DanG

I got the results of the leakdown test today. Looks like the noises with my car MIGHT be only in the head...

Cylinder # . . . . . . 1 . 2 . 3 . 4
Percent Leakage . .6 .16 . 5 . 5

So 1, 3, and 4 are good, 2 is leaking through the valve (can't remember which one they said).

They were able to start the car after the test. I started up fine, but definitely made a big racket. But if its just ONE valve, this repair might not be as expensive as I was thinking it would be. If it does only need headwork, I'll probably go ahead with a full 3/5 angle valve job + a little gasket matching and casting flash cleanup.

However, I can't help but think I should go with a full rebuild. As far as I know this car has a 160k miles on the bearings in there now, the last 20k with the bigger turbo and higher boost. So I'm thinking dropping the money on a rebuild now might be better than getting the car, driving it for a few months, THEN blowing the bottom end of the engine.

I'll have to wait and see though. It will really depend on how things look when the head comes off on Monday.

Also, a little bonus is that the car already has a Tial WG on it. So thats about $300 I won't have to spend. Looking back through my pictures, it seems like it has the two piece crossover tube as well...


Last comment, I just spoke with Kevin Johnson of http://www.crank-scrapers.com/ on the phone. I had sent him an email about 45 minutes ago and he had already called my shop to track me down to discuss payment options. He said the scraper will be built today and shipped out! Amazing service. I decided to order it today just incase it was going to be a long-lead item. Fat chance, with this kind of turnaround. If the rest of the rebuild can go like this order, I'll be thrilled.

Click here for more info on the crank scrapers...
https://rennlist.com/forums/924-931-944-951-968-forum/209369-new-924-944-968-performance-part-available-crank-scraper.html

Skip

Great looking car, Dan - congrats!! Email me for some info on the crank cross drilling. Not sure if you already have it, but never hurts to trade notes. I just had mine done.

DanG

Skip, will do, or you can just post the notes up here for all to see.

I'm pretty sold on "perp" drilling, unless I hear some good points on doing it different.

My 944 NA has a cross drill and Turbo oil system, including a baffled pan. It makes 4-5 bars pressure at any condition over 1500 rpm, and even during extended corners on the track.

M758

I just had my last crank cross drilled in #2 & #3 only.

Some results from NA racing and bench testing by Greg Fordhal in the northwest seems to show drilling of 2 & 3 only do a better job of balancing the oil flow vs non cross drilled or even doing all 4.

I have not run this motor yet.

Skip

No secrets, just scared about posting for shops that don't sponsor, but since Joe already did...

Mine was done through Fordahl. 3/16" cross drill on #2 and #3. Not perp, though I don't know which is preferred if there were a choice. This is what Greg uses on the 944 spec-like cars up here with good success so I trust that. Also getting the rod and main bearings coated by either Calico or Swain.

Also, have your crank guy check the main thrust surfaces - mine had to be welded and reground because they were too far out of tolerance. Can cause lower than optimal oil pressure - like we need any help there, eh!

Good luck with the new car - looks like another save for rennlist! I wouldn't be afraid to contact Chris about it if you have some questions.

M758

Well, It was not a post for a "Shop". Greg posted his drill process on NASA forums. I had my local crank guy do the work. Anyone that can cross drill all 4 can also just do 2. Nothing special here. I did post that Greg came-up with this for two reasons. 1) Don't want claim credit for something not mine, 2) Gives a bit more credibility when "someone who knows" comes up with something rather than just me.

Good luck with the motor Skip.

Skip

Joe, are you coating any of the bearings?

DanG

What about crank coating? My shop says they typically sandblast then coat the crank with "oil shedder" (obviously not on the bearing surfaces). I've never heard of this.

Hmm, I've never thought of doing JUST #2 and 3, thats an interesting idea. Seems logical, although I can't say I've ever heard of a #3 bearing failure. Still, I'll take advice from 944 race engine builders over what "makes sense" in my head. I guess I'll have to keep researching the debate between perp and cross drilling.

What does it cost to coat a set of bearings? I used to work closely with a very successful Ducatti motorcycle engine builder and racer. He was nuts about coatings, coated almost every moving part of his engine and trans with something, but can't remember what. Maybe it was through Calico/Swain, I'll have to ask.

Skip thanks for the heads up on the crank thrust surface check. Every bit of oil pressure helps.

Pauerman

Joe or Skip,

My last 2.5L crank was done by the folks at Pauter rods. They perp drilled the rod journals and also enlarged the oil galleys running to all rod journals. The larger oil galley holes were tapped and now use a plug.

Did your crank work from Fordhal include modifying the oil galley size? I'm wondering if this is necessary and am interested in some feedback - I'm getting my 3.0L crank drilled next week.

Thanks
Vic

M758

Nope.

