1974 911 probs

[mullin]

Hi
I gave my husband a lesson driving stick in our new 1974 911 - now the the car vibrates and the tachometer is bouncing. We've done a search for other threads but this is a specific scenario.

- The car was pulling smooth and strong this morning through all the gears before the lesson.
- the lesson mostly practicing clutch control only.
- the was plenty of stalling and starting
- it doesn't accelerate in the same way now and topping out at 50mph.
- there is vibration in 3rd, 4th and 5th.

We just bought the car two days ago.
any ideas folks would be amazing.
we'll try them tomorrow.

many thanks!
Emily and Tony

[356911930]

Hi Emily,

Welcome to the air cooled family!

Only had the car two days...well a little history on the recent maintenance would be a good starting place. If no history I would do a complete tuneup to get a base line and then re-evaluate the symptoms.

Wife is calling gotta go for now,

Rahl

[mullin]

Thanks! Very excited to be part of the fam! Cheers Rahl

Hopefully taking it for a tune up on Monday is the fix.

The car was sitting for many years until the seller took it to a pro. It got a full quality rebuild this year and a long list of fresh parts.

Its currently running on brake-in oil, a full tank of gas and a can of 44K fuel system cleaner. Still in the break in phase.

[Mark Salvetti]

Welcome Emily! Post some photos of the car when you get a chance.

I'm wondering if you are seeing some fuel system issues. Do you have the invoice for the work that was done? I'm curious whether the fuel tank was replaced, or at least thoroughly cleaned after sitting for a long time.

Mark

[Joe Bob]

Post your location,,,,,we do house calls......

[Arminho]

First off, congratulations. Can you provide more specifics as to what was done with the last rebuild?

Also send us some pics, this community has hungry eyes and we get really excited.




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[rwest]

If the tach is bouncing around and the engine isn’t doing the same thing, then you should suspect an electrical issue.

Might want to check the health of your points and other ignition components as well as the electrical connector in the rear of the engine compartment, grounds and starter wiring- lots of power is fed through the starter to the back of the car and engine along with the alternator power.

Welcome and best of luck.

[Harpo]

Congratulations, 74's are awesome, please post photos and tell us about the car

David

[356911930]

Hi Emily,

You can do the tune-up and regular maintenance yourself. 1974 911s are very easy to work on and having a 45 year old car you will need to be able to analyse and repair issues when you are left on the side of the road. You will be amazed at what you will be able to learn and repair on your 74 911. I like to read the tech section to see what issues others have had use that info for myself many times.

Rahl

[Bobboloo]

As previously stated by rwest, an electrical issue is most likely, more specifically possibly the points. If the distributor shaft is not properly lubricated the points will close up on you. Conversely if the set screw was not properly secured then the points can open on you. Since the tach runs off the pulse from the points it's a good place to start.

[mullin]

Hi Folks

Totally agree Rahl, we never owned a car and figured why not but an old Porsche and learn to fix and maintain it than something full of computer chips.
The 74 is a barn find that had been sitting for over 30 years before it went through a full internal rebuild. The car smells of hay and cigarettes, the paint is chipped and scratched but it adds to the charm. The engine work is beautiful.
To add to the fun we are planning to drive it back across the country from CA to NY.
(We checked - the heater works!)

[mullin]

Thanks everyone. We will have a look today - We think turning the ignition over a few too many times might mean an electrical problem - Can that drain the battery?

Here's a short list of the work done on the car this year. We didn't list every gasket and bolt...pics coming

Oil and filter change
Drain Crankcase and oil tank
New fuel tank
Fuel level sender
Fuel filter replaced
Fuel pump replaced
Fuel accumulator replaced
Clean out pressure and return lines through body and rear.
Machine shop - block, oil bypass, stud case savers, deck cylinder spigots, deck all case half fastener*flats, clearence for 964 oil pump, check align bore.
Machine shop - valve job 911
Replace valve guides, cut seats, test springs, set spring height, flycut heads.
Crankshaft cross drill and micro polish
Camshafts standard regrind
Recondition rocker arms
New 911S pistons and Cyl
Timing Chain tensioner upgrade
New Alternator
New Spark plugs
Fuel filter replaced
Fuel accumulator replaced
Sway bar bushings
Accelerator linkage bushings
Brakes rebuilt front and rear
Brake hoses replaced Front strut insets replace
Rear shock absorbers replace
Engine pad replaced
New Clutch kit
New Main bearing set
New Rod bearings set
Alt belt, gaskets, and hosesFuel accumulator replaced
Shift linkage bushings
Mainshaft seal replace
New Battery
4 wheel Alignment

[mullin]

Bitter chocolate 1974 911 with 62k original miles. Sitting in a barn, smooth out the teething problems and get it ship shape for a 3600mile roadtrip...hopefully photos appear below...

[jpnovak]

Sounds like points to me. vibrations are from the mis-fire. tach bounching is due to the incomplete openin/closing of the points.

The points are located inside the distributor cap. This is the spring loaded switch that opens and closes as the hexagonal center shaft cam of the distributor rotates past.

There are several articles about adjusting points on a 911. I would start there. It only takes a screwdriver and feeler gauge and about 10 minutes of time.

Often the earlier cars with points will have them converted to more modern trigger mechanisms. For example, Pertronix or a Crane Optical. These are both a one-time setup during first installation.

[mullin]

We are starting an instagram account for the road trip across the south...
Follow @beans.911

Pray for us.

[eastbay]

southern route, good idea

[fintstone]

Originally Posted by jpnovak

Sounds like points to me. vibrations are from the mis-fire. tach bounching is due to the incomplete openin/closing of the points.

The points are located inside the distributor cap. This is the spring loaded switch that opens and closes as the hexagonal center shaft cam of the distributor rotates past.

There are several articles about adjusting points on a 911. I would start there. It only takes a screwdriver and feeler gauge and about 10 minutes of time.

Often the earlier cars with points will have them converted to more modern trigger mechanisms. For example, Pertronix or a Crane Optical. These are both a one-time setup during first installation.

This was my first thought as well. Either this or a loose wire/connection in the ignition circuit (between distributor, coil). When you check for loose/burned points, take a good look at the rotor and inside of cap.

Nice car. Welcome to Pelican/911 ownership.

[manbridge 74]

Nice car! I’ve had three of these 74s and my current one has been a lot of fun.

I certainly wouldn’t entertain a long trip with rough running/on five cylinders but perhaps you have the issue resolved? Might be a good idea to check your fuel pressures and CO (fuel mixture) along with the other good advice above. Reason being, with all the reviving of fuel system the fuel distributor could have some rusting due to ferrous parts. The base fuel pressure might be a little low as the pressure regulating valve can be “weak” after 45 years. It is adjustable to some degree...

I will be watching your trip and can offer service/parts (and certainly prayers) from Colorado Springs if you come through this way.

[manbridge 74]

Good on you for removing engine w/o trans though it sounds like a real pain and I’ve never done it like that...

Nice fog lights that look original to the car I think. Only in 74 were they chrome (on mid-years).

[mullin]

Well, this car is a sassy little mare - we took it out for a run and over an hour it slowly came back to form - tach bounce was easing out and the shifts up through the gears were smoothing - though the speed and pull in 5th that was there before was a little less strong.
Then the drama - in the evening as we were going up a hill it died. The alternator light came on. Tach was bouncing. Several starts caused backfires through the exhaust. We got it to a car park thankfully and towed it back.
Monday we are towing to the mechanics for help.
Might take a look at some Crane products - we need reliable running not racing from this Pcar.
Wish us luck.