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Rough running and subby mountings


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#1 Pavel

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Posted 08 March 2005 - 05:31 PM

Right my car is in a sorry state!

Probly dan can help me lol :cool: but if anyone else can too that's great!

1) Car starts within half a second of cranking and will idle forever. It also doesn't die when revved and revs freely when parked. However, shakes and doesn't pull too well when driving. Could this be a bad needle in the carb? Mixture in general seems to be okay (judging by plugs and exhaust) but might be flat spots. If it's this then I can live with it another month till I get a carb with the right needle.

2) Cylinders 2 and 3 run much weaker than 1 and 4. Last time this happened a head gasket failure... but this time my compression is 170 170 170 185 so doesn't look like a head gasket. I replaced the spark plugs (for some used ones and all 4 are different) and my plug leads are also weird (3 the same for 1,2,4 and cylinder 3 has a different one since its problematic). Cylinder 3 is the most often failure but taking the plug off 2 also has very little difference (take from 1 or 4 and the car is about to die).
Could this be due to my exhaust manifold blowing at the head connection only on the centre branch (since the flanges on the inlet are thicker so the end exhaust branches are held tightly but the second one isn't)? Since this would result in worse backpressure.

Ignition will be changed once I get some new leads and spark plugs. I have a mint ducellier dizzy that I might consider fitting since it looks in much better condition than my lucas one (plus I have another spare ducellier so can take bits and pieces off that one).

3) Tower subframe mount. Dan will know most about this problem and after lookign at it today I don't think I can fix it and a solid mounted bush won't help either, it's really deformed and the metal has actually been really distorted, not just bent backwards. What I was thinking was could I just weld a small 2" by 2" square 3mm thick steel plate over the hole with a round hole in it precisely the diameter of the bolt and not use bushes altogether? Since I can't get to the underside of the hole to even attempt (god knows if it will work) to fix it without taking the subby off which right now I really don't want to do!

4) My vacuum gauge (incidentally the ONLY gauge my car has right now) used to show "idle" when idling (wow :( ). However after a decent long run, when the car warmed up properly, now when idling the gauge shows close to 60cm which is about 1/4 of the way into the "DECELERATING" zone... Now if my understanding of an engine is correct too much vacuum never hurt anyone... but maybe this will help someone find a problem with my mixture or timing?

Cheers everyone

#2 Rob

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Posted 08 March 2005 - 06:11 PM

First job on the list for your engine is to match the inlet and exhaust flanges so you get a good tight fit. This is probably the cause of most of your engine problems.

#3 Purple Tom

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Posted 08 March 2005 - 06:16 PM

pavel is your timing accurate?

#4 Pavel

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Posted 08 March 2005 - 06:28 PM

Umm don't see why it shouldn't be. There's no pinking and the car revs fine under no load. I guess I could check it but I'd rather wait and do that when I change the leads and plugs etc.
Would that affect combustion in the 2 and (esp.) 3 cylinders though?

#5 Rob

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Posted 08 March 2005 - 07:15 PM

timing may do but a loose centre branch will definatly affect 2 and 3.

#6 Boab

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Posted 08 March 2005 - 07:23 PM

My mates Mini had the same problem with the manifolds. All he done was grind a few washers on one side, put a few on the studs and tightened. Bingo, it doesn't half go now.

#7 Dan

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Posted 09 March 2005 - 07:00 PM

The last bit of your post makes it sound like it wasn't warm enough when you tuned it Pavel. And you really need to get the manifold sealed up, making stepped washers as above is a good idea or grind the flanges so they are about even (don't take too much off the alloy though or it'll seriously loose its strength).

#8 Pavel

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Posted 10 March 2005 - 09:37 PM

I never did tune it :(

Any ideas anyone on welding a plate onto the bulkhead and excluding the tower bushes?

#9 Dan

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Posted 10 March 2005 - 09:48 PM

You could try cutting the same part out of a scrapper and seam welding it over the top of your existing one, but how safe and strong that would be is anyones guess. And you'd need to do a bit of work to exclude the rust between the layers since it would be double skin now. You'd need to use the bolt and bushes in the subframe to get it lined up properly. In fact in just three days time you should have some nice solid bushes to use which will line it up really well.

#10 Pavel

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Posted 10 March 2005 - 09:51 PM

Yeah but tjhe deformation of the hole is pretty severe, I'm not convinced that a solid bush will solve it.
I'm only planning on using the plate method if the bush still moves after I solid mount the thing..

As for rust, that's hardly an issue around here (this car needs to survive only about 2 years, and otehr parts of it will rust away far earlier than this bit :()




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