Skip

No - nothing to that level was done. Honestly, this is a weighted precautionary measure. Paying $300+ just to have this done to a $500 engine, $50 for the baffle, $45 for the oil tube mod, then considering I'll put another $200+ into rod and main bearings, then add all the other parts and consumables needed to put the engine back together, this gets pricey for a 944na racecar. I can basically buy $500 engines once a year or less and change the bearings regularly and save lots of money and time. Of course, having the engine blow out on track is no fun either. I just don't try to spend too much on consumables - since this is only my third engine in 7 years, it's a relatively inexpensive consumable. If I were building engines with big power for big money, like you, I'd go as far as I could with prevention. i.e. don't use me as an example of what to do - I'm a cheap ol' bastard

Skip

Nope, nothing that high tech here.

It may be happening more often than we know - some who have the failure never really know what happened since they don't do their own work and the easy answer from the shop is that #2 rod bearing spun (meaning, #3 looks bad as well, but that's gets fixed with the lot). My last experience (of two) was that #3 locked the engine up only after #2 completely let go. Also, if we are to believe Greg Fordahl (yes, we do), he says it's very normal for #3 to be damaged as well as #2, though #2 is usually the one that is visibly FUBAR'd. For you viewing pleasure:




#2 was almost non-existent. #3 was nearly welded on the crank. Logic follows what Greg has reported. #2 failed well before #3 caused engine to lock up. Increased flow thru #2, or, simply reduced oil pressure appears to have affected #3 as the next weakest link. #1 and #4 looked fine. All of this happened within a few hundred feet. I hesitated when I thought I felt a loss of power coming off a corner pretty hard (lefty, #2 at Pacific) - high in 3rd - looked at the OP gauge and immediately let off the gas and turned off the engine. Coasted to a stop, then just tried to bump the starter to see if it would still turn - no luck, locked up hard. Luckily did not throw a rod off. My excuse is that I was chasing a turbo - thou shalt not use na's to chase turbos... bad things happen.

I believe it's about $50/set (4 cyl). Calico is what Greg recommended, but I've always heard good things about Swain as well.

I was a bit surprised by this but have sinced learned that it's quite common on a high mileage 944 engine - though, it appears that many crank shops do not check the thrust surface wear. Engine is an 88na and had 120+k miles on it.

M758

For me it is less effort to do all this work and not have an engine fail on me. I have spun two bearings. First one blew-up the block, but not he head. This last one just took out the crank. Even so I don't like popping engines. They are pain to remove and replace and am believer doing solid job on it. Nothing fancy, but solid anyway. You also need to remembe that blown engine cost more than just the $500 for the engine. Gotta figure the envent cost is down the tubes. So there is another $300 to 500. Plus then you need to find the engine and a $500 may be hard find when you need one. Then all the time an effort, plus any littling things needed to fix on that motor. Belts, waterpump,etc.

Best to spend $1000 during motor rebuild to give to you the best chance of having a long life motor.

DanG

News report from the shop:

The head looks ok, it will be pressure checked. Bonus - it has had some porting done. I just hope it was by someone with a flowbench and some experience, rather than a monkey with a die grinder. Its kindof cool though, as the car comes apart more and more, I find more and more pluses! 2pc crossover, Tial WG, ported head... it goes on.

The bad news is #2 rod bearing is shot. Although this isn't necessarily all that bad, as I was strongly considering a bottom end rebuild whether it "needed" it or not. Now I know my money will be well spent. The walls are supposedly still in good shape, although if they can't find anything wrong with the head, I'll have to assume the #2 rings/wall is the reason for the high leakdown numbers.

I'll most likely do perp drilling on #2 and #3, then the typical crank R&R including thrust surface check/refinishing, and then install the new coated bearings and crank scraper. We'll see if the pan is already baffled or not, theres a chance it will be.

Also, the head has been oringed, but the block still has a flat mounting surface. So the oring was just a single circle of extremely elevated pressure. I'll have them cut the groove into the block as is typically done w/ oringing.

Thats it for now. Will know more about the bottom end on Wednesday.

M758

Make sure you check the crank carefully. I know the one from my last spun bearing look not too bad, but was going to be quite expensive to fix. It was a little bent and would need like 3rd undersize bearings. The became quite costly. So I just source used crank from a rennlister.

So make sure they check the crank an tell you what is up before the shop does any cutting.

Re.. O-ring. I thought it was common to jsut o-ring the head as you take the head off have it cut, but typically leave the block in the car. That is why the block is not cut. Also I work in aerospace and we use o-ring in various places. No where do I remember having grove on both surfaces. Usally one surface gets the grove and the other is flat. The reason is that it can be very hard to machine both groove so they line-up all the way around the mating surfaces. If they did not you could easily cut the ring.