Machine specs for 2 piece case?

[Richard Alexander]

Hello to All,

The machinist needs the case specs to alignbore a 53 2 piece case, 1500cc.

I do have a data sheet showing 60.000- 60.019 mm and 50.000 - 50.025 for the no. 4 bearing. However hand writing mentions this is not applicable for all engine numbers.

Any information to share on this matter? What are the specs for the case question?

Thanks

Richard

[Harlan Halsey]

Line boring is not a maintainance operation. It often does more harm than good. Find a competent, experienced, machinist familiar with VWs and Porches, measure it, and then decide. Unless that is one of the rare aluminum cases, it is just a 36 HP VW case. Do not line bore unless it is absolutely necessary, and then only when you have all the bearings in hand.

[Alan Hall]

Most pre-a 2-piece case motors had the 60.25mm bore for bearings 1, 2 and 3 and 50mm bore for bearing 4. Same as for the 3-piece case motors. Very early motors may have had the 60mm bore for bearings for 1, 2, and 3, which was the standard size for 25hp and 36hp VW motors. But I agree with Harlan that you need to measure what you have to determine if a line bore is necessary. The typical first over line bore bearings for 36hp VW are 60.5 and 50.5 so if a line bore is necessary you will probably have to go to that size. Tolerances would probably be the same as for the 36hp VW specs (which I don't have offhand).

[Martin Benade]

Wasn’t the the two piece case a VW case but already rebored by Porsche to the VW first oversized?
I hadn’t seen Alan’s post when I posted this

[Jacques Lefriant]

Hi
source the bearings first and have the case machined to achieve the proper crush
j

[Richard Alexander]

Thank you for your input so far.

The machinist is highly skilled. The case will be brought back to “standard” (not first over).

We did order some new bearings still I would like to know what Porsche published and why the hand writing? Was it alu vs magnesium or Porsche vs vw?

Thanks

Richard

[Martin Benade]

Did you see Don Gale’s interesting post linked to “camshaft raceway damage”? He explains how lapping and boring back to standard tends to be imperfect. If your saddles have very slight wear it could be ok to lap and bore but it might not be that great

[Jacques Lefriant]

Hi
back in the day i used Hunger adjustable reamers to size cases just like in the 911 manual. now most machine shops will line hone. i would only use a single point boring bar to go to the next size or rectify a welded case.
j

[Jacques Lefriant]

Hi Alan
yes VW used to go .5 over as their first size. you could go .25 and end up with the Porsche std 60.25 and some 36hp bearing suppliers offer the .25 also which would work for Porsche as std.
j

[Olivier Auvray]

Hi
back in the day i used Hunger adjustable reamers to size cases just like in the 911 manual. now most machine shops will line hone. i would only use a single point boring bar to go to the next size or rectify a welded case.
j

Some shops still have the Hunger tool set..........

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[Joris Koning]

Pretty cool Olivier, thanks for sharing.

[Olivier Auvray]

The technical bulletin from July 1953.
Sorry, it's in French but it explains why they decided to jump to 60.25 mm case bore on any engine except 1100 cc.

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[Jacques Lefriant]

Merci Olivier
if i read this correctly they decided to leave the #4 brg at 50.mm
j

[Olivier Auvray]

Merci Olivier
if i read this correctly they decided to leave the #4 brg at 50.mm
j

Yes!

In fact they used VW engine case and VW bearings and they got trouble: not enough crush (case/bearings) and they found damaged engine cases.
The "Porsche" design gave them more crush and the chance to save worn engine cases

I don't understand why they didn't use VW bearings with a custom sized engine case to obtain the proper crush:

Align bore + special bearings is more expensive than align bore + mass production bearings