3.0SC Engine Problems (LONG!)

Hi Folks,

I originally posted this first section on the Rennlist 914list, but I feel that the engine discussion is more appropriate here:


...I'm hoping (no doubt in vain) that rebuilding the carbs will clear up the running problems (it didn't run) that I've been experiencing. It all started at an auto-x, one run the car was fine, then in the middle of that run, it started stuttering at redline, like it was banging on a rev limiter. When I got back in line it was backfiring, wasn't idling so well, and as I drove it home noticed that it wasn't pulling so well at low revs, which gradually turned into running rough and stumbling at mostly all RPMs (at least up to about 3k rpm).

I had and still have a few theories on the problem. One is a clogged carb, the fuel level was quite low, and all that sloshing
could have loosened up some sediment that had accumulated in the 10 years it sat before I bought it this summer. Unfortunately, spraying cleaner through the idle jets didn't help, the filters (inline and banjo)all seem to be pretty clean, and none of the various jets/tubes I've just removed
have visible blockage (maybe the other side will show something when I tear it apart). I
did find that the carb/intake, intake/head gaskets were soaked with gas and it was even leaking out in a few areas, even if this isn't
the main problem, I think fixing it'll at least help.

Second, I was thinking a burnt valve. I've heard this can cause rough idle, and poor low-end running. But the valves had just been
(under 1k miles before) adjusted by a reputable pro., and it doesn't seem like something to happen so suddenly. With the carbs off I can see the intakes, and they seem to my untrained eye good. A little
carbon buildup on the backside of the valves, but the guide seem to well sunk into the heads, and holding the valve tightly.

Third idea, is one or more snapped head studs. When I bought the car, all info. I had seen seemed to indicate that Dilavar was the
stud of choice, but I've read here (Pelican) that Bruce A. and others are recommending factory or raceware studs. I'm thinking this would explain my very poor compression test readings (I can't remember exactly something
like, 90, 60, 120, 90, 90, and I couldn't get the tester screwed into #6). Awfully low, eh? These numbers also don't seem to bear out the
burnt valve theory either now that I think about it.
________________

In the last day or so, I have removed the exchangers, and the valves are sooty, and 2 are visibly wet (gas I imagine), but appear to be intact. I have also removed the right side exhaust valve cover (without first draining the sump/oil tank though), and can't really tell if there are any stud problems. If I have a broken stud, will it be readily apparent? Will it wiggle? Will it just have fallen out? Would there be external signs, on the valves or on the exterior of P/C's?

I guess it's not a burnt valve, unless it could be damaged and I don't know what to look for? Some people have asked about compression test procedure. I had the throttle WOT, and the engine was warm with a charged Optima bat. What I didn't do was disconnect the fuel pump, which may have cause the cyls to wash down, but even still the 60psi reading is vexing, and the 90's still awfully low, shouldn't it be around 150?

Something that I didn't mention in my original post, was that I had been hearing an odd noise for 500 miles before the problem. It seemed to happen less at higher RPMs (but maybe I just couldn't hear it). It was an intermitting tink/pinging sound, that seemed to start after the motor was warmed up. It didn't really seem to speed up with engine speed. I had been hoping that it was a nut that I lost in front of the fan, and hadn't been able to find, that had gotten stuck in the fan. But the sound seemed to come more to the rear of the motor, on the 4-5-6-cyl side.

Anyway, I'm not sure what to do at this point except put it all back together with the rebuild carbs (the kit came today from Pelican), and hope for the best. Anyone have any suggestions for stuff to check while the engines semi apart? I would do a leakdown, but the car doesn't really run under its own power, and I don't have shop air.

Thanks,

Adam
'70 914-6 3.0SC with Weber 40IDT's

Adam,

The 24 head studs should be checked with a torque wrench and 3/8" drive 10 mm hex bit ... the nuts are Allen nuts and either a special long reach tool or a 4"-6" extension on a regular drive bit is used. The spec for the '78-'81 SC engines is 33 Nm or 24 lb-ft, or the '82-'83 SC engines with Optimoly HT on the threads is 32 Nm or 23 lb-ft. ... per the spec books! It sounds like one or more Dilivar head studs are cracked or broken, and you should resolve this issue befire putting the engine back in the car.

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Warren Hall
1973 911S Targa

Wow, really an answer for every sort of problem on every motor (except maybe SBC's), you even included torque specs. Thank you. I suspected it might be head studs, especially after just now reading the post about the 964's snapped stud, the noise seemed about the same. I tried wiggling a few, but since the studs nuts are supposed to be hex head, I think I was wobbling the wrong ones. I'll check it out tomorrow.

So, should I attempt to do this myself? I just read you say that the case around the stud needs to to be heated to 375deg, short of sticking it in an oven how is it recommended to do this. I see in BA's book, that there is a special tool for removing them (one also made by snap-on), I'm guessing I'll need this and can't just double nut them? Also from reading, it looks like this motor had Dilivar studs from the factory, but just on the bottom row, with steel ones on top. I should probably do all of them though?

