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Shudders when enginebraking 
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Joined: Thu Sep 10, 2015 7:54 am
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Location: Uden (Holland)
GTM: Cox/Coupe
Post Shudders when enginebraking
Hi Guys,

When I'm driving my Coupe, acceleration goes well, but when braking on the engine sometimes there are shudders from the back side. Mostly at lower revs, from 3000 rpm down.
Sometimes I think that the problem must be a bad engine- or subframe-mount.
Sometimes I think that it gets a push by a not wanted ignition.

When the car is warm, sometimes when I pull out my key, it keeps on turning for a few revolutions. Can this be caused by a bad timing?
And can this be the cause of the shudders too?

Anybody with good ideas?

I don't know the exact specifications of the engine.
It's a 1275cc with Hiff 44 carb, that I do now.
The guy from whom I bought it said that the cylinderhead had been flowed by the owner before him. He sais it has not.
It even isn't sure if the cylinderhead likes unleaded fuel.
The former owner always added leadsubstitute when refuelling, just in case.
There is a website on which you can check your enginenumber, when I do so it should be suitable for unleaded fuel, but I don't know if the original cylinderhead is still on.
I should check my valveclearances soon, see how they are.

Cheers
Harold


Fri Jun 03, 2016 3:40 pm
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Joined: Wed Jul 31, 2013 11:47 am
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Location: Kano north Nigeria
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Post Re: Shudders when enginebraking
Hi Harold,
Your 2 problems are not related, the running on after the ignition is switched off is caused by something in the head, maybe carbon, having enough heat to ignite incoming fuel to keep he engine running a few seconds, the easy solution put it into gear, lifting the clutch and stalling the engine. I any time you remove the head make sure you have no sharp corners that could retain heat to cause this problem.
Your engine judder when slowing down I would guess is caused by engine movement against the engine mounts and steady, the standard Mini/GTM has one steady I found this was not enough and fitted an extra steady from the thermostat housing and another underneath on the R-H bottom of the drop gear housing to the sub frame, it will put extra vibration/noise into the car, but with bigger more powerful engines you need to stop all forward and backward movement.
John


Sun Jun 05, 2016 5:35 am
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Post Re: Shudders when enginebraking
Agree check your mounts and steadies. When I was A series powered I ran two lower and one upper steady.

Also running on, where the engine continues after turning off the ignition, Agree with John it could be carbon deposits but it was a common problem when Unleaded fuel came out. My A series use to do it when hot and due to running a bit more ignition advance. I use to stall it as John describes.

The later metros came with an anti run on valve due to this problem, quite a few cars had them. The simple explanation to how one of these work was to cause a big vacuum leak in the inlet manifold when the ignition was switched off.

Neil

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IF wile e coyote had a GTM he would have one with Nitrous too! watch out road runner! The First GTM into the 11s then the 10s, PB 10.87 @ 125.5 Mph on A048 tyres, and fully road legal at Santa Pod


Sun Jun 05, 2016 8:51 am
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Location: Uden (Holland)
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Post Re: Shudders when enginebraking
Thanks guys,

My car also has one upper steady bar and two lower ones.
When I was crawling under my car, besides an oil leak, I also saw that one bolt holding the bracket from the left lower steadybar was loose, an other one I could tighten half a rotation too.
I tightened them both ofcourse.
The rubber seemed not new, but also not very bad. I will order new rubber anyway, for all three bars. Are they all the same? I don't think I will go for polyurethane, as that will cause more resonance.
I just drove around, the judders seem less but not totally gone.
As my revcounter shows too many revs, it's hard to say at how many revs they occur, bot mostly at lower revs.
I should adjust the counter if possible, or get a new one.

Afterrun, it does that sometimes, not very long, just one or two seconds.
As it can do no harm, I don't really have a problem with that.

Cheers
Harold


Sun Jun 05, 2016 4:10 pm
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Post Re: Shudders when enginebraking
If you need a good revounter I have a Scitsu electronic unit meant for race bikes that was on my Jedi and now no longer needed available :wink:
John


Mon Jun 06, 2016 9:28 am
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Location: Uden (Holland)
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Post Re: Shudders when enginebraking
Thanks but no thanks John, I like the old looks of my car, an electronic unit wil mismatch.
Any idea how I can get the proper amount of revs on my counter? Can it be adjusted?

Cheers
Harold


Mon Jun 06, 2016 6:44 pm
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Post Re: Shudders when enginebraking
Hi Harold,
There are people who recondition rev counters, there is a company in Swansea Wales, but I would have to search for the and my office pc crashed today, I have a very nice (old) Smiths cronometric to go in my car but that needs a cable drive off the end of the camshaft.
John


Tue Jun 07, 2016 5:50 pm
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Post Re: Shudders when enginebraking
Mine is a Yazaki, doesn't sound british to me :wink:


Tue Jun 07, 2016 6:10 pm
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Post Re: Shudders when enginebraking
Not an old British name :roll:
log on to www.speedycables.com they overhaul and re-calibrate instruments, maybe some body closer to your home if you google it.
John


Tue Jun 07, 2016 7:37 pm
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Post Re: Shudders when enginebraking
Or just buy a (second hand) Smiths one, and see if that shows the correct revs?


Wed Jun 08, 2016 1:21 pm
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Location: Uden (Holland)
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Post Re: Shudders when enginebraking
Do all steady-bars use the same size rubbers/bushes?
Mine all are dogbone kind of bars, so all rubbers are strained sideways, not axial.

As I see it on minispares site, there are five kinds:

A) One-piece rubber: https://goo.gl/y9pnuk
B) Two piece rubber with conical plastic inserts: https://goo.gl/Mwf5Vc
C) Two piece rubber with conical metal inserts: https://goo.gl/1QBQEU
D) Two piece purple PU bushes: https://goo.gl/t5lx64
E) Two piece PU race-grade bushes: https://goo.gl/Q2O2Vv

E) seem not the right ones for street-use, to much vibrations and noise.

To me C) or D) seem the best choice. Is there a lot of difference between these two in enginemovement, vibrations or noise?

Cheers
Harold


Tue Jun 14, 2016 10:14 am
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Post Re: Shudders when enginebraking
Hi Harold,
B,C or D should be OK I've used the plastic cones long ago in a Mini and did not rust :wink: because they are available I used Peugeot 504/505 lower arm inner bushes and make my own dog bone steadies, the 504 bush is slightly bigger diameter and a bit shorter than Mini lower arm inner bush.
Been making steadies and seat belt fixing brackets for 4 point harness over the last weekend.
John


Tue Jun 14, 2016 10:29 am
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Post Re: Shudders when enginebraking
PS. I have never used the PU bushes, they did not have them when my old Cox was running around, but think they should last longer, but because they are a little stiffer maybe more vibration
John


Tue Jun 14, 2016 10:33 am
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Location: Uden (Holland)
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Post Re: Shudders when enginebraking
Thanks John,

I want very little enginemovement but no vibrations or noise... :lol:
I think I will try C, and when I think there still is to much movement I will buy D.
Have to try to know...

Cheers
Harold


Tue Jun 14, 2016 10:59 am
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Post Re: Shudders when enginebraking
I try to reduce all engine movement as it affects the gear change, my car has no sound proofing or carpet, so I'm expecting just a little noise inside, if too loud I'll drive with my fingers in my ears :mrgreen:
John


Tue Jun 14, 2016 11:07 am
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