Tune Up 1973.5 911T

[HarryD]

Today, I decided to do a tune up for my 1973.5 911T. It has a stock motor with pertronix. I replaced the plugs, cap and rotor and checked idle speed and timing.

Car currently has 172,000 miles. Last tune was at 158,000.

Overall pretty uneventful. Found that the #5 cap terminal wire had corrosion and I cleaned that up with electronic cleaner, a wire brush and emery cloth to make the connector shiny again.

Idle speed and timing were spot on.

Plugs 3 and 4 were more oily/crudy than the other plugs.

Dirty pictures for your enjoyment.

[hitch911]

Any thoughts on why the corrosion in #5 cap/wire and not elsewhere? Loose?

[fizeus]

if i were you i ll check valves lash (or do a compression test on the engine) if a valve do not fully seat you can see oily or corroded plugs because burning is really slow

[thor66]

plugs may need changing more often

[LakeCleElum]

Harry, with 172,000 miles, curious how your oil pressure is?

For my 73.5, I was having issues by 125K miles. When warm, oil pressure very low at idle. I ended up putting in a high compression 3.2.

Looking at the engine I pulled, the engine oil cooler was very oily and dirty.....Always wonder if I'd cleaned it, may not have had to do the engine change?

[HarryD]

Originally Posted by fizeus

if i were you i ll check valves lash (or do a compression test on the engine) if a valve do not fully seat you can see oily or corroded plugs because burning is really slow

Ever since the top end, it has used oil. Leak down was in the 10% range with flow through the crankcase. I suspect some of the rings never seated properly. Oil consumption has been always about the same. This is the first time I looked at the plugs.

[HarryD]

Originally Posted by thor66

plugs may need changing more often

This is the plan forward. I will check at 500 and determine an interval.

[HarryD]

Originally Posted by LakeCleElum

Harry, with 172,000 miles, curious how your oil pressure is?

Oil pressure has always been fine. About 10 psi/1000 rpm.

For my 73.5, I was having issues by 125K miles. When warm, oil pressure very low at idle. I ended up putting in a high compression 3.2.

Looking at the engine I pulled, the engine oil cooler was very oily and dirty.....Always wonder if I'd cleaned it, may not have had to do the engine change?

I typically pull the fan/alternator every year or two to clean the top of the motor. I do not think I have a debris problem.

[thor66]

10k used to be a std. interval for spark plugs - on the old timey motors with carbs

or maybe you aren't giving it the 'Italian tuneup it wants

[E Sully]

Harry, what did your top end consist of? Did you hone and re-ring, valve guides, Etc..

[HarryD]

Originally Posted by thor66

10k used to be a std. interval for spark plugs - on the old timey motors with carbs

Yep. Remember those days.

or maybe you aren't giving it the 'Italian tuneup it wants

It gets those all the time at Autocross and HPDE.

Car uses about 1 quart every 6-700 miles.

[HarryD]

Originally Posted by E Sully

Harry, what did your top end consist of? Did you hone and re-ring, valve guides, Etc..

Hi Ed.

It was done when I had a backfire snd apparently dropped a screw into cylinder 3. The work consisted of reconditioning barrels, pistons, rockers, new valve guides etc. Crank snd bottom end bearings were left alone. After rebuild compression was around 125 and leak downs in the 10% range with blowby into the crankcase. Given the age of the motor, I figured it was good enough.

[HarryD]

Replaced the corroded end of my wire to plug 5.