Twin H Carbs
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This seems to be a familiar thread, but I'm going to post it anyway. I've rebuilt the 968S carbs and one is still running lean. The back carb is running lean, popping and rough idle that smooths out when I choke it some. I'm still not sure the function of the check ball in the low speed idle, it's just floating around free in the passage, the jet doesn't contact it. Screwing in the adjusting screw doesn't affect the running of the engine. I know these carbs must balance and adjust I'm just not sure how to make that happen. Who is the Twin H specialist on this list?
Harry
Harry
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Comments
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Harry Hill wrote:This seems to be a familiar thread, but I'm going to post it anyway. I've rebuilt the 968S carbs and one is still running lean. The back carb is running lean, popping and rough idle that smooths out when I choke it some. I'm still not sure the function of the check ball in the low speed idle, it's just floating around free in the passage, the jet doesn't contact it. Screwing in the adjusting screw doesn't affect the running of the engine. I know these carbs must balance and adjust I'm just not sure how to make that happen. Who is the Twin H specialist on this list?
Harry
TWIN H CARB ADJUSTMENT (Click on the title to see a Twin H Linkage diagram)
The key to a proper adjustment of a Twin H set up depends on several factors. The most important of which is that the system does not leak vacuum. This means the intake manifold is not leaking nor is the individual carburetors. A quick test to determine if the engine intake or carburetors are leaking can be performed with a vacuum gauge. Connect the vacuum gauge to the vacuum intake port on the intake manifold. The correct reading for a properly running Twin H car at seal level will be approximately 18 -22 inches of vacuum. A complete vacuum check of the engine should be completed and all other discrepancies corrected PRIOR to adjusting the carburetors. (A MOTORS or similar manual will provide you with pictorial and written explanation of how to run a vacuum check and interrupt your findings)
Assuming the vacuum check is complete you are ready to adjust the TWIN H carb set up.
How to Adust the Twin H
To complete the adjustments shown in the mechanical procedures manual you will need a UNISYNC
carburetor balance tool. Using the UNISYNC will the be the topic of a future update to this site...
Ken Cates July 2000
More on the Uni-Sync0 -
I cannot say enough about the uni syn. It is a terrific tool, easy to use!
if you need one, check out the links in my signature, for 21st century, (randy and russ maas) tell the hudsonkid sent you. I'm working on commission... j/k
(I see they are not on the site, e-mail them, and ask about availability, they can get them, if not, I will figure out an alternative plan for you to get one...)
One thing I will say, is it sounds like you might be having greater problems other than carb syncronization... I think one carb sounds like it might be rebuilt improperly, or maybe bad, still gummed? I would consider checking it first.... before trying to sync the carbs...0 -
Thanks guys, I pulled the carb I thought was trouble apart again and put it back together, I've found that I can semi choke either carb and clear up the misfire so that is telling me I have a vacuum leak. My next step is to pull the intake manifold and check for cracks or a leak between the manifolds. Spraying the outside of the manifold doesn't produce more rpm's so I'm thinking where the two manifolds clamp together. When I ran a vacuum check with a gauge I had about 12 inches of vacuum so that tells me there is a leak somewhere also. If I can a two barrel manifold and carb I may put it on while I fix the twin H manifold. If not then I'll fix the twin H manifold and get it back together. I'll see if I can get a Unisync guage while I'm working on the manifold. I'm pretty sure I couldn't put the carbs together wrong enough for both to have a vacuum leak so the next step is the manifold. These kinds of problems drive me crazier than I already am.
Harry0 -
You don't necessarily need a unisync. If you have a factory Hudson manual it will walk you through how to do it. In fact I did it that way and when it was later checked by another member who had a unisync, it was right on.0
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Since I don't have either and without finding this vacuum leak it won't matter which I don't have the first thing I need to do is cure that problem. The info Ken Cates posted will be a great help getting the primary carb settings and if I have the vacuum leak fixed the Uni Syn or manual will get things right.
Harry0 -
Everyone should have a manual as it will get you through a lot of things. I got mine through Faxon Auto Literature in Riverside Ca. They have about every kind of automotive manual you can think of. I believe the club sells them too. Good Luck!0
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Thank you, I ordered the shop manual this morning, so far everything I've done to get it running has been without a shop manual , just info off this list, asking members like Bill Albright questions and the members here who are always willing to help and I've got it running though not well, the manual should help greatly
Harry0 -
Harry, I had a problem with my 54, being hard to start, and idling rough. When I detailed the engine last winter, I took the manifolds off and........I found a cracked exhaust manifold! It was cracked across the bottom of the 3-4 cylinder ports. I don't know why this affected the starting but after replacing the manifold, it starts and runs and idles just fine.
Bob0 -
Hudsonkid bought me a uni-syn for Father's Day and we got to use it on his car. Edelbrock still makes them and simple to use. We spent about five minutes and he says it resulted in a noticeable improvement, and we only made very minor adjustments to the linkage.0
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yeah, the uni syn is such a great tool. to think you can sort out all issues without it, makes me worry, after using it. My car ran pretty decent. The uni syn actually made it better. For the price, it is a worthwhile investment. they are priced anywhere from $25-35 I think.
BTW, support the HET club, the club store has all of the manuals in reprint format. just a heads up....0 -
Okay, I pulled the manifolds today, someone please tell me why they didn't notch the intake manifold to just lift off the exhaust side? Also, which bozo designed the car so that you have to take a motor mount loose to remove the manifolds, for cryin out loud someone wasn't thinking. Anyway, whoever worked on it last left the last two intake manifold bolts loose so I was sucking air on the last two intake ports. Now I need to get ahold of Bill Albright and get some manifold gaskets and a header gasket, then I need to hunt down the designer of the 55 engine compartment and beat his kids, I had to learn some new cuss words today. At least I think I'm making headway now.
Harry0 -
Harry Hill wrote:Okay, I pulled the manifolds today, someone please tell me why they didn't notch the intake manifold to just lift off the exhaust side? Also, which bozo designed the car so that you have to take a motor mount loose to remove the manifolds, for cryin out loud someone wasn't thinking. Anyway, whoever worked on it last left the last two intake manifold bolts loose so I was sucking air on the last two intake ports. Now I need to get ahold of Bill Albright and get some manifold gaskets and a header gasket, then I need to hunt down the designer of the 55 engine compartment and beat his kids, I had to learn some new cuss words today. At least I think I'm making headway now.
Harry
BEEN there DONE that.... found out the kids were eaten by a fellow who was angry about this in '56! :mad: Gosh what a way to go... BBQ spit and all.... 0 -
Also check the 3 small 'freeze' plugs on the bottom of the intake manifold. Carbon builds up inside & pops them out. Remove plugs, clean out carbon & replace with new plugs. 15/16" I think.0
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In defense of the engineers.. That engine was designed long before they ever thought of puting it in a Nash body. There were several changes made in '55 to both the intake and exhaust manifolds to accomodate the large spring towers in the 55. Still not much fun to work on the manifolds on a step down either..0
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I don't know, I'm not an engineer and I can see if you stack two manifolds together with no room to get them out you should at least notch the manifolds so the top one can be removed without pulling a motor mount apart. The problem with most engineers is they have lots of schooling but no real life experience. I told my son when he wanted to be an automotive engineer to get a job working on real cars first, so he understands what mechanics have to go through. I'll have the intake checked for straight and replace the freeze plugs while I have it all apart, when I get it back together I don't want to have to take it apart again. All that engine room and everything squished up against one fender, at least the starter was easy to pull.
Harry0
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