Castillo817

I was just wondering if anyone has gone this route since every setup I've seen is to drill a hole on the clutch fork. I called Martin and he said it would be better to not that route that he used to do. Is this the right way or should I go with drilling a hole on the clutch fork? Seems a little sketchy the way I'm doing it.

tbone heller

I used the stock hole in the clutch fork, but I put a spacer between the slave & its mounting bracket.

Castillo817

How do you like the feel? Also, how big of a spacer?

tbone heller

It feels fine. I think I spaced it with a piece of 3/16" bar stock.

Castillo817

Cool. I'll space it out since it looks like it will be needed.

V8MiataMike

I actually have the hole in the fork further in than you do. I clearanced the bell housing a little so the slave and push rod would clear and I could move it in closer to center line of the trans.

Castillo817

So what you did is to drill a new hole on the clutch fork?

V8MiataMike

Yes. It looks like you have Martin's parts there. He said not to drill a new hole into the clutch fork?

Right now the geometry of your setup looks way off with the rod at an angle to the cylinder. My clutch rod points inside the bell housing and actually goes inside when clutch is depressed (have to make sure it does not contact pressure plate by the way). I also added an extra washer between the bell housing and clutch fork pivot ball.

Castillo817

From what I remembered, he did say not to drill a new hole into the clutch fork. I'm going to double check with him and see what he says.

Yeah there's an angle which doesn't seem right to me.

MRM331

The idea behind drilling a new hole is to correct the slave cylinder geometry. Because the slave has an iron bore and an aluminum piston is is essential that it's pushrod is not angled to the bore of the slave. If it is it will cause the piston to wear unevenly, begin to break down and eventually (meaning a year or so of hard use) fail. To correct this you have two options, move the slave cylinder out from the centerline so that it lines up with the existing hole or drill a new further inboard hole in the fork to correct the angle. The advantage of the first approach is that it can be done easily. The advantage of the second approach is that it also gives you a little more throw because you are reducing the distance between it and the fork's pivot. Unfortunately doing this requires drilling a new hole in the case-hardened metal of the fork which is not easy. It also locates the end of the pushrod in the bell housing which may make it slightly harder to adjust. However it also does make for more room in the trans tunnel to get at it and adjust it so maybe that's a wash. Whatever you do make sure to put some type of backing plate in the bell when you drill and tap the bolts that hold the kit's L bracket or make up some struts to brace the slave against the trans itself. The flat portion of the bell housing that the L-bracket is attached to is not strong enough on its own to not flex when the clutch is disengaged which will cost you some throw movement and further mess with the geometry of the pushrod.

Because you are increasing the movement of the piston in the bore of the slave its also recommended to purchase a new slave for the build. The inside of the bore that does not experience movement in a stock Miata will begin to rust slightly. When the rubber piston seal of a used slave begins to move over the rusted inner portion of the slave it will quickly break down and begin to leak.

Good luck with your project,
-Jason McCully

movieboy4fun

Hello All,

Just starting my Master / Slave set up, I have a CJ Master with 13/16" bore and the stock 3/4" bore Miata slave, (new). I am curious about the slave push rod I see in Castillo817 photo's. To my eye the push rod appears to be a chunk of grade 5, ( prolly Chinese grade 3, LOL ) 5/16" Ready Rod, Nyloc nut with a flat washer and a old rocker arm pivot. Just want to confirm that the course tread and grade 5 ready rod is up to the long term task. I would be inclined to use at least a grade 8 bolt with enough thread length for adjustment, possibly fine thread. Skip the Nyloc and use a shouldered nut with a jam nut, ( another shouldered nut ?), then rocker pivot on the end. The reason for the two shouldered nuts is so one side shoulders the rocker pivot and the second would be used to catch the slot in the stock rubber boot. OVERKILL !?, open to opinions / ideas of tested current set ups.

Ford5.0

I did a 302/T5 swap into a Ford Ranger years ago. I made up a clutch slave using a push rod made out of grade 5 all thread. I used that truck as my daily driver for 175k miles and never had any issues with the clutch or anything else for that matter. My Miata setup using Martin's kit seems to work, although it will probably be several weeks until I attempt to start it. I don't understand the need to adjust anything once its set up. In my mind, if clutch pedal push rod has no preload or slack at the master cylinder and the slave cylinder is completely retracted and its push rod is adjusted so the throw out bearing is just touching the pressure plate, you should be good to go. It should then be self adjusting for any clutch plate/pivot wear.

movieboy4fun

Ford5.0
Exactly what I wanted to hear, great info

Dean0