94mm cylinder bottom diameter..

[ALB]

What minumum clearance are you all using when cutting the cylinder bottoms to fit the 90.5mm spigot hole? Is .010" difference in diameters enough?
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On a lifelong mission to prove (much to my wife's dismay) that Immaturity is Forever!!

[neil68]

Hi Al,

My 94 Mahle slip-ins from lowbugget.com would not fit into my 90.5 case, so I sanded the case by hand until they just slipped in...I would say a couple thou, but I didn't actually measure.
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Neil.

Der Kleiner Rennwagens
68 Beetle 2332 cc, 204 WHP
12.5 seconds @ 107 mph
Dynojet Test: https://www.youtube.com/watch?v=M9B_H3eklAo

[modok]

How tight are the cylinders in the head?

[ALB]

Hi Neil, how the heck are you? Good info; I was under the impression there had to be a few thou clearance for expansion. The case I got from GBE (many moons ago) had .010 or .012" diameter difference for the 90.5's.

Anybody else?
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On a lifelong mission to prove (much to my wife's dismay) that Immaturity is Forever!!

[KopfenJager]

I know I like my cylinders to lightly tap in. Not hard but just a little nudge to get them in. The last idiiot who machined my case had em so loose you could wiggle the cylinders in the holes! (hand hitting forehead) DUH... WhenI complained he said they seal on the shoulder, neadless to say aviation form a gasket would keep the oil in the case, had to switch to silicone to fill the gap. I swear I'm not letting anybody in the Roseburg area touch my VW stuff again, bunch of hacks!

[nsracing]

If you are precision machining the case w/ a boring head on a miling machine, you can bore it w/ 0.002 -0.004 inch clearance, and that is plenty. At least that is what how much clearance I use w/ my jigborer. The new cylinders are not that round on the outside. They have about +/- 0.001 -0.002 inch out-of-round in finish.

But if you are boring w/ a GeneBerg-type tool, then it will need to be loose as a goose... 0.010 - 0.012 which is about normal you see w/ this bore job.

[mark tucker]

there is a problem with all of this.that is some times overlooked.depending on who, where or how the case/heads were bored.with a bolt on jig,mill,centering jig,or what ever . it is easy to get them right. and it is easyer to get them off a few though left right,up, down, so you get them off just .005 to the right on the #2cyl head&.007 to the left on #1 head, then .007 left on the case for #2&.only.005 right on #1 cyl.see where Im going????? you you can still get the cylinders in and tighten them up and yes they will more than likely seal just fine. but what you dont see is the ring seal is shot to hell and so is the round cylinder, now add some heat.I think this is where the 94mm cylinders got such a bad rep with al the cheep ass handheld or drill press bored cases & heads. if there a bit loose no issue, it there tight???? think about it. what happens to a round cylinder if cocked & tightened up. and yes off center is cocked. I was a bit surprized whan I got a set of cnc cb heads that had just over .025 cylinder clearance but I understood why. I think it's a little much but better than tight on a afu case. just something to think about.unless you know everything is dead on I would stay with .008-.0012"

[nsracing]

What the hell are you smoking, Mark?? You cannot center the boring head in the original hole in the case to what the tolerance on the gauge will read?

There is no 0.005" on #2 or 0.007" there on #1.... What kind of mill is that you are using?? If your gauge can read 5/10,000" then you should be able to center that hole to that tolerance. Unless you already had a six-pack on board while you are machining is the only way what you are saying can happen.

Now the drillpress units of course is anyone's guess how centered it will be.

Now if you are talking about to tolerance of the size of the ID of the bored hole, that is also read accordingly to what your boring head is made for. Most boring heads out there can read at least 1/1,000 inch. ARe you saying you cannot cut a hole to within 1/1,000 inch tolerance?? I can see that if you are using just your feet and/or blind.

Geeze.

[mark tucker]

you moron,cant you read. I can put it where I want it, but a lot cant, and a lot dont.and a lot havent been. sort of like a halfass balance job for the street that isant balanced but it is charged for balancing.or a street/strip balance job that is almost balanced and charged more. have you been smoken&drinken your dinner again??cheezzee.
go grab up 6 cases that somebody did and you dont know who did them and check to see how many are the same. probably less than 10%.

[neil68]

Mark,

With all due respect, please learn how to type properly. I'm sure you've got some interesting information in some of your posts, however, it is very difficult to understand what you are trying to say. Mostly, I give up trying to figure out what you are saying.

