2.0 Aluminum Case Mods ??

[Jimmy18E]

Guys,

I currently have a pretty maxed out 2.7 Short Stroke built on a fully prepped (Ollies) 7R case that is putting down 264 Wheel HP. Was shooting for 270 RWHP, fell short by 6 HP, not broken in yet, so maybe on the next dyno run.

After reading all the horror stories about mag cases in high HP applications I picked up an early aluminum 2.0 case that has already been bored out for the cylinders, but that is it.

I am planning on having it sent out for all the mods and either swap everything over to it very soon or sitting on it until (if) the 7R case acts up with any problems.

So, what needs to be done?

Already bored out for the jugs. Besides oil squiters and being machined for the newer cam boxes, what needs/should be done?

Ok to shuffle pin an aluminum case? Does it need to be lined bored like a mag case?


Thanks for the help.

Jimmy

[tadd]

For a high rpm long stroke, shuffle pinning is good. I used the later (and bigger) 993 squirters. They are however longer. If I had it to do over I would just use two of the turbo squirters with a big oil pump instead.

Requiring a line bore is very, very rare.

I also did the threaded oil galley plugs just because.

Only other thing... I'd also have the case modded for a replaceable IMS bearing. I didnt do that on mine. I am using straight cut gears and the early cases required the torque from the helical drive gear to locate the intermediate shaft. With the straight cut it just kinda floats and Im not thrilled with that...

t

[Steve@Rennsport]

Jimmy,

Have the case machined for intermediate shaft bearing inserts and add the studs to accept the later chain boxes for improved sealing.

Oil squirters are a must for any Nikasil cylinders.

Do the oil bypass modification if you use an SC/Carrera or larger oil pump.

At your power level, I would shuffle-pin the case.

[Jimmy18E]

Steve and Tadd,

Thanks for the replies.

Question for you about the intermediate shaft.

My case came with the intermediate shaft and gears. By doing the IMS bearing inserts or as Tadd says do the replaceable IMS bearing. Do I still use my IMS shaft and gears or do I need a different set up?

This motor is spun to 8K, want it done right.

I was going to go with a stright cut gear also.

Thanks again guys.

Jimmy

[Jimmy18E]

Bump....

Do I go with the original IMS shaft or change to the newer with the bearing inserts?

Thanks.
Jimmy

[Daves911L]

If you modify your case to use the replaceable bearing shells, you must use the newer style intermediate shaft to match. The rear bearing journal of your original shaft is a considerably different size than the bearing shells, does not have the forward thrust surface, and the rear thrust surface is different. I suppose it might be possible to modify your original shaft, but it would involve extensive welding and machining. The newer style shafts are very easy to come by and inexpensive (you pretty much can't give the things away). But early style shafts are fairly hard to come by and someone will probably be very happy to have yours.

[Walt Fricke]

Craig Garett (CGAR) has a method of bushing the throughbolt holes at the centerline (similar to how Porsche does it with the throughbolts at the #1 bearing) instead of shuffle pinning. It guarantees that the bushes are in exact register with their corresponding holes.

I didn't "invent" that - a machinist who used to do good work around where I work did because he doubted being able to get shuffle pins in precise register. But I've used it for 20 or so years on my various motors, and it has done the job. Of course, they are aluminum cases, and sand cast at that. Which means this may not really have been necessary at all.

Conventional wisdom is that the sand cast cases don't need align boring. Doesn't mean checking that might not be a good idea, just in case.

I am still using the old IM shafts, but wishing I had a shop do the machining to update to the late shafts and its bearings and relative availability.

[Jimmy18E]

Ok, this is what I am doing.....

Picked up a GT-3 IMS shaft and gear from my shop, sold/traded off the gear (because I want straight cut) and picked up a JB Racing Straight cut gear.

I will have Ollies machine the case for bearings for the newer shaft and will have the best set up....I think.

Now, what is a VG+ condition 2.0 aluminum case IMS shaft and gear worth? I will sell it off now that it is not needed.

Guys, thansk for all the help.....

Jimmy

[stownsen914]

Originally Posted by tadd

I used the later (and bigger) 993 squirters. They are however longer. If I had it to do over I would just use two of the turbo squirters with a big oil pump instead.

Tadd - can you comment on the use of two 930 squirters? I heard something similar from the machine shop that did my case years ago, if I remember correctly. I'm potentially interested because a previous owner of my early alum. case had early 911 squirters installed at an odd angle, pointing more to the side than the factory did. It seems to have worked OK in my 2.7L race motor, but when it comes apart some day I'd like to do something about it. I'm guessing that trying to re-angle the squirters would be difficult (would require welding I'd think), so I'm wondering if just adding a second set of squirters would be the right fix. Any thoughts appreciated. Thanks.

