TheSamba.com :: View topic - 96 Bore

Sat Feb 03, 2018 11:52 am

I don't necessarily have a budget. I like the idea of straying from the norm if just to push the envelope.

I've ordered some 94mm thickwall barrels, 103.4mm O.D., which is a .185" wall thickness. I'm going to have them honed to 96mm, which would leave me with a .145" wall. Standard 94s are approximately .149". The head will need to be opened another 1.2mm all the way around, which may or may not break through. I'll still have the majority of my sealing surface.

Is there anything I'm not considering? This is going in a 67 hardtop, street use, 10 miles a day, 6500 rpm max, 82mm stroke, 28mm pin height

Sat Feb 03, 2018 12:19 pm

How much room is there between say 8mm studs for one? 101.6mm cylinders in a type 1 case??.

Sat Feb 03, 2018 12:40 pm

None. 4" cylinders require relocation of the studs and holes in the cylinder head. For my 96 bore, everything remains the same.

Sat Feb 03, 2018 12:47 pm

Just measured a Mexican AS-41 Case and measuring between Studs X pattern it's 104mm X105mm. Inside edge of the 8mm studs!

Sat Feb 03, 2018 12:56 pm

I remember Berg's doing 96.5mm on their super street race engines which require stock head stud locations. I would not expect very long life on a street engine. It would be much cheaper to build a 84 or 86 stroke engine.

Sat Feb 03, 2018 1:07 pm

Yes, I am sure there are better ways to make power. Maybe the secret would be in a specially made copper head gasket. Even at 94 mm bored heads it's cutting into the stud holes.

Sat Feb 03, 2018 1:16 pm

What is the diameter of the window of the case? The cylinders I have measure 96.7mm, so if you bore them to 96mm, your paper thin on the case side. I think most guys remove that portion of the cylinder. Sounds terrible for a street car.

Sat Feb 03, 2018 2:07 pm

I think normal 94s are 97.25", so if they're the same, they'll have a .0275" wall at the base. I could cut a lot of the base off if I run negative deck. I'd still be well supported at BDC.

But I don't think they're the same, IIRC. I asked once, and was told they were slightly larger at the base.

Sat Feb 03, 2018 2:11 pm

It would be nice to find cylinders that can fit on a wbx case, 100mm case opening.
Type 4 cylinders fit fine, but the stud relief location needs to be adjusted.

Sat Feb 03, 2018 2:13 pm

If they only would stop drilling the heads 11mm for the head studs. 8,5 would be great for a 95,5mm bore.

Sat Feb 03, 2018 2:27 pm

CB's new heads have reduced cooling fin depth and should be able to accommodate a cylinder several MM larger....maybe it is part of a master plan? :D

Sat Feb 03, 2018 2:39 pm

I was thinking about the same thing. New CB heads and use an undrilled new aluminum case. Then drill the studs for 10mm with no case savers.

As mentioned, would be really nice if they did offer the heads undrilled.

Brian

Sat Feb 03, 2018 3:12 pm

Ok, here we go:

Shown is a normal 94mm cylinder. 110mm is the pin at BDC. 138mm is the skirt at BDC. I forgot that the T/W cylinder is a long barrel, so I'll increase the base diameter after cutting off the lower fins, and cut away most of the orginal slip-in portion. The base size that I'll end up with depends on how much I can safely cut without breaking into the inserts (12mm). Just roughly measuring, it looks like I can cut another one mm, which would leave me with a decent base thickness.

Sat Feb 03, 2018 3:19 pm

BTW, I might be working on fitting 103mm T4 cylinders into a T1 case. It's going to require waay more work, but I think I've done a lot of the problem solving. T4 cylinders are short, so they won't allow huge strokes. 78mm seems to be the max. Maybe a little more if you use some sort of spacers at the bases to support the skirts, like JPM does for their drag engines.

Sat Feb 03, 2018 3:38 pm

A waterboxer case would be a better starting point especially for 103. They use them for 4" bores. Which is 101.6 maybe. Also the deck is much higher on a wbx so the shorter cylinders might work out better but it still comes down to the heads. You used to be able to buy undrilled heads from cb I think.

Sat Feb 03, 2018 3:43 pm

Danwvw wrote: Yes, I am sure there are better ways to make power. Maybe the secret would be in a specially made copper head gasket. Even at 94 mm bored heads it's cutting into the stud holes.

Hey those are my heads lol

Sat Feb 03, 2018 7:35 pm

I remember the Berg 96’s from around 2000. They were Porsche turned down and were really expensive. They even said they were expensive. I inquired when I bought a crank from them.

Bugguy you should talk to Jeff Denham. He does the 4 inch bore stuff and is really cool to talk to. He may have some pointers for you

Sat Feb 03, 2018 9:32 pm

I'm friends with him on FB. I'll inquire if I end up doing the 103mm bore engine.

Jason, you should shoot thru when I get this 96x82 engine going.

Sat Feb 03, 2018 10:59 pm

Definitely

Sun Feb 04, 2018 12:27 am

yup they need to stop putting those gigantic holes in the heads.and move them outward some too. so..make the holes 8.2mm and move them outward.020"past the exzisting holes....thats a lot of extra room. and the same on the cases too!!! :wink: