drola

i've made some progress. the p/c's are off and ready to go along with the heads. i found some scrapes on the inside of the case from the timing chain. not sure if i should open it up to check it out. time to put the parts washer together and get cleaning.

Gregg-K

Sorry about the delay in getting back to you, for some reason I did not get a notification of your message.

Anyhow, the flanges I'm referring to are the ones where the crankcase halves come together and the bolts go through. It would be a pity to be this far along and then have a leak at the crankcase joint afterward.

..> Gregg

Gregg-K

The things that will determine whether you need to re-ring are bore wear, and ring wear ... both of which your machine shop can easily determine for you if you send along the parts .... but be sure to mark which piston went into what jug.

The thing that will determine *if* you can re-ring is excess bore wear, piston wear, or ring land wear in the pistons.

If you are OK wear wise, I would most certainly fit new rings ... preferably ones by Total Seal.

.. Gregg

drola

what do you think about those timing chain scrapes? someone mentioned it might be machining evidence from when it was made but that pattern looks more consistent with chain rub.

if i split the case, that would mean new rod, main, int. shaft bearings, rod bolts, timing chains, and probably a whole bunch of other stuff. i don't know why i'm so reluctant to split it but something tells me to leave it alone..
there seems to be nothing wrong with anything else. my leaks were from base seals, timing covers, and badly clamped breather hose. so the flanges should be good.

i think i'm ok with the wear on the p/c's, but that will be determined soon. so i'll get the jugs honed and a new set of rings.

KirkF

I would split the case. In my opinion you are doing too much work to neglect the last 10% of the job.

Kirk

Gregg-K

Kirk and I are in agreement about completing the strip down at this point, but of course it is you who is spending the money ...

As for the scrapes, what I can see of them in the photos look to me like factory grinding marks from trimming the flash from the original castings.

If you happen to have a lot of slop in the timing chains, that would mean you have a failed hydraulic tensioner ... so check those out carefully in any case.

... Gregg

KirkF

I will give you this info now. It is the result of many experts best advice on sealing a rebuilt 911 engine.
(From pelican motor rebuild forum). I followed it on my own rebuild.

911 engine sealing:


Outer Case Halves: Threebond 1104
Bearing Saddle Surfaces: Loctite 574
#8 Bearing (balancer end) O-Ring: Threebond 1211
Case Thru Bolts: Dow Corning 111 on Green Viton O-Rings
Flywheel Seal: Preferred Dry
Balancer Seal: Curil-T
Intermediate Shaft Cover to Case: ThreeBond 1211
Oil Breather Cover to Case: ThreeBond 1211
Cylinders to Case: Curil K-2 or ThreeBond 1211
Cam Towers to Cylinder Heads: Threebond 1104
Cam Chain Housings to Case: Threebond 1104
Cam Chain Housings to Cam Towers: Threebond 1104
Cam Chain Housing Cover to Cam Chain Housing: Threebond 1104
Gaskets: Thin coat of Loctite 574

If you want to see what I is involved with the bottom end, there are some good pics in my rebuild thread:

https://rennlist.com/forums/showthre...ferrerid=10545


Kirk

drola

kirk,
yes, i had seen your post. it was one of the determining factors in getting this project started in the first place. with that much info how could i possibly screw this up? (yours, sundog, and axl911)
i will take yours and gregg's advise and split it open. i'm already there.
my car has 89k miles on it. do you think the timing chains would need replacing? chain ramps?
i'm really at a loss right now trying to come up with a list of parts and suppliers for this rebuild. i don't even know where to begin. so far i've accumulated some parts for the top end, which was my original plan. do you by any chance have a list of "mandatory" parts to replace? once i'm in there i'll see what else needs attention. i know that the rebuild kits have most of the seals/gaskets.

Gregg-K

My approach to a rebuild is based on the notion that I do not ever want to have to go into that engine again ... life is too short to be doing things more than once.

Clearly one replaces the worn out components ... but if one leaves "semi-worn out" components in service, that only means that I, or someone else will have to get in sooner than later to replace them.

Now, if a semi-worn component is easy to access with the engine in place, then sure, leave it for replacement later on. However, things like rings, rod and main bearings ... its a no brainer: replace them while the engine is apart.

