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MG MGB GT V8 Factory Originals Technical - Clutch pedal stop
|Has anyone had a problem with a htoh possibly overtraveling the pressure plate. Thas is a V6 conversion using a 9 1/8" camero pressure plate and disc. Every once in a while after depressing the clutch and then releasing it , the the pedal returns with a light feel and the clutch doesn't engage. Each time it happened I pumped the pedal repeadly, fifteen or twenty times and the clutch finally engaged. I'm wondering if it could be overtraveling the pressure plate. Is this possible? I've heard mention of stops being installed. I was unable to find anything in the archives on it though.|
|I have a 78B and followed the Zaks conversion instructions with the following modifications.|
1- Attached two small wires to the pot so I could get the pot outside of the tachometer case and make adjustment with the tachometer mounted in the MG.
2- With the tach mounted and the electrical connections properly made. I used a hand held tach meter to calibrate the MG tach. Held the engine RPM at a steady 1000 rpm. And adjusted the pot to get the MG tach to read 1000 RPM.
Tach conversion works just fine.
|Oops posted to the wrong thread|
|Has anyone else had this problem with the htob? I installed a pedal stop yesterday, but it may take a long while to see if that cures the problem. I hope so as each time, I was stuck in heavy traffic. Has anyone else experienced not having the clutch engage after letting out the clutch pedal?|
|I have had the problem when racing but still haven't sorted it out. Thought it must be something in the way I set it up or the way I was rushing the change. Just had a thought, that it may be somewhere in the master cylinder area. Will have a look next weekend.|
|I installed a stop to prevent possibly overextending the pressure plate travel if thats possible. I'll have to wait to see if it happens again. If it does, what the heck do you replace? Is it the pressure plate or the HTOB that is at fault?|
|John . . . . It could mean that the HTOB has too much pre-load on it and is over-extending the clutch travel. It could also be that you have the incorrect clutch master cylinder and it is moving too much fluid into the slave cylinder. What brand of HTOB and which clutch master cylinder are you using? Did you measure the clearance between the HTOB and the clutch fingers when you installed it?|
|We have used the Mc Leod HTOB without any problems. The key is in setting up the bearing correctly. if you do not set it up with the proper end gap, it can either drag (slip) or possibly hang up on its own seals. Did you adjust it to exact specs? I know this is what it takes on the Mc Leod..|
|BMC Brian McCullough|
| Brian, I used the Webber, which I understand is the same as the Mc Loed. I was real careful with the measurement, I actualy made up a piece of steel .112 thick to use as a feeler gauge to get it real close. Thats what was puzzeling when I started with this problem. I.ve also never heard of a pressure plate being faulty and doing this. Somewhere I've heard of a problem being corrected by a limit on the clutch travel, such as using a stop. I don't recall where I had seen it. or the exact problem. At this point I'm sort of guessing. I'm using the stock 73B clutch master cylinder. Normally everything seems to be working great and the car with the 2.8 runs good. This is the way they should have built them to start with. And by the way this is a chrome bumper car, WITHOUT running any kind of hood scoop. With the hood closed the car appears every bit origional. I just have to try to sort out this intermitant problem.|
|John, you could also post on http://www.v6mgb.com|
Maybe someone else has had this problem too, but not that I have seen of yet.
|BMC Brian McCullough|
|Weber and McCleod are the same company. |
Does anyone have the newunit?? I got a new unit over this winter and noticed that even with my adjuster bottomed out I cannot get a gap betweent he HTOB and the presure plate?? I am going to havet o call Red today and see what he says..
|I'm not sure about wether its a new. I got it early winter, But had no problem installing it and setting the gap. This problem suddenly showed up after about 500 mi. of local driving. It has happened three times on two days, both within the last month. luckly I was able to get going both times by depressing and releasing the clutch repeadly, perhaps 15-20 times or more.I would hate to have it happen on the way to or from a distant show. So far I've been within maybe 20 mi. of home each time it happened.|
|I just bleed another McLeod HTOB for a 2.8L motor in a 1980 MG B.. As always, the unit takes forever to pump up to get the air out, then once you get there, you bleed it and it takes 50 more (no joke) pumps to bleed it out again. |
Every time I hear of someone installing on eof these units I hear of the frustration due to all the pumping... Thus people do not feel like bleeding it out again.
Here is my sugestion-Make sure that the bleeder is on the top hose and the line is on the bottom unit, then pump it up so it have full clutch plate travel- as you are holding down the clutch pedal, have your partner release the bleeder and see if you can get more air out.. Do this about three times and make sure to keep the MC full of fluid!
By the sound of it, now that I have read it and done anther unit within the past two days, thats what this sounds like.
Hope that helps,
|BMC Brian McCullough|
|The instructions on the McLeod (same as the Webber) clearly indicate that a pedal stop is required, & instructions are included as to how to set the stop. Because of the many different possible installations, no instructions are provided to build the stop.|
What can happen is the pressure plate springs will invert due to over travel. Should this happen, plan on pulling the trans & clutch. If you are lucky, it will only stick & may free itsself as was previously described.
