Clutch and Brake Help

[Talonaer]

Few little bits and bobs I can't quiet get my head around.
Working with a car that was previously heavily modified and trying to identify parts can be an issue.

In regards to the clutch and gearbox:
Is this a standard clutch cover from any of the models or an after market? It is marked Borg and Beck.

The rest of the system is a bored 948 +0.060 engine into this, what appears to be a standard flywheel (whole drivetrain is balanced), into this, standard looking clutch plate, and then into a ribbed gearbox with a set of gears with ratios that are very very close to the later 1500 gearbox (I am assuming they're aftermarket and that you can't transplant 1500 gears into a ribbed box.).

Also the slave cylinder is unknown size and is heavily pitted and needs to be replaced.

Front discs are on the front, with original drums on the back.

Next question is: What setup of Master cylinders and Slave cylinder would be most effective? Currently have a dual 7/8 but the valve is holed in the brake bore and I am happy to make up a dual system (Aka sebring style) with girling or modern master cylinders.

I unfortunately have little experience with brake and clutch systems and so am finding the information out there confusing.

My understanding at present is that my best option would be a later model slave cylinder, a dual 3/4 master cylinder (or 2 seperate master cylidners of 3/4 bore with a pressure relief valve on the front brake spur...)

Given that the engine is pretty well modified (948 +0.060, flat top pistons, 12g295 head, ?camshaft) I want to make sure I have a good way of stopping....

Thanks in advance. I know this is a subject area that is covered in alot of places unfortunately the complexity of this setup is proving to not be the best of starting points for someone who is new to Sprigeteering!

 

[Spridget64SC]

Looked through a couple of manuals last night because of the current discussions on these clutches. 6 springs seems to be the original standard factory setup across many 948 applications. 9 springs seems to be a very common aftermarket replacement and may have even been a factory change for the later 9CG engine units.

7/8" sized M/C will give plenty of fluid movement from the M/C to the brakes. Weakness is the single cylinder and less adjustability. Dual system will give about 1/3 more fluid displacement with the most popular cylinder sizes (5/8 front & 3/4 rear). Dual system will probably be less in pedal effort as well.

For the clutch setup, I think it is a tossup. Depends on clutch cover, release arm, release bearing and pushrod used. The whole deal has to release the clutch disc adequately throughout its wear life. I would go with the original slave (7/8") and either a 7/8" or 3/4" M/C. 3/4" M/C especially if you convert to the 1275 type clutch cover and disk setup (requires redrilling the flywheel for the clutch cover locating pins and bolts).

HTH
Mike Miller

 

[BlueMax]

The OEM pressure plate for the 948 engines are 6 spring, but if you want something that can handle more torque you move to the 9 spring. The 9 spring clutch fits the 1147 Spitfire as standard equipment, which bolts right up to the 948 flywheel and friction disc. You don't have to change slave cylinder it has a nice postive pedal.

 

[aeronca65t]

Yeah, I have an orignal 948 that came from an A35 sedan. I'm pretty sure it's never been touched since new and it has the 6 spring clutch plate too.

But I've seen the 9 spring plates in other 948s.

The Spitfire clutch swap sounds like a great idea.

 

[Talonaer]

the big problem on the brake front is the residual valve (metal type 10psi) has holes in it where the spring has worn. Also with discs the later type uses a 2psi restrictor valve (plastic).

If I could find a source I would just put a plastic restrictor valve in the dual 7/8 system, make do with the increased pedal effort, and get on with it.

No way am I putting it back together with a holed wrong valve and wrong bore size...

Sorry by dual system I meant one brake and one clutch M/c (not 2 brake). Ideal here would be 2 3/4's as the 7/8 is as rare as rocking horse ****. If I went for this would I be better with a later type slave (1" ? ) or the earlier 7/8 type?

 

[BlueMax]

The 9 spring was never used a standard equipment however you can see the 9 spring in the competition section of the factory parts manual. At times cars would come in to the dealer for warranty work due to a driver that was hard on the clutch. Service advisor would get the authorization through the BMC manger and they would substitute the 6 spring for the 9 spring so that the customer wouldn’t be back for clutch issues. That is why you see cars with the 9 spring in place of the 6 spring. Also sometimes the parts department was out of the 6 spring, what they would do is just subsutitue the 9 spring for the 6 spring, the customer would never know.

 

[Gerard]

Sorry by dual system I meant one brake and one clutch M/c (not 2 brake). Ideal here would be 2 3/4's as the 7/8 is as rare as rocking horse ****. If I went for this would I be better with a later type slave (1" ? ) or the earlier 7/8 type?

