Robert Longstaff Posted June 9, 2017 Report Share Posted June 9, 2017 During my engine rebuild last year I fitted a SS exhaust manifold, as yet unwrapped until making sure all is well during the run-in and shakedown. I have been told by some that I must wrap it or it will run too hot, others that it will reduce underbonnet temperature and improve exhaust gas flow. Others say ceramic is the way to go (if somewhat expensive), and I remember reading that article in TRA, yet others say it can cause the head to run too hot! I have seen examples of supposedly superior grade SS manifiolds rotting out very quickly (a stag, 6 and P6. It has been suggested that this was because the wrap was put on wet and not allowed to dry out fully, so to use the wrap dry. Spoke to 2 highly respected race prep mechanics today who both said I would never get a tight enough wrap without wetting it. While I would always expect to get at least 12 different answers if I asked 6 TR-ers the same question, this one is leaving me very unsure what to do, so she is still unwrapped at the moment. Would appreciate comments, particularly those of a helpful nature Quote Link to post Share on other sites
barkerwilliams Posted June 9, 2017 Report Share Posted June 9, 2017 Does your wallet have too much money in it that you wish to dispose of? My PI is a full SS system and although it gets hot (well it would wouldn't it) There has never been an issue. If you plan lots of continental travel at the height of summer, or want to race, or track days then the increased heat generated could need tackling. Exhaust system & manifold removal is pretty easy so my advice would be to try it naked, if you have a problem that will be the time to splash the cash. Don't tackle problems you may not have. Alan Quote Link to post Share on other sites
Robert Longstaff Posted June 9, 2017 Author Report Share Posted June 9, 2017 wallet quite comfortably emptied thank you. Thats what I am doing, but want to make sure I am not going to do any damage by not wrapping. Thanks, this is exactly the sort of comment I need to hear! Quote Link to post Share on other sites
RogerH Posted June 9, 2017 Report Share Posted June 9, 2017 Hi Robert, the fabricated pipes will let out more heat into the engine bay. This extra heat could annoy the PI. As Alan says - run it and see what happens. Some form of insulation is defo good on Carb cars - evaporation of fuel in float chamber etc. If you choose to insulate then you have a couple of choices. TRactor lagging that must be fitted wet - and will do no harm. Becareful not to get it oily etc as it may present a fire hazard. Ceramic coating - two choices again - Zircoat - not tried this; but those that have have been happy and much lighter in the pocket. CamCoat - I have tried this and am happy. Inside and outside the pipes are coated, The coating has retained its colour (silvery stainless steel). Slightly cheaper than Zircoat, slightly different process. The exhaust gas is much hotter suggesting that less heat is escaping (but I don;t know how much). The head does not run hotter - it all goes out the back. The ceramic coating is a much neater solution the fabric wrap is more in-keeping with our agricultural ancestry Roger Quote Link to post Share on other sites
Peter Cobbold Posted June 9, 2017 Report Share Posted June 9, 2017 (edited) Why keep the exhaust gases hot? - that's only needed for turbo engines. For the PI the faster exhaust gas heat is lost the sooner the gas shrinks and back-pressure drops. I have a 30 years old unwrapped ss manifold and its fine. The PI has a cold air intake. So that leaves radiant heat off the exhaust pipes to the intake manifold, best cured with an ali reflector plate. Peter Edited June 9, 2017 by Peter Cobbold Quote Link to post Share on other sites
RogerH Posted June 9, 2017 Report Share Posted June 9, 2017 Hi Pete, does the drop in heat of the exhaust gas slow it down through the system and thus create back pressure. Keeping it at a constant temp allows it to exit quicker.(?) Roger Quote Link to post Share on other sites
Ben Freer Posted June 9, 2017 Report Share Posted June 9, 2017 There is a third option for ceramic coating - Performance 1 at Didcot just around the corner from TR Register HQ. I am reserving full endorsement until after next weeks rally but so far so good ???? Quote Link to post Share on other sites
Peter Cobbold Posted June 9, 2017 Report Share Posted June 9, 2017 Hi Pete, does the drop in heat of the exhaust gas slow it down through the system and thus create back pressure. Keeping it at a constant temp allows it to exit quicker.(?) Roger Hi Roger, Once the gas is past the valve it needs to cool and shrink. However while passing the ev it is best it is hot since, in the final stage of ev opening, its velocity is sonic. And the hotter the gas the faster the speed of sound and the greater its velocity. Once in the exhaust pipes it is best it cools and shrinks fast and so reduces back pressure, as it is no longer sonic due to the much greatr bore than the ev curtian area. With exhaust manifolds resonance-tuned to a high overlap cam the situation might be different as the inertia of the gas in the upper exhaust pipes should be kept high. Inertia follows mass and velocity so cooling and slowing the gas might be a small disadvantage....I dont know..that's racers' territory. Peter Quote Link to post Share on other sites
RogerH Posted June 10, 2017 Report Share Posted June 10, 2017 Hi Pete, thanks for that explanation. I think I shall stay away from Racing. Roger Quote Link to post Share on other sites
brian -r Posted June 10, 2017 Report Share Posted June 10, 2017 (edited) I have a friend who has run a PI car with ss manifold and sports exhaust which is unwrapped. It's been like this for at least 10 yrs with no problem and he does drive it hard. My 6 runs standard exhaust so no personal experience,however (at the risk of being banished) I did wrap the ss exhaust on my previous MGB to no detectable advantage. Cheers Brian Edited June 10, 2017 by brian -r Quote Link to post Share on other sites
Peter Cobbold Posted June 10, 2017 Report Share Posted June 10, 2017 Hi Pete, thanks for that explanation. I think I shall stay away from Racing. Roger Me too Roger, they dont approve of blowers...... And I'm too old anyway Peter Quote Link to post Share on other sites
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