1973 2.4 L Compression Results
 

1973 2.4 L Compression Results
Ok - got the results from a compression test.
1 = 75
2 = 80
3 = 85
4 = 85
5 = 85
6 = 85

He is telling me normal range is 120-140 PSI so he says it needs are build.
Oil pressure was 30-80 PSI Warm Engine.

I was doing some research and couldn't find what the specs should be...

you guys agree on the rebuild??

those numbers are low, but they are also very even
different compression gauges can produce different results

I have a cheapo ebay piece of crap gauge that always shows 30lbs less than a 2nd decent gauge I own.

Hmmm..
does it smoke somewhere?
maybe get a leak down?

brant

Ask the guy who did the test if the throttle was wide open during cranking.

If the throttle plates are not wide open, you get a pressure drop across the throttle plate that will depress all the readings.

How many miles on the engine. What is the gas mileage and oil consumption like? Those compression numbers are low.

The engine has 106K miles on it and there is definite smokey out the exhaust...no clue on gas consuption as I haven't been tracking that. Oil does burn, but there is also an il leak which I can't figure out how much burns vs. leaks. It is a small leak but about a month after an oil change I had to add 3 quarts (probably drove no more than 200 miles)!!

I'd prepare for at least a top end, rings and valves. Not sure about the lower end. I've read that once the mag case is split there is some warpage in the case. That could get expensive. Rod and crank bearings aren't too expensive, but machine work to prep the case can get pricey.

Have your mechanic do a leak down test on the engine when warm. Have him listen for the source of leakage to better pinpoint the problem.

If he doesn't know how to do this, find another mechanic.

you know...i asked for a leak down test and he said with those numbers, there is no point... valid statement? This guy is a total Porsche mechanic, his whole shop is filled with old porches and an engine room in which is seperate from the shop closed off in which he does all his rebuilds. - i gave him the benefit of the doubt...should i have?

with this many miles does it make sense to bite the bullet and get it done once and for all?

This sounds stupid - so sorry, but what is the difference between overhauling the top and not bottom vs. doing the whole engine??

No that is not a valid statement. A leak-down test would give a better indication of what elements of the motor are problematic (i.e. rings, intake or exhaust valves). The test takes very little time to perform and is a better indication of engine condition than the compression test. As others have stated there is some variability in compression tests, the leak-down is the better way to go.

Tell us a little more about the smoking. Does the car smoke out of the tail pipe constantly or do you just notice it mainly during start-ups and/or at stop lights?

BTW, that is a clean looking car and the interior looks to be in great shape considering it is a targa (there isn't even a crack in the dash!).

But what difference does it make whether it is rings or valves at this point? We know he needs one or the other or both. At the minimum he should do both, so the leak down test is a moot point. Why would you only do one, when you are already in there? The question is, should he split the case and do the bearings? A leak down test will not tell him this. At a 106,000 miles, if it has good oil pressure and the case is not leaking, I would do just the valves and the rings, assuming that the cylinders are within spec and savable for honing. In terms of getting the best bang for his buck, that is how I would tackle it. So the next step would be to get some mechanical oil pressure readings at operating temperatures to determine whether he should split the case.

EDIT: I just noticed that oil pressure readings have already been performed and they look good. I would just perform a hone/re-ring and valve job and he will be good to go...

This is a 100,0000 mile 35 year old engine.

You are correct....Your rebuild should include splitting the case to replace the crank bearings and rod bushings. Once you have the pistons and cylinders off, which you'll need to do to assess their condition and replace the rings, splitting the case is very little extra work.

gsjohnson,

This is not a slam, I'm just backing up my post and responding to yours...

A compression test is only an indication of general engine health as opposed to the leakdown test which determines each cylinder's ability to hold compression. As has been stated before, there are many factors that influence the actual compression readings. We don't know if the compression test was done properly (was it done cold or hot? was it done wet or dry? is the gage reading correctly?). The readings present a fairly even reading with ~9% difference between min and max. This is less than the generally accepted 15% maximum difference. Regardless of the fact that the mechanic should have performed a leak down test to begin with he should have followed up with this test atleast on a couple of the cylinders to better infom the client of the possible issues and cost associated to remedy the situation.

The mechanic should not assume the customer's financial situation and should strive to give the best indication to the client what is wrong and what it will take to fix the issue when ever possible. The approach of "we will see what is wrong once we get the motor out of the car and tear it apart" or rather "your motor sucks and it needs to be rebuilt" is not a good one. With a proper leakdown test a best case and worst case estimate could be provided. This conversation could have taken place but I would suspect not if the mechanic said "there is no point".

We do not have a full history on the car so we don't know what has been or has not been done to it. The car presents itself well in the pictures so it may have been well maintained mechanically too. With a 100K miles on the clock, a PO may have already done a top end job for all we know.

The car may very well need just rings or it may need P's&C's but we just really don't know at this point. It would be interesting to know if this is a MFI "T" or not (possible cylinder washdown). The expense of a top end or bottom end re-build may not be the end of the line to get the motor back in proper running order. Things like this should be factored in the equation so that an informed decision can be made by the customer (in this case pcivalero).

You have all been SO helpful so thank you!!

For what it's worht it is a MFI T.

I was able to find this paperwork in the stack I got with the car. Hopefully it can help determine what was done!! the date of the invoice is 2/4/2002 so not that long ago given that the mileage was 98K and I am at 106K now. Looks like some work was done with repect to seals, hoping someone can tell me what it means.

http://forums.pelicanparts.com/uploa...1260398950.jpg
http://forums.pelicanparts.com/uploa...1260398971.jpg
http://forums.pelicanparts.com/uploa...1260398990.jpg

Not a slam either. Just opinion here. He has stated that the engine smokes and uses excessive oil. Theses are irrefutable facts. The source is either the rings or the heads (valves, guides, seals) or both. This problem is not going away no matter how much you wish it to. A compression test has been performed by what appears to be a knowledgable shop. Evidenced by the numerous Porsches at the shop being worked on. The compression readings are very low indicating a problem. So we have excessive smoke coming from the exhaust, excesiive oil consumption, and low compression readings. And you need more evidence by insisting upon a leak down test? At an additional cost, I'm sure. Whether it is the heads (valves) or the rings, both are stacked against each other in terms of engine assemble and labor. It's obvious that you should do both, and this would save you money over the long haul and a ton of labor by doing both now. The money to do both is not that much more when you are already in there. Besides, you can inspect both issues at teardown anyway.

pcivalero,

The report you posted is very helpul. I especially like the line "Extensive discussions with the owner regarding repair/replacement" with estimates for the repair. This should be the way all repairs should be worked out with the owner (before digging in to the motor - which was my point in the previous posts). A few interesting nuggets are found in the repair bill.

1). The car had a leakdown performed for the PO and it was found in that test that the a top end rebuild was needed. It appears that the PO decided not to proceed with that repair. It is also interesting that a replacement engine was considered at that time.

2). The rings most likely need to be replaced. Unfortunatly when the MFI cars run excessivily rich they wash down the cylinder walls (causing the rings and the cylinder walls to be damaged). Depending on the condition of the cylinders they too may need to be replaced. The oil dilution is a real cause of concern as there is a good possibilty that if the rings/cylinders are badly damaged the main and rod bearings have probably been damaged as well. Fixing the bearings would necessitate splitting the case or a complete rebuild.

3). The car has had the chain tensioner update and this mechanic finished the repair by updating the ramps and idler sprocket arms.

4). Some attempt to fix the oil leaks was done (including the replacement of the oil return tubes and some repair to the chain housings). I'm assuming that this was done to make the car more sellable.

5). The old exhaust system was replaced with SSI units. This is a good thing. The fact that he took the old system in trade is interesting though. Maybe the PO had a performance exhaust on the car since it says "no heat" and loud muffler.

