Overhead Cams

[Da1Duc]

Nice work. The machine shop hours had to have been staggering.

D

[BOBTAIL]

Originally Posted by Da1Duc

Nice work. The machine shop hours had to have been staggering.

D

Not really, the thinking time was the greatest.
Once the ideas are planned out the machining was the easy bit.
I suppose that when I think of machine shop ,I think of lathes and millers and stuff. So that was a very small part .
The welding took the most time I guess. Still it turned out cheaper than going to Pauter heads and probably more reliable too.
After all It doesn't really have any non stock parts.
The cams are cut and pegged 911
The pistons are stock 944
The rods are stock 2.0 as is the crank


No you're right the machining that went into it are ,indeed staggering
I just hadn't added it all up.

This season it will have custom pistons, full engine managment, bigger turbo, redesigned inlet manifold and it'll look a lot prettier
Well at least for a week or so.

[vennard]

How do you get away with all that engine and using a non c/w crank shaft? I would have thought it would be one of the first things you did. Damn cool though I remember the magazine feature on it.

[Wally]

Speaking on OHC type 4 engines, has anybody ever heard of the 'Overfly' engine that Rolf Holzapfel developed for the Kaefer Cup?
Alex maybe?


It was a new development in 1995 from Holzapfel in which he also used the Porsche 964 cylinder heads AND the 100mm cylinders and pistons. He also used those with a 86mm stroke SCAT crank to give exactly 2,7 ltr.
He used a cam housing that his tuning workshop made themselves.
The test engine with 10,4 compression and self developed Melcher cams produced 247 (DIN) hp at 6250 rpm and 294 Nm at 5500 rpm! The engine used twin spark (from the dual spark 964 heads) and 51mm Weber carbs.

Personally I don't understand how you can use the stock 100mm cylinders which ran with 76,4 mm stroke in the 964 engine for 86mm stroke, but the picture in the german mag 'Gute Fahrt' showed all these parts indeed together!

Unfortunately these never did make it into the Kaefer Cup due to the 2 liter restriction the following year(s).

As you would supect, everything has been done already by some one.

Greetings,
Walter

[BOBTAIL]

During the design stage we came across that article from Gute Fahrt.
I got the impression that Dr Gerolds car was powered by "that" type of engine ,By "that" I mean cast cam boxes( that was the bit that nearly made us give up!)
For the amount of machining, it was much more economical to do the job the way we did.
We also noticed that they cut out the barrel registers and welded in new peices to change the stud spacing.We just redrilled the heads and cambox to accommodate the difference.
Its funny seeing all the different 911 headed motors and we all seem to use the same belt setup.

Crank......Seems that too many people throw away too many stock parts to replace them with parts of an inferior quality.

[SuperRSi]

Bobtail,

Very nice work. Do you think any of you would be willing to share drawings of what you welded or machined so we could build something on this side of the pond? I can weld and machine in house, so in my spare time I could probably build one up in oh say four years.... It would be interesting to do it piece by piece as one had time and money for parts. It also would help to learn from the mistakes ya'll (from Texas) made. So whip up some plans and sell them to me.

Thanks,

Randy

[BOBTAIL]

Originally Posted by SuperRSi

Bobtail,

Very nice work. Do you think any of you would be willing to share drawings of what you welded or machined so we could build something on this side of the pond? I can weld and machine in house, so in my spare time I could probably build one up in oh say four years.... It would be interesting to do it piece by piece as one had time and money for parts. It also would help to learn from the mistakes ya'll (from Texas) made. So whip up some plans and sell them to me.

Thanks,

Randy

Drawings? you realise we write with a tig torch

Really its quite simple to work out what goes where and what needs modding, No, honestly Ive been trying since we got it running to convince folks its doable for not very much cost.

We kept the stud spacing as T4 and modded the heads and camboxes.
The head oil returns go into the deep sump.

You're lucky in that you can get the bits together and mail me, we didn't have that luxury.

The crank drive was machined to adapt the T4 taper which went to 2 polo crank sprockets, just a simple top hat design.
We had to buy the bits and make them fit together ,not knowing it would work.

Just go buy your carrera 2 twin plug heads and 2 cam boxes, with cams and take some measurements.
Ill always be here for advice.