Pigsy
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| posted on 23/5/19 at 11:52 PM |
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St170 to Mazda rx8 gearbox.
Hello everyone. I have mated an st170 to an rx8 6speed box. St flywheel. Ford transit heavy duty clutch complete. Rx8 slave cylinder and thrust
bearing and pivot lever/arm. 10mm adapter plate.
I’m getting problems getting in to gear. I understand the problem of needing a longer slave pusher “pin”. I made one 10mm longer to make up for the
adapter plate thickness.
Has anyone any useful suggestions as I don’t want to pull the engine and box again. It’s a lot of work in the mgb gt that I’ve put it in. Only just
fits.
Thanks ”Pigsy”.
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Nickp
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| posted on 24/5/19 at 07:43 AM |
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Are you getting full travel of the slave cylinder?
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Pigsy
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| posted on 24/5/19 at 09:05 AM |
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Yes I believe I am. It’s a new slave cylinder and it’s bled well.
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big_wasa
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| posted on 24/5/19 at 09:52 AM |
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Nobody uses the St dual mass flywheel, it's a very heavy piece of scrap.
They are a lot thicker than a solid flywheel. You may be over compensating if your bassing it on what others have done with a solid flywheel.
Have you used the transit cover plate or the st ? The st won't take the cush drive off a conventional clutch.
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Pigsy
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| posted on 24/5/19 at 04:14 PM |
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Hi. I did use the dual mass. It was recommended by quite a few people who had problems with the single mass flywheel. Ho hum. The clutch was complete
and had the cover. I’m using the Rx8 thrust bearing. The clutch was very much like the st170 set but had the different spline count. I don’t know the
Rx8 cover depth.
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CosKev3
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| posted on 24/5/19 at 04:16 PM |
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Does the input shaft reach to the spigot bearing?
Presuming you've fitted a spigot bearing for RWD set up?
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Pigsy
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| posted on 24/5/19 at 04:33 PM |
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Prompt reply thanks. I believe it does. There are no unusual sounds or vibrations coming from that area. I had the car on stands until yesterday
evening and could run it and once in gear to start it. Interestingly, I could with difficulty change gear to second using the clutch pedal. It won’t
go into gear with the clutch depressed and just crunches cogs. It just did not push the pivot arm enough to get it in gear or for a good change. I
have lengthened the slave cylinder arm this afternoon, but just too much and it’s not in the car yet.
I’m chasing the receipt from the clutch and cover plate. I want to be sure of what I’m saying regarding what it goes into.
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Pigsy
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| posted on 24/5/19 at 04:38 PM |
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Sorry but what did you mean by: The st won't take the cush drive off a conventional clutch.
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big_wasa
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| posted on 24/5/19 at 04:59 PM |
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The st uses a dual mass flywheel and a solid clutch plate. Conventional clutches would have springs to cushion the drive line and a solid flywheel.
This hub of springs and rubber has to fit in the cover plate or sometimes the flywheel. If this is the wrong way around or in a cover plate that
doesn’t clear, you won’t be able to depress the clutch properly. But I don’t know the clutch you have used.
I still haven’t heard of anyone picking an St fly over a solid one. Any ideas why ?
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Pigsy
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| posted on 24/5/19 at 05:22 PM |
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A local mechanic with and st converted had this problem: The new flywheel had a very slight vibration. He took it for a ride and while revving the
engine it smashed throught the side of the block, smashed the bellhousing to pieces, smashed the rad and dented the bonnet. It shattered in 2
sections. Could have been faulty but it was too damaged to tell. It was a lightweight but not cheap. He tunes st’s. Has happened to him more than once
but not this seriously.
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rusty nuts
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| posted on 24/5/19 at 05:46 PM |
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Was he using a flywheel that had been lightened or was it a lightweight steel flywheel? In suspect your lever pivot maybe too short , a longer one
would bring the thrust bearing closer to the cover ? Think you would have to measure the clearance you have at the moment?
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CosKev3
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| posted on 24/5/19 at 07:08 PM |
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quote:
Originally posted by Pigsy
Prompt reply thanks. I believe it does. There are no unusual sounds or vibrations coming from that area. I had the car on stands until yesterday
evening and could run it and once in gear to start it. Interestingly, I could with difficulty change gear to second using the clutch pedal. It won’t
go into gear with the clutch depressed and just crunches cogs. It just did not push the pivot arm enough to get it in gear or for a good change. I
have lengthened the slave cylinder arm this afternoon, but just too much and it’s not in the car yet.
I’m chasing the receipt from the clutch and cover plate. I want to be sure of what I’m saying regarding what it goes into.
You believe it does have a spigot bearing?
Pretty sure you would have had to add one when you converted it?
