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Mar 14, 2015 23:52:25 GMT
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I managed to blow the headgasket on the Hillman Hunter last week when a waterpipe burst on the motorway  The motor is an original 1725 with an alloy head. Does anyone have any ideas why it has a lumpy tickover after the rebuild? So far : I've had a spare alloy head checked, skimmed, and all the valves machined & lapped. Fitted this head (with the matching rocker shaft and arms), new plugs were fitted at the same time. Tappets were miles out (due to old block + older rockers + recently machined head) but have been adjusted and the motor sounds sweet  Ignition timing is normally set by feel, it refused to tickover using the old settings but is a lot better after moving the timing around (doncha love the manual adjustment on Lucas distributors  ) Gunsons colourtune shows the mixture is about right Took it out for a gentle 10 mile run to warm it up, the motor runs fine at cruise and pulls well but has a very lumpy tickover. I'm guessing the mechanicals are ok or it wouldn't be so good at speed. Any suggestions? Is it worth trying a different carb needle? Archive pics from the last time I had the head off -     |
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Seth
South East
MorrisOxford TriumphMirald HillmanMinx BorgwardIsabellaCombi
Posts: 15,513
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A different carb needle won't affect the idle unless your one is badly scored as they are all pretty much the same size at the fat end.
Maybe you've got an air leak on the inlet somewhere?
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Follow your dreams or you might as well be a vegetable. |
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ChasR
RR Helper
motivation
Posts: 10,191
Club RR Member Number: 170
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Mar 16, 2015 17:34:18 GMT
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I was going to say that this sounds like an air leak. I would be looking at the gaskets and carb separators myself. A can of carb cleaner will soon show an air leak up.
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Mar 16, 2015 17:39:40 GMT
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Did you get my old carb off me when you picked the engine up Nomad? If so the fuelling might be slightly out as i had enlarged the jet on the carb by about 0.1mm.
Also check for air leaks around the inlet as that could cause the idle issue (don't test by spraying carb cleaner or easy start at suspected leaks as the exhaust below likes to ignite it. I cant possibly comment on how i know this)
James
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Too many projects, not enough time.
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Mar 16, 2015 17:41:11 GMT
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The plastic spacers between the carb and manifold are also very fragile on these, but I think you can still get replacements from Minispares if they are the cause of an air leak!
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Too many projects, not enough time.
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Mar 16, 2015 18:51:21 GMT
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Popular opinion is pointing at an air leak so that's where I've been checking today but no luck so far : Manifolds removed from head and faces cleaned/refitted. all ok. Plastic carb spacer removed and checked ok, refitted with new gaskets. James - I still have your carb but never get it to run happy so have been using my original carb (good thinking tho' ) Clearances on a couple of vales have opened up a couple of times and been reset to stop them tapping - no sure why they would creep? Compression warm is 125-150-150-175 wish I could work out why the big difference. Will have a run to the workshop tomorrow and recheck with a different gauge. It's still not running right, I'm still puzzled but the help is appreciated. |
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Mar 16, 2015 19:44:58 GMT
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What sort of gasket are you using for the head to manifold gasket? Is it a thick paper one or a thin one? and did you put any of the black sealant on the faces before bolting up?
If the head was warped it might not be sealing correctly on there so a little extra sealant might help eliminate an air leak there.
Its unlikely but the unlikely things are the ones that get you stumped haha
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Too many projects, not enough time.
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Mar 16, 2015 21:16:46 GMT
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I have always smeared inlet manifold gaskets with regular grease, it was a tip i learned from my dad when I was a little lad, you don't need too much on there, just a light smear on both sides does the job, it seals better than horrible gasket sealer
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Last Edit: Mar 16, 2015 21:19:26 GMT by fordperv
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Mar 16, 2015 22:02:39 GMT
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that servo hose looks like a prime suspect to me might be worth a look
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if it hasn't broken yet chances are it will for me
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djefk
Part of things
Posts: 844
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Mar 17, 2015 23:24:28 GMT
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125 psi is low, even my totally worn out Hunter 1500 pushed 150 from all four cylinders!
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Mar 22, 2015 22:44:07 GMT
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Problem fixed (sort of  ) Turns out the combination of me, feeler gauges, and rocker-arms with grooves worn in them (making it impossible to measure gaps properly) was causing the shakes. Oops! Resetting the tappets has cut down the vibes at tickover, I'm now looking at getting the ends of the rocker arms reground to make things easier in the future  Other bits : I normally use grease on gaskets when assembling, all seems ok. The servo hose looks shabby but checks out ok, and the 1-way valve is fine. All bores have a lip at the top so compression is never going to be good A new set of £300 pistons + £100 rebore + £££'s for a other bits means a rebuild isn't going to happen Credit to our local engineering place for fitting in a quick headskim & valve grind Rosamond Rebore Service, Tel: 01670 353287
Unit 19, Grasmere Way, Blyth, Northumberland, NE24 4RR Thanks for the ideas & support! |
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The motor is an original 1725 with an alloy head.
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