New 97 carb for my 51 F1..now pings

[37coop]

Hi guys this carb malarkey is not my thing so a little advice please.
I put a new Stromberg 97 on my 51 F1,it fires right up,accelerates good and runs smooth till I push the throttle going uphill and it pinks ( as we call it over here) ,my mechanic friend fiddled about with the mixture adjusting screw when I first fitted it on and it ticks over nicely, could it be its too lean or too rich, no problem with this pinking on the previous carb so I assume it's the mixture on this one..maybe,I was told the timing maybe but all ok with the previous,the doom and gloom boys have told me pinking can burn the Pistons ,any advice appreciated ,thanks. Jim.

[scicala]

Yes, pinging (detonation) can cause piston damage if it's excessive or happens frequently. The more engine load, the worse it is when it happens. It's caused by excessive spark advance, lean fuel mixture and/or hot spots in the combustion chamber. Hot intake air can effect it too. Since all you did was change the carb, that has nothing to do with the spark advance, and since it never pinged before, I would say the carb may be too lean. Maybe take a look at the spark plugs after driving a while and see if they are more of a white-ish color rather than tan (normal).
If that's the issue, maybe go to a larger power valve and main jet. One size at a time until you like it. Or rebuild the original carb.


All the two mixture screws do is adjust the idle air/fuel mixture. Won't affect your problem.


Sal

[37coop]

Thanks Sal,I,ll do as you suggest,I,m reluctant to go back to the old carb after paying £ 300 for the 97,I will persevere .many thanks

[JWL]

How/where did you connect the distributor vacuum tubing?

[aussie merc]

simple fix check the jetting in your old carb against whats fitted in the new one [Dont get caught by assuming that they are the same if the numbers match someone at sometime may have had the same problem and either soldered or drilled the jets ] check them with either jet drills or wire gauges the other question to ask is why did you change the carb in the first place ? wrong /worn out /damaged / remember petrol varies greatly and you will always have to retune your carb to suit your local supply

[flathead4rd]

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Where did you connect the vacuum line that goes to the distributor? If it's connected to a manifold vacuum source that's wrong. I think your problem is timing which is controlled by the vacuum source from the original carb which is different than manifold vacuum.

[rotorwrench]

The Load-O-Matic distributor relies completely on the carburetor that was designed to function it. If the 97 type has no connection then the spark advance wont work at all. If this is the case, you may have to change your distributor to a Chevy or Mopar type that is modified to fit and function with the proper advance specs. The vacuum spark control for these can also be modified with an adjustable vacuum can to work on manifold pressure. The other alternative is to go with a Mallory or other mechanical advance type with no vacuum spark control.

[supereal]

With the correct carb, the vacuum for the later distributor is drawn from above the throttle plate, not simply manifold vacuum, as was true for the early weight advance type where the vacuum was used just to control advance.

[uncle max]

There are new Stromberg bases available with a ported, just above the throttle plate, vacuum source.

[scooder]

Max,
The ported vacuum bases on the new stromberg 97, aren't compatible with the Loadamatic.
The loadamatic doesn't use ported vacuum, it uses a combination of above the throttle plate (ported) and venturi vacuum. Supplying just ported vacuum to to a loadamatic will slam the ignition fully advanced just off idle, not good. That'll make it ping under load like crazy. Way to much advance.
So coop, correct carb or change distributor to chevy type, with mechanical and vacuum advance. Or chevy aftermarket mechanical only, the mechanical only won't be an improvement on a properly working loadamatic.
Martin.

[uncle max]

Originally Posted by scooder

Max,
The ported vacuum bases on the new stromberg 97, aren't compatible with the Loadamatic.
The loadamatic doesn't use ported vacuum, it uses a combination of above the throttle plate (ported) and venturi vacuum. Supplying just ported vacuum to to a loadamatic will slam the ignition fully advanced just off idle, not good. That'll make it ping under load like crazy. Way to much advance.
So coop, correct carb or change distributor to chevy type, with mechanical and vacuum advance. Or chevy aftermarket mechanical only, the mechanical only won't be an improvement on a properly working loadamatic.
Martin.

Martin,
Please explain whyisit - ??? - the unmarked EE-1-1 Elmira Stromberg 97 replacement units for the Holley (using the Loadamatics) ran so well with only ported vacuum. Were all the engineers wrong?
Max.

[scooder]

Max,
I have heard about Stromberg "8BA" replacement carbs from the 50's but never seen one in the flesh, so I can't comment on how they are setup vacuum wise.
I have seen a couple of 97's that have only a ported vacuum. They would be unsuitable for the loadamatic, I would imagine that the "8BA replacement" replacement ones should have the correct combined vacuum source. But as I said, not had one to play with.
This combined vacuum is a good chunk lower than ported or manifold vacuum.
I have just had a quick look at Stromberg's Web site, it states that these ported vacuum 97's are not compatible with the loadamatic
Martin.

[scicala]

I agree Martin. With ported vacuum, as soon as the hole is exposed, it's basically manifold vacuum to the vacuum advance. With the Loadomatic the same channel in the carb is shared by ported vacuum and venturi suction. The distributor diaphragm never sees more than 4" hg. I don't think there are even springs in the advance diaphragms. Just light springs on the advance plate under the dist cap.


Sal

[JWL]

I am afraid Martin is correct. It would work only on a limited basis.