Jonathan Kidson Posted June 18 Report Share Posted June 18 I have a TR4 just being re commissioned. Engine rebuilt and firing but misfire on N0.1.Good compression on all cylinders. Using a glass plug it is apparent No 1 is sparking but not being fuelled until it hits 2500 rpm. Below this plug stays dry. What would cause this ? Have re skimmed head, new distributor, leads etc and plenty of sparks, timing fine just this problem. Could it be a broken ring not making enough 'suck' on the in stroke ? Any ideas very welcome. Quote Link to post Share on other sites
RobH Posted June 18 Report Share Posted June 18 Welcome to the forums Jonathan. Have you removed the inlet manifold to check there is no obstruction in the air-way? I seem to remember an instance of someone discovering a rag stopper in there, left by mistake after some head work. Of course, another possibility is that the inlet valve isn't opening properly. Quote Link to post Share on other sites
John Morrison Posted June 18 Report Share Posted June 18 Hello Jonathan welcome to our forum I have altered the title of your post to hopefully better target replies Hope that’s OK John Quote Link to post Share on other sites
Motorsport Mickey Posted June 18 Report Share Posted June 18 Jonathon, not being fuelled until about 2500 revs, a likely very bad air leak. The extra revs overcome the leak giving enough vacuum to lift the fuel. If you’ve just recommissioned the engine, check the inlet manifold with carbs fitted against the gaskets against the head. You’ll often find the manifold hangs up on 1 of the dowels ( there’s 2, ) one in between each inlet port of the head. The head may appear flat against the manifold but the dowels are a close fit and if you tighten one too much it tilts the manifold leaving an air gap next to the head. Use brake cleaner or Easy start and spray around the inlet manifold where it touches the head, masking the front of the carbs with your hand so non is sucked in there. If the revs increase you have an air leak, refit the manifold and try again MickRichards Quote Link to post Share on other sites
Jonathan Kidson Posted June 18 Author Report Share Posted June 18 Thank you for your responses. Will see if these are a solution J Quote Link to post Share on other sites
phil Dean Posted June 19 Report Share Posted June 19 Exactly what I found, Rough Running, when I took the inlet manifold off the ears (clamps) that hold the inlet and outlet manifold to the head on the rear one although tight had twisted and was not clamping the inlet manifold . Phil Quote Link to post Share on other sites
Drewmotty Posted June 19 Report Share Posted June 19 You may also find that if the head has been skimmed the bottom of the inlet manifold can overhang the head and hang up on the side of the block. Quote Link to post Share on other sites
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