Good news bad news!

[john walker's workshop]

[QUOTE=db_cooper;6892454]The 10% leak down is fine..I don't understand how the compression test could be so low and even across all six cylinders.
As I recall, those old 2.4 mechanically injected engines had a low compression ratio. ( something like 8.0 to 1 or 7.5 to 1 ) They never pumped up the compression gauge much over 120psi when new.

QUOTE]

my guess is they did not open the throttles when doing the test. there's always a noticable difference. same with carbs.

[313green]

Green: Sounds like no drama with your oil pressure and temps...That's good news....Just drive it and keep an eye on the oil level......How many miles on the engine?

Around 120k miles.

[Two Rivers]

John I agree with you. The throttles have to be open when doing a compression test. I would do one with the engine cold and then with the engine warm. And see what you get.

If doing it yourself remember to disable the spark and fuel pump.( Ask my neighbor who he knows this)Dam near burt his car and garage down.

[313green]

first one at idle after hard drive. second one while driving around 60-70 mph. also, here's a video of gauges while driving 911 driving - YouTube

[db_cooper]

Originally Posted by 313green

and for extra credit, here's a fun sound coming from the MFI. still haven't figured it out. no air leaks, maybe a fuel leak? too lean? 911t motor sound - YouTube

The injection pump and injectors were always noisy when warm, even in the 70's. I would suggest using some Marvel Mystery Oil in your fuel. 4oz per ten gallons is the recommended dose. You may want 6oz for a few tanks.

Modern gasoline has ethanol. Those FI pumps were designed with leaded fuel in mind. The lead acted as a lubricant. Lead is not in road fuel anymore. MMO will help lube the pump/injectors and should quite them down too.

It helps CIS injected engines too by lubing the seals in the fuel distributor and injectors. I believe it helps reduce the valve guide wear in most 911s.

[Tinker]

Oil level looks high?? You are checking the oil level at the dip stick, at idle and on a level surface?

Other than that pressure and temps to good / normal.

Tinker

[db_cooper]

[QUOTE=john walker's workshop;6892890]

Originally Posted by db_cooper

The 10% leak down is fine..I don't understand how the compression test could be so low and even across all six cylinders.
As I recall, those old 2.4 mechanically injected engines had a low compression ratio. ( something like 8.0 to 1 or 7.5 to 1 ) They never pumped up the compression gauge much over 120psi when new.

QUOTE]

my guess is they did not open the throttles when doing the test. there's always a noticable difference. same with carbs.

Yep..had to be. Throttles closed, probably on a cold engine, 7.5 compression pistons and thirty year old starter. Time for an engine rebuild$$$$.

[313green]

Mechanic just changed oil Thursday. Not sure why it's so high. He even said gotta be careful not to over fill...

Oil level looks high?? You are checking the oil level at the dip stick, at idle and on a level surface?



Other than that pressure and temps to good / normal.



Tinker

[313green]

Many thanks to all who posted advice. Great forum!

Mike

[313green]

Update and more questions....

Been running the car pretty hard. Feels strong but still smokes at idle, especially when I rev. sometimes smoke on downshift too. Steady, light smoke at idle. Can't tell if it's blue, gray or dull white. Smells oily. Also noticing heavier oil use and one really hot engine, although temp and oil gauges look good.

Should I get a second opinion from a mechanic? Is this eventually a top end? 130k miles, no rebuild yet.

Trying to plot next steps. Thx for the advice.

[jsoderbe]

Hi, second opinions is always good to get, especially if compression and leakdown point in different directions.

It is easy to overfill a 2,4T since most are used to the oil volume in a later model 3,0 or 3,2. Ask me how I know.... :-)

If you chose to do the engine rebuild, you might consider to buy a running engine and put it in just to keep that beautiful car on the road.

I would keep driving it while keeping an eye on the gagues all the time. If the engine has been sitting it might need time and miles.


Regards,

Johan

[Grady Clay]

313green,

This is really good advice.

Originally Posted by jsoderbe

Hi, second opinions is always good to get, especially if compression and leakdown point in different directions.
It is easy to overfill a 2,4T since most are used to the oil volume in a later model 3,0 or 3,2. Ask me how I know.... :-)
If you chose to do the engine rebuild, you might consider to buy a running engine and put it in just to keep that beautiful car on the road.
I would keep driving it while keeping an eye on the gagues all the time. If the engine has been sitting it might need time and miles.
Regards,
Johan

Pack-up the 911 (and your sweetheart) and drive to the High Rockies from Michigan. Yellowstone and Grand Tetons N.P. are great in September.
A good (I-80/90) road trip will either cure the smoking issue or tell you it is time for a rebuild.
If it strands you, ship it home and rent a car to continue touring. No big deal.

I agree about finding another (place-holder) engine during a rebuild.
Too many wonderfully roadworthy 911s languish unnecessarily during rebuilds.
Keep your 911 on the road and enjoyed. Any MFI engine is a 'bolt-in' swap using some of your original '72 parts.

If you find a rebuild necessary, a 2.4T converted to 90 mm Nikasil RS P&C is a very desirable combination.
Your MFI will easily accommodate the change.

Enjoy, life is short.

Best,
Grady

[mreid]

Mike, that is one beautiful Porsche!

Lots of good advice here and I agree that you should check the oil level carefully, keep it a quart low and put some miles on it. Check it again and see if the smoke issue goes away. Your gauges and leak down are excellent. Drive and enjoy!

[Sharonkerry]

Seems like my car was overfilled with oil more than once. I've ended up supplying 8 quarts (I have a 73.5 with the original 2.4) and toping it off myself.

BTW Love that color!

All the best!
Sharon