stromberg larg logo 97's

jan bogert

jan bogert

Senior Member
i got two large logo 97's which way leans them out? I have them set since last year with a unisyn. today I changed my plugs, and they are black/sooty. the screws are only out about ONE turn. fuel reg. set at two and a half. exhaust tail pipe black/sooty
 
got a pressure gauge to check presssure from the regulator??....if you screw in the idle mixture screw, does the engine lose rpm's?....Mike
 
Jan, I looked in my logbook and found that I sent your two carbs with .043" main jets and #69 powervalves...
This has nearly always been the combination that makes most small to mid size flatheads happy.
With this stuff they call gas today, my theory might be subject to change.
Check your fuel pressure, because if it's too high, your carbs will think they have larger jets!
If need be, PM me with your address and I'll send more jets. Free.
 
uncle max said:
Jan, I looked in my logbook and found that I sent your two carbs with .043" main jets and #69 powervalves...
This has nearly always been the combination that makes most small to mid size flatheads happy.
With this stuff they call gas today, my theory might be subject to change.
Check your fuel pressure, because if it's too high, your carbs will think they have larger jets!
If need be, PM me with your address and I'll send more jets. Free.
Click to expand...


Can't beat that with a stick. Pretty sure Speedway won't do that with their "97" knockoffs.
 
Max, I had been running it at 2 3/4, then went down to 2 1/2. i'll pm you with my address. thanks Max. 52 Henry, I don't want to ever hear speedway again. I experienced there super 97's I went back and forth with them. uncle Max, did me a good deal with these 97's, and I do know that you can't just get a pair bolt them on an things will be perfect. always will need a little adjustment.
 
JM 35 Sedan said:
Jan, if you are running air cleaners/filters, make sure they are not too restrictive.
Click to expand...

Agreed. I had a sooty plug problem that turned out to be a choke plate that wasn't opening 100%. You'd be surprised what a big difference a little restriction can make.

Try this to read your plugs: Take a cruise, warm up the engine, get on a nice straight road section. Go wide open throttle for a short distance, kill the engine with the ignition key, coast to a stop. Read plugs.
 
This is just a comment, but judging from all the things Uncle Max does for all his customers including me, why would anybody buy anything to do with Strombergs from anywhere else?
 
Mike51Merc said:
Agreed. I had a sooty plug problem that turned out to be a choke plate that wasn't opening 100%. You'd be surprised what a big difference a little restriction can make.

Try this to read your plugs: Take a cruise, warm up the engine, get on a nice straight road section. Go wide open throttle for a short distance, kill the engine with the ignition key, coast to a stop. Read plugs.
Click to expand...

You mean you don't need a chassis dyno, an A/F meter, and a computer?

+1 for old school

Another old tip. Get a stopwatch and use that same long straight section of road (a slight uphill is even better). Get a baseline time from say 40 to 60 mph in top gear (or from road sign to road sign, whatever you want to use). When you make an "improvement", you can check it.

I know, you need to compensate for air temp, barometric pressure, humidity, etc., etc., but this will keep you out of trouble (plus reading the plugs).
 
Put a vacuum gauge on the engine and when warm adjust the four "IDLE adjustment" screws to get the highest vacuum reading and at the same time smoothest IDLE. For two 97's the final should be ABOUT 2 to 2-1/2 turns out on each screw. This will not cure soot covered plugs. Your going to have to change the main jets and a small change here will make a big difference. Usually one to two sizes smaller. It is better for the engine to run slightly rich than lean. To sync the two carbs together use your Uni-Syn and just adjust the IDLE RPM adjustment so the front and rear carbs match.
 
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