K head conversion, timing cover and jackshaft thrust plate questions
Turbo Mini Forums

Searched. Looked at all the K head conversion pics and explanations I could find. Now I am cutting my plastic mockup pieces before cutting metal. But I am not happy with the block front (timing) cover designs I have seen. Most of the timing covers I have seen use a cam/jackshaft pulley similar to those old belt-drive conversions, the ones for replacing the stock timing chain with a belt. Those pulleys have a large diameter spindle with a big machined recess, big enough to allow a socket in there to tighten the Mini cam/jackshaft nut. Then the big spindle needs a big oil seal, and the seal needs the cover to have a big hole, and so on. I have one of those on an engine over in the corner, I will take a pic and post it here later (camera needs charging).

My thinking is that I am never going to need to remove the jackshaft as an individual unit, well not unless I am doing an engine rebuild, in which case I would be removing the front timing cover plate anyway. This is bringing me to a different timing cover and pulley design, where the jackshaft snout is drilled for a central bolt, similar to the K head cams. I have sketched everything out but haven't cut yet. My next conundrum is what to do for the thrust plate. What was that babbitt material on the Mini cam thrust plate? Are all the conversions using a stock tricorner thrust plate? What is a suitable thrust plate substitute material if I choose to not use the stock thrust plate? If I have to, I will go back to the textbooks, but I thought it might be faster to just ask for help. Any guidance or links to references is much appreciated.

Edit: took a pic...

Edited by scooperman on 5th May, 2012.

There's lots of pics on my build thread of how I did mine.

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=169346

Here's sprockets build too.

http://www.turbominis.co.uk/forums/index.p...id=229847&fr=50

https://www.facebook.com/pages/Fusion-Fabri..._homepage_panel

www.fusionfabs.co.uk



1/4mile in 13.2sec @ 111 terminal on 15psi

I never understood wht the cam thrust plate only has one babbit face when both sides bear thrust loads. This is one reason I decided that a thrust of aluminium woul work just fine. The cam no longer bears any real load anymore other than the oil pump.

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A flat tappet cam shouldn't walk a lot. However, that clockwork distributor gear put some wobbles into the cam every time a valve spring accelerated/decelerated the cam within the chain slack. My impression was that the oil pump took any inward load, and the thrust plate took the outward load. I have looked at many old thrust plates and didn't see much wear on the gear side, only the cam side. Anyway, one more reason to get rid of the distributor.

Oil pump takes no thrust load. The thrust plate takes it all in both directions

You can have a look at my build thread aswell, it its similar to matty's.
(Pinkys build thread)

"So wat we gonna do tonight Brain?"
"Same thing we do evernight Pinky!"
"Try to take over the world!"

thank you Matty, Sprocket, Pinky. I went back and read them all again, mucho good stuff. I also found a Sprocket build thread on the Efiminis forum, but the pictures are all gone, just text now.

For now I will continue trying to make a timing cover without the removable/separate seal holder components. Since I will be chopping up an old cam to make my jackshaft, if needed I can trim its length as well, so that gives me some thrust plate options other than the original design. Sprocket tells me the thrust plate handled thrust on both sides, one side of my head is bald now from scratching it. I could have sworn the stock thrust plate only had babbitt on one side. I need to dig through my old parts and find some that show a lot of mileage, see if any of them show any wear at all on the steel side.

One odd thing, when typing in "pinky's build thread" into the forum search, nothing is found, and it changes the spelling, putting a slash in front of the apostrophe. To find it, just type "pinky" in the search.

Edited by scooperman on 7th May, 2012.

The thrust plate prevents thrust movement in both direction within the specified tollerance. If the cam is touching the oil pump housing, which it can, you need to use a thicker front plate gasket, which is why good quality gasket sets supply either one thick gasket, or two different thickness gaskets for the same application.

You can see the mechanics of it simply by fitting the thrust plate onto a loose cam, and then install the sprocket and retaining nut. You can then measure the running clearance between either the cam and thrust plate, or the thrust plate and the sprocket.

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well dog bite my cats, Sprocket is correct. I found old thrust plates and there are witness marks on the steel side. How do I come up with tolerances/numbers to design a new timing cover, should I try to copy the measured amounts from an old engine, or is there some spec?