pockers Posted September 5, 2012 Share Posted September 5, 2012 So just as show seaon finishes for the winter i get a noisey ticking sound from the engine - yup exhaust manifold gasket has blown So new gasket and new brass nuts purchased ( old nuts stripped off when removed) Manifold off - cleaned /scraped old gasket off - fitted new one and tightened up nuts All seemed ok but lessthan 2miles now its blowing again - tightend nuts some more but still blowing from top middle Face off manifoled is a bit pitted but not too bad(or so i thought) So my question is ----- Do i try tightening the nuts some more - scared that i might strip nuts or worse snap the bolts? Fit two gaskets? Use a belt sander on the manifold to get rid of pitting? Or a more sensible suggestion? Thanks Quote Link to comment Share on other sites More sharing options...
Big ray Posted September 5, 2012 Share Posted September 5, 2012 Put a straight edge along the face of the exhaust manifold to check that its not warped, if its warped you will need to get it faced, two gaskets are not the answer. Quote Link to comment Share on other sites More sharing options...
pockers Posted September 6, 2012 Author Share Posted September 6, 2012 Many thanks What sort of places are able to resurface them? Ie what sort of place should i search for ? Quote Link to comment Share on other sites More sharing options...
Big ray Posted September 6, 2012 Share Posted September 6, 2012 Many thanks What sort of places are able to resurface them? Ie what sort of place should i search for ? Automotive Engineers, ask one of your local workshop garages, they will know someone. Quote Link to comment Share on other sites More sharing options...
Pete Ashby Posted September 6, 2012 Share Posted September 6, 2012 Ray is right, you need to get the exhaust manifold faced but remember you will need to take both inlet and exhaust in together and have them both faced off by the same amount, as Ray points out in his last post an auto engineering workshop will know what needs doing. Pete Quote Link to comment Share on other sites More sharing options...
griff66 Posted September 6, 2012 Share Posted September 6, 2012 (edited) so for a skim on manifold you would want distance between carb and engine shortened by equal amount? me confused! Edited September 6, 2012 by griff66 Quote Link to comment Share on other sites More sharing options...
Pete Ashby Posted September 6, 2012 Share Posted September 6, 2012 so for a skim on manifold you would want distance between carb and engine shortened by equal amount? me confused! No not the carb to inlet flange........ the inlet manifold to block face. Both manifold flanges need to be parallel and and in line vertically with the block face. If this is not the case then when you pull up the manifolds the exhaust manifold will be held off the block face by the inlet manifold by the amount you have had machined off. I should say I have assumed that the M38a1 has inlet and exhaust bolted together via a hot spot and that you haven't got a multi branch manifold?. Pete Quote Link to comment Share on other sites More sharing options...
pockers Posted September 7, 2012 Author Share Posted September 7, 2012 No not the carb to inlet flange........ the inlet manifold to block face.Both manifold flanges need to be parallel and and in line vertically with the block face. If this is not the case then when you pull up the manifolds the exhaust manifold will be held off the block face by the inlet manifold by the amount you have had machined off. I should say I have assumed that the M38a1 has inlet and exhaust bolted together via a hot spot and that you haven't got a multi branch manifold?. Pete Am slightly confused infact alot confused Quote Link to comment Share on other sites More sharing options...
griff66 Posted September 7, 2012 Share Posted September 7, 2012 if its like my ferret engine ie exhaust manifold bolts directly on to engine block and air intake carb etc is on other side just get exhaust manifold checked for straitness and if necessary get it skimmed level or get new manifold . Quote Link to comment Share on other sites More sharing options...
Pete Ashby Posted September 7, 2012 Share Posted September 7, 2012 Am slightly confused infact alot confused It's me that confused I'm afraid. The penny has dropped, you have the inlet valve in head exhaust in block engine don't you :red: ? Sorry for muddying the water, I thought you had the older up rated side valve. Just do as Ray said in the first place and get the exhaust manifold faced and you'll be good to go with a new gasket. Apologies Pete Quote Link to comment Share on other sites More sharing options...
pockers Posted September 7, 2012 Author Share Posted September 7, 2012 Fantastic Is all clear now Found a handful of auto engineering companies nearish me so will put some phone calls in and see if they can oblige Many thanks for th e help Ill update the thread withthe result Quote Link to comment Share on other sites More sharing options...
pockers Posted September 15, 2012 Author Share Posted September 15, 2012 Ok - found a local auto shop who were willing and able Cost £40 Looking to try and fit it today (got a torque wrench too) With regards the gaskets , do the metal rings insert into engine block or the manifold ? Manual says insert into exhaust port which I'm assuming is the engine block - They are a v tight fit into engine block but just drop into manifold Thanks Quote Link to comment Share on other sites More sharing options...
