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Group Buy: Solid Lifter Upgrade
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Min  



Joined: 04 Nov 2002
Posts: 2368
Location: Vernon, British Columbia, Canada

PostPosted: Thu Feb 21, 2008 5:24 am    Post subject: Reply with quote

interesting idea, except that I don't have a set of good followers I'd trust my new cam touching.

The lash also has to be set based on all the bits being hot. My integral cam came with some pretty specific instructions I'm going to follow.

Min
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dpw928  



Joined: 02 Nov 2002
Posts: 1860
Location: owasso, ok 74055

PostPosted: Thu Feb 21, 2008 6:08 am    Post subject: Reply with quote

Quote:
The retaining wall can be machined...right? That's the whole point, you don't use the stock lifters, so any lifter can be made, with or without retaining wall.

I first thought they'd go on top, never seen shims beneath the lifter... always on top or the lifter itself (opel).

The weight loss is a serious advantage imho!

If it is possible to go hydraulic, that would be awesome... could there be a way to split the oil tube above the cam? if so, you have oil pressure from there and in theory no oil loss because the lifters don't use oil themselves...which doesn't affect the oiling of the cam...

but there have to be channels in the head to feed the lifters and I guess that isn't easy to build in the head.... can't bolt on something which feeds the lifters..

I'll think about this... with some creativity it could be done


Only problem is that there is nothing to machine. Porsche didn't leave a wall on the sides like VW and Audi.

Steve,

The new lifters don't have adjusters and using the old lifters to imbed the new cam is not acceptable. I can't see how it can be done right without 2 or three cam removals.

Dennis
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bass gt  



Joined: 02 Dec 2004
Posts: 971
Location: Johannesburg for now!!

PostPosted: Thu Feb 21, 2008 6:19 am    Post subject: Reply with quote

Dennis,

You're bedding in the cam, no tthe lifters. As long as the followers are not damaged, they will suffice to get the initial bedding in done. Re the hot works. Fire up ypu engine, and get it good and hot. You will be suprised at how hot it isn't Pop it in the oven and measure the hot lobe value and compare to the cold. This will give you the expansion value. Now you can calc the hot lash value. And it's better to be slightly lose, as the followers need to rotate under the cam when in use. If the follower binds on the cam, real damage can occur, especially if the valve is not closing sufficiently, which will burn the vallve seat.
Te bedding only takes 20 mins or so. Old followers really are OK for this. Better to bed it in slightly tappety, than bind a new cam with new followers and wreck the lot.

Steve
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dpw928  



Joined: 02 Nov 2002
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Location: owasso, ok 74055

PostPosted: Thu Feb 21, 2008 12:17 pm    Post subject: Reply with quote

Steve,

Switching from an old concave lifter to a new flat lifter can damage the cam lobe and definitely will accelerate the wear on the lobe. This is why all the manuals recommend that lifters and cam lobes not be interchanged during teardowns.

The gap can be estimated cold. Just keep in mind the head, being alloy, will expand more that the valve/lifter when hot.

Dennis
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Martijnus  



Joined: 29 Dec 2006
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Location: Netherlands

PostPosted: Fri Feb 22, 2008 12:28 am    Post subject: Reply with quote

dpw928 wrote:
Quote:
The retaining wall can be machined...right? That's the whole point, you don't use the stock lifters, so any lifter can be made, with or without retaining wall.


Only problem is that there is nothing to machine. Porsche didn't leave a wall on the sides like VW and Audi.



I thought new lifters were made...? so that has nothing to do with what porsche did or didn't do... because the porsche stuff is thrown directly in the junk bin...

I'm not sure if you don't understand me, or that I don't understand you
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924 "50-jahre", 1981.
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dpw928  



Joined: 02 Nov 2002
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Location: owasso, ok 74055

PostPosted: Fri Feb 22, 2008 12:37 am    Post subject: Reply with quote

The Porsche HEADS (not being replaced) do NOT have a sidewall to retain the upper shims like the VW and Audi heads. I've gone through the same drill with a machine shop that cut down the lobes on my 80 NA cam. They ended up rewelding the cam. Take a look at the head pictures in the Haynes manual. If you put a shim on top of the lifter, it will be pushed off on the first cam rotation.

Dennis
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Rasta Monsta  



Joined: 12 Jul 2006
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PostPosted: Fri Feb 22, 2008 1:59 am    Post subject: Reply with quote

I think the shim goes inside the bucket.
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jazz guy  



Joined: 26 Nov 2002
Posts: 411
Location: Colorado

PostPosted: Fri Feb 22, 2008 5:13 am    Post subject: Reply with quote

I'm not sure I will help clear things up or make them even murkier, but here goes...

I've done a fair piece of work on '75-'90's VW and Audi watercooled engines and their lifter set up is different from what Dan is talking about doing. The Piper/Arrow lifters use a shim, sometimes called a lash cap, that fits between the top of the valve stem and the bottom of the lifter. The valve lash is adjusted by using shims/caps of different thicknesses to arrive at the appropriate lash gap. The downside is that the cam and lifter have to come out to change the shims/lash caps. I have used this type of setup on a couple of VW engines after I had installed reground sport cams.

