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Tue Apr 12, 2005 6:22 am

My original thread from the Performance/Engine Forum:
http://www.thesamba.com/vw/forum/viewtopic.php?t=109984

It was suggested I try my question out in the Type 3 forum:

"I recently picked up a 67 Ghia that had been sitting for about 8 years. In going through it, I removed the heads and found 83mm domed pistons inside. I noticed that there is extremely low wear on the cylinder wall surfaces. This is an H case engine.

Is this some sort of variant, high output, optional engine? Or is it possible these were fitted in during an old rebuild (I am assuming that 83mm pistons have been unavailable for some time)? My research shows that Type 3s had a 1500S with domed pistons for a couple of years, but this is definitely not a Type 3 case (no lower oil filler connection).

Any insight?"

Tue Apr 12, 2005 9:34 am

i would assume that a PO fitted these during a rebuild some years back. these are NLA new but do come up from time to time at swaps and online.

these pistons were used on 1964 & 1965 1500 S model type 3's only. i believe they offered higher compression and slightly more horsepower compared to the regular 1500 engine.

Tue Apr 12, 2005 9:40 am

Since the engine has a single port set up, stock distributor for 67, and a stock carb for 67, should the timing be set differently than the 7.5 degrees BTDC? Should higher octane fuel be used as I have read is recommended for the 1500S Type 3?

Tue Apr 12, 2005 10:36 am

Domed pistons and the higher compression require Super Premium gasoline

Tue Apr 12, 2005 10:45 am

Dual carbs would help you optimise their compression. Were there any shims under the jugs on the case side or even any in the heads? The builder may have dropper the compression in leu of the dohmed pistons for a smoother performer, based on the SP single 28mm carb?

Tue Apr 12, 2005 11:18 am

No shims. My first clue something was up is when I did a pre-disassembly compression test and all four cylinders were in the 140 to 150 lb range.

Tue Apr 12, 2005 3:23 pm

Nice sounds like it was a straight forward install. Maybe you can make a mock type Okrasa deal? Dual carbs, Fram oil filter and the dohmed piston 1500cc motor. Thats a cool combo for a Ghia. Think of it as Vintage speed!

Tue Apr 12, 2005 4:42 pm

Putting 1500S pistons in a T-1 style engine was a favorite performance increase, back in the late '60's early '70's. Then VW went to the 1600cc, and dual port heads, the the popularity went away.

Tue Apr 12, 2005 7:05 pm

Plus they put case savers in too! :wink:

Tue Apr 12, 2005 7:43 pm

YellowSplittie wrote: Plus they put case savers in too! :wink:

I put case savers in all my engines up to when they went with the AS41 cases.
BTW, I need some more case savers. the Genuine VW ones.

http://classicvw.org/gallery/Engine-progress/caseinserts
If anyone spots some, let me know.

Thu Apr 14, 2005 11:13 am

I was at one time planning on building a super 1600 with dohmed pistons. So thats a 74mm crank with the dohmed 83mm pistons. Not much in way of spectacular performance but a cool vintage speed motor none the less. Maybe Ill do that to the 64-65 Nutrina mock S notchback vert someday :wink:

Thu Apr 14, 2005 11:17 am

notchboy wrote: I was at one time planning on building a super 1600 with dohmed pistons. So thats a 74mm crank with the dohmed 83mm pistons. Not much in way of spectacular performance but a cool vintage speed motor none the less. Maybe Ill do that to the 64-65 Nutrina mock S notchback vert someday :wink:

That's my ultimate plan for my 34, but fed by fuel injection! :twisted: