47 bxvd-3 resize jets?

[casper50]

Since I'm going with two of these carbs, and everyone tells me that 2 will let way too much fuel in, what size jet should I use to replace the stock one?  I've found a chart that says the main metering jet is .061, should I go down to a .030 in both?

[Plymouthy Adams]

is you log common or split?

[casper50]

going on an offy intake.  common I believe.

[Plymouthy Adams]

you need to determine if common log or split before going further...

[casper50]

It's common.  Blow air in one carb it comes out all 3 outlets

[Don Coatney]

I have these mocked up on a common log but it does have a small split in it.

 

[Plymouthy Adams]

Don is making a general ash statement....it may or may not apply to your build...some may even be board by that remark..

[Don Coatney]

He`s made it clear enough it ain`t no good to pine.

[Plymouthy Adams]

I WOOD have to look closer at the setup...it may or may not go against the GRAIN...if I had some drum stick I could probably figure out the LOG RYTHYM of the two carbs...

[Don Coatney]

So you are stumped

[Plymouthy Adams]

KNOT at all, will get to the ROOT of the matter shortly...just careful not to go out on a LIMB here..

Edited April 9, 2015 by Plymouthy Adams

[Don Coatney]

I am going out on a limb but more than carpentry skills are required here.

[casper50]

Laughter is great medicine but how about a little help?

[Plymouthy Adams]

_{this is a very hard question to answer...and even with the right jetting you got to be aware that you MUST have the carbs synced and that the linkage and central pull be solid and strong and that only central revving point is allowed with dual setup..but...given that it is common log and the CFM is shared in this set up I think most folks start with two size leaner jets when setting up based on single stock jetting size}

Edited April 9, 2015 by Plymouthy Adams

[casper50]

Thanks Plymouthy

[Lloyd]

Are you running headers, high lift cam? You can add more fuel and air if you have a way to get rid of it. May consider changing the heat on your plugs as well.

 

Also, you have opened up another portal in your intake with the new manifold. Pistons will still be pulling the same amount of air as before cept now they have 2 holes to pull it from. To much carburetor can actually cause an engine to lose power and even start washing down the cylinders in the extreme. So I would say if the motor is stock then yes you should consider reducing the jet size on both carbs. Dont know what to but I dont guess it would necessarily have to be half of the total. Little more might not hurt.

[casper50]

I have headers and the engine was just rebuilt back to stock.

[Plymouthy Adams]

headers will help it breath but as you have not upped the volume in the chambers it is no real relevance but at the same time does not hurt...if you had significantly increased you intake and enhanced your squish..the exhaust would come more into play..and shuld you consider this in the future...do get your cam with a tad more duration in exhaust due to the

fixed port size and often just a modified cast manifold..

[casper50]

Update.  Phoned The Carburetor Shop, he's suppose to be one of, if not the guru for Stromberg carbs. He says to try them bone stock first.  Sync them with the vacuum gauge.  Let the engine warm up to operating temp making sure that it doesn't overheat.  If it overheats I need to go to larger jets.  Then if needed I might have to change jets either up or down.  

[martybose]

The thing most people overlook is that by adding a second carb you are reducing the amount of air going through the carb at any given RPM by half.  That alone will reduce the amount of fuel being pulled into the air flow.

 

Marty

[casper50]

bringing this back up.  Synced the carbs with the stock jets in them.  Runs okay but not great.  popping, cylinders 1,2 and 3 are running rich 4, 5 and 6 are running fine.  Won't go past 140 degrees no matter how long I run it.  I have put new coil, condenser, points and plugs.  I'm thinking it's either the jets are too large or the vacuum advance is bad.  Any and all help appreciated.

[Don Coatney]

What are you using for air cleaners? What brand spark plugs are you using? Do you have a thermostat installed? What is the timing set at? Do you have a dwell meter? If so what is the reading?