Fiat twin cam clutch actuation

Larger 4 cylinder engines, body mods, major brake and handling modifications.

Fiat twin cam clutch actuation

Postby MM » Wed Feb 02, 2011 4:52 pm

I have a 1965 2-door Minor fitted with 2-litre Fiat twin cam and Fiat 5-speed gearbox, but am having some issues with achieving satisfactory clutch actuation.

It has a Marina pedal box, and operates the clutch via a cable. Snag is, the Fiat clutch actuator lever seems to require alot of travel and I end up with a rather high pedal that touches the steering column.

I'd be interested to hear how other Fiat twin cam Minor owners have gone about their clutch mechanisms.
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Postby dp » Tue Feb 08, 2011 5:28 pm

Having a Marina pedal box and 131 gearbox I also have the high clutch pedal but I've noticed that the first part of the pedal travel doesn't do anything, only the last part. I've adjusted so that the pedal is a bit higher than usual, (maybe an inch) but doesn't disengage clutch until a fair way down. Never had a clutch slip issue.  did think of putting a limiter on the pedal to hold it a bit of a way down but I prefer that the clutch is definitely disengaged.

If you push the clutch all the way down and slowly let back up you should feel where the clutch bites and how much further up the pedal travels. I suspect you can lose some of the distance after the clutch bites without it affecting the pressure on the clutch.

Oh, on mine there's an adjustment nut on the cable where it fits into the marina pedal box. You may need to offset or inset this if you don't have enough adjustment.

Sorry if not explained well.

PS are you the same guy with clutch problems on the GC site?
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Postby MM » Tue Feb 08, 2011 11:38 pm

Hi dp,

Interesting to hear that your Marina pedal box also gives that issue! Like you say, it is reassuring to know that the clutch is fully disengaged and that there's no dragging of the release bearing.

I also have that adjuster going into the pedal box, so it's really a case of tweaking it for optimum setting.

Mine originally came with the Marina's hydraulic setup, but I couldn't get it to work the clutch over the required range, so I gave up on it and fitted a cable instead.

And yes, I was the very same guy who posted on GC's forum! :)
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Postby dp » Sat Feb 12, 2011 6:55 pm

It's a small world :)
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Re: Fiat twin cam clutch actuation

Postby ohc_turbo » Fri Dec 02, 2016 7:05 pm

i know this is like "holy thread revival batman" but it seems pointless making a new post about the same issues

1. my clutch is very heavy
2. my clutch bite is really low to the ground
3. I'm using a marina pedal box which was designed for hydraulic not cable, adjustment on the cable just makes the pedal go up
4. my clutch started to slip only after a run down the block, didn't slip it as far as i know and put a new friction plate in and throughly cleaned flywheel and pressure plate however car was built few years sat still didn't move, could this be rust on the flywheel burning off???

i though about a few remedies :

i have bought a new cable and going to install as the old was rather tatty
i am thinking of welding a section on the pedal to stop pedal rising, this will enable the pedal to be under slight tension and thus hopefully raising biting point.

haven't drove the car since, do you think the above are the only options and a good idea?, i can't think of any other alternatives, don't want to go to hydraulic as it was more difficult in finding a good way to mound the slave on the gearbox and haven't got a tig welder to fab a bracket/mounting plate onto the box..

Thanks

Neil
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Re: Fiat twin cam clutch actuation

Postby Panky » Sat Dec 03, 2016 12:20 am

In no way am I any sort of expert on the Fiat conversion (actually know less than zero) but the cable will need two fixed ends to be properly adjustable, so I guess your suggestion should work. It's just a matter of where the fixed point on the pedal should be, with that I can't help sorry :(
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Re: Fiat twin cam clutch actuation

Postby ohc_turbo » Sat Dec 03, 2016 9:41 am

its got one fixed at the pedal box and one adjustable on the gearbox end, its a pain to get the cable to work with the marina pedal, ill see how it goes with a new cable and a few mods and report back
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Re: Fiat twin cam clutch actuation

Postby dp » Fri Dec 09, 2016 8:05 pm

From memory, I welded a bit of metal onto above the Marina clutch pedal pivot point as my marina clutch was also originally hydraulic. Hydraulic needs push, cable needs pull. The Fiat clutch cable I had (I think for Fiat 131 gearbox) had adjustment at the firewall end. My cable went in through the hole as per the attached pic based on approx 2.5" of metal above the pivot point. This was too high as there was much too much movement in the pedal. But when you are making from scratch you learn these things the hard way. Approx half that height would have reduced the pedal travel and made the clutch twice as light. Then it would be a matter of moving the attachment point on the firewall forward or backward to get the pedal in the right place, not pulling the clutch at rest.
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Re: Fiat twin cam clutch actuation