As a start, try using punctuation, and upper case letters to begin your sentences. Some complete sentences once in a while would be useful, as well.

Thank you
_________________
Neil.

Der Kleiner Rennwagens
68 Beetle 2332 cc, 204 WHP
12.5 seconds @ 107 mph
Dynojet Test: https://www.youtube.com/watch?v=M9B_H3eklAo

[modok]

[nsracing]

I can still write pretty well even when I am drinking. I just don't machine.

When MackTuckey writes, one cannot tell if he is drinking or not..or a LOT!

People will bore these cases or heads to the way they like. There is no set standard.

With regard to dynamic balancing, there are tolerances we follow for that. It is not a hack-job. These machines cost some real money to the shop. And it is a very important job to put into the build. There are 3 levels or degree of balancing we use to compliment an engine's application. That is, after all, is what you are paying for.

[mark tucker]

well I dont drink, and if the motor isant balanced it isant balanced.just a lazy machinest, or one that dont know any better, either way I would stay away from a half balanced machinest. No matter how good his grammer or spelling is. if you cant read because a letter isant cap'd, you may have other issues.and my spelling aint going to help or hurt them.my grammer died 3 years ago in cali.and we miss her.

thanks modock I think thats what I was trying to say, but I miss spelled&for got to add caps.hmm might of been a space missplaced too.

[hill]

Are you guys friends, or what?

My wife was going to an ancestry forum filled with women claiming to be part indian, or part irish, or part stupid and the bitching in there was too much for her. I took a look once and told her she'd best leave lest she pick up some bad habits and find herself divorced. How could I show here where I'm hanging out after that, what with you guys all wanting to be crowned pissiest?

I've got a good Bridgeport mill and a bunch of tooling but never really learned to use it too well mostly because of the cutter costs and the risk of ruining some pretty expensive guns. Maybe you all can take a pause to let me know what I'd need to bore a pair of heads from 85.5mm to 94mm?

[damicotile]

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[RWK]

The reason/purpose of the clearence .01 (min. on dia) between the cylinder wall and case bore is to allow for the fillet or radius at the base of the cylinder wall and cylinder seat. In mass manufacturing of the cylinder the tool has a radius on its tip that cuts the o.d. of the cylinder this is usually a min of .008 usually more. (necessary for strength in cast iron parts) (also why a radius is suggested on head bore corner also a cast part) Therefore cutting any less clearence on the head case bores is not necessary and usually can cause problems.
If .005 clearence is used on the dia. of the bore and a large radius is cut in the cylinder by the manuf. the radius will crush into the sharp edge of the bore/deck intersection, this can be helped if you chamfer that edge, other wise a mechanical seal will be achieved at this point, it should never leak oil! assuming you torque cylinders down first to make this "interference seal" then dissasemble and add your sealer. Other problem we all know is the cyl. seizing in the case bore.
Factory intended for the cylinders to set perfectly flat and seal on case deck and head deck with no interference from the bores/dia's and cylinder fillet (see any Bently/factory manual). for the very reason listed above., hence their use of the paper gasket here to make the seal. Larger cylinders could have up to .015 clearence, (should always check the radius in the corner)
IMO, reason everyone uses silicone now for rebuilds, fills the inaccracy gaps, seals the dia and the corner mentioned above.
If you need to check your case deck/head flatness you can put high spot blue on both ends of the 2 cyl.s (assuming they have been checked to be parrallel and equal) carefully set cyl's in case then carefully set head on and press gently, if machining was done correctly you will have full dia. blue rings on both head and case as wide as the cylinder edges, this method probably best if you dont have access to a surface plate and test indicator, (way to check machining accuracy).
Also, machining done on verticle knee mills (Bridgeports) can be done inaccuratley if mill head is not trammed (squared) with table, these mills can be adjusted for tilt in both directions and need to be checked and adjusted frequently, this is especially important if you are facing a deck or boring close clearence bores,if your mill is out .001-.002 per inch (and can be off in both directions) and your cyl stands up 4 in. off case, u can do the math! and if heads are done on same machine,same tilt in other direction same direction who knows??
Just be aware when having machine work done, good machining on a VW case is easy work for a machinist and is easy to confirm the accuracy of,(bluprinting of an engine) fortunately stock engines are more forgiving, not so with high performance engines.
my 2 cents worth,
RWK

[MURZI]

[KopfenJager]

You know your winning when someone attacks you spelling and grammar.

[the2ndcashboy]