlike your comments about a quick start and smooth tickover the Tilly was seriously lumpy at any speed. Frustratingly though the compression tests at cranking speed were all on the money, it was only when it was actually running did the cracks (there were two in a wedge shape) open and cause chaos. If the valve went a while ago then I assume that the engine has been stood idle for the same length of time - and all sorts of simple things can happen. Could I clarify that when you say backfire you are talking about banging out of the exhaust (normally very retarded timing or a stuck exhaust valve or two) rather than popping back through the carb (very weak mixture, over advanced timing, plug leads on wrong (although i doubt it would run smooth at tickover in this condition) or crossover where a spark from one lead jumps over to another (cracked distributor cap or duff and leaking leads))? As an aside I have had tons of trouble from recent purchases of so called new items - particularly spark plugs. I did a 28hp non-running bedford recently that had all new ignition components - and it only ran when I put all the old stuff back on! So if you have spares of anything, including rotor arms, swap them out one at a time and give it a go. Hi Paul, thanks, yes its been stood for over 2 years, although I have run the engine from time to time once I rebuilt it, guess it was stood idle for about 6 months before it ran again? The banging is actually the "popping " you refer to, comes through the air filter and almost lifts the lid! I do get the occasional bang from the exhaust, but rarely. I am actually now wondering if I have messed the leads up? I did put my old plugs back in as it wouldn't start with the new ones I bought, and I do swap the old and new elecs about to see if there is any improvement but nothing dramatic. I have been reading on here about unleaded fuel causing valves to stick? If it sounded rough on tickover or in 2nd gear etc I could understand but its when driving and in 4th / 5th gear, it even died twice on Saturdays road test. maybe fuel starvation?? Quote Link to comment Share on other sites More sharing options...
Richard Farrant Posted June 9, 2013 Share Posted June 9, 2013 (edited) Hi, no I didn't check this, must admit I didn't know it could happen? I don't have a compression gauge but will happily buy one to test this, but I presume I need one with the same thread size as the plugs? Hi Mike, I am not sure if you have 18mm plugs or the normal 14mm, but my compression gauge has both thread sizes, so check that out. also, if you have not done a comp check before, make sure the throttle is wide open when doing this test, with all plugs removed. Popping in the air filter if due to a warped head and blowing gasket, is one cylinder firing through to its neighbour when it has an open inlet valve. regards, Richard Edited June 9, 2013 by Richard Farrant Quote Link to comment Share on other sites More sharing options...
mikemids Posted June 9, 2013 Author Share Posted June 9, 2013 Hi Mike,I am not sure if you have 18mm plugs or the normal 14mm, but my compression gauge has both thread sizes, so check that out. also, if you have not done a comp check before, make sure the throttle is wide open when doing this test, with all plugs removed. Popping in the air filter if due to a warped head and blowing gasket, is one cylinder firing through to its neighbour when it has an open inlet valve. regards, Richard ok thanks Richard, I have the ex radio truck, so not sure but will take a plug with me when buying tester.. Quote Link to comment Share on other sites More sharing options...
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