... Gregg

altarchsa

I replaced #3 rod without splitting the case. I don't know if they're all accessible though.

I've done five 911 rebuilds, both top end and top/bottom end, and I disagree with the previous comment about splitting the case if you're a weekend engine rebuilder. Preserving a non leaking case is much better than splitting it and running the risk of not getting it sealed up as well as the factory did it. This is truly a case of "if it ain't broke don't fix it" in my opinion.

If you try to replace the rod bearings without splitting the case, even if it can be done it's tricky to avoid dropping the bearings, rod bolt nuts, etc. into the case. Suggest you use a thick engine lube to hold the bearings in the rod cap and to hold the rod bolt nut in a socket on an extension. You can hold onto one rod bolt and ease the cap, with bearing and bolts installed, around to the back side of the crank. Make sure the crank is positioned as close to the opening as possible, but a little toward the bottom to provide maximum room. A telescoping magnet can be used as security. Really risky to use the fingers.

If you decide not to machine for head seals:

I didn't machine the heads for the "recall" seals. What I did was an experiment. I used a thin coat of high heat grey gasket maker in a tube, by Permatex I think, on the mating surface of the heads just before assembly. Tightened the heads down quickly to push any excess out. I think what was left formed a very thin seal that took care of scratches and irregularities in the surfaces and it has resisted blow out so far. Also, no leaks so far!!!

My theory was, if you have a little money to buy a second set of new top end gaskets for a "second time around", but you don't have the big bucks for the "recall" head seals route, the only other thing you're risking is your time to pull it back out and do it over. This is the unfortunate logic of necessity of "poor boy" Porsche ownership.

Good luck. Let us know what happens. It sounds like you're gravitating toward conventional, recommended complete overhaul with assistance from the pros for machining, etc. I would highly recommend you go this route. New rings are cheap, etc. You'll enjoy the results and peace of mind is priceless.

KirkF

I dont think its difficult to get a well sealed case given the modern products available. Loctite 574 was an excellent choice for the factory, but they were using shiney new cases. The threebond products make it easy to get the case back together without a hassle.

It is the same as yamabond, a sealant used on modern motorcycle cases. (Which also have a wet split along the middle).

Altarchsa has done more 911 motors than I have so maybe he has run into more issues with the case sealing than me.

I forgot to mention about gasket sets. I strongly recommend the wrightwood racing set available from EBS Racing. I had both the victor reinz set and the wrightwood set, and the wrightwood one was definetly a superior product. The only seal I didnt like in it was the RMS. I found the factory porsche seal was the best one for that job.

Kirk

altarchsa

I defer to KirkF. I have not used the Threebond product. If it has a better success rate than the 574, I'd split the case.

Be sure to check all the main and rod bearing tolerances. My experience with the used 964 I bought is that the crank has worn. They used to be bullet proof. Maybe I just got an abused one, but it's worth checking on reassembly.

Gregg-K

Threebond sealants were developed for Japanese motorcycle crankcases, and have an excellent reputation in that industry.

. Gregg

dcbailey

FWIW, there's a class in engine rebuilding at http://www.911handbook.com/, starting December 4th. I'm just a newbie, but I'm planning on attending the maintenance class for a day.

KirkF

I have heard that the Bruce Anderson class is excellent. I really wanted to take it when I was doing my rebuild. (As long as you can get past the fact he has been slamming the 964 for all these years. )

Most of the wear in my engine was on the top end. The cams were pitted and the valve guides were screwed. A previous shop had done a bad job of replacing the valve guides and made a mess of them. Between those issues and machining the heads to accept the updated sealing rings, my machining costs were pretty high. (I had to replace every valve)

I had the machine shop replace the rod bushings as well.


For my crank I had a local machineshop magnaflux it and measure the tolerances. (Not that I didnt measure them myself, but it cost nothing to have them take the measurements again while it was in there) I had no problems with bottom end wear. I just put in new bearings, checked them with plastigauge and put the case back together.

The best part about splitting the cases is that you get to replace the weakest part of the motor. The rod bolts. I used ARP. But of course the costs go up.

Kirk