To build a stop, you can limit the travel of the pedal, or limit the travel of the master cylinder push rod.
|So is this overtraveling only a problem on diaphram type pressure plates?|
|There's a lot of cobwebs in my memory about this - but in the mid 1960s, it seems that General Motors had this problem with their diaphram clutchs (of course it was all mechanical linkage then). But the way to adjust the clutch was to use a feeler gauge to determine the air gap between the flywheel and clutch disk when the clutch was depressed. Of course, you have to have access to the clutch with the inspection cover removed and I'm not sure there's a way to apply this method to the HTOB.|
|Overtravel was a real problem with flat diaphraghm springs. By going to a spring with bent fingers centrifugal force was now available to both assist in applying clamping force to the pressure plate and to help prevent an inverted diaphraghm. Centerforce clutches took the concept even farther by adding weights to the spring. Your stop should be set to give good disengagement and stop the pedal as soon as it begins to feel light, as that is the point at which it begins to travel across center. It is likely you were able to recover primarily due to centrifugal force, but 'bouncing' the spring may have also helped. I'd certainly avoid overcentering it again.|
|I'll have to look up those instructions. I don't know anywone that has had to install a pedal stop, but that is what it feels like is happening. Perhaps this is not a problem with the Rover or Buick conversions due to the larger pressure plate. My car being a V6 conversion is using a Camero diaphram type 9 1/8" pressure plate. It would make sense that it would require less travel. Mine is the only V6 conversion in the local club. The other tewo conversions are the a Buick 300 and a Rover. I'm very happy with the performance, It's not as quick as the other two, but mine is a stock engine and theirs are both modifyed. But I'm happy with this. It makes the car very highway capable, which is what I was after.|
Thanks for the helpful advice,
|I changed to a master cylinder with smaller bore. I got less htob travel and a lighter clutch pedal. Even 1/16" bore difference is measurable and noticable. I saw a calculation for it in the archive somewhere.|
|Gordon, where did you find the smaller MC and what size was it?? Was it a direcct bolt in swap?? I know my clutch pedal was quite heavy and it was overthrowing the pressure plate, though I never had that clutch get stuck like has been mentioned.|
I think the MGB GT V8 used a smaller MC from the factory. I got one from MGB Hive in the UK.
My car is still in pieces so I have not tried it out yet with the HTOB.
|Larry . . Mikes right. Also, the late cylinder is near 3/4" and the early cylinder is smaller. I swapped from late to early and solved my problem.|
|Gordon, By early, are you refering to the mark 1 MG 63-67? The Moss catalog doesn't give any details.|
|HRMMM sounds so simple I HAVE to do it!!! |
Just let us know about which one.
Your using the Webber/McCleod HTOB unit?? was your pedal just to hard with the late model (I have a 78) Master?? The early one lightned it up a good bit?? I would think it would also lessen over-extending the HTOB as well.
|OHHH update on my HTOB issue, I got the motor out of car today and tore clutch down. found out that the adjuster ring had not seated fully against the spacer, the rubber o-rings has adhered to the input shaft and stopped it.. had about .150 gap, so there is my gap needed. I finally got them off, cleaned everything and coated the input shaft with antisieze and the adjuster slide right on and seated fully, YEAHA!!!|
Engine is not back in the car, hopefully now I can start the long and final assembly and wiring. Also all the new guages, ughh, gonna be a long many weeks.
|Larry . . . I didn't think the later style cylinder gave too much pedal pressure, but I definitly like the lighter pressure of the early style cylinder. Much easier for my wife to drive, as well. The HTOB I used is a Howe Steet unit for chevy trans. the instructions say to use it with a 3/4" Master cylinder (same as late model), but our MG pedals must have more available travel than some cars. I should have observed the clutch travel and installed a pedal stop, but . . . . .|
It's fixed now and I'm please with it so far.
|Maybe it is the cheap clutch kit I have that has hard springs?? Being that it is all ford stuff it could very well be stiffer than the BOP stuff. I was OK with it, just compared to my Mazda truck it took a bit to get used to.. It will soon be out only manual trans car though, so no future worries about adapting..|
|After putting on close to 2000 miles to and from and during the 2003 meet with my Webber/McCleod HTOB in our MGB/Olds V8 with GM T5 I found the pressure to be just fine as did Amy. But upon getting into my 1998 Ranger 4.0L V6 on my return I thought there was something wrong with that clutch as it took nearly no effort to push the pedel to the floor. Its been 3 weeks now and I'm just getting used to the Ranger again. Detroit and Japan make the new cars and trucks for wimps and 16 year old girls!|
|Michael S. Domanowski|
|I also installed the larger bore MC with the Webber unit and find the smaller one would have been the better choice. It's perfectly OK as is, but has more travel than needed and less pressure would be nice. When time comes to replace the MC again I'll go with the smaller bore.|
Another thought: I haven't checked for a few years on prices, but there are some companies making a 2 or 3 disc clutch in something like an 8" diameter with a diaphraghm type pressure plate. Needless to say, pedal pressure would be noticeably less and so would the weight added to the flywheel. Something else I may look into on the next engine.
This thread was discussed between 15/04/2003 and 21/05/2003
This thread is from the archive. The Live MG MGB GT V8 Factory Originals Technical BBS is active now.