Thanks,

Adam

Originally posted by Early_S_Man:
Adam,

The 24 head studs should be checked with a torque wrench and 3/8" drive 10 mm hex bit ... the nuts are Allen nuts and either a special long reach tool or a 4"-6" extension on a regular drive bit is used. The spec for the '78-'81 SC engines is 33 Nm or 24 lb-ft, or the '82-'83 SC engines with Optimoly HT on the threads is 32 Nm or 23 lb-ft. ... per the spec books! It sounds like one or more Dilivar head studs are cracked or broken, and you should resolve this issue befire putting the engine back in the car.

As for the headstuds, any competant person should be able to do the switch. I was able to remove all my studs with vice grips and I only needed to heat a few with a MAPP torch. Depending on mileage, consider doing the whole engine or atleast the top end while you in there.

As for the headstuds, replace them all. I had a top and a bottom stud go in my SC. BEtter safe than sorry. Use either Raceware (expensive but excellent) ARP (similar to Raceware but cheaper) or Microencapsulated Steel studs from Porsche (very good aswell and a little less expensive).

I'm doing my whole engine right now and I have never cracked ANY engine before, let alone a Porsche. Give 're ****!

Adam Roseneck

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1978 911SC 3.0
roseneck@cyberbeach.net

Adam,

Adam from the North is correct ... no big deal about the studs, Propane or Mapp-gas torch, or I've even heard of using an incandescent heat lamp or shop lamp without the heat shield laid next to the block for 45 minutes or so will heat it up enough to soften the thread locking compound, and Vise-Grips or stud remover to loosen the offending stud. Be sure to run a tap down the threads, carefully, to remove any remaining thread-locking compound before replacing the studs. The new studs need to have Loctite High Strength (orange) thread locking compound put on the threads before installing into a (room-temperature) clean bore in the crankcase. Double nuts on the new stud, tightened together are used to install the new studs at 24 lb-ft of torque. The Loctite cleaning/priming compound should be used to prime both the new stud threads and the bore in the block, following the instructions on the container. Good luck!

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Warren Hall
1973 911S Targa

Your mechanic that did the valve adjust should have noticed if there were any broken studs, I always inpect studs at a valve adjust. If all the nuts are in place than chances are the studs are OK. Look for oil leaking out between heads and cylinders, broken studs will sound like a exhaust manifold leak. Your compression test was off I would suggest doing or having a leak down test done it will help you pin point the problem.
If your studs are broken they can be very difficult to remove because some can brake almost at the case level. You will have to heat the case with a mapp torch or even a propane torch to around 375 degrees to melt the threadlocker used at the factory. I use a melting temp. stick that you can buy at a welding store to make sure you do not overheat the case. As for studs, Motormeizer sells reasonably priced stud for 299.00 a set that I have used at least 10 sets of and have never had a problem, the ARP and Raceware are overkill for any engine under 300Hp. Also you do not seat the studs in the case at 24FT/Ib you have to insert the studs to a certain depth that is outlined in Bruce Anderson's book.
One word of advice, if you have never set cam timing before have an experienced tech. do it or show you first hand. It is very important and remember you will have to disassymble the engine down to the case so it is a good time to have the heads rebuilt, if your engine has more the 60-80K on it you can bet that they will probably need it.

Hope this helps even if it is from the SBC powered Porsche owner.

Keith

I am not sure that the studs are going to solve your problem, but a good step to do anyway.

It kind of sounds like the plugs were slowly getting fouled leading to the motors running deterioration. I would suggest taking a close look at the ignition system and check your plugs and wires. If you are running a MSD or whatever the ground could be bad and cause these problems. I had a similar CDS(captive discharge) problem with a VW type 1 engine. Eronious little problem because I suspected the carb/fuel pump/coil the whole time.

Good Luck!

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Adrian Pillow
1979 911 SC
1966 VW Microbus
PCA - Peachstate Region

I too have considered that the ignition system may be the problem, but the plugs are newish (100mi), and seem to be a little on the dark side but on the whole pretty clean. It does make me think a little of a CD problem, the motor has the original Bosch CD box, some of the wiring isn't hooked up (I think that has to do with the missing FI). It's an '83, and I had been considering replacing it, but from what I understand I can only get a permatune replacement? I'd like to go with an MSD, but would this necessitate a whole conversion to crankfire? doesn't crankfire also allow you to run higher CR without detonation?

Thanks,

Adam
'70 914-6 3.0
'63 Type 1
'54 Type 1 Ragtop

Originally posted by Pillow:
I am not sure that the studs are going to solve your problem, but a good step to do anyway.

It kind of sounds like the plugs were slowly getting fouled leading to the motors running deterioration. I would suggest taking a close look at the ignition system and check your plugs and wires. If you are running a MSD or whatever the ground could be bad and cause these problems. I had a similar CDS(captive discharge) problem with a VW type 1 engine. Eronious little problem because I suspected the carb/fuel pump/coil the whole time.

Good Luck!

[This message has been edited by 3liter914-6 (edited 03-01-2001).]