6). The car may have more miles on it than what is currently showing on the odometer. The bill indicates that it was inoperable at the time and that it was fixed.

7). The bill indicates that the MFI system was set back to factory specs but at the bottom it says that it needs to be removed and rebuilt.

Given all of this along with the info provided in your first post you have some big decisions to make and should discuss all of the options with whom ever is going to do the repair work (I would recommend soliciting opinions from this board and checking with more than one local repair shop). A full rebuild of the motor seems to be needed here. In addition the MFI system most likely needs work. This is probably not just limited to the pump and injectors but probably requires rebuilding of the intake manifolds (which is common for a car of this age).

Depending on what you want to do there are some great options that you may want to entertain. You could rebuild the motor so that it makes more power (i.e. a high compression E) or you could swap out the motor for a larger displacement motor (such as a 3.0 Ltr. with carbs). In a nutshell, you don't have to rebuild it back to stock specs for just a little more money (or a little less in the case of an engine swap) you can really improve the performance of the car. If you do decide to swap the motor you should get some money for yours (despite it being in tired condition) I hope this helps...keep us informed and ask questions whenever you need to.

Hmmm...So you are recommending a full rebuild including rings and valves.
I dissagree with your cylinder wash down theory damaging the bearings, as the oil pressure still reads very good.

Agree, however it sure would be nice to know prior to ripping open the engine as to whether or not the valves are leaking or not. Even though it would be prudent to recondition the heads during a rebuild (that is if it is even close to being needed) it sure would be nice to know before tearing the motor apart that an additional $500+ is needed to recondition the heads.

Disagree, just because a shop is busy does not make it a knowlegable or for that matter reputable. Using this logic Motor Sheister would be considered a top Porsche engine builder.

I don't need more evidence that the motor needs major work. I need more evidence to provide the customer with a better estimate of the scope and cost of the repair...before I yank the motor out of the car and tear it apart. This way the customer and I can have a discussion about what options are available before he has his car in a hundred pieces and he now realizes that he does not have enough money for a complete or timely repair. As for additional cost, ignoring the issue that the leakdown should have been performed instead of the compression test, the mechanic should have done it at the same time when the additional labor to do so would be minimal. This goes back to the reasons stated above...good customer service.

Bringing this back to a local analogy, I can have water stains on my ceiling indicating a problem with my roof. But without getting into the attic and/or up on the roof there is no way I can tell if it is a $200 patch repair or a $20,000 new roof. I sure would want to know before I start tearing shingles off of the house.

I don't know this shop in question and for all I know they may be very good (as there are many very good shops here in Florida). Being an ex Porsche wrench, it is my opinion that the shop should perform the right diagnostics not only for thier benefit but the customer's as well.

I don't want to replace the engine, I want to keep the original engine, however I am totally open to ideas on performance improvements. The problem is that everything I have seen is SOO expensive. I am waiting for a quote from this current mechanic, however he has verbally quoted me: - will post the paper quote tomorrow.
40 hours @ $90 an hour for the service = $3,600
Parts for upper and lower = $1,500
and then I can't recall something else for another $1,000 or more. This is really really expensive and this is just a stock build. Assuming I have another $1,200 - $1,500 for the fuel injector rebuild I am really out lots of DOUGH!! - What recommendations do you have for a stock engine for performance improvments. Again, seems like I will be out of $7-$8K....

Yes, unfortunatly repairs on these cars get pricey really, really fast. This is why you should do your homework (like you are doing now) but you should really talk directly to some experts (many of which frequent this forum). I'll send you a PM on this.

Your analogy is apples and oranges...
You went down this long road of a supposed discovery process only to end up admtting that it would be prudent to do both the rings and the heads at the same time. I'll even go out on a limb and say that it would be foolish of him not to. And this is exactly what the shop told him when explaining why a leak down test would be pointless. That is all I was trying to point out here. If he is looking to save money, it should be based on the decision of the splitting of the case and doing the bearings IMHO. What shop would guarantee the repair by only performing one of the two???