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Changing 40hp round boss to square boss
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Glenn Premium Member
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PostPosted: Tue May 24, 2022 8:25 am    Post subject: Re: Changing 40hp round boss to square boss Reply with quote

Dan Ruddock wrote:
or swap out the rocker block for late ones.

So just replaced the rocker shaft block with ones from a 1600??? I have a few sets laying around.
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PostPosted: Tue May 24, 2022 8:54 am    Post subject: Re: Changing 40hp round boss to square boss Reply with quote

Correct. I have done few square boss 40hp engines with 1600 rocker arms, shafts and blocks. Easy swap, and the tiny bit of extra lift can't hurt anything.

These heads also respond really well to blended intake bowls, a back cut intake valve, and a good valve job. Don't touch the exhaust port. It already flows to much. Just the seat cut on the exhaust.

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PostPosted: Tue May 24, 2022 10:43 am    Post subject: Re: Changing 40hp round boss to square boss Reply with quote

Glenn wrote:
So new heads, 8 top studs and drill the rocker pedestals for the larger rocker studs is all that needs to be done.

My understanding is that the pushrods need to be changed too. The late 40HP square boss heads used pushrods that where 2mm longer. VW knurled one end to mark them.
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PostPosted: Tue May 24, 2022 12:15 pm    Post subject: Re: Changing 40hp round boss to square boss Reply with quote

EVfun wrote:
Glenn wrote:
So new heads, 8 top studs and drill the rocker pedestals for the larger rocker studs is all that needs to be done.

My understanding is that the pushrods need to be changed too. The late 40HP square boss heads used pushrods that where 2mm longer. VW knurled one end to mark them.

2mm sounds minimal
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PostPosted: Tue May 24, 2022 12:34 pm    Post subject: Re: Changing 40hp round boss to square boss Reply with quote

There are some kits that do what you are asking for the round boss heads. But you broke the boss - hoss.

I may have some of the stud kits if that would help you.

Hopefully this thread tells you what you need:
https://www.thesamba.com/vw/forum/viewtopic.php?t=587766&start=0
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PostPosted: Tue May 24, 2022 12:56 pm    Post subject: Re: Changing 40hp round boss to square boss Reply with quote

heimlich wrote:
There are some kits that do what you are asking for the round boss heads. But you broke the boss - hoss.

I may have some of the stud kits if that would help you.

Hopefully this thread tells you what you need:
https://www.thesamba.com/vw/forum/viewtopic.php?t=587766&start=0

This engine already had the repair kit installed. It was the steel repair insert that ripped out and broke the boss.

Engine is apart, just need to finish the research and order parts.

Gonna check if the shop has 40hp pushrod tubes. If not i'll be in touch.

BTW, do you have 40hp flywheel shims?

Image may have been reduced in size. Click image to view fullscreen.

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PostPosted: Tue May 24, 2022 1:40 pm    Post subject: Re: Changing 40hp round boss to square boss Reply with quote

40HP flywheel shims were all but gone years ago. A customer told me that Wolfsburg West started making some recently.

I've got a couple 40HP heads laying on the floor under a workbench. They were used and came with a pile of new heads. I'll probably never do anything with them if they'd be of help.

I've got pushrod tubes. They are nice ones too from Brazil. When I say nice I compare to what's made now for 1600. Those are really thin metal. These are a bit thicker and are covered in sticky oil.
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PostPosted: Tue May 24, 2022 2:18 pm    Post subject: Re: Changing 40hp round boss to square boss Reply with quote

....

Last edited by fl59bug on Wed May 25, 2022 12:01 pm; edited 1 time in total
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PostPosted: Tue May 24, 2022 7:22 pm    Post subject: Re: Changing 40hp round boss to square boss Reply with quote

OK... next question:

Who sells new/rebuilt 1200cc 40hp square boss heads?

I've checked the usual vendors and 99% don't even have a listing. I did find a handful but all say they are out of stock.
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PostPosted: Tue May 24, 2022 7:58 pm    Post subject: Re: Changing 40hp round boss to square boss Reply with quote

I probably have some of the shims.
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PostPosted: Tue May 24, 2022 7:59 pm    Post subject: Re: Changing 40hp round boss to square boss Reply with quote

Square boss is hoss. The racers usually take them all.

You can pick them up in singles. You'll need the correct size crush washer when you install them. There are two sizes 32MM and 34MM.
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PostPosted: Wed May 25, 2022 5:14 am    Post subject: Re: Changing 40hp round boss to square boss Reply with quote

modok wrote:
I probably have some of the shims.

The engine has no "feelable" endplay. I'll get around to using a dial indicator to measure. If needed I can have the snout of the flywheel machined to what's needed.

Or I can just leave it alone since that's how it came in... i'll let the customer decide.
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PostPosted: Wed May 25, 2022 5:38 am    Post subject: Re: Changing 40hp round boss to square boss Reply with quote

Glenn, I have a pair of nice round boss 40hp heads. Looks like they were rebuild many years before I got them, but they've been sitting and would need to be at least gone over. Pm me if you're interested. They came from a closed shops inventory
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PostPosted: Thu May 26, 2022 6:33 pm    Post subject: Re: Changing 40hp round boss to square boss Reply with quote

first off, if you decide to run square boss 1200 or 1300 heads, you need to use "1600" style push rod tubes.(i think)
the square boss 1200 heads are physically taller.

I can snap an early 40hp push rod with my pinkie toes. a 1600, not so much.

just buy 1300 heads or make it easy and find some good round boss cores. heimlich has some NOS 1200 and 1300 heads.

also, i bought my 40hp tubes from Heimlich. he may still have some.
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PostPosted: Thu May 26, 2022 6:37 pm    Post subject: Re: Changing 40hp round boss to square boss Reply with quote

Bought a good clean set of round boss heads from esde (Seth)... thanks.

Don't want to reinvent the wheel, just want to get this engine back together for a reasonable cost to the customer and send it down the road.

Plan is to have them gone through by our machine shop and reinstall.
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