1947 Super Six anemic engine performance

[Cornelius Brudi]

Hello,

Our 47 Super Six has its original engine, and many parts have been overhauled. Recent repairs include the distributor, as well as grinding the manifold so that it sits perfectly flat on the engine block & gasket. 

Carburator was rebuilt twice, and we installed an electric fuel pump.

Still, the car runs at approximately 3/4 of its original power. Without seeing and testing this engine yourself, I understand it is difficult to analyze - but I’m asking anyway: does anyone have an idea what might cause the car to perform sluggish, and crawl hills in second gear?

Thank you in advance for your suggestions.

Cornelius

[TerryB]

First order of business is a compression test, that will help figure out if it’s internal engine problems.  From that info a plan can be formed.

[Spinneyhill]

My first boss taught me never to do things twice. Those parts are right and if they are not and you haven't any more information, you will do it wrong the second time too. The problem(s) will be somewhere else.

 

So, why "overhaul" the carb. twice? What was different the second time? There is an oft-repeated adage that 90% of fuel (carb.) problems are electrical.

 

As well as a compression test, have you spent some time tuning it? I assume your distributor repairs included the bush it sits in so it doesn't wobble (which allows timing to vary as the distributor moves around) and the centrifugal and vacuum advance systems. And the plug leads are in the correct order to the plugs. Any other vacuum off-takes that might be leaking?

 

Have you looked at it running in the dark? Any spark plug lead leaks?

 

Why the electric fuel pump? If the pressure is too high, it will be drowning in petrol = flooding all the time. Why not fix the original pump?

 

 

[JFranklin]

How well is your timing advance working?

Edited January 16, 2019 by JFranklin (see edit history)

[Rusty_OToole]

How many miles are on it? Typical engine life back then, about 50,000 to 80,000 miles with a ring and valve job at 30 to 40 thousand.

 

I would start by doing a compression test. Then check for timing chain wear by hand turning the crankshaft back and forth and observing how far you can turn it before the distributor rotor moves.

 

Next would be a tuneup and careful inspection of parts.For example are you sure you have the correct model carburetor with the right jets? They do get changed sometimes.

[plymouthcranbrook]

Vacuum Leak?

[Cornelius Brudi]

Thank you everybody for your feedback. Most of your comments address issues we already checked. Carb rebuilt twice because the carburetor repair shop that rebuild ours used faulty parts, and it ran worse afterwards.

I suspect rings as well, as mentioned by one of you, and I think these can be purchased from Egge, unless you have other or better suggestions.

Will check the timing chain - good idea.

Thank you all again for your advice!

 

[cahartley]

If the timing is running late the engine should overheat.

The gas of today needs as much advance as the engine will stand.

Try opening the spark plug gaps to .050-.060" and see the difference which there WILL be.

I ran two cars that burned almost as much oil as gas without a readily noticeable lack of power.

There's more going on with your engine.

[JACK M]

I would take a look down its throat and be sure that the butterfly is opening all the way. That would be step one.

Along that same line I might also make sure that the exhaust doesn't have a potato stuck in it.

[Alfa]

Just a small thing, but check also that the air filter and the exhaust silencer (muffler) are clear. I have seen similar problems with a silencer that has collapsed internally and blocked the exhaust.

[PFitz]

 A good vacuum gauge - tee-ed into the line to the distributor- will tell you things that guessing won't.  Not expensive, and they highly underrated for diagnosing engine troubles.

 

A carb out of adjustment, late timing,  sticking valves, restricted exhaust, and more, are all things that show up when doing the tests listed for vacuum gauges.

 

All the tests you can do with a vac gauge are ususlly covered in the instructions that come with the gauge. If not, there are many versions available on line by doing a search for one such as this. https://www.onallcylinders.com/2015/05/08/quick-tech-how-to-read-a-vacuum-gauge-to-pinpoint-engine-problems/

 

For anyone who's going to work on engines, there should be one in every tool box. Better yet, leave it hooked up and mount it on the dash. It will tell you things about your driving that your right foot can't !

 

 

Paul

Edited January 18, 2019 by PFitz (see edit history)

[Frank DuVal]

The vacuum gauge should be tee-ed into the intake manifold vacuum. Some distributor's vacuum advance canisters are fed from ported vacuum, which is 0" vacuum at idle and rises (more vacuum) as the throttle plate opens. One example, Corvairs.

 

Mounting the vacuum gauge on the dash will show you how to drive very economically! it will teach your right foot.😁

[PFitz]

11 hours ago, Frank DuVal said:

 

Mounting the vacuum gauge on the dash will show you how to drive very economically! it will teach your right foot.😁

 

 

Yup. After years of driving with a dash-mounted vac gauge in most of my vehicles, my right foot is a lot smarter.   But, my left foot is still a clumsy idiot.

 

Paul