Longblock Compression & Leakdown test

[911 tweaks]

I was wondering and hoping, that the experts and all others could chime in on what is the best (most accurate) method to check the cylinder compression and cylinder leak down ratings for a 911 SC 3.0L long block. Presume it has been stored indoors and not used/tested for 6+ months per seller.
ALSO, after checking these out, what is the best way to store the long blocks till they will be torn down for rebuild or used in some way.

I was thinking the following, however I wish input from Henry, Grady, John Walker, and any and all others that have experience doing this and frequently volunteer their help here...
1. put LB (longblock) on stand w/ starter adapter to be able to turn over engine as it would be normally started.
2. drain all old oul out of LB and look at condition of oil for "foreign" objects and any tell rails of condition of internals. Re install magnetic drain plug if dosent have.
3. add 1 gal of what weight oil via top of engine breather inlet.
4. put some lubricant onto clyinders i.e marvel mystery oil or engine oil or CRC or fogging oil used on outboards...ADVISE PLEASE
5. NOW WHAT??
Thanks all!
Bob

[304065]

I wouldn't ascribe a great deal of value to a leakdown or compression test performed on an engine that had been sitting. First of all, if it's not up to operating temperature the clearances won't be the same as when the engine is operating. Second, if you get an adverse finding, such as high leakdown in one cylinder, are you going to blame the cylinder or the test conditions?

An engine that cannot be validated should be priced as a core.

That said, if you plan to turn the engine over, remove the plugs and shoot some MMO in the plug holes. This will skew the compression values to the positive side, but that's better than scuffing the rings against dry cylinders with no lubrication. Then GENTLY turn the engine over using a breaker bar on the crank pulley nut until the oil is distributed. Then perform the leakdown test in the conventional way.

If I were storing an engine for the long term I would pickle it in oil by filling it entirely. I heard of a 1947 Bonanza that had a pristine engine like this-- a prior owner added double the oil quantity which effectively preserved the engine for a couple decades. Dessicant plugs in the intake and exhaust, cover the breather so oil doesn't leak out, etc. Grady has already written extensively on the procedures for long-term storage and more importantly bringing the engine back to life.

[911 tweaks]

thanks John. I will search for the info that Grady has previousley posted, however, if anyone has this info readily available, please post.

Also, what can I hang my hat on then as far as the condition of potential purchased cores? I have had 1 shop tell me that, "well, the #'s were great when we pulled the engine out of the car x months ago, but, now the #'s are a lot lower". Kind of sounds like a bait and switch or more like buying these core motors is a pig - n - poke, no?
Especially when the sellers want $3kmin + shipping for a 150k+ mile long block...how does one truley, subjectively asses the condition??

[304065]

Here's one of a few by the Man. Winter storage checklist?

Buying anything sight unseen involves risk. Signs of oil leaks? Remove sump plate and look for fuzz/hair? Remove chain covers and look? Remove valve covers and look? Excessive varnish buildup? Crap in the cooling fins? Obstructed oil cooler? Obvious wrong parts/hack repairs? Or an engine that's way too CLEAN to have ever run in a car?

My point is that you can't: buying a core engine, you have to assume that the cylinders are scratched, the rings broken, the valves burnt. When I tore my '66 engine down I found FIVE broken compression rings, but the engine only showed 45% leakdown in TWO of the cylinders. The other three with broken rings weren't showing that bad-- so my point is, you don't really know what you've bought until you tear it down and find out. In that regard, you ARE buying a pig in a poke, and it comes down to the integrity of the seller in accurately representing the KNOWN condition of the motor when it was last run, or if UNKNOWN, accurately representing that. Then you pays your money and you rolls your dice.

Good luck!

[911 tweaks]

thanks John!
maybe if I find a "lb" (funny as I type the acronym for Long Block as "lb", I think I may be buying pounds of well seasoned metal OR pounds of metal hamburg...oh how I crack myself up), has anyone posted a subject detailing how to document the "dissassemble" of a 911 engine so as to accuratley note the condition of parts?
maybe it is called the workshop manual?? I know everyone is always trying to save time and all with the salient points of the task to complete it as quick as possible.
Bob

[911 tweaks]

so let me ask you this John: what if I got a 150k mile long block, did as you suggest for slowly turning it over w/ MMO in the cyls and I would put 1 gal of oil in the case, and the #'s are ~150# and no cyl greater than 10% leakdown, is this an engine to put in service?
Maybe a better way to ask the question, I realize that the LB is giving partially false #'s since it is not been warmed up, however, is there a guide or spec that says something like the following:
190-200 # compression = as new engine/recent rebuild
180-190 # " = 25k mile wear level engine
170-180 50-75k miles
160-170 75k-125k miles
150-160 125k-150k miles

if any of this makes any sense, are their corolating leak down #'s that represent valve and/or ring condition?
Basically, I am trying to determine when to tear down, give it a try, it is tired and wont have any b&lls when you accelerate...you get me drift.

Bob

[TibetanT]

I am no expert Porsche engineer, but I would hazard to guess that each engine will "wear" at its own pace. Sure, there probably is some average number for compression over a span of miles, however, I would tend to agree with what has been said here prior.
First, do we know if the engine was properly maintained while it "lived" within the PO's car?
Second, if it was maintained properly, did the PO drive the car like it was the family car or did they drive it as a track car, for long hours at very high speeds. If they did drive it at very high speeds, did they overheat the engine at some point due to bad oil cooling or not changing the oil at proper interval. In other words, are the main studs ready to pull out of the block. Are there any broken head studs?

As mentioned earlier, check to see if there are signs of abuse like the cooling fins are completely filled with crud. Is there large metal fragments lying on the sump cover when removed. When the valve covers are removed, what is the condition and appearance of the rocker arms, valve springs, etc., etc., etc..

Lots of stuff to think about, huh?

If you have the time, take the heads off and inspect tollerances and take measurements, then compare those measurements to what the Official Porsche Workshop Manuals state.

Good luck with your decision. I do hope some of this helps you.