100 mm cylinders to a 3.0 block?

JYRI ERAMAA · 12-30-2009, 04:06 AM

hello, what is needed to do this? i compared 95 cylinders (95ZN1W5) vs. 100mm cylinders (s34460) 100ZN8 cylinders...i found that theres different bolt spacing... around 5 mm... so to fit those cylinders do i need to change the bolt spacing & machine the cylinder holes bigger...but what to do with the heads? how can it be done?
i already have the 76.4 mm crank and rods... looks like the easiest thing would have been to get a 3.6 liter engine. :-) but in the inspection this 3.0 sleeper would be great.

any suggestions?

sjf911 · sjf911's Garage

There are aftermarket 100mm cylinders that can be used in a 3.0 case. One type requires machining the case spigots the other are slip fit. They all require custom pistons.

JYRI ERAMAA · 12-30-2009, 05:51 AM

Ok, i thought that the originals fit... Hmmm the wont... I would guess that the aftermarket ones cost a zillion? ;-)

maybe a hi-comp 3.0 would also run pretty good... But it' doesnt sound so rad anymore... :-/

Flat6pac · 12-30-2009, 06:58 AM

Be happy with 3.2 SS
Bruce

Steve@Rennsport · 12-30-2009, 07:50 AM

We have done quite a number of these conversions over the past 30+ years and we use the Mahle 100mm P/C's made specifically for this application.

The head stud spacing is identical to the 3.0 litre engine so the only machine work necessary is to enlarge the case spigots and modify the heads for the larger bores.

We don't use stock rods for these engines, preferring lighter, stronger aftermarket ones such as Pauter's.

JYRI ERAMAA · 12-30-2009, 08:03 AM

Hmm how to make a 3.2 ss engine of these? I would think that a 76.4 is also a very short stroke. Compared to the vw-boxer scene... There a 78mm crank is nothing... ;-) (i used to have 86x94 8000 rpm engine) what i really wanted is hot rod six in a light package... Have to go back to the start... :-( what would you guys do? I would like a fast reving engine...

Steve@Rennsport · 12-30-2009, 08:24 AM

A 3.2SS engine uses 98mm P/C's with the 70.4mm crank. This is a quick revving motor if the rest of the components are chosen correctly.

With regard to stroke, its difficult to compare VW motors to the 911 six due to crankcase dimensions. In the Porsche world, the 76.4mm crank is considered a long-stroke one.

If you want a fast revving motor, I would focus on large-bore, short stroke combinations such as the 3.2SS (above), a 100mm x 70.4mm combo, or even a 100mm x 74.4mm one.

Naturally, the choice of induction, cams, ignition, and exhaust are all very critical in order to meet your objectives.

JYRI ERAMAA · 12-30-2009, 08:35 AM

We have done quite a number of these conversions over the past 30+ years and we use the Mahle 100mm P/C's made specifically for this application.

The head stud spacing is identical to the 3.0 litre engine so the only machine work necessary is to enlarge the case spigots and modify the heads for the larger bores.

Thanks Steve for this, i thought that these would be the ones, but no. I was wrong, i bought then from us chrome... (what is your opinion from their products?) one way would be to machine these cylinders to accept the 5 mm difference... But how is the head gasket then? Any ideas? Any pictures? I could sell the original crank plus the p/c's if someone is interested...

JYRI ERAMAA · 08:58 AM

have you done original 100mm cylinders to the 3.0 block? how would you do it?

Steve@Rennsport · 01-05-2010, 09:41 AM

Quote:

Originally Posted by JYRI ERAMAA

have you done original 100mm cylinders to the 3.0 block? how would you do it?

Oh my, yes,........quite a number of those over the past 25+ years,....

The case spigots must be machined to fit using Mahle cylinders. Also, the heads must be modified for the larger bore.

jwasbury · 01-05-2010, 11:07 AM

Quote:

Originally Posted by Steve@Rennsport

Also, the heads must be modified for the larger bore.

Curious what needs to be done to the heads. I am doing 100mm pistons and cylinders on my 930 (LN Engineering Nickies with JE pistons at 7.5/1 CR) and was under the impression that its a bolt on deal (other than boring case spigots). I think SC heads and 930 heads are similar in dimension. Perhaps the difference is that an SC will run higher CR, so the piston dome may interfere with the head with the bigger bores?

Steve@Rennsport · 01-05-2010, 06:15 PM

Jacob,

The squish bands must be widened for the 100mm pistons otherwise they will hit the heads at TDC.

jwasbury · 01-05-2010, 06:24 PM

Quote:

Originally Posted by Steve@Rennsport

Jacob,

The squish bands must be widened for the 100mm pistons otherwise they will hit the heads at TDC.

Mmmmn sorry for the threadjack, but this has me concerned...am I correct that this head machining is not required in the lower compression turbo applications like I am building since the pistons are flat topped or nearly so?