:roll:First time user here. I have a 64 valiant conv. and I am trying to put an Offenhauser intake manifold that uses two one barrel holley 1920 carbs(if those are even the right size)I can never get a straight answer about what size are stock jets for this carb. They came with 50 size jets so I was looking for 48s because I have heard you need to go two sizes smaller then stock. Now Iv'e been told that 48s are the stock size so I would be looking for 46s. Probably should have went with two barrel manifold but I wanted to give this a try. Does anyone know where to pick up jets of this size? I guess Holley would be the place to start. Thanks Mytdaddyo

I just have my local auto parts order them for me or go online to Jeg's or Summit racing. Good racing shops have them. I wouldn't worry about getting the smaller jets until you get it running and see how the plugs look verses the performance your getting.

Stock sizes vary through the years if you look at a Factory Service Manual. In the 70's they went up from #55 to #61 jets actually 612. I am running a #58 in my 1920 in a 3380 pound Dart Swinger. It has plenty of get up an go

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Aggressive Ted

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74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

The regular Holley 4 barrel carb jets will fit your carbs. Even the Advance stores carry some but not many of these jets. Any performance shop around you should have or be able to get them for you.


My 1920 did come with a 48 jet, but when I tuned it for my car a 58 jet is what worked the best. By best I mean best comprimize betweem power & economy. I was getting 21 MPH plus on the highway and making great power with a pure stock engine and only a stock exhuast manifold & 2 1/4 pipes & muffler. A 60 jet gave me just a little more power but lost MPG.


I am not sure how the one barrels will act on that intake, others have run them and should have a good idea on what jets work good. Most of the time you need to go bigger on jets when you run duel carbs. I know this seems like it is backwards becuase you think you have twiced the fuel. What happens is you dont have as much vacuum pulling on each carb so it needs the bigger jets just to get enough fuel in. It may not work that way with the Offy duel because it has a small plenium area but I am not sure.


Like I said many have run that combo and should be able to give you a good idea where to start. Then you just need Holley 4 barrel jets to fit it. They say it works good with two 1920 carbs if you have two matching carbs in good shape.



Jess

I also run 2 1bbls,went fishing with all sorts of jet sizes,think I am happiest with 56,s,mark

OEM Holley 1920's varied in jet size by the year and application, so far out of the 4 I have: 1967- #56 jet, 1966 -#55 jet, economaster version #57 ... 1961 Ford Van application #54 jet...

That should give you a good range to go from...

-d.Idiot

Thanks for such a quik response. Cool!!! Iv'e had this car sixteen years and its never ran like I think it should. Iv'e been told everywhere that i have called that two or four barrel jets wont work in the one barrel carb. I'll give it a try though. I can get those anywhere. It helps when you read (and pay attention) to a manual. Come to find out we (my friends and myself) have been over tourqing the intake and exaust (by about 90lbs) manifolds the whole time. Both are brand new now. Maybe get it right this time. Any suggestions on what type of gasket to use. All I can find are the paper composite ones :shrug:

don'tnt have any trouble with the cheap gaskets. I am even running them with a set of headers and have no leaks what so ever. As long as everything is straight and even between the two manifolds it should do good. If your having problems with it sealing you may need to have them surfaced with the two manifolds bolted together.

Also if your over tightening them that could cause problems so try with a good clean surface and not over tightening them. Its not real important about how much torque to use as long as you go over them and get them all even (with in reason) . I start out by snugging them all starting from the center and work out in both directions. Then let it set a few minutes and go over them again with a " little" more torque starting from the center and working out again. They do need to get tight, but I only use a 1/4 ratchet and socket with a 15" extension so this keeps me from putting a lot of power on them because the extension will bow before you can do much. AFter the install, and you run it and get the engine good and hot, go over them again one more time. Doing it in steps like this has worked for me everytime.



On the jets just be sure and get Holley jets, the only different ones Holley has is for the Dominator carbs and alcohol, which run a bigger size jet. Most places don't have these so it should not be a problem. Just a standard Holley jet will fit right in. Unless you live at high altitude I would think that some where in the high 50's would be a good place to start. I will bet you have been running to lean and that is why you have not been able to get the power you should have. Probably didnt want to run until it got warm and even then might have had a bog at light throttle tip in, plus not much power until you opened the throttle up alot.



Jess

there ar numerous threads on gaskets,and this link is just one.
it will give you a couple of choices - your locally produced Remflex or our Aussie GPRS.
both are very good .
http://www.slantsix.org/forum/viewtopic ... 6b8#169320

the search function on the board is a very useful tool when you are looking for answers to things like this.


regards,Rod

Smallest jet I've seen in a 1920 carb is 54, and yes, they are exactly the same jets as the aftermarket 2bbl and 4bbl Holleys.

Lou

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