Scott

[Walt Fricke]

Scott - I think the fix for your oddly angled squirters is to tap and plug those holes, and have new holes drilled. Twice the number of squirters could be tricky when it comes to oil pressure to crank and rods. Maybe if you run a 930 or GT3 pump it wouldn't tax the system? But in a race motor you want more than the what - 45psi? - cracking pressure of the squirters, and if you don't have a big enough pressure pump that could be a problem.

My 2.7 race motor's sand cast case was modified for the early squirters. I've never seen any evidence of overheating of the piston, which is what the squirters are there for.

You might want to find a somewhat current discussion about oil pressure and pumps for an attempt to gather specifications for the various parts of the system, one of which shows how much oil (on a much later motor) flows where.

[tadd]

The 993TT squirters are 2 mm orifice. The standard SC are 1 mm. So 1+1=2 .

So I should think with a turbo pump or GT3 (read large pump section) there should be no issues since it is within the factory 'specs'.

As for the angle problem... unless its really canted over, I don't see an issue of leaving it the way it is. It just has to get to the piston crown. Although I have read on the BB that oil squirters are required for the nickkie coating, after having a long chat with a Millenium plating engineer I was informed that squirters are not necessary from a material standpoint. Only thing you can use Nickkie on is diesels becuase of the sulfur content making nitric acid and eating away the nickle 'glue that holds the silicon carbide particles. The ultra low sulfur diesel is in theory going to open up alot of new places to use the nickkie coating.

Long story short, the squirters are about cooling as with the current coatings there is no material problem according to the folks that do it. Having the PhD at the end of the name ususally gets me to chat with the senior folks that know their stuff.

So if its a cooling issue, and your concerned, I should think it would be way cheaper to use the lowest cost SC squirters and add the second set.

Beyond that, I would really think about doing a diamond coating on the underside of the piston to greatly improve wetting and thus improve heat transfer. The surfacants used in Redline water wetter to break the surface tension and improve wetting (and thus heat transfer) is good for 10-15*C on my old RZ350. Toss in a quick acid etch in the water passages and it was more like 20. Never had another heating problem.

t

[Walt Fricke]

Actually, safer than that, now that you are quantifying things. A 2mm hole is Pi mms in area, no? But a 1mm hole is one quarter that area, isn't it? So two 1mms would add up to a half the total area of a 2mm, and by inference flow?

I've never quite understood how it is that squaring a fraction results in a smaller fraction for, but I drew a square, and quartered it, so verified to myself that my fraction multiplication was not not amiss.

I think of DLC coatings as being for wear issues. I thought that was due to hardness, but is it due, or also due, to surface rugosity allowing pockets for lubricants and thus a larger surface? Aren't there other coatings which would promote heat transfer? Perhaps less expensive? But I suppose not the black ones for radiant, nor those which promise to shed oil faster.

[tadd]

Walt:
Yea, that was humor...or lack there of . You are correct, flux is flow per unit area, so Pi(d/2)^2 which gives me 1.57 (2x0.785), 3.52 (2x1.76), and 3.14 for two SC, two turbo (1.5 mm orifice), and 993TT respectively.

DLCs are typically wear coatings due to their hardness. Gotta love sp3 hybridized carbon though! It's diamond, so it's very hydrophobic thanks to the lack of polarization within the lattice. So it will wet very nicely with aliphatic hydrocarbons. It also has excellent heat transfer. Aluminum, is less so interaction wise with oils. So it's all about the oil getting as good contact with the hot surface as possible. Hydrocarbons are typically about half as efficient as heat transfer as water, so you literally need twice as much by mass to move the same number of joules.

There are other coatings, but the DLCs should make a nice interfacial aluminum carbide layer between the two.

t

[Walt Fricke]

So, ceramics on top, anti frictions on the outer sides and maybe the ring grooves, DLC on the inside of the crown, and maybe an oil shedding coating on the skirt insides? Maybe one should invest in coating company stock?

I'm kind of glad I didn't ceramic the tops of the J&Es I had cut for me, because first I had to enlarge the intake pockets, and then deepen both pockets. Though now I have more of a spec to work from if I win a lottery or two.

[tadd]

Walt:
Coatings are opinions...you'll get a lot of choices :-). I don't do ceramic tops either. No one has been able to explain to me why a very thin ceramic layer in thermodynamic equilibrium should be useful... It don't make sense to me :-). I've never been shown data that supports their use. I have seen data that says polishing the crowns provides an improvement over not...

All I use (so far) is the ring land coating and the anti scuff on the skirts (cause its so cheap to do).

Again, my two cents...no data, I usually don't.

t