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Engine Stalls When Pressing Clutch.


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#1 Minigman

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Posted 25 June 2020 - 11:32 PM

I’ve got a 1330 pre A+ engine. Stage 3 head, 276 cam, lightened flywheel, orange diaphragm (pre verto set up).

Unless I set the idle at 1800rpm the engine just stalls when pressing the clutch. All clutch components are new (and I do mean every last part of it).

The engine has done about 1400 miles since first built. In that time it’s had 2 new gearboxes fitted (the first broke when an idler bearing obliterated). The end float was measured when I recently dismantled the engine to replace the box and transfer case, and was measured at 5 thou after new thrust washers were fitted. It was 4 thou upon dismantling with the original thrusts fitted.

The car produced 92 bhp and 88lbft torque on the Slark RR, so a lighter standard clutch diaphragm will struggle I believe.

Options;
Ditch the orange diaphragm for a standard one?
Ditch the lightened flywheel and fit a standard one?
Do both?

How do I stop this stalling issue please?

#2 MiniMadRacer

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Posted 26 June 2020 - 06:46 AM

Have you adjusted the Clutch properly ?



#3 Minigman

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Posted 26 June 2020 - 08:20 AM

Have you adjusted the Clutch properly ?


Pretty sure I have. It goes into and changes gear ok.

#4 r.tec

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Posted 26 June 2020 - 08:36 AM

I once expirienced a similar habit of the engine. Problem here was that the thrust washers of the crankshaft were fitted the wrong way round. I fitted the biggest thrust washers I could get the right way and everything was good, although the seating on the central crank webs were a bit scuffed.



#5 Minigman

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Posted 26 June 2020 - 10:18 AM

I once expirienced a similar habit of the engine. Problem here was that the thrust washers of the crankshaft were fitted the wrong way round. I fitted the biggest thrust washers I could get the right way and everything was good, although the seating on the central crank webs were a bit scuffed.


I’m 100% positive they are fitted correctly. I even doubted myself during the build and took the cap back off to check.

I’m pretty sure this is clutch / flywheel related.

#6 imack

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Posted 26 June 2020 - 10:35 AM

I'm running a 1380 with 649 derived cam, an orange clutch cover and ultralight steel flywheel. Idle is about 1500rpm with no noticable rpm drop when pressing the clutch.
I can't imagine it being a clutch or flywheel problem.
I presume if there's enough resistance to stall the engine that you're unable to even crank the engine with the clutch depressed.

#7 Minigman

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Posted 26 June 2020 - 03:01 PM

I'm running a 1380 with 649 derived cam, an orange clutch cover and ultralight steel flywheel. Idle is about 1500rpm with no noticable rpm drop when pressing the clutch.
I can't imagine it being a clutch or flywheel problem.
I presume if there's enough resistance to stall the engine that you're unable to even crank the engine with the clutch depressed.


It will but it didn’t like it.

#8 Minigman

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Posted 26 June 2020 - 03:21 PM

I'm running a 1380 with 649 derived cam, an orange clutch cover and ultralight steel flywheel. Idle is about 1500rpm with no noticable rpm drop when pressing the clutch.
I can't imagine it being a clutch or flywheel problem.
I presume if there's enough resistance to stall the engine that you're unable to even crank the engine with the clutch depressed.



So if not flywheel or clutch and I’m positive it’s not thrusts what else can it be?

Is it possible to bend the crankshaft? That said, there is no noticeable vibration once up and running. The engine pulls very strongly without complaint.

#9 imack

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Posted 26 June 2020 - 04:54 PM

I'm running a 1380 with 649 derived cam, an orange clutch cover and ultralight steel flywheel. Idle is about 1500rpm with no noticable rpm drop when pressing the clutch.
I can't imagine it being a clutch or flywheel problem.
I presume if there's enough resistance to stall the engine that you're unable to even crank the engine with the clutch depressed.



So if not flywheel or clutch and I’m positive it’s not thrusts what else can it be?

Is it possible to bend the crankshaft? That said, there is no noticeable vibration once up and running. The engine pulls very strongly without complaint.

I don't know what to suggest at the moment. If the engine cranks ok with the clutch released it cant be a bent crank.
It almost sounds like excessive clutch throw to me causing loading on the thrusts.
How far do you have to depress the clutch pedal before it starts to slow the engine rpm?
You've got clearance on the clutch release arm haven't you?

#10 Minigman

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Posted 26 June 2020 - 05:10 PM

I'm running a 1380 with 649 derived cam, an orange clutch cover and ultralight steel flywheel. Idle is about 1500rpm with no noticable rpm drop when pressing the clutch.
I can't imagine it being a clutch or flywheel problem.
I presume if there's enough resistance to stall the engine that you're unable to even crank the engine with the clutch depressed.



So if not flywheel or clutch and I’m positive it’s not thrusts what else can it be?

Is it possible to bend the crankshaft? That said, there is no noticeable vibration once up and running. The engine pulls very strongly without complaint.
I don't know what to suggest at the moment. If the engine cranks ok with the clutch released it cant be a bent crank.
It almost sounds like excessive clutch throw to me causing loading on the thrusts.
How far do you have to depress the clutch pedal before it starts to slow the engine rpm?
You've got clearance on the clutch release arm haven't you?

When you say clearance are you referring to the stop bolt if so yes it’s set at 20 thou. I have had a lot of problems with the clutch and ended up replacing all the hydraulics, arm, plunger, release bearing and clevis pins, spring etc. The whole thing. The clutch plate is new and also the flywheel and diaphragm, the throw out stop was adjusted by the book but it crunched into gear a bit so had to wind it back out a fraction, but it does come into contact with the wok when pressed, just.

#11 MiniMadRacer

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Posted 26 June 2020 - 06:20 PM

I wonder if the Primary gear is sticking



#12 imack

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Posted 26 June 2020 - 07:20 PM

I wonder if the Primary gear is sticking

I considered that but surely that would give gear selection issues wouldn't it, not stalling when pressing the clutch?

Thinking about it that could cause a problem if the cars in gear, I'd only been thinking about it in neutral and the clutch being pressed.

Edited by imack, 26 June 2020 - 07:23 PM.


#13 MiniMadRacer

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Posted 26 June 2020 - 07:48 PM

The Primary gear should spin freely on the crank when fitted.. it has two bushes one front and one rear... if one of those is breaking up I wonder if it woukd cause this issue. I have seen issues where people over enthusiastically hammer on a flywheel and it "pinches" the primary gear. A flywheel should be fitted so far up the crank taper and no further. 

 

Does the issue get better or worse if the engine is hot or cold



#14 Minigman

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Posted 27 June 2020 - 01:19 PM

The Primary gear should spin freely on the crank when fitted.. it has two bushes one front and one rear... if one of those is breaking up I wonder if it woukd cause this issue. I have seen issues where people over enthusiastically hammer on a flywheel and it "pinches" the primary gear. A flywheel should be fitted so far up the crank taper and no further.

Does the issue get better or worse if the engine is hot or cold


You may have a good point there!

Bear in mind after the first 1200 miles the idler gear bearing obliterated for no apparent reason. When I stripped the engine down I checked over the primary gear and it did look ok, and it does spin freely. I wonder if a problem with the primary gear could cause idler problems? How to I check if it’s pinching? It does sem to be worse if sat in traffic - but then I’m using the clutch more too.

#15 Minigman

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Posted 27 June 2020 - 01:40 PM

I think I’ll change the flywheel for a standard one and I’ve got a new standard unused clutch blue diaphragm. This will at least start to rule in / out some ideas.




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