Postby dp » Fri Dec 09, 2016 8:09 pm

Zooomed in
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Re: Fiat twin cam clutch actuation

Postby MM » Fri Dec 16, 2016 7:09 pm

dp, your setup looks very similar to the one I made for my twin-cam Moggy, after I discovered I couldn't get the previous owner's hydraulic setup to work:

Marina clutch pedal with a pivot fork welded on:
Image

The Marina pedal box with Fiat 131 clutch cable fitted:
Image

This setup worked pretty well, though I always had a rather high clutch pedal, and one that rubbed up slightly against the steering column (hence why I bevelled arcs half way along the pedal in the first pic, to provide some clearance) - ideally of course, the pedal should be heated up and bent to clear the column, and IIRC, ohc_turbo's pedals are already modded in such a way...

ohc_turbo, clutch slip and low biting point could be caused by incorrect adjustment of the operating mechanism, and possibly a worn clutch release bearing - though I guess you would have checked/changed that when you fitted a new clutch plate?
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Re: Fiat twin cam clutch actuation

Postby ohc_turbo » Sun Dec 18, 2016 9:27 am

i believe its had a new friction plate only, worst case scenario if i can't get it to work i will buy a new 3 piece clutch.

What i need to do is re investigate the clutch pedal and the height i have the attachment for the cable, i will try to lower this as close as possible to aid a lighter clutch as posted below. i will also weld a bracket so i will limit the height of the pedal, this will laid a slight pressure on the cable to aid take up of slack.

i have a bit of time over x mas so will have an update shortly.

Thanks for all your input
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Re: Fiat twin cam clutch actuation

Postby MM » Sun Dec 18, 2016 2:11 pm

Be wary of how much you limit the pedal travel; I had a similar problem with mine, where the pedal was rubbing against the steering column, so I fitted an 8" or so length of Bowden (bike brake) cable between the pedal and the bulkhead to limit the pedal height, however, shortly afterwards I noticed the clutch was slipping going up hills, etc.; thinking that the clutch was shot, I ordered a new kit, but one day the cable snapped and the clutch went back to being fine again - obviously, I'd inadvertently created a setup where the clutch plate was being partially pushed away from the flywheel! :roll:
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Re: Fiat twin cam clutch actuation

Postby ohc_turbo » Tue Dec 27, 2016 1:53 pm

i removed the clutch pedal today, the height of the pivot point that i welded on was quite high, as previous posts this caused the clutch to the quite stiff to operate. A little cutting and welding later the pivot is now about 10-15cm lower. Hopefully i have now resolved the heavy clutch.

next i looked at restricting the movement, using a spare pedal box i found it difficult to find a place where i could weld a bar or something to reduce the movement, i suppose i will have to have the springy clutch. i will fit the new cable and take it for a test run and report back.
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Re: Fiat twin cam clutch actuation

Postby ohc_turbo » Wed Dec 28, 2016 12:31 pm

i fitted the cable today and seems like the cable i have got is shorter, maybe is for a non TC fiat, lucky it has the same ends and fits OK, the cable does not need to be long and run along the slam panel

The pedal as is moves the clutch arm only 15MM, not sure if this is enough, one other issue is that raising the pedal via the nut at the pedal box end bottoms out the eyelet causing the clutch to be under tension, i do feel that Maurice is right and my slipping clutch was because its tension was too tight causing the friction plate to be lifted off slightly, lucky i noticed this by revisiting the fitment of the pedal and cable

I can rectify this by releasing the tension and lowering the pedal however lowering the pedal will give less of a throw on the clutch arm, i will try to release the cable via the nut just so its slack, hopefully the biting point will not bee too low though as on the last test drive it was really low causing me a concern thus making me start off this thread again.

On a plus note, lowering the pivot and buying a new cable has made the press quite soft and easy compared to before.
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Re: Fiat twin cam clutch actuation

Postby MM » Thu Dec 29, 2016 4:52 pm

Good luck with that. It's always a matter of lots of trial and error with these sort of mechanisms before you hit the 'sweet spot' and it all works well...
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