Good point about the clutch plates above,dual mass flywheel use a unsprung clutch plate,solid flywheels use a spring plate,they ate not
interchangeable
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big_wasa
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| posted on 24/5/19 at 07:50 PM |
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St comes from the factory with a spigot bearing.
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Pigsy
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| posted on 24/5/19 at 10:14 PM |
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I believe that the splined lay shaft that the clutch slides on goes into the spigot bearing. It has a spigot bearing. I would not have left it out.
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Pigsy
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| posted on 24/5/19 at 10:26 PM |
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The flywheel came from a company selling lightened steel flywheels. Don't ask me who.
The clutch cover was a Ford Focus Transit 1.8 Borg & Beck. The plate was an MGB 1800 BORG AND BECK HEAVY DUTY CLUTCH.
The cover fitted the flywheel as it should. The plate was the right size and thickness.
I have lengthened the slave push rod by 13mm. 5mm to make up for the adapter plate and 8mm to take the slack with the push rod seated deep in the
slave cylinder. I will try it tomorrow and let you all know.
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Pigsy
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| posted on 24/5/19 at 10:31 PM |
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The lever pivot is the standard rx8 item as used with this gearbox. It fits well.
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CosKev3
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| posted on 25/5/19 at 08:31 AM |
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quote:
Originally posted by Pigsy
I believe that the splined lay shaft that the clutch slides on goes into the spigot bearing. It has a spigot bearing. I would not have left it out.
Does the shaft reach the spigot ok though once the 10mm adapter plate is added?
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big_wasa
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| posted on 25/5/19 at 09:00 AM |
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I’ve never heard of one of the reputable steel flywheels exploding ie Ttv, Turbosport, Raceline.
I have seen some pretty scary looking lightened cast flywheels.
But if you where worried an Oem Zetec flywheel would be a better start than an St170 flywheel. They where so crap that you where lucky if one lasted
three years and the clutch couldn’t cope with a standard St so was changed half way through it’s life and upped from 230mm to 240mm. In cars with more
torque like a diesel Mondeo they chewed through the flywheels even quicker with the debris taking out the csc and the starter at the same time.
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Pigsy
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| posted on 25/5/19 at 11:08 AM |
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Thanks for that, but, as it's all fitted and in the car I will leave it there. Hindsight is the only exact science and at the moment if it
comes to it, then i will do it. You no doubt have a wealth of knowledge that is far greater than mine.
By the way, its not my first engine swap, Ive done many on Morris minors, cortina's, escorts and the like. Its the first new school with a
modern ecu, electronic ignition, itb's etc
Im in my 60's and not well at all. i"m struggling but wont give in. its taken 2 years so far. A couple of decades ago it was a months
work. Ho hum.
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Pigsy
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| posted on 25/5/19 at 11:14 AM |
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Does the shaft reach the spigot ok though once the 10mm adapter plate is added?
Adapter plate is actually 6mm.
As I said, I believe it does. I measured before hand and I have no vibrations or wobbling when the gear is engaged and everything is turning over at
high rpm with the wheels of the ground. I have no problems with the spigot shaft. Take it as engaged. The problem is i'm sure the slave cylinder
and pivot arm length. Im hoping to know this afternoon.
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Pigsy
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| posted on 25/5/19 at 11:16 AM |
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I have lengthened the slave push rod by 13mm. 5mm to make up for the adapter plate and 8mm to take the slack with the push rod seated deep in the
slave cylinder. I will try it and let you all know.
Please read the threads. I appreciate the help but please see what is written first.
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CosKev3
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| posted on 25/5/19 at 11:24 AM |
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I'm out,help yourself!
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Pigsy
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| posted on 25/5/19 at 02:40 PM |
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Thanks. If anyone else is listening, the slave cylinder is not getting full travel from completely compressed. It’s the clutch master not pushing
enough.
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big_wasa
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| posted on 25/5/19 at 04:46 PM |
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If your not getting enough travel at full stroke the option is to change master to slave ratio. Ie one or both with a bigger or smaller bore.
I am not telling you I know better or I know everything. I am just sharing my opinion and research and experience on the St flywheel and clutch combo.
The combination you have put together is pretty unique.
[Edited on 25/5/19 by big_wasa]
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Pigsy
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| posted on 25/5/19 at 05:23 PM |
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Thanks so much for the reply. I appreciate it very much. The mgb clutch master is an 18mm bore with a 25mm throw. I noticed this on eBay: Tilton 74
Series Universal Brake / Clutch Master Cylinder 1 1/8" Bore Size. The bigger bore will make for a very stiff pedal I expect but I can live with
that. The extra throw will be good. I think that there is another 6mm travel in the slave cylinder. I hope I’m right.
I have no problem with any suggestions. I was just being asked the same questions repeatedly and being told of for using a dual mass flywheel.
I appreciate your genuine help. I will just be happy if it works reasonably well
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