77mm pistons with 90mm bores?

[Oblique]

Building a 1200, thought I found a good set of jugs using the piston size but the bore is 90mm instead of 87mm on my 5978732 numbered case.

The pistons also appear to be dished. What are these for? I am reading some late 1300's were configured this way but not sure about dishing.

[viiking]

That was a bit of clickbait in the heading. I immediately thought you were going to have a bit of blow-by using those smaller pistons.

I am sure you mean the bore in the case is 90mm.
_________________
1968 1500 RHD Lotus White Beetle since birth. In the hospital for major surgery
1966 Lancia Flavia Pininfarina Coupe - in the waiting room
Discharged: 1983 Vanagon, 1974 1800 Microbus,1968 Low Light,1968 Type 3

[glutamodo]

Those are for 1200 blocks made in Germany from AUG 1969 to JAN 1978. VW Germany got rid of the 1200-specific block and just got different cylinders. Which are a lot like the 1300 cylinders but shorter for the 1200 stroke.
_________________
Andy T.

"What is Glutamodo, Horror of Toyko, besides total, fiendish, quality-a-you brain!"

[Oblique]

[glutamodo]

You could use them to build a 1200 out of a late model case. You'd have to put a 1200 crank in there.

Was there a VW part number on the box? I don't know Mahle numbers. It looks like someone wrote WRONG S on there, was the rest of that "SIZE" and did you write that or was it like that when you got them?
_________________
Andy T.

"What is Glutamodo, Horror of Toyko, besides total, fiendish, quality-a-you brain!"

[zerotofifty]

Assure you get a good compression ratio. measure volume.
_________________
Sorry About That Chief.

Give Peace a Chance.

Words to live by.

[Oblique]

[glutamodo]

Yeah, and there's another issue I forgot about.

VW dropping the 1200-only block in German production was at the same time as they changed to the dual relief oil pressure system. Probably not a coincidence. Easier to discontinue that casting line than re-work it. And that's all fine.

However I don't think the 1200 block ever got the later upgrade to 8mm head studs. I don't know if you can get M8 head studs in the 193mm and 229mm lengths. That might make it more difficult to try to build a 1200 on a brand new engine case.

When the production of the 1200 model shifted to Mexico in 1978, the engines they made there still had cases with the 87mm openings.
_________________
Andy T.

"What is Glutamodo, Horror of Toyko, besides total, fiendish, quality-a-you brain!"

[heimlich]

What size are the wrist pins? That is usually how you can tell the difference.
_________________
www.vwnos.com [email protected]
Classic Brands. Classic Quality.
Not all parts are made the same. NOS OE/OEM parts made mainly in West Germany, Early Germany, and Early Brazil are where VW produced the best quality parts and best fitting products.
5% Off your order with coupon code: 5%OFF
Restored Distributors Available (<--Click here)

[Oblique]

[Oblique]

[heimlich]

[glutamodo]

Looking at the photos from the initial post, not sure why there would be dished pistons. VW did make engines with build code M240 with low compression and those used recessed pistons. However the 34bhp 1200 never had such a variant. While the 77mm E-series 1300SP and AC series 1300DP did, and they used "muldenkolben" recessed pistons to drop the compression ratio down to 6.6. (M240 engines were never made in very large numbers, so are pretty rare)

To confuse things, the VW parts book shows that the 34bhp 1200 changed to "kalottenkolben" DOMED pistons starting around the beginning of model year 1973.

_________________
Andy T.

"What is Glutamodo, Horror of Toyko, besides total, fiendish, quality-a-you brain!"

[Oblique]

Thanks for this info! The 1300 m240 makes the most sense.


Can anyone why the cases I have arent drilled (dont have fasteners) for the engine tin/shrouds?

[glutamodo]

I was admitting my confusion as to why a 1200 set would not have flat top or domed pistons, those are the only one shown in the parts books. The non-US 1200 Standard model still had the 36HP engine up to 1965 which was 6.6 compression, so maybe that was why they didn't make the 34bhp/40HP with a low compression variant.

As mentioned above though, check the piston pins for 20 or 22mm size!

As for cylinders themselves, original cylinders had fewer fins on them, this kit is from later when they improved the design.

However the 1300-1600 cylinders were taller and had one or two more fins on them. I did a side by side comparing an aftermarket big-bore 40HP (83mm) next to a stock 1500 cylinder (again, 83mm) a few years ago. Of course this the 40HP is the 87mm-bottom style, but you get the idea between the 64mm and 69mm stroke cylinders looked.

Ah, the drilled and tapped ears on the bottom of the case for the "sled" shaped tin, that answer I know very well.

My 62 has never had anything in it but the original "stale air" heating. This was used up until DEC 15 1962. The heat exchangers on those were much more primitive, and self-contained and they did not bolt to engine case.

I've had a few different blocks in my 62 over the years, but the one in it now is a factory remanfuctured block that was originally made for the 1961 model year, same era as your block. So it lacks those drilled ears. (and at one point I acquired the correct thermostat bracket that wraps around the case, you adjusted the thermostat at the throttle ring, not the thermostat back then)

_________________
Andy T.

"What is Glutamodo, Horror of Toyko, besides total, fiendish, quality-a-you brain!"