1500 with Domed Pistons

YellowSplittie · Samba Member Joined: September 30, 2003 Posts: 1167

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?"

hoss · Posted: Tue Apr 12, 2005 9:34 am Post subject:

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.
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YellowSplittie · Samba Member Joined: September 30, 2003 Posts: 1167

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?

EverettB · Posted: Tue Apr 12, 2005 10:36 am Post subject:

Domed pistons and the higher compression require Super Premium gasoline
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notchboy · Posted: Tue Apr 12, 2005 10:45 am Post subject:

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?
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YellowSplittie · Samba Member Joined: September 30, 2003 Posts: 1167

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.

notchboy · Posted: Tue Apr 12, 2005 3:23 pm Post subject:

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!
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Russ Wolfe · Posted: Tue Apr 12, 2005 4:42 pm Post subject:

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.
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YellowSplittie · Samba Member Joined: September 30, 2003 Posts: 1167

Plus they put case savers in too! Wink

Russ Wolfe · Posted: Tue Apr 12, 2005 7:43 pm Post subject:

notchboy · Posted: Thu Apr 14, 2005 11:13 am Post subject:

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

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Tram · Posted: Thu Apr 14, 2005 11:17 am Post subject:


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