I bought an 82 SC Euro spec coupe w'178k on the clock, never had valve or ring job. The P-mech, who did the test said the #s ranged between 5 & 7%. I later learned (perhaps this is wrong) that up to 10% is within factory spec. If this is true, did I get an exceptionally good motor that tests w'such low #s at 178,000 miles?

I've had the little beast about 8 mo.s & it's my daily driver - and it uses next to NO oil in the 3k mile intervals between oil changes. Being a Newbie, am I just experiencing what finely engineered cars these truly are, or is my engine the exception? I did have to have the slightly pitted cams reground when my mechanic went through it, but no other top or bottom end work was needed.

Love the car!

 

Yup, anything below 10% is good. You are also looking for consistency in the numbers and it looks like you got that too! Looks like you got a well maintained example, congrats!

Matt

 

You are experiencing the true wonder known as the SC! Keep the oil changed, stay with your service schedule, fix it when it breaks, and have fun! And yes, Matt's correct, your leakdown numbers are great.

Pete

 

IMHO the SC's are the ONLY air-cooled p-car that maintain good leakdowns regardless of mileage. Certainly not the 3.2's with their crap valve guides and fragile rings. 2.7's anyone??964"s?? Did a 933 TT PPI the other day. First cylinder 70%. No amount of persuasion could drop it. They couldn't make guides for them either. Maybe that's why everyone wants an old cheap SC. Great cars.

 

LOL,.....Au contraire, Sir.

Having done thousands of Porsche heads here in our shop since 1977, Porsche used the same crappy, soft guide material since 1978 and even to this day in the GT-3,........no change.

What we DO see is wide variations in stem-to-guide clearances which might explain why some motors use more oil than others. We've used our own phosphorus-bronze guides for many years with excellent results and properly fitted, will outlast the factory ones 3-1.

Insofar as rings go, Mahle uses Goetze rings which are pretty darn good. The metallurgy is the same from the 3.0 engines to the 3.6's. None of them will tolerate detonation for long caused by insufficent octane, aggressive ignition timing and too-lean mixtures.

 

Hi Steve,
No mistake, I do respect your opinion; I've seen quite a few heads myself since '72. And the guides I've used- either silicon or phosphor bronze- have never given me a comeback, regardless of application. As I'm sure you do, we do all our own head work. So why do the 3.2's eat original guides up and the SC's don't?? It can't all be octane/ compression ratio/ ignition timing. I saw a few 3.2's with broken rings at under 20 K miles in the mid- to - late '80's and was shocked. Then I saw a lot of radially broken intake valve guide seals, even with reasonably good guide clearance numbers. Then as time has gone on I have seen horrible guide wear on all the late motors. I personally think that manufacturer quality slipped in these years, don't you??
Regarding rings- little breakage after 3.2's, just high leakdowns.
PS I wouldn't mind taking this discussion up over email, esp. if you'd prefer.
Regards,
stephen@poudresportscar.com

 

Hi Stephen:

Thanks for your response! Its enlightening to hear that your experience largely mirrors our own,.....

Indeed, we do all of our machine work here in-house just like you and we've seen the same kinds of things.

The 3.2's represented a conundrum; some of them needed valves & guides by 50K miles and some went the full distance (well over 100K). Since the only variable was valve material, fitment, and operating conditions, its difficult to say with any certainty. I think the broken guide seals were caused by the valve wiggling around in the guide since I've seen plenty that were simply unbelievably loose.

IMHO, you're right; manufacturing quality control slipped during this time without a doubt,......

The broken ring issue, in my opinion, is all detonation related as I've seen that in SC's, Carrera's and Turbo's. I find other supporting evidence such as pinched ring lands, peened pin bosses, and hammered rod bearings,....

The 3.6's had twin-ignition, knock-sensing, and excellent engine management. Many leakdown issues were caused by bad guides that permitted the valves to move laterally on the seats and out-of-round cylinders caused by heat.

All in all, these engines are still rugged as hell and a LOT better than other manufacturer offerings.

 

My experience certainly parallels that of Steve's, certainly closer than Stephen's. In SoCal we never saw the ring failure (finding a broken ring in a 911 with less than 200K miles was an exciting moment for us!)discussed here - there is too much traffic in L.A. for cars to detonate! Seriously, properly serviced cars that use great oil (such as Kendall GT-1) and great fuel (Chevron Premium) live a long time. I took it upon myself, back in the '70s, to counsel people on how to drive, as well as how often to check/change their oil, etc. Even that couldn't save many 3.2 engines, we did valve guide replacement as early as 40K miles on a few. Of course, we felt that the damage to those engines occurred early in their life (bad dealer oil, like Pennzoil, bad 1,000 mile valve adjustment, etc.). Yes, SCs survived, and some 3.2s didn't, but Steve is right on the money - the 911 is the best damn little engine ever built, in my opinion.
Pete