Can't get these carbs to sync up/Won't idle down

[rlich8]

OK

Just installed my sweet new HS6's from Chester Gillings of SUCarbs.com. They're wonderful looking and I'm sure wonderful performing but I can not, for the life of me, get them to sync up.

They sync up fine on idle. They match with the Uni Syn. When I race the motor, they are absolutely not synchronized. One is always pulling more than the other at race. I tinkered with the linkages a bit, then I thought I got it, but didn't. This went on for over an hour. I tried synchronizing them on two different days to no avail.

Then, I absolutely can not get these carbs to idle down. I tried greasing the linkages, but that didn't work. All springs are in place.

Any ideas??? I'm stumped - and I'm pretty good at syncing up my SU's normally!

 

[Brosky]

Can you loosen each carb mounting nut slightly and wiggle them back and forth to make sure the shafts are not binding? It sounds like a possible stick linkage to me.

 

[Geo Hahn]

...One is always pulling more than the other at race...

Is it the front one that seems to be drawing more air? I think that may be typical in carbs that are sync'ed at idle, just a bit of flex in the throttle shaft & hence lag from the front carb to the back.

 

[TexasKnucklehead]

I assume if you have the HS6, you've converted to center pull linkage.

Are you sure the throttle position isn't moving between checks? I wedged a ruler in the linkage to be sure the position was the same for each carb and was as if I was pressing the actual pedal. How far off are they? Is it possible that your uni-syn is defective? Have both butterflies been centered? With the carb off, and the idle backed out, you should see almost no light coming from around the disc when held up to a light.

One of mine wouldn't idle down because the body of the carb was out of round, so the disc couldn't quite close. I filed a little off the disc, so it could, and now it idles fine.

 

[Banjo]

Carefully check for vacuum leaks. Do you by chance have the distributor vacuum advance line disconnected, or maybe it's cracked?
I chronic high idle is usually a sign that there is air sneaking in somewhere.
Another place to check is where the intake bolts to the head.
Spritzing some carb cleaner around some suspect areas and listening for a change can help spot a leak as well.
I'd bet money, you find the leak, you'll be able to get the idle down.
and I'd also bet the slow acting piston is closer to the leak.

 

[rlich8]

Wonderful suggestions everyone. Thank you. Here is some more/new information.

-Throttle plate of left carb needed to be adjusted. The throttle shaft was having a tough time returning after racing the engine. I suspect this is a major reason if not THE reason it was refusing to idle down.
-No vacuum leaks - very thoroughly checked at every place there is vacuum on the engine w/ an unlit propane torch
-Distributor vac line OK - recently replaced
-Uni-Syn is OK - I have three and tried all three and am getting the same results
-I do have the center pull linkage

I have gone ahead and disconnected everything and checked it all over. The linkages have been thoroughly cleaned. Unconnected to the carbs, the pedal works perfectly and smoothly and returns to position. We now know it's not a linkage problem.

I found that the throttle plate needed to be adjusted on the left carb, like I said. Also, some new return springs would do me good. One of them is sprung.

I will reassemble everything tomorrow and report back. I suspect the findings will be good. I am almost there I have a feeling.

 

[Banjo]

That plate being off will definitely affect your settings. That was the vacuum leak. When syncing the carbs the air flow through both has to be equal at idle, and idle needs to be within spec. otherwise everything will be off. having a throttle plate stuck open a tad throws everything off.
Keep on with your plan, I bet you get better results. Good detective work.

 

[rlich8]

Lots of odd little problems here. Found one more thing. This is what happens when a car is 45 years old. Thanks to me, it'll be perfect by the end of the day. I'm working in small spurts.

The throttle linkage was installed completely wrong. There's that little preventer that hits the choke linkage - that was underneath the choke linkage as opposed to bigger than it.

Next issue - front/right carb is pouring gas out. Stuck float, I assume. I hate to say it but I'm losing faith in this guy that rebuilt my carbs. :smirk:

I'll try adjusting the float height tomorrow, will report back.

 

[rlich8]

OK -

All problems solved. I was able to surmise the following. At the end of the day, there were two major problems:

1. The throttle plate was incorrectly centered. I fixed this by loosening the screws and snapping it shut a few times and carefully tightening to ensure the plate didn't go out of alignment

2. The carburetor linkage was incorrectly installed from the get go - when I obtained the car. This is how I saw it and this is how I reinstalled it. The linkage is designed to hit the choke linkage on WOT - the arm that performs that task was actually UNDER the choke linkage. Upon seeing some pics that other members provided, it was rather obvious I needed to fix this.

I also needed to set the float heights. A minor problem but a little nervous, gas spilling all over the place is never fun.

The car is all set now. Carbs synchronized, mixture tuned, air cleaners reinstalled. She idles like I have never seen before. I am truly happy.

I'm about to crack open a nice pale ale - this was truly eating at me for the past week or so. As with other jobs, this small job turned into a fairly frustrating operation. Correcting other people's mistakes and trying to make things perfect is a large part of owning these cars.

Cheers all, and thank you very much for your help.

 

[tdskip]

Happy car makes for a happy man. I bet that ale was pretty darn tasty.

 

[Brosky]

Just like marriage....a happy wife is a happy life.

 

[rlich8]

Just like marriage....a happy wife is a happy life.

LOL!!!