Tom M'Guinn

I got the 105mm pistons from Tom C today, picture below.

How do you work the coily wrist pin clips? Need a special tool?

The spec sheet lists .001" (.025mm) cylinder wall clearance, but says to subtract .002" (.05mm) if pistons are "PRO-COATED" ... I'll check with Tom C, but assume that means these are not "PRO-COATED" (since that would create negative clearance).

DDP

Pretty!

Jakerx

sweet! i can't wait for my 106 mm...

Crazy Eddie

LUCKY DOG !!!
I know who's gonna have trouble sleeping tonight !!
It been awful quite over there !!

Zero10

Hehe, you had the same puzzling statement I had. I got an explanation from my machine shop. If they were pro-coated, you would have a much larger piston-wall clearance.

You have never installed sprial clips before? Their purpose is to avoid all the frustration, and special tools. They're very handy. They're also used on the Rennbay balljoint kits.

I wish I could draw a diagram of how I installed mine, but it can be done with a scratch awl, and 2 fingers. I use the awl to press them down, and make sure that they're fully clipped in.

I insert one finger (my forefinger) through the middle of the sprial, and catch the very end of the bottom part of the sprial under my fingernail. Then insert that into the groove for the circlip. While holding the sprial clip with my other thumb and forefinger, rotate the one on my right hand (the one through the clip) to seat about half of one circle of the clip. Once it's this far, it will hold itself. I then remove my finger, and use the end of the scratch awl (or on the first one, a flat-head screwdriver) to press the rest of the clip down, a little bit at a time, until it seats all the way around. I wouldn't look forward to removing one of them though, lol.

IMO they are superior to the circlips for installation, but who knows for removal.

Once fully installed, their outer diameter is larger than the inside diameter of the circlip bore, and they aren't coming out.

I hope something I said was helpful, and made sense. It's getting pretty late here.

theedge

Tom once you figure the spirals out, youre going to look at them and say "Now thats a damn fine idea" or something similiar. It took me a few trys to get the spirals in on the rennbay ball joints, but once theyre in they look VERY strong, and easier to remove than circlips I think.

For tools, a small flat blade screwdriver worked for me. Removal looks to need the same, just one or two of those.

Zero10

I remember now, one end of the sprial is tapered, so to remove them, you can pull that end with a flathead screwdriver, then removal is the reverse of installation (haha! opposite of the Haynes manual!)

They are better than circlips IMO.

ehall

Nice Tom. Are those for Alusil blocks, or sleeved blocks? I'm guessing sleeved, but you could have bored out a 3.0 block. I can't remember what exactly you were up too. Anyway...Damn shame sumtin that purtty hasta get durty!

Ski

The coating is a mixture of iron and graphite; iron for Alusil friendly and the graphite for durability and oil retention. Coat the skirts with a light coat of 30wt dino oil and a light coat on the cylinder bores before install. .001 is the clearance to tell the machine shop for the bores, look great Tom.

Chris White

OK, I'll bite - why 105? Are you boring out a 2.5 that much? That should leave you with just a tad over .200 wall thickness vs the stock .316.
What are you going to use for a head gasket?

Just curious! Looks like it will work OK, I do worry about the cylinder movement when the walls get thinner but I don’t have any data points to say when the walls are too thin.

Chris White

PS – I just ordered some 105mm pistons for a sleeved project…

Ski

Toms got a 3.0 block Chris but it had some scoring.

Chris White

Doh! Homer Simpson moment….I have been working on a 106mm engine based on a 3.0 for long enough I was thinking that 106 was the stock size!!!

Tom M'Guinn

Right, it's a 968 block that got botched up a bit when the machine shop tried to take it to 104.5 for Mahle/Andial 104.5 8v turbo pistons.

(Those 104.5 pistons will be for sale soon btw, but I'll be away for a week or so before I can deal with that.)

ehall

Tom, let me know when the pistons go up for sale.