Degsy Posted September 15, 2012 Share Posted September 15, 2012 You are correct in assuming the port is the block. Quote Link to comment Share on other sites More sharing options...
pockers Posted October 28, 2012 Author Share Posted October 28, 2012 The saga continues got the old one resurfaced put it all back together and the manifold bloomimh well cracked!! So one lump of scrap cast iron! Acquired a new , cleaned up the block and the pipe, new gaskets, some hightemp silicone as well just to be sure put it all together and. Hey presto BUT its still blowing! From the top of the centre two ( can see the blackening) and from the downpipe / flange I must be doing something wrong- surely it cant be this difficult Any help / tips greatfully recieved Quote Link to comment Share on other sites More sharing options...
redneck Posted October 28, 2012 Share Posted October 28, 2012 "I must be doing something wrong" Hi temp silicone for a start. Put it together dry or with a very very light smear of exhaust paste. I assume you are are torquing up the manifold evenly not just winding up the bolts to full torque from slack, possibly why the first manifold cracked. Start torquing the middle bolts first, and work your way out to each end alternating from one side to the other. Retorque the bolts after a 50 miles or so. Quote Link to comment Share on other sites More sharing options...
griff66 Posted October 28, 2012 Share Posted October 28, 2012 is block badly pitted is new manifold flat? if u are bolting up two flat surfaces with correct gaskets cant see how it can leak, have u put straight edge along exhaust ports to check for pitting etc Quote Link to comment Share on other sites More sharing options...
pockers Posted October 28, 2012 Author Share Posted October 28, 2012 Hi thanks for replies New manifold appears flat and checked with straight edge The block itself is v smooth with no apparent pitting, however i have not checked with an edge yet - but i will -if the block is warped are there any solutions? Nuts wise i did tighten up each grDually and only up to torque at last thing but will work from middle out next Exhaust paste? Something like Holts gun gum pastee? Will this be suitable? If not any brand suggestions? Ive used this before and found that it gets very brittle and cracks hence why i used the silicone but this has proved useless On this occassion Unfortunaly i wont be able to look at it till next weekend plus i also now need a new set of gaskets again (costing me a small fortune) Quote Link to comment Share on other sites More sharing options...
Tony B Posted October 28, 2012 Share Posted October 28, 2012 Hermitie do a very useful high temprature gasket in a squirt tin with a variable nozzle. It allows you to go from a very fine bead to a thick dollop. Quote Link to comment Share on other sites More sharing options...
pockers Posted October 28, 2012 Author Share Posted October 28, 2012 Thats basically what i used, a hi temp (300degrees) silicone but it basically wasnt up to the job Quote Link to comment Share on other sites More sharing options...
Richard Farrant Posted October 28, 2012 Share Posted October 28, 2012 It should not be necessary to use any sealer on an exhaust manifold face if it is true and has a good gasket. Sealer, especially silicone is the last thing you need on there as it will not last long before a blow occurs. Hope you are tightening the nuts progressively from the centre outwards. Quote Link to comment Share on other sites More sharing options...
Pete Ashby Posted October 29, 2012 Share Posted October 29, 2012 With regards the gaskets , do the metal rings insert into engine block or the manifold ? Manual says insert into exhaust port which I'm assuming is the engine block - They are a v tight fit into engine block but just drop into manifold Thanks One thing occurs to me are you sure your port inserts are not bottoming out in either the block or manifold I had that problem once with a GMC in this case they were French repros and bottomed out in block and held the manifold off the block face by about 4 thou, impossible to see with a new gasket but held the manifold off the block so it would not compress the gasket enough under torque to form a compression seal. Consequently it would run for a few hours until the exhaust gasses burnt through the gap and gasket and then start to leak again. When you take the manifold off again check for burn/track marks on the block face and or manifold. It may explain why you cracked the first manifold. The simple answer is to put the rings on a flat plate with some wet and dry and rub then down until they locate but do not prevent the manifold block interface without the gasket in place. Pete Quote Link to comment Share on other sites More sharing options...
Richard Farrant Posted October 29, 2012 Share Posted October 29, 2012 One thing occurs to me are you sure your port inserts are not bottoming out in either the block or manifold Good point Pete. I have had to make narrower ones to suit on a few Bedford and Austin engines after the manifold was faced. Quote Link to comment Share on other sites More sharing options...
HWade Posted October 29, 2012 Share Posted October 29, 2012 Yes that could well be the problem I recently replaced a manifold on a GMC and after having the manifold skimmed, I had to narrow down the inserts, an easy thing to forget to check, and as pete said could explain why the first manifold cracked. Regards Howard Quote Link to comment Share on other sites More sharing options...
Pete Ashby Posted October 29, 2012 Share Posted October 29, 2012 Good point Pete. I have had to make narrower ones to suit on a few Bedford and Austin engines after the manifold was faced. Yep been there done that Richard, I think over the years I've had more trouble with those little suckers on six cylinder engines than anything else. The temptation is to just chuck them in the workshop bin but their function is two fold, 1. to locate the ports accurately 2. prevent burn through of the gasket material under high load conditions I also suspect that they help to normalise the heating/cooling stress on long single cast manifolds......... although the number of banana shaped GMC and Bedford manifolds I seen/changed/owned makes me wonder if this is not just wishful thinking on my part :-( Pete Quote Link to comment Share on other sites More sharing options...
pockers Posted October 30, 2012 Author Share Posted October 30, 2012 One thing occurs to me are you sure your port inserts are not bottoming out in either the block or manifold I had that problem once with a GMC in this case they were French repros and bottomed out in block and held the manifold off the block face by about 4 thou, impossible to see with a new gasket but held the manifold off the block so it would not compress the gasket enough under torque to form a compression seal. Consequently it would run for a few hours until the exhaust gasses burnt through the gap and gasket and then start to leak again. When you take the manifold off again check for burn/track marks on the block face and or manifold. It may explain why you cracked the first manifold. The simple answer is to put the rings on a flat plate with some wet and dry and rub then down until they locate but do not prevent the manifold block interface without the gasket in place. Pete Im sorry for sounding so thick - but can u just clarify what u mean by bottoming out? ArQe the gaskets / rings possibly too thick? Yes I am getting leaking gasses and blackening where the gasket is being blown away Quote Link to comment Share on other sites More sharing options...
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