Engine runs like shhtt!
 

I've had a couple of 911 owners (who have driven my car) tell me my engine is not running the way it is supposed to.

My car is an 81SC with the stock 3.0. I just had the valves adjusted. I also had my wrench put in new Magnecore 8.5 mm ignition wires, cap, rotor, Bosch copper core plugs, as well as new lower valve cover gaskets. The car idles very well (smoothly) while cold, warm, and hot. Engine runs cool throughout. I also have a cat bypass tube, and an aftermarket 1 in 1 out muffler. The addition of the tube made it run stronger and cooler, as I removed the stock cat.

I've never had a compression test done.

What do you all think could be the problem? Broken head stud(s)? Faulty or clogged injectors? Other CIS component? Fuel mixture?

Help!:confused:

What were the specifics of other people's comments; ie. what did they feel was not right about the motor? How do you feel about the way it runs?

A compression test would give some hard data on how efficiently the engine is running. A tester is fairly inexpensive and easy to use if you can get the plugs out. ;)

ianc

How'd it run before the Magnecores?

Joe

ianc,

The comments have been generally been that it is simply not running to its potential, as if it lacks power, lacking "pick up" under the lower RPMs.

I think my runs and pulls great, particularly in the higher RPMs. I have driven two other SCs, a 78 an an 80. The 80 was bone stock and it just seemed "torquier" under lower RPMs in comparison to mine. In higher RPMs it was close to the way mine felt. As for the 78, it had aftermarket headers and a sport dual in/out muffler so it just felt more powerful overall.

Joe,

As far as before and after Magnecores, it runs just as smoothly as it did before, really no improvement, and definitely not running worse.

Start with a compression test. Even with Magnacores :) , you've got to start with sound mechanicals.

Sherwood

Could someone please give me the ideal compression results, by range maybe? Please excuse my ignorance, but is this the same as a leakdown test? I know I am getting ahead of myself, but if the results are bad, how does one go about fixing this problem?

Also, do injectors clog up periodically in these cars?? Can anyone recommend a maintenance tip?

Please advise.

-Jorge

I'm not convinced you have a problem. SC cams are a bit peaky. Mine had little power under 4000 rpm until I installed 20/21 cams. Just make sure the darned thing is tuned up. Frankly, most of us run with our O2 sensor unplugged, the mixture richened a little and the timing advanced. Optimum timing is as advanced as possible without detonation. Try 35 degrees at full advance (5000 rpm should do it, and 6000 briefly to make sure). If it pings, back it off. This should give you optimum performance without changing parts.

I'd trust your judgement over what someone else says about your car. Drive a few more sc's and compair for your self. When I drive someone else's car I'm not generally going to drive full out, maybe they just aren't driving it quite as hard as they would their own car?

Maybe you aren't getting full throttle out of it. A bunch of people have checked and discovered that with the pedal all of the way down they are getting 75-90% throttle. It'd be nice if it was something that simple, and even better if you discovered that before you tried a bunch of other stuff.

That's the first thing I'd check. I've seen a number of 911 that weren't going WOT when the pedal was to the floor.

1) Get the wife in the drivers seat and have here put the pedal to the floor while you loOK at the linkage at the throttle body. the linkage should be hitting the stop there.

2) If it doesn't, check to make sure the carpets aren't balled up under the throttle pedal.

3) If that's OK, then start adjusting your linkage.

WARNING :

Carrera guy about to make ass.

I thought that I read somewhere that the SCs changed their power curve after 1979-ish to get better low end? More power too?

Fog settling in as my archives are getting dusty.

If not, please disregard this as useless gossip :)


I'll go back to my pig now......

-Chris

funny chris.

i vote throttle too. if not, i think your buddies are wrong. why not drive their cars? you know, in the spirit of science :)?

check out your throttle linkage, I was only getting about 66% of mine until i had it fixed and that made the biggest performance improvement yet in my 911 ownership. I have also heard that this is a common problem that is not noticed a lot of the time.

Compression check like Sherwood said. If the comp is down the rest is BS.

Hmm. So let me see if I have this right:

1. Start with a compression test (acceptable range anyone?),

2. Check throttle linkage,

3. Unplug O2 sensor (already done),

4. Richen fuel mixture,

5. and finally, advance timing as much as possible.

Oh and 6. drive more SCs and find new friends!

You all are the BEST!!

It's no wonder I spend most of my free time on this forum!

-JorgeSmileWavy

Check the throttle linkage first - that's free.

If 1 and 2 are to spec, your car should run like anybody elses. Forget the workarounds.

Let's try ballpark compression readings of around 130 +/-10 as a start. More importantly, they should be <10% of each other.

Let us know so we can continue guessing. :-)

Sherwood