Cracked DHSA2

[MadBeez]

I was in the process of cleaning and then refurbing the DHSA2 carb as the last thing before joining the engine and gearbox back together. What I thought at first to be a scratch on the secondary & fast idle valve assy turned out to be a pretty severe crack. I've spent hours on the interwebs looking for a used 28/36 DHSA2 but no luck. Do you think this could be brazed? Anybody have one they want to sell? All I need is the bolt-on binacle as in the photo. If not, I guess I'll be plopping down some more cash for a new DFEV.

https://drive.google.com/file/d/1-90Fk4 ... sp=sharing

https://drive.google.com/file/d/1-CXt-0 ... sp=sharing

~Rich

[18Fiatsandcounting]

Rich, the 28/36 DHSA carbs occasionally pop up on Ebay, but no need to go to that extreme. Slightly roughen up around the crack surfaces with a wire brush or the like, and use JB Weld to fill the cracks and build up a "bead" along them. When dry, smooth the joint surface to the carb with sandpaper if needed. Unless you plan to drive your car in extreme environments (like pressures at the surface of Jupiter), you should be good.

-Bryan

[MadBeez]

Along with searching for an old parts carb on the web, I also researched JB Weld as well as welding cast aluminum alloy - might as well try the JB - it seems to be made for this kind of repair.

Is this opening supposed to have some sort of cover or plug?

https://drive.google.com/file/d/1TRZs_R ... sp=sharing

All the exploded views show the other side of the carb.

Thanks, Rich.

[SteinOnkel]

Are you guys serious? JB welding a carb...? Come on, it's common knowledge that cracked carbs can't be repaired.

And jb weld is glue. I don't care how many times they put "steel reinforced" on the label.

Plus which, when your engine develops another issue in the future, you will be constantly second guessing this "fix". I'd like to see that jb after you've doused it in brake cleaner to see if there's a leak 3 or 4 times.

I've used jb before and it has its merits. This is not it. Fix it right. Your 50 year old classic car deserves better.

[18Fiatsandcounting]

Are you guys serious? JB welding a carb...? Come on, it's common knowledge that cracked carbs can't be repaired.

Yes, I am serious about JB Weld. We're not trying to fix a cracked cylinder head, but rather a crack in a carb that does not have any real force on it, with only moderate temperature cycling, with minimal pressure differential across the crack, and that does not experience appreciable amounts of oil, gas, water, etc. I certainly agree that finding a new part would be a better solution, but that vacuum secondary / fast idle assembly for the DHSA series is not easy to find. There are really talented people who can do great work with welding aluminum, but you'd have to find that talented individual.

As for the open port in the picture, something doesn't quite look right. That barrel shaped protrusion from the main carb body should have a linkage rod coming out the bottom that is activated whenever the throttle is opened, so that the carb bowl is vented when you step on the gas but it only open to the charcoal canister when at idle (or turned off). The linkage rod, vent fitting, and the internal spring appear to be missing. Will it work without these? Yes. You might smell gas around the engine compartment when the car is turned off, but for an older car, that's just part of the charm.

Weber has different versions of the top cover for its carbs, but that mystery port doesn't look like what I've seen for other DHSA carbs.

-Bryan

[MadBeez]

Bryan,

Here's a picture of that port that I found online - is there maybe something that hangs over it from the air cleaner? When I shine a light in there, I can see the gasket but it sort of looks like this is an empty chamber for something not used on this model carb. I could easily make a plug out of silicone rubber and close it off.

https://drive.google.com/file/d/1VNtKMh ... sp=sharing

It's really tough to find a picture of that side of the carb.

[18Fiatsandcounting]

It could easily be that this "feature" is not used on your variation of the DHSA. For some reason, your images on Google drive aren't loading for me (but they were earlier). At any rate, take a look at this picture:

http://www.fiatplus.com/1608-28-36-DHSA ... RETOR.html

You might have to expand the picture, but you can see the rod that comes out of the bottom of that well on the side. That rod attaches to a linkage that pivots on the secondary throttle shaft, but is actuated by the primary throttle shaft. So, when you give it gas, that linkage moves and allows air to flow into the vent bowl so you don't build up a vacuum when gas is flowing into the engine.

