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devnet H120
United Kingdom
81 Posts |
 Posted - 20 Apr 2013 : 17:21:05
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Afternoon All,
Looking for some help if possible. I finally got my engine to go after having the head off etc. and it initially runs very well and sounds great. However after its been running for a good 15 - 20 minutes the idling speed suddenly drops off and you have to keep feather the throttle to keep it going and it gradually gets worse so you can’t take the rev's above 2000 rpm without it dying off. Then eventually you can’t start it. Come back the next day and its starts fine but again eventually it happens again. I can't figure out if its heat, fuel not getting through etc.
Thanks in advance,
devnet H120 |
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arrocuda
United Kingdom
501 Posts |
Posted - 21 Apr 2013 : 09:04:03
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Cold compression test followed by a second test after the engine has warmed up to normal running temperature would be my first move. Where abouts are you? Maybe someone on here could help you out with one if you are local to them.
I'm assuming that you would have already checked compression levels if you had one to hand, so could be worth buying one cos they aren't that expensive, but will most likely turn out to be a fueling problem once you have shelled out the money. Sod's law etc! 
Building the 'Mark II' fastback Rapier ('Arrocuda'). |
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bigt80
United Kingdom
1052 Posts |
Posted - 21 Apr 2013 : 18:57:55
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| I had something similar many, many years ago, but that turned out to be electrical: fault with condenser when it got hot, but yours does sound more like fuel starvation when hot. With the 4-branch exhaust a lot of heat is generated: Not on H120, but rebuilding my std. Fastback I found the push-on union pipe from pump to carb intake had collapsed at carb end when it got hot and this stopped fuel getting through. Failing that I would think it is something to do with carb set up, but then it is odd it is fine cold. Sorry, probably not much help, but a couple of things to check. Cheers. G |
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Tony Fearn
United Kingdom
60 Posts |
Posted - 06 May 2013 : 23:12:39
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Hello Richard,
Have a look further down the page and you'll see 'Poor starting when hot'.
This will add to the probable causes.
Tony. |
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janmarine3
South Africa
286 Posts |
Posted - 07 May 2013 : 06:50:23
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For what it is worth..
I have a story to tell, but don't ask me any why's or what's...
I fitted a 1725 engine in to my Ser 3, and twin sidie webers from a H120.
I battled from the start , modified inlet manifold to get the carbs level, getting the jetting right, etc.
every time I had tinkered with the jets, the car would idle fine, put the jet caps back, then the same thing happened as you are describing here.
So - when my jet caps are off, there is no problem, when the jet caps are replaced the problem is back. Now my jet caps are on, but half cock, if you know what I mean - I don't know why, but my engine runs like a dream, and I get 12 Kms to a litre. Perhaps there is a hole blocked off somewhere in my gaskets or similar, but I am not tinkering any more , it's fine like it is.
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1922
United Kingdom
549 Posts |
Posted - 07 May 2013 : 11:59:32
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Jan - if you mean the brass domed covers on the top of the float bowl then you should have some spacers under them that have vents in them (they look like the crenelations on castle wall).
I can do pictures if it helps.
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janmarine3
South Africa
286 Posts |
Posted - 07 May 2013 : 15:06:51
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Hi 1922.
I was so relieved that the fault was gone I did not bother to check further after that. I know that the spacers with vents are there and I have no idea whether I have something upside down or something silly ,I will go have a good look now that it has come up again thanks.
Jan |
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Fastback Thomas
Belgium
423 Posts |
Posted - 08 May 2013 : 06:26:25
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Is it a standard 1725 or with H120 camshaft etc..
'68 sunbeam rapier fastback {B341006846 OD/LHO}
I like a car that looks normal but really knocks your socks off!!
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janmarine3
South Africa
286 Posts |
Posted - 08 May 2013 : 10:23:54
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| it is a standard 1725 overhauled engine and box from a Humber Sceptre with electronic ignition and distributor fitted, I made my own 4 into 1 exhaust manifold which works ok. |
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janmarine3
South Africa
286 Posts |
Posted - 22 May 2013 : 13:50:57
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quote:
Originally posted by 1922
Jan - if you mean the brass domed covers on the top of the float bowl then you should have some spacers under them that have vents in them (they look like the crenelations on castle wall).
I can do pictures if it helps.
1922 - Can I ask you to please take some pics of exactly how the domes and spacers are supposed to be fitted on the webers ( as they came off after removal )I think I have mine mixed up somehow. |
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1922
United Kingdom
549 Posts |
Posted - 22 May 2013 : 20:39:36
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No problem:
This is the spacer only:
Spacer and cover:
Last the diagram from the workshop manual:
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janmarine3
South Africa
286 Posts |
Posted - 23 May 2013 : 08:03:20
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Thanks a stack .
Jan |
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Topic |
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New Engine Problem (Fastback H120)
