DUI ported or manifold vac? HW5200 problems

['68falconohio]

I got my NEW 200 in the falcon and IT'S ALIVE!! Myself and a couple buddies did the swap two Saturdays ago, but I havn't been able to go home and work on it due to midterms and work. We got everything hooked up and did the engine break-in before I left and I'm going home this wkend(physics midterm be damned) to wrap up the carb linkage and gauge mounting.

The specs for the engine are in my signature and I'm wondering if I should use ported or manifold vacuum for the DUI advance. The HW 5200 sheet that I got from Stovebolt shows me which port to use on the carb if I decide to go ported, but I hooked it up to the manifold during the break-in because I read on the CI site that the DUI likes manifold vacuum better. Suggestions? What sort of total advance should I shoot for. I realize that my total advance will likely be different than everyone else's due to fuel choice, CR, driving characteristcs, etc. I'm just looking for a ballpark # here fellas.

Also, when I shut the engine off after break-in the carb started steaming fuel, and then puking liquid fuel out the side...... I spoke to Tom at Stovebolt about it and he said that he pressure checked the carb before it was shipped and that I likely had something in the needle&seat allowing it to seep. He recommended that I set the idle as low as possible and use a flashlight to look down the carb throat for dripping fuel. I'm not a carb expert by any means so I was wondering if you guys had any other suggestions.

After I spoke to Tom, I called my buddy who has the garage that the car is at. He's a late model racer with more carb experience than I could dream of and he said that the needle&seat leak shouldn't cause the fuel to seep out of the linkage side of the carb and that I'm likely going to have problems with this carb. I'm stressed out, I need to get this car running reliably so that I can return the company vehicle and I was banking on this rebuilt carb from Stovebolt doing the trick.

I'm going to do as Tom requested this wkend, but if you guys have any other suggestions, they would be greatly appreciated.

Thanks,
Stephen

 

[Ronbo]

It would cause that to happen because with the throttle closed the gas has no immediate place to go. It collects on top of the butterfly and is going to take the least path of resistance which in this case must be around the throttle shaft bushings. Is this one of his rebuilds or a new one? If its a rebuild the bore for the throttle shaft may be a bit worn and he missed it during the rebuild. It'll give you a nifty little vacuum leak and slow down the secondary from opening if its worn too much. Too heavy a throttle return spring speeds up that process.


Ron

 

[aahsac]

Are you using the stock mechanical fuel pump? and, are you using a fuel filter?

 

[cfmustang]

Personally, I run manifold vac with my Weber 38 and Unilite. I say try it both ways and see which way it runs better. The only real difference between the two is at idle anyway.

As for the fuel issue, Weber carburetors like low fuel pressure. I don't remember the exact number but Google Weber carburetor troubleshooting and you will see it listed all over. I think it is around 3 psi. My suggestion is a fuel pressure regulator. I know Holly and Crane make them that regulate pressure between 1 - 4 psi. I used to use the Crane version, but the diaphragm inside burst and the thing started spewing gas all over the running engine. I am lucky I didn't have a fire. With that in mind, I would recommend the Holly (http://www.holley.com/12-804.asp).

I still haven't replaced mine and while I don't have the problem as bad as you, when I shut down the car after it has warmed up, I have a hard time restarting because the carb is flooded.

 

['68falconohio]

Thanks for the help guys. I'm running a brand new fuel pump from NAPA and the problem does not seem to be too much fuel pressure. The carb bowl is boiling the fuel. I'm pretty sure it steamed the fuel during the break in because the car sat in the hot garage for 30 minutes running at a high idle. I got the carb linkage hooked up which was easy as cake. I used a ball type end off of a Ford truck and ran a die over my orig. linkage so that the cup end would thread on. Unhooked the kickdown cable to give it enough throw to engage the secondary and BAM! carb linkage done. I took it for a test drive for the first time with the new engine and she purrs alright. Temp climbed to the 200* mark which was not cool but I believe that to be the jets in the carb I got from Stovebolt. It has a pretty bad lean bog also when the secondary comes in. I intend to use the info in the Weber sticky to rejet the carb and get it running better. From what I hear, these carbs can be tricky, but run good once the debugging is done.

The carb didn't steam when I got back from my short test drive and due to the direct mount, I have two inches before my air cleaner hits the hood with the current setup. I think I'm going to eliminate one of my carb adapters(3/4" thick Al) and machine a 1 1/2" thick adapter out of phenolic for the insulating properties. Right now the carb bowl sits very close to the valve cover and is picking up heat there. I also rerouted the heater hoses to the fender wall because they were laying right next/on top of the choke-side of the carb. McMaster-Carr has the phenolic and we order from them everyday at work....time to capitalize on some cheaper shipping.

cfmustang:
My great concern with the flooding issue I was having was that my engine had 0 miles on it. just a 30 minute break-in. One of the guys that helped me put the engine in said he built a 390 in high school and put it in his truck but had a carb that flooded out when you shut it off. Well, the fuel ran into the cylinders, seeped through the rings and washed the rod bearings.....and then it started knocking. Not something I wanted to happen.

I'll get some pics up when I get the car in my hands for more than just a test drive.
Stephen

 

['68falconohio]

Also, if anyone has suggestions on my total advance they would be greatly appreciated. The engine builder that did all of my machining/ engine work told me he would ballpark it a 34* He openly told me he doesn't do much work on these inlines and he was guessing from my cam and other mods. He also told me to play with it a bit for better torque or hp.

Thanks again guys,
Stephen

 

[falcon fanatic]

I use manifold vaccum. Simple reasons are that it provides maximum advance while starting, while coasting off-throttle and at idle. These are three times that having that extra vacuum advance can make a big difference in terms of fuel economy (when coasting) and in terms of starting and idle quality. In fact, when I had the car originally using ported vaccum I could barely get it to idle without turning the idle screw in too far, which in turn affected the shifting of my transmission. Switch to maniforld vacuum and the idle shot right up, allowing me to back off the idle screw, and restoring the proper behavior of my c-4. I get 2mpg better with the manifold vacuum, too.

 

[aahsac]

I use manifold vacuum on my HW and DUI combo as well. I haven't had it hooked to ported vacuum so I can't give you a comparison.