Which case to build a 2.5

Padrino · 03-30-2004, 09:58 PM

I've got a 2.2S crank and I'm going to get started on next winters project's stock pile. Next purchase will be a block. I want to go to 2.5 using the 66mm crank and 90mm p/c's.

Question is...What block would be the best one to start shopping for???

Ken

YTNUKLR · YTNUKLR's Garage

Probably an aluminum case from '65-68 if you're racing, or else a '74-77 7R case with case savers. I've got a 2.7 I'm taking apart (with a nice 7R case) if you're interested. I also have a nice '69E magnesium case...

Padrino · 03-31-2004, 05:06 AM

If I go with a 2.7 block can I use the big bore 95mm p/c kit with the 66mm crank?? I don't intend to do a lot of racing but just want to have a hotrod engine "sleeper". Would I be better off using the 2.4/2.7 crank with this oversized 95mm kit and selling 2.2S crank?

YTNUKLR · YTNUKLR's Garage

Well, I would probably not recommend doing a 95mm bore-out of a 2.7 case. Get an SC case, it already has 95mm spigots, and it's aluminum. With the 2.2S crank, you'll have a 2.8 motor with a very short stroke=very high rpm CAPABILITY (depends on what else is in the motor). With the 2.4/2.7 crank, and the 95mm pistons and cylinders, you will basically have an SC engine. The 3.0 crank is the same as 2.4, 2.7 except it has 9 bolts on the flywheel. SC (and 3.2 Carrera) also had 95mm p's and c's. I like the idea of a 2.5 short-stroke (90mm, 66mm), personally.

911ctS · 03-31-2004, 10:00 AM

If your gonna stick with the 66mm crank... Go with the 2.5L, its a good race combo. But note that if you expect to be buzzing this beast up to 8K than I'd go with an aluminum case if possible. High RPM's tend to take toll on Mag. cases.

Padrino · 03-31-2004, 11:20 AM

I'm not going to the 95mm! I like the 2.2 crank with the 6 bolts. I'm not sure the 2.2 crank fits into the 3.0 case. What series has an aluminum case that would hold the 2.2 crank?????

Shuie · 03-31-2004, 11:30 AM

the euro carrera or early turbo cases can use the 66mm crank. type 930/02

Scott Clarke · Scott Clarke's Garage

Keep in mind that an early aluminum case will require the addition of piston squirters. I decided to use a 7R to avoid yet another expense. Also, the aluminum cases are surprisingly heavy. 22 pounds more than magnesium, or so I've been told. Unless you are going to use big ports and big cams, chances are the RPMs will be reasonable enough for a 7R.
-Scott

Shuie · 03-31-2004, 12:03 PM

A motor config that really got my attention was a 2.8 that Grady Clay mentioned in a thread over on the engine rebuild forum a while back. Sounds like it would be a great engine. E spec MFI motor with twin plugs and a set of 92mm RSR P&Cs. very cool. Made me wish I still had a 7R case.

rswannabe · 06:09 PM

If you want to use the 66mm S crank, consider the option of pairing it with the 92mm RSR p's & C's. The short stroke brings the compression down into the mid 9's so you don't have to twin plug and gives you 2.6 liter displacement. If you go with the 90mm P's and C's you end up with something like 7.0:1 (unless you ar using custom high comp pistons). I've been thinking hard about building this engine myself. I've really become hooked on the RPM's and the sound of the MFI on my 2.2S. I gotta think a high RPM, high compression 2.6 with MFI would be a 'lotta fun.

Padrino · 03-31-2004, 07:14 PM

rswannabe: funny, this is where I've ended my thinking as of today. The 92mm's with the 2.2 crank are exactly my goal. Now to find a block that will handle all this. I understand I need to go with the aluminum might be the way to go but don't know my success on finding one these days.

Any input??

YTNUKLR · YTNUKLR's Garage

A 7R case can take 92mm, but that's it. I think that sounds like what would work best for your use. It doesn't sound like you are going to have this car on the track, hitting 8000rpm with every shift. If you are, you need aluminum. They're available for $500-700. 7R will work well for street, and some 7000-7500 rpm use. They're much cheaper, too, at usually about $350-400.

Scott Clarke · Scott Clarke's Garage

I decided against 92mm after seeing some nasty failures between the cylinder wall and groove for the head sealing ring. I saw this in a post on this board. I think that the new Mahle 92mm sets do not have a groove at the cylinder tops in order to avoid this kind of failure. That solves the problem if you are buying Mahle, but not otherwise.
-Scott

ttweed · ttweed's Garage

Quote:

Originally posted by Padrino
I understand I need to go with the aluminum might be the way to go but don't know my success on finding one these days.

Any input??

Archnraft was offering one in trade for an exhaust system in this thread on the classifieds forum.

TT

Shuie · 04-01-2004, 05:50 AM

Here are the two threads where Grady elaborates on his MFI 2.8.

2.4L --> 2.7RS MFI questions

2.8 question

Scott Clarke · Scott Clarke's Garage

One more caveat: a 7R case will require a later distributor, and an early aluminum case requires an early distributor. They are not interchangeable. Ask me how I know!
-Scott

Marankie · 04-01-2004, 06:28 AM

Hello Guys,
I have researched this 2.5 issue and in fact have most of the parts for one. You will need some 10:1 JE pistons which with the 66mm stroke will give you about 9.2:1. You will need some Nikasil cylinders for them (hard to find). If you use a 7R case you will have to get it line bored (90% of magnesium cases, once the motor is dissembled need to be line bored). I am going to use my early Aluminum case with about $800 worth of machining upgrades including squiters etc,etc. I have been collecting parts for a couple of years now, and if you go to the Porsche swap meets, and are not in a hurry, over time you can pick up the parts you will need at reasonable prices.
Martin

Scott Clarke · Scott Clarke's Garage

To add to Martin's comment's: an alternative to Nikasil is to have alusil cylinders refinished with nikasil. EBS does this, and it makes no difference if you send alusil or nikasil cores.
-Scott

Evans, Marv · 04-01-2004, 07:44 AM

Ken:
Sounds to me like you would be just as well off with a 3L to start off with. You would avoid the problems/expense of upgrading an early aluminum case, & the problems with a mag case. You could put the type of pistons, cylinders & cams you want in it & use your carbs. You wouldn't have a little hi revver like you seem to want, but it would rev out pretty nice & you'd end up with more torque (acceleration). I don't remember if any of the 3Ls came with Nikasil cylinders, but if you went with JEs, you'd need them - whether new/used or refinished. By the way, I haven't located that info I promised you, but I'll send it as soon as I find it.

Padrino · 04-01-2004, 06:00 PM

Hi Marv. Appreciate you meeting you the other day. P-car's at Black Forest and tomorrow I'll know the outcome. I'll be talking with you again shortly on the longblock.

Meantime, my next winter's project is building one of these for myself interest in how it's done. Figure I've got plenty of time if I'm living half time in wonderful Bakersfield. Best to work on the engine at night then those cowboy bars!!! Probably cheaper too.