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rail carb advice
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Burdmahn
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Location: Sioux Falls South Dakota
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PostPosted: Tue Mar 21, 2023 7:09 am    Post subject: rail carb advice Reply with quote

Hey Guys,
Ive got a beat up old rail thats been my side project for the last 9 or so years now, and one thing that irritates me is that Ive never been happy with how I had the carbs set up. Its got a sort of tired single port 1600 in it now, but Ive got plans to put together a dual port 1641 for it. Neither one is or will be very high dollar or high performance, just decent reliable buggy motors. Anyways, I used to have a set of electric choke solex kadrons on it, and while it ran amazing on the street, as soon as you got into anything bumpy, even a washboarded gravel road, they would flood out like new orleans. Even with the original vents plugged and external vents installed, as soon as you went from smooth street to anything close to offroad, it would become a sopping blubbery mess. I tried a few things to combat this, but nothing ever worked.
At some point, I came into ownership of a pile of parts, including a weber dgv and an intake for it, so I read up on how to get those to work right and added heat riser ports to the tri-mil stinger headers, swapped from a 009 to an 043, set up the jetting just like ACN's article said to, and each step helped a bit, but still, after years, Im still constantly monkeying with it trying to tune out the last of the low speed stumble. It is much better offroad though, it never floods. I know these intakes need a lot of heat to work right, and while the last few times Ive took it out for a ride its been about 40F out, the manifold gets up to 55 ish, so at least its above ambient I guess. Maybe its just not a cold weather carb?

So I guess my question is, im about out of ideas and was wondering what you guys do for carb on your buggies. Im still 50/50 on the single vs duals schools of thought, I just dont know if I should keep trying with the progressive, go back to trying to get the kads to work, or try something new, like a IDF 40 or something similar. I like how the centermount doesnt suck up gallons of dust and water from the tires, but all the progressive troubles irk me as well. Theres no sand up here in south dakota, but there is a lot of dusty gravel roads and cornfields, and I do like to take it out in the snow too, so I like having a choke so I dont have to feed it ether for the 0F starts.
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rayjay
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PostPosted: Tue Mar 21, 2023 8:01 am    Post subject: Re: rail carb advice Reply with quote

The first thing I would do is limit the mechanical adv so you can dial in more initial. Having more initial makes the motor much more responsive and this may take care of the low speed stumble. Next I would come up with an air filter arrangement that has heated air from the header. This will definitely help the fuel atomization.
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oprn
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PostPosted: Wed Mar 22, 2023 3:19 pm    Post subject: Re: rail carb advice Reply with quote

^^^What he said.^^^

Plus I might add, 55*F is pretty lame. You need to revisit your heat riser setup and see why it is failing to give you heat.
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Burdmahn
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PostPosted: Tue Mar 28, 2023 6:56 am    Post subject: Re: rail carb advice Reply with quote

I dont know how hot it will get on a normal day, I guess Ill find out once springtime hits
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oprn
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PostPosted: Wed Mar 29, 2023 5:20 am    Post subject: Re: rail carb advice Reply with quote

The advantage of bigger carb/carbs on an engine is to increase the higher RPM power range. Our single port VW engines are RPM limited by the heads already. Small gains can be made on them like you mentioned with the Kadrons or as VW did with the early type 3 that had dual Solex carbs. I have questioned whether a progressive is worth the effort on a SP but some say it will make a difference.

Personally I am very happy with the way my 1941 SP runs with the stock single Solex and matching distributor in my sand rail. I got all the power I need by using a Bus transaxle and fairly rear short rubber. I have good flow through the stock intake heat riser (90*F at the tee below the carb) and a cookie tin on the air cleaner that takes heat off the muffler and gets me 60*F air to the carb for winter driving.

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Burdmahn
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PostPosted: Wed Mar 29, 2023 1:45 pm    Post subject: Re: rail carb advice Reply with quote

Wow, now that is a real nice setup. Anyways, in true vw fasion, Ive been hammering on this motor for 10 years and its been loyal to a fault. Now, when I try to slow down and do things right it rebels. it dropped a valve seat, then after I swapped the heads for a set from a sprayer motor, the bottom end has started knocking. Ive parked it for now, to preserve whats left of the case, and Ive started putting together a 1641 dual port based off a dual relief case. I just got the case cleaned up and linebored to .40, and found a set of good shape 87s and some dual port heads in the parts pile, just handed off the crank, rods, and pistons off to my machinist buddy to get turned down .10 and balanced. Ill probably keep it fairly tame, probably a eagle 2280 cam. With that combo do you think trying a idf style single would be worth it, or is that still within the range of a pict do you think?
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oprn
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PostPosted: Wed Mar 29, 2023 9:02 pm    Post subject: Re: rail carb advice Reply with quote

Stepping up to dual port heads is going to open up the upper RPMs some so it should respond better to more carb. If it were me I would give the progressive another try on a fresh engine. You already have it and with a fresh engine with a stronger vacuum signal things could change for the better. Especially if you can get more heat to it.

As for a single Weber 40 IDF... I have no personal experience. Some claim to be quite happy with them and some not so much. It will also need some heat. I can tell you one thing for sure, unless you can find an early Weber that still has the cold start enrichment intact (pretty rare these days) you will not be very happy trying to start it in the winter. None of the modern Weber IDF copies have any cold start capability.

A good Solex 34PICT would do a pretty respectable job on that engine too, don't overlook that option if you get a chance.
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