Using the MSD is a snap, they are designed to work with any kind of trigger, be it point, hall effect or magnetic. The instuctions are included. Have probably installed 5 ignition systems on 2.7 to 3.2s and they are great. Buy them from Jegs or Summit for 175.00 and 30.00 for a new coil if you choose and have at it. Be sure to use the 6AL as it has the built in soft touch rev. limiter. I don't trust the mechanical ones used on the Porsche CD system.

Keith

It sounds like you could have a whole lot of problems; or just one big fat electrical gremlin living in your engine bay!

Those compression #'s do not sound to good though!

A leek-down test would tell quite a bit; but it sounds like you are already into the engine!

Is the engine still in the car? if it is you might want to consider putting the carbs and exhaust on and getting a leak-down test done! would be a shame to spend a lot of time on the carbs, and head studs to find out they are fine!

How are the plug wires, distributor(is it original?, rotor, timing etc... ?

Regarding the intermittent noise; check the side rocker panels on the car, the right one on my 914-6 was rattling against the body and made an intermittent noise that I thought was the engine for a while!

If the engine is as tired as those compression #'s sugest; you may want to drop it and go through the whole thing; painfull and expensive but worth the effort in the long run!

Hi Folks,

I have an update on my motor progress. I had to get someone to help with the balancing the motor on the jack, but it is now out of the car. I checked the head studs, and they all held torque @23ft/lbs. I was going to take the motor over to the closest porsche rebuild wrench ~2hrs away, and tell him to open 'er up and replace the head studs anyway (dilavar), and see if he could find an explanation for the problem. But fate has semi-intervened.

I just happened to talk to a retired Porshe master tech, and he said my symptoms sounded an awful lot like bent valves. I initially dismissed the idea, as despite the tricky 914-901 shifting (even with the side shift conversion)
I haven't missed a shift. I further explained that I have the exh. and intake off and could see the valves/guide, but he stated that I really wouldn't be able to visibly tell. After our conversation, I gave it some thought, and realized that my tach doesn't exactly keep up with the motor. In the heat of an auto-x, with the steep 1st and 2nd, it's possible I could have bent the valves by accidentally running the motor over 7K (maybe well over).

Tomorrow, I'm going to try and check the clearances of the valves. I don't have the special valve adj. tool, but the motor is out of the car, is it possible to check the clearance with a regular feeler blade tool, or just the single blade? Spec is .004" intake/exhaust right?

Also, even though the engine is disconnected from the exhaust, intake, oil tank, I could still do a leak down on it, correct? With each piston at TDC, it shouldn't really matter right? If anything it should make it a little easier to tell where the leakage is coming from, right? Or am I not understanding things?

More bad news for me is that my P/C's are believed to be the dreaded Alusil. If I had to rip the heads off, I had hoped to get some JE's to run in my bores, looks like I'll either be getting re-nik'd Mahle's with Pistons from EBS, or getting new Mahle 98mm units. I think I can get these for $2300-2500. Is anyone seriously interested in doing this upgrade as well? I'd like to see if they'd give say a 10% discount for 2 sets or more. So say $2100-$2300. Let me know if anyone is put up money interested (I don't care to get stuck with more than 1 set afterall).

Thanks,

Adam

Adam,

Well, he could be right! I probably didn't read your original post close enough ... if the symtoms showed up right after one run, then it probably wouldn't be broken head studs, certainly not enough to affect all six cylinders!

But, it would be very unusual to bend valves with the cast iron rocker arms, without breaking at least one of the six intake rockers ... that is why Bruce Anderson calls them (the rockers) the 'safety valve' in the valve train! So, if you find one or more broken rockers ... under those valve covers, then he was right, and all you really need is some head work like new valve guides and valves, and a three-angle valve grind.

I recommend that you get one of the factory-style P213 valve adjustment feeler gauges, as it will be very easy to adjust all of the valves with the engine out. Then do a compression test, again.

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Warren Hall
1973 911S Targa

Hi Warren,

Thanks for the response. I will check the rocker arms more closely today when I look at the engine. I don't recall seeing any broken rocker arms, will they be visibly cracked/broken, or will there maybe be a barely visible crack in the arm?

Also, do you know if I can check leakdown without intake manifold, exhaust and oil tank on? I think I should be able to as long as the piston is at TDC.

Thanks again, it's nice that you share your knowledge so freely with everyone.

Thanks,

Adam

Originally posted by Early_S_Man:


But, it would be very unusual to bend valves with the cast iron rocker arms, without breaking at least one of the six intake rockers ... that is why Bruce Anderson calls them (the rockers) the 'safety valve' in the valve train! So, if you find one or more broken rockers ... under those valve covers, then he was right, and all you really need is some head work like new valve guides and valves, and a three-angle valve grind.

Well, if you are looking at replacing the headstuds then the top end has to come off anyway so you can inspect the heads for valve seat damage.
I understand that replacing the valve seats is an expensive operation and most people just replace the bad head.
Other than a bad valve, I think maybe you lost a piston ring on the cylinder with 60psi on the compression test?

Just a shot in the dark but like I said if you have decided to get rid of the "damned" Dilvar studs (I myself am a fanatical Dilvar hater) then you will dissassemble the top end as a minimum which will give you access to the heads, pistons and cylinders.
Good luck!

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Leland Pate

___79 SC Targa