Mazda Motorsport SUB question
 

I've got a set of the MMD SUB lifters and need to get shims for them. I've read 2 different things and am not sure which is correct. I know you either use 5.5mm or 6mm lash caps (from supertech) and they can either go on the stem of the valve or the stem of the lifter. I have seen it mentioned that some shims won't fit over the valve stems because the part of the valve stem that sticks out of the retainer is possible short.

So which is it 5.5mm or 6.0mm and on the lifter or on the valve.

For the Supertech buckets, the 5.5 caps sit on the lifter itself (upside down) and the 6mm caps sit on the end of the valve. The lifter has a 5.5mm stem and the valve is 6mm obviously. The 5.5mm caps are less of a hassle because you don't have to be worried about interference between the shim and the lifter. If you put 6mm caps on the valve, you have to be sure that the cap is sitting on the tip of the valve and not touching the retainer or Bad Things(TM) happen. Not sure what size the MMD lifter stems are but that's an easy thing for you to check.

Thanks. I think the supertech lifter stems being 5.5mm is what started my confusion. I'll check the diameter when I get home.

MMD lifters are around 5.56mm. Wonder if I can just toss them in the lathe and turn them all down to 5.5mm. Seems easy enough...

$20 says they're 5.5mm nominal.

I have a set of new MMD solid lifters, and a whole stack of 5.5mm and 6mm shim caps. I'll check for you in the morning if the 5.5mm shims fit fine... I hadn't tested as I assumed they did.

I run two shims per valve due to the smaller base circle cams... a 6mm on the valve stem and a 5.5 on the solid lifter. The 6mm shims all had to be machined so they don't touch the retainers.

Thanks guys. If I can run the 5.5s I'll have a bit more peace of mind.

I run Mazdaspeed lifters and super tech 6mm caps on the valves. They don't touch the keepers, the NB keepers have a groove around the top that they fit nicely into. Been running this setup for a little over a year I think with no issues.

The lifter stem to lash cap can be a very tight fit. I had a hard time getting them off of some of the stems. Some will fall right off when a lifter goes in or out of the bore. It really sucks to install the camshaft and find out the cap is floating around between the stem and inside lifter wall.

A bit of oil on them stops them falling off. Plus if they do the lifter clearances will be out.

Stem of lifter I measure as 5.56mm too. My '5.5mm' caps measure at 5.565mm ID. Maybe it's a standard sizing. I'll call and ask my shim supplier as I need to order some soon.

So the 5.5mm supertech caps fit on the MMD lifters?

Yes, and a steady slow hand [Insert Mom joke].

Spoke to my shim supplier. There are two sizes they do (not supertech) 5.5mm and 5.6mm. He said the 5.5mm shim caps are pretty much exactly 5.5mm ID and won't fit on. He said to run the 5.6mm shims and they will be fine. If loose install with some grease to stop them dropping off.

I can't help you with the Supertech sizing. You'll have to call them.

With some more reading I found this. https://forum.miata.net/vb/showthread.php?t=567672. Looks like I need 6mm shims, or throw the shims in a lathe (lol). Just need to be sure there is no retainer to shim interference

If you are unsure and want to put the issue to rest, just order one or two and do a trial fit. Once you are comfortable with how it all goes together, order what you need to finish it. When I set mine up, I ended up ordering caps on a few occasions until I was completely comfortable with the whole process of setting them up.

I'll do that. Apparently cutting down the stem on the lathe is actually a thing. Maybe I'll just do that.

The lifters are hardened but you'll be able to trim them down on the lathe with a carbide easy enough. You only have to take off a small amount so you won't go through all of the hardened layer but it's not ideal. I think it's better to run 5.6mm shims or 6mm shims on the valve. I have to run both for my engine.

With the 6mm caps on the valves, you need to make sure the cap shims are a low profile shim so they don't hit the collets. My shim provider has two profiles with the low profile only 2mm or so which should clear the collets. Last time I rebuilt the head I did have to sand a couple of the shims down for better collet clearance as my valves had also been machined and some had more clearance than others, It only takes 30 seconds or so on some 400 grit sand paper to drop a few thou.

I stick some wet and dry paper to a sheet of glass with some oil, then just circle the shim on the paper with a finger. You can easily take off up to 5 thou off the top to get tolerances tweaked but you need to make sure they stay level. Sanding the bottom the shim is even faster as the surface area is next to nothing, so you can take off 1mm or so without any issue, plus it's not so critical to get perfectly level.

I'll order a 6mm supertech shim to fit. Hopefully will be getting my head/block back this week, i think it will all make a lot more sense with the parts in front of me.

Here are the options:

https://cimg3.ibsrv.net/gimg/www.mia...326cb169c7.jpg

Awesome thanks. Looks like i can only get 5.6mm shims from AUS. So i might be going on the valve.