small clutch issue...

[demus]

I've just got the Cob back on the road with the new 4.6, and is going really well, just the clutch is dragging a little, I can get all forward gears, just can't quite get reverse (unless I turn the engine off). Gearchange is unbelievably better with Castrol SMX-S too.

Does anyone know the easiest way to engineer a little more movement to the clutch.
I did consider machining a little off the slave cylinder mounting to push it in further, or does anyone know of a different master cylinder with a larger bore that would suit if its not pushing the slave cylinder far enough?
When the engine was rebuilt an uprated clutch was fitted.

Any suggestions will be appreciated,

Cheers,

[Sidecarbod]

Originally Posted by demus

I've just got the Cob back on the road with the new 4.6, and is going really well, just the clutch is dragging a little, I can get all forward gears, just can't quite get reverse (unless I turn the engine off). Gearchange is unbelievably better with Castrol SMX-S too.

Does anyone know the easiest way to engineer a little more movement to the clutch.
I did consider machining a little off the slave cylinder mounting to push it in further, or does anyone know of a different master cylinder with a larger bore that would suit if its not pushing the slave cylinder far enough?
When the engine was rebuilt an uprated clutch was fitted.

Any suggestions will be appreciated,

Cheers,

Hi,

I also have a 4.6 lump with a hydraulic clutch which was supplied as a kit byTonyM, it works very well, the reason that I mentioned this is that he can give you the bore sizes for both the master and slave. Having said that the mechanical leverage side of things must be taken into account.

What setup do you have?

There are a couple of things that you need to check apart from the obvious one of air in the system.

I'd check that you are getting full movement of the master cylinder, you want the piston right at the end of bore when the clutch pedal is in it's rest position. when the pedal is pressed you want the piston to move the full length of the bore, this ensures that you are moving as much fluid as possible. If this is not happening it might be possible to change the mechanical leverage to get this bit right.

At the slave end you want the piston as far up the bore as possible, maybe just 2 mm off the end to allow for expansion of the plate and other bits and bobs when things get hot. Doing this should mean that the piston does not run out of travel before the clutch disengauges. You really want the clutch to disengauge with about another 30-45mm's worth of movement left at the clutch pedal, this will enusre that the clutch REALLY is disengauged fully before you change gear.

If the slave piston is not fully up the bore the easy way to move it is to make a longer pushrod, I have about 30 old valve pushrods so I cut one of them up and used that, it worked really well, one end has a nice ball on it that fits the lever in the bell housing, the other end was ground into a blunt point and that fits the slave piston really well!

You can have some of my spare ones if you want to go down this route.

HTH,

Pete

[oglyoodoo]

When you fitted your new uprated clutch plate did you check it slid easily onto the Gearbox input shaft splines? I have another car I built years ago and I was plagued, for thousands of miles, with clutch drag which would vary. Some times it was OK at other times it wouldn't disengage when approaching a junction. I tried everything including making up a longer pushrod. After about 50,000 miles the clutch started to slip and on dismantling, the friction plate was worn down to the rivets on one side only the cause, I assume, being it was sticking on the splines. The new plate was also slightly stiff on the splines but I made sure it was free to move after an hour or so fettling with some needle files. It's been as good as gold ever since..

Denis

[srv8dave]

I've had exactly the same problem! Turned out that no matter how much I bled the system, the symptom remained. Eventually I bled the slave cylinder by gravity (no pedal) after removing it and pointing the bleed nipple upwards (cracked open slightly) as the engine is canted back in an SD1, not so in a cobra which meant air always remained. Still seems to work.
Dave

[chr15w]

Not really able to offer a solution to your clutch problem but wondered what you thought of your new engine/
Do you have a guestimate as to the bhp/torque figures etc, how does the car perform now?
How much was the new engine (if you dont mind sharing) and any snags you hadnt thought of (apart from clutch of course)

[demus]

Hi all, thanks for the reply's.

As far as I can see the master cylinder has full movement, the old clutch needed to be pushed fully to the floor to get reverse, so its always been a little on the close side, I believe it is standard SD1 master and slave cylinders. I will try and bleed it a little more tomorrow.

The clutch was fitted to the flywheel ready to be bolted to the bellhousing, but once in line the two went together quite smoothly, the route I'd like to go down is the one that doesn't involve the engine and gearbox coming apart if possible.
The clutch is quite light at the moment so if it turns a little heavier wont be a problem, if there's a slave and master with slightly more travel.

The engine is superb, I must say John did a cracking job, I've attached the dyno results, peak torque was 317lbs/ft, (well over 200lbs/ft at 1100rpm) and 277bhp @ 5000rpm.

The increase in torque is amazing, the power is instant from any revs and most noticable in 3rd and 4th, all went back with no real issues only this tiny clutch one. Also runs cooler than the old 3.5 too.
Cost was just shy of 5k, which was new X bolted block, forged pistons, all balanced with lightend flywheel and clutch, recon heads fully gas flowed with big valves, 218 cam, recond front cover, new dizzy and ignition, various other new parts, sump, rocker covers, jets etc, all setup and run in on dyno. Came back looking brand new. Built by John Eales, JE Developments.

Thanks again guys..

[chr15w]

Hi Mark, thanks for your reply, you may have guessed Im thinking of upgrading from my 3.5 to a larger lump. Id thought of going the usual route of 5.7 Chevy or Ford but the cost would have been quite high, so much so that it would be cheaper to sell the car and buy new but a larger Rover would be a much simpler option.
Did you have to change gearbox or rad?

[Sidecarbod]

Originally Posted by chr15w

Hi Mark, thanks for your reply, you may have guessed Im thinking of upgrading from my 3.5 to a larger lump. Id thought of going the usual route of 5.7 Chevy or Ford but the cost would have been quite high, so much so that it would be cheaper to sell the car and buy new but a larger Rover would be a much simpler option.
Did you have to change gearbox or rad?

I have also upgraded from a 3.5 to a 4.6 lump, you do not have to change the gearbox or rad.

In fact I just bought a short engine (block, crank, and pistons) You can then fit all the 3.5 bits onto it. My heads were already stage III so I wanted to retain them. Even though you could just bolt it all together and it would run I wanted to get everything just right so there was a fair bit of machining done to the heads.

My lump is in a sumo, the only mod that I did to the rad was to make some fibreglass panels that are fixed at either side of the rad to stop the air spilling round the rad rather than going though it.

Like Mark, I'm very pleased with the way the car runs now, it is very relaxing to drive and will pull top gear from about 1400 rpm but also goes like stink when you floor it!

There is a big long post that explains all the mods required to build a 3.5/4.6 hybreed somewhere, I'll dig it up if your interested.

Mark, what carbs are you running? I know JE is keen on Dellortos.

Regards,

Pete

[demus]

Pete,

I'm running quad Dellorto DRLA 45's, which were on the car when I bought it.

I spoke to John a few years ago when I first got the car, it originally had a linkage setup similar to what TVR used to use, and was a total pain in the backside, had new lingages and center quadrant made and there fine now.

I too left the original rad in the car, I did wonder if it would be ok as I've heard people say the 4.6 can be a bit harder to cool, but in near on 30 degrees the other day was fine, Pete, have you got any photo's of your fibreglass panels?? I considered something similar on mine as there is nothing at the top of the rad, and I'm sure a lot of air rides straight over it.

Gearbox is untouched apart from better oil, Castrol SMX-S I used, and made a world of difference.

I haven't yet given it a really hard time, but I'm still using the Facet Red Top fuel pump, and it seems to deal with it fine. I have considered changing it though for a Carter or similar..

Cheers guys,,

[Sidecarbod]

Originally Posted by demus

Pete,

I'm running quad Dellorto DRLA 45's, which were on the car when I bought it.

I spoke to John a few years ago when I first got the car, it originally had a linkage setup similar to what TVR used to use, and was a total pain in the backside, had new lingages and center quadrant made and there fine now.

I too left the original rad in the car, I did wonder if it would be ok as I've heard people say the 4.6 can be a bit harder to cool, but in near on 30 degrees the other day was fine, Pete, have you got any photo's of your fibreglass panels?? I considered something similar on mine as there is nothing at the top of the rad, and I'm sure a lot of air rides straight over it.

Gearbox is untouched apart from better oil, Castrol SMX-S I used, and made a world of difference.

I haven't yet given it a really hard time, but I'm still using the Facet Red Top fuel pump, and it seems to deal with it fine. I have considered changing it though for a Carter or similar..

Cheers guys,,

Hi Mark,

I don't have any pics but I could take some, I presume that you running a sumo?

My rad is vertually touching the body work at the top, it was the 10" gaps at the side that I was worried about, the panels fill in these gaps and butt up to the inner wings. I made some cardboard templates that I've got kicking around, you can have them if they're any use to you (if you have a sumo).

My motor runs between 75-80 degrees even in this weather, I have just changed the twin fan setup for a 14" Pacet Pro jobbie, it was a pain in the arse to get the rad out! The new fan pulls more CFM but less current which is nice.

I also made up a box of tricks as an electronic fan switch, I could not find a normal bi-metalic one that worked in the range that I wanted. The nearest one came on at about 83 but would not go off until about 74. This ment that as soon as the fans kicked in they would not switch off again no matter how much air was going through the rad. It's alot better with my new switch, I'm still adjusting it but at the moment it comes on at 82 and goes off at 78. I also run a 74 degree stat.

You should check that your pump can flow about 2 litres of fuel per minute Mine does 190cc). If it can flow this much you should be OK. I run a facet but I'm not sure which model, I presume that you run a regulator, the edelbrock that I use can handle the psi.

I looked into running quad dellortos but decided against it as it would have cost too much to set them up. During my investigations I did learn a few things. You need to run low pressure, 2.8-3 psi only. Also the carb that feeds cylinders 5 and 7 can suffer fuel stavation if you have set the 'fuel rail' up so that this is the last carb in the chain. You should T off the main feed and feed each bank of carbs so that the bank on the right and left are fed separate supplies. As 5 and 7 fire in close to each other this does not help although I would have thought that the carb then has more time to refill. I mentioned this to 2 tuning shops and whilst they agreed with my theory they still said that carb seems to suffer the most.

V8 Development stated that they can make up some insulation plates to stop the carbs overheating, they reckoned that fuel and boil up and sit on the butterflies, when you start the engine if it spits back the fuel can then catch fire! You can blip the thottle to make sure that the fuel is dragged into the engine as a safe guard.

I run Redline MTL in my LT77 box which is similar to what you run, the gearchange is slow when the box is cold but I live with this, you don't want to be thrashing the motor and hence the gearbox when the engine is cold as the oil pump drive gears are weak. (This is assuming that you don't have a crank driven pump!).

I was very interested in your dyno run, if I can stop fiddling with mine for 10 minutes I will also put in on a rolling road. I'm about to remake a set of headers as the pilgrim ones are crap! Was your run on a RR or an engine dyno?

What pipes are you running and what ignition? Do you know the total advance of your igintion? Sorry about all the questions but this is all very interesting to me!

Regards,

Pete