I don't recall any connection to the air cleaner from this port. On mine, there is a rubber hose from the vent connection to the charcoal canister over by the battery to capture gas fumes when the car isn't running. Part of emissions control.

I also don't know if there are variations between the DHSA-1, DHSA-2, DHSA-3 in terms of this vent feature. You could give the owner of the fiatplus website a call, as he's very knowledgeable and might be able to help you out, and he might even have a spare vacuum secondary/fast idle assembly he could sell you. Chris Obert is his name.

-Bryan

[MadBeez]

I took apart the top of the carb to get at the float etc and got a good look at that little chamber - I don't see any outlet, so I think it's just not used on my version. I'll give the guy a call - maybe he can sell me just the binnacle from that one in the picture.

Thanks, Rich.

[18Fiatsandcounting]

Rich, check your Private Messages. Might have found a solution for you.

-Bryan

[MadBeez]

It's been awhile but I'm back on it. I bought the DHSA1 from Brad Artigue and swapped the secondary & fast idle valve assy over to my DHSA2 (replaced seals etc) Everything was going well until I noticed the tail of the small spring on the far right connected to the choke linkage was loose. I figured out that the tail was supposed to be up and over the mount but I couldn't get it in there without removing the outer portion of the linkage. (see pics) As soon as I removed the bolt and washers from the outer linkage, the big spring unwound and I have been unable to get it back into a sprung/loaded condition. I got the small spring seated correctly but the big spring is now the problem. It appears that after you put the bottom pin in the pinhole, then you need to rotate the spring clockwise to load up the spring - I can't make that happen and it is just loose, sitting there doing nothing.

Any ideas?

Thanks, Rich.

The first pic is of the carb that I got from Brad showing a nice tight spring and the second one is of my loose spring.

https://drive.google.com/file/d/1x1iiyj ... sp=sharing, https://drive.google.com/file/d/1z5f2MA ... sp=sharing

[18Fiatsandcounting]

Any ideas?

Thanks, Rich.

Yes. The spring orientation is a bit counterintuitive, but you want the spring to push the choke lever open (when nothing else is attached). So, your spring is on the wrong "tang" of that choke lever held by a screw and washer. The hook on the end of the spring should be moved about 90 degrees counterclockwise as you look at it, so that the hook is on the left side of the tang that has the connection for the choke cable. In other words, the hook in the spring that the lower blue arrow to the left is pointing to, should be moved one tang counterclockwise as you look at it.

I just looked at my DHSA on my '71, and that is how it's set up and it seems to work fine.

Hope this makes sense. I struggled with mine for a while until I finally figured it out. Note that the picture of the one from Brad appears to be incorrectly mounted. Not that I am worthy of questioning his expertise, but this isn't how I think it should be.

-Bryan

[MadBeez]

Thanks Bryan,

Seems like that will work well enough - not as tightly sprung as before but probably good enough.

New question: I have 2 new gaskets to go between the carb and the intake manifold - one about a quarter inch thick and the other paper thin. Which one do I use?

Thanks, Rich.

[18Fiatsandcounting]

New question: I have 2 new gaskets to go between the carb and the intake manifold - one about a quarter inch thick and the other paper thin. Which one do I use?

The thin gaskets function just like any gasket is that they seal up minor imperfections in the machined surfaces. The thicker gasket actually performs a different function in that it is a thermal barrier to help keep the carb from heating up. Depending on which carb and intake manifold you have, the thicker gasket can also provide extra room for the throttle plates to open up all the way without hitting the sides of the opening(s) in the intake manifold.

I actually use three gaskets on mine, and going from carb downward: thin gasket, thick insulator, and another thin gasket. If you only have one thin gasket, I would put the thick insulator on the top of the intake manifold, and the thin gasket on top of that so that it is against the bottom of the carb.

I also check the flatness of the intake manifold and carb base with a straightedge ruler, but I've never come across any real issues. Except for one used carb many years ago where someone had managed to warp the base...

-Bryan

[MadBeez]

Wow, thanks. I thoght it was one or the other - I'll use both.

~Rich