Lotus Elan and Lotus Elan Plus 2 Forums

In connection with the Elan 5-speed transmission must likely we will need to employ a concentric slave cylinder for the clutch. So I thought it would be useful to begin collecting such information -- particularly dimensional data.

Searching ebay I found concentric slave cylinders for Ford, Chevy and Jeep applications, but no hard data. At LocostUSA.com I found several references to using a unit from a Saab 900, specifically cylinder nmbr. 4776308 with throwout bearing nmbr. 8721995. Doing a search on the cylinder nmbr lead me to the following interesting AP Racing drawing,

http://www.apracing.com/car/drawings/cp3959_1cd.pdf

and the AP Racing web page.

http://www.apracing.com/car/slave/push.htm

Also, apparently Saab has used several different concentric slave configurations.

http://www.partsforsaabs.com/default.php?cPath=86_89

"Demon Tweaks" (sp.?) have a fair selection together with mounting adaptors & release bearings in their catalogue.
Good luck
John

Burton Power has a selection of concentric parts ? I?m sure they can tell you exactly which parts to use for your set-up.

https://www.burtonpower.com/product_main.aspx?home.aspx

I am aware that the Alan Voigts T9 kit uses Saab parts, but exactly which I do not know. Perhaps a call to him may help. 0151 630 3575.

John,

I forgot to ask - please let us know what conclusions you come to.

johnc wrote:In connection with the Elan 5-speed transmission must likely we will need to employ a concentric slave cylinder for the clutch. So I thought it would be useful to begin collecting such information -- particularly dimensional data.

John,
I have not lost interest in this discussion, the "day" job has just been very busy lately. The annular slave cylinder must fit over the cylindrical "nose" of the input shaft bearing retainer. Diameters following:
Elan 4-speed: 1.19" (30.2 mm)
Ford T-9: 1.32" (33.6 mm)
Tremec T-5: 1.44" (36.6 mm)
The AP slave cylinder for which you supplied the drawing has a bore of 30.4 mm and so is only useful on the standard Elan box. Annular slave cylinders are available from Burton for T-9 and T-5 gearboxes, McLeod also has them for the T-5. There really is no shortage of options for annular slave cylinders regardless of the gearbox of choice.

Russ, I agree with your observations.

The reason I posted the link to the concentric slave drawing was because it provides some comprehensive dimensional data. Granted it is only one data point in the scheme of things. Todate I have not been able to locate on the Internet similar dimensional data for other concentric slaves. My current assumption is the overall dimensions given are in the ball park, and thus provide a basis for getting a feel for space allocations within the bellhousing.

There are a number of concentric cylinders for the T5. I'm using one from McLeod engineering. I got a nice Ford 8.5" clutch from them also.

Tom

There seems to be two styles of hydraulic concentric slaves -- bolt-on, and slip-on which slide over the cylindrical "nose" of the input bearing retainer. According to McLead web site the rule of thumb is to use the bolt-on if the bellhousing depth is 6.5" or less, or if the distance from the rear face of the bellhousing to the clutch pressure plate fingers is less than about 3".

On my stock Elan S1 the distance from the rear face of the transmission to the pressure plate surface is 2.75". Using the Mustang 2.3L bellhousing would increase this to 3.5".

Ah, the elusive 3/4" of input shaft length. Given the larger pilot bushing from Bean, I think no modifications to the Ford T5 input shaft are necessary if you use the 2.3L bellhousing.

My unit bolts on to replace the T5 input shaft housing. I guess I'd call it a bolt-on, but it is available in very short lengths and has worked fine in this application using a standard Lotus pressure plate. I have detailed meaurements in a notebook somewhere.

Tom