I think what Martijnus is referring to is the VW/Audi old style solid lifters that look similar to our stock 924 lifters, but don't have the adjuster mechanism built into them. They too, adjust with shims, but the shims fit into the top of the lifter, not underneath the lifter/follower like the Piper/Arrow units that Dan is talking about. The shims are solid metal, puck shaped pieces that fit into a recess, or bucket, in the top of the lifter. The shim itself becomes the surface that touches the cam.

There are several advantages to this design. If the top surface of the lifter/follower gets worn or damaged, all you do is replace a cheap shim, and you are good to go. Also, the lifter has a shoulder around top that forms the sides of the bucket that hold the shim in place. VW makes a tool to lever down on the top of the lifter shoulder, depressing the lifter, which allows you change shims without pulling the cam.

The downside is that I doubt there is any weight savings. The shims/pucks are pretty thick and are solid metal, so that design probably weighs as much or more than our oem 924 lifters. Though I have never weighed them.

I think Martijnus is saying that aftermarket followers for the 924 could be designed/machined to function in the manner of the VW units, with the shim on top.

Cheers, Brian
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Min  



Joined: 04 Nov 2002
Posts: 2368
Location: Vernon, British Columbia, Canada

PostPosted: Fri Feb 22, 2008 8:33 am    Post subject: Reply with quote

jazz guy wrote:
The downside is that I doubt there is any weight savings. The shims/pucks are pretty thick and are solid metal, so that design probably weighs as much or more than our oem 924 lifters. Though I have never weighed them.


The other disadvantages is the tendency for the VW shiming system to come flying out and bouncing around inside your motor at high valve lift..... Their system was designed for low revving low lift motors. And even in those there is the occasional occurance of shims coming out.

as previously mentioned, the lash caps don't go on the valve, they go on the lifter.

Min
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jazz guy  



Joined: 26 Nov 2002
Posts: 411
Location: Colorado

PostPosted: Fri Feb 22, 2008 3:58 pm    Post subject: Reply with quote

Quote:
The other disadvantages is the tendency for the VW shiming system to come flying out and bouncing around inside your motor at high valve lift.....

I guess that could happen, I've just never seen it, and I've had a lot of Vdubs. That is how I developed an interest in German autos. I used to run a Schrick cammed VW GTI at club events, SOLO, and track days and never had any problems. Though, as you say, the engines were relatively low rev designs. Even with the hotter cam and porting, it really wasn't worth pushing much past 6500 rpm.

Here is an example of the lash caps I used when running reground cams.

They are designed to sit on top of the valve stem, and don't fit into the bottom of the follower. While they may differ in design from Piper shims (though I've never seen a Piper shim in person), effectively they work the same. They both affect the lash gap by shimming the distance between the top of the valve stem to the bottom of the follower.

See I knew I was going to clear as mud. Sorry.

Cheers, Brian
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jazz guy  



Joined: 26 Nov 2002
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PostPosted: Fri Feb 22, 2008 4:03 pm    Post subject: Reply with quote

I'm also sorry for the slightly off topic hijack of your thread, Dan. I really enjoy following your progress, keep up the good work! I'll be quiet now.

Cheers, Brian
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Min  



Joined: 04 Nov 2002
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Location: Vernon, British Columbia, Canada

PostPosted: Fri Feb 22, 2008 4:47 pm    Post subject: Reply with quote

those are exactly the same shims, you just flip them over and put them on the nib on the bottom of the follower instead of on the valve.

Min
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ideola  



Joined: 01 Oct 2004
Posts: 15506
Location: Woodstock IL

PostPosted: Fri Feb 22, 2008 11:33 pm    Post subject: Reply with quote

Good discussion guys!

Bottom line is that I trust Bass GT. He's using the Piper solid lifters, and if they're good enough for him, they're good enough for me

We have three so far with their hat in the ring:
Me
Tom Cooper
Raceboy

Any others interested?
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Martijnus  



Joined: 29 Dec 2006
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Location: Netherlands

PostPosted: Sat Feb 23, 2008 12:47 am    Post subject: Reply with quote

jazz guy is right about what I mean

about those weight savings, the shims themselves are indeed solid and 'heavy' material, depending on how thick the shim will be.
A 6mm shim will weigh twice as much as a 3mm shim which is quite a regular size...

I can't imagine that those 'top-shims' get out of the bucket... but in theory it could happen... most of the time it's hard to get these shims out because of the oil film between the shim and lifter...but who knows how hard it is at 90 degrees centigrade with thinner oil and moving parts....

for me this option would be the easiest, from the viewpoint of wear, availability of parts etc...

for track use I can understand that everything has to be as light as possible and it doesn't matter if you have to spend more time and money to obtain parts (however the lash caps were available everywhere as I read..)
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"Rule: Turbo's make torque, and torque makes fun." (C. Bell)

924 "50-jahre", 1981.
MSII/extra, LPG, ITB's, 5lug.
To be turbo'ed in a while.
Killed her at the Nurburgring, Porscheless at the moment
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ideola  



Joined: 01 Oct 2004
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Location: Woodstock IL

PostPosted: Wed Feb 27, 2008 11:35 am    Post subject: Reply with quote

Now posted at Pelican. Awaiting approval at Rennlist.

Bump. Reminder: cutoff is 5 PM EDT 15 Mar 2008.
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