Talonaer.

You should review the write up on my web site. As mentioned previously by several others, I have been supplying these for about 5 years now.

https://gerardsgarage.com/Garage/Tech/DbrakeUg.htm

Tom Colby has ordered a number of these conversions, as have dozens of others.

 

[Billm]

Bluemax
I am surprised that it wasn't original but I will believe you-
I have only seen one 6-spring on a 948(in a Morris), all others were the 9-spring.
BillM

 

[Talonaer]

Gerard, I have perused your fantastic resources before and found them msot helpful. I have even been in contact with pastparts from the linked MASCOT article but they cannot supply pistons or valves which is what I would require.

Unfortunately I am on the wrong side of the pond to yourself. And once you add up the costs of: resleeving the M/C, adding in pistons, seals and push rods it becomes cheaper to source individual M/Cs and create a dual pedal box along with the other advantages. Unless I am working out costs badly!

I am just lost in regards to the clutch side of things if I split the M/C in this way. I would use a 3/4 M/C on the brake side + an inline 10psi restrictor valve. But on the clutch side I am unsure which M/C (7/8 [expensive] or 3/4) I require to use with which slave cylinder.

I am obviously not explaining myself well as every which way I phrase this problem no one quiet gets me :frown:.

The cheapest option, and one I would PREFER to try first would be to fit a restrictor valve (plastic type) into the original 7/8 M/C and to see how the system functioned. Unfortuantely sourcing the valves seems impossible. I need a replacement Residual valve just to return the current tandem M/C to a useable state for anyone. If anyone knows a source on these valves that would be fantastic...

 

[Westfield_XI]

Summit racing, Pegasus racing and others in the US and possibly the UK will carry the Willwood residual pressure valves in 10 and 2 psi. A quick google found speedflowshop.co.uk.......

 

[Gerard]

Gerard, I have perused your fantastic resources before and found them msot helpful. I have even been in contact with pastparts from the linked MASCOT article but they cannot supply pistons or valves which is what I would require.

Unfortunately I am on the wrong side of the pond to yourself. And once you add up the costs of: resleeving the M/C, adding in pistons, seals and push rods it becomes cheaper to source individual M/Cs and create a dual pedal box along with the other advantages. Unless I am working out costs badly!

Talonaer,

A couple things...

I don't know how you've calculated things, but Express Mail (USPS) is under $55 to the UK, Priority Mail is $41-$45. (We've shipped these as far as South Africa) It may not be cost effective to ship one<span style="font-style: italic"><span style="font-weight: bold"> from the UK and back</span></span>, but I could supply you with a core, which would probably be less than you shipping one over here. (I order all my Morris Minor parts from the UK, and shipping rates seem to be very high)

10PSI residual valve is way too high for disc brakes. That would be OK to use for the rear drums and you can get in-line residual valves for that. I do that all the time when converting Morris Minors to disc. I use 2PSI for front discs on a Morris, but that is only because of the physical position of the MC in relation to the front discs. It would be a solution on the Sprite, but you probably wouldn't need one at all for the discs. I would try just the 10PSI for the rear first.

If you want to try the plastic restrictor, they believe they come in the 3/4" rebuild kits. That would be the easiest, cheapest source.

Regarding your clutch, 3/4" or 7/8" MC coupled with a 7/8" slave would be fine. If you are talking about doing the two separate MC's, there isn't a 7/8" clutch MC for the Spridgets (other than the original), so you would want a 3/4" MC with 7/8" or 1" slave.

You can email me at pixelsmith@gerardsgarage.com if you want to pursue the conversion MC.

If you still have questions, let me know.

 

[Talonaer]

Thanks for the replys guys. Really is appreciated.

Thanks for noting the WIlwood valves, had spotted these, I meant the standard originals.

I did indeed mean sending you a unit to then receive it back.

I think I will rebuild the 7/8x2 MC. pop on a fresh 7/8 slave. stick one of these:
https://www.speedflowshop.co.uk/wilwood-residual-pressure-valve-569-rpv-1181-p.asp
along with a proportioning valve https://www.speedflowshop.co.uk/wilwood-proportioning-valve-1180-p.asp Seems the safest bet without totalling the currently non existant bank account.

Probably fretting over nothing but with the engine tuning/lighting of the car etc I don't really fancy going out with a dodgy braking system.

 

[Gerard]

Talonaer

Those are the residual valves I use (mentioned in my previous post).

 

[Talonaer]

thanks again to all for the help.

If it keeps me out of a ditch I will very even more happy .