Project DCOE

Interesting, I like real world testing like yours. Ed suggested I get a wireless meat thermometer to check temps in various locations of the engine bay and I'll probably do that when everything is buttoned back up.
 
Was installing new manifold gaskets and found the new ones had smaller openings than the head or intake and exhaust manifolds. Another set of new gaskets was the same and in fact the old ones had the same problem. I guess the head was ported at one point but the engine builder didn't bother opening up the gaskets. The header flange ports are much bigger than the even the exhaust port opening but nothing much I can do about that. I suppose the proper task is to use my air grinder to open up the gasket passages, I'll practice on the old gaskets.

This is my first time playing with DCOEs and I did not realize there is an inspection port for each venturi that lets you see where the throttle plate edge is relation to the transition holes. What an amazing "tool" to allow you to see if the throttle shaft is bent, if the two carbs are mechanically balanced or if your linkage is really letting your throttle plates close.
 
I was thinking about header wrap for those sections where the carbs are too close. But a baffle between the headers and the driveshaft boot also make sense. Thanks for sharing. It's nice to know the paths others did with similar modifications.
 
Hi. Put idf 40. And i can tell you a good setup. My 1500 tunning before i have dcnf 40. Is very better carb idf 40. More power for all rpm. And more torgue. I have the diferents power dcnf vs idf. 138 full. F11. 180air 50 indle 32 venturi. If you dont want idf because you have manifold for dcoe my opinion is put dhla 40 dellorto F. The car for sure take more hp more torgue and tjob perfect for all rpm than dcoe.the diferents is big. Some times 4 5hp.
 
carl said:
The header flange ports are much bigger than the even the exhaust port opening but nothing much I can do about that.
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That step is intentional. I prevents back flow of the exhaust gasses. Glad to hear things are coming along, can't wait to hear/see the car. I remember the PO told me his biggest problem was the gaskets, that's when he started using the white plastic sheet things that were in the box. Also I recall he had the dogbone motor mount changed to bushing on one side only, I think in an attempt to minimize the movement of the carbs.
 
I got rid of those strange plastic gaskets and got new carb to manifold gaskets. The problem I noted above was the gasket between the block and the intake and exhaust manifolds....the one on the motor was a generic stock type gasket. I found many things with this motor and indeed the car it came in (the yellow race car) that were of subpar quality for a street car, let alone a race car. The DCOEs came from you, Erwin, and obviously had nothing to do with the motor I put them on. You will have to make time to come to the house to check out and drive the car, after all, it's your fault I'm doing this.
 
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Pictures of final modification to the cross-member. I welded in an L-section on either side of the cross-member and then boxed in the small gabs on the ends. The holes across the horizontal members are where the holes I drilled for the "spot welds" were too big and my welds did not fill them in all the way. The braces were 18 gauge metal, fairly close to the original metal gauge. I'm going to check but I think if the carbs were mounted on the manifold with bolts instead of studs the modification to the cross member could have been much less intrusive.
 
Looking much better and probably better structural integrity. In my case, it is a nightmare to put back the air horns. There is no space to insert a socket and even an open key didn't get much place to move. So I had to use a small screwdriver to turn the nut until it is become harder then finish it by using the open key, turning the bolt 1/32 turn each time... Repeat 8 time... I would say putting the 4 air horns back involved nearly an hour of work... Hope I will not have to remove them often! I will take pics... when it's done. But it is looking real good with the filter socks in the trunk, filling the 4 round holes I drilled.
 
I have a pair of huge K&N filters that go with these carbs but I'm curious how you install filter sox on tapered air horns. I had so me Uni sox on my spider's IDFs but those had factory velocity stacks that were just straight with no taper.

My modification to the frame was designed to allow total access to everything. Fortunately this car was not a queen and any radical mods like this are easy to defend. I think rust is the only thing holding the windshield in place.
 
I guess this is a wrap up for now. The carbs are installed and they work fine. Do they work better than DCNFs or even IDFs, who knows as this is an internally stock motor with just headers and a free flowing exhaust on a car driven on the street.

If you go this route you will encounter two fabrication issues. You will have to trim the bottom of the crossmember for clearance. Some folks have done very minimal trimming and I think the only way you can minimize cutting is to mount the carbs to the manifold via bolts rather than studs so you can slide the carbs vertically into place. In my case the manifold already had studs in place so I kept trimming the bottom of the crossmember until I could install the carbs without any hassle. Once the carbs are in place, all the jetting can be done without removing the carbs. I trimmed about 2"-3" off the bottom of the crossmember and then boxed in the opening to get some strength back in the crossmember.

The bigger hassle is throttle linkage. The stock X linkage pulls the carb ball connector forward....this works great for stock carb or DCNFs but the DCOE ball connector arm rotates the opposite way. Most folks use an intermediate rod to change rotation direction (just Google "X1/9 DCOE" for lots of images of this setup). Fortunately for me the carb kit I had came with a modified linkage rod on the cam cover and with some fiddling and very tight clearances got it to work.....I'm not real big on using an intermediate shaft.....just more hardware and monkey motion.

These carbs are 40 DCOEs with 32mm chokes and I suppose you can say they should function the same as DCNFs or IDFs of the same configuration, again for street use. My jetting seems pretty close but I want to verify and that means a trip to the dyno (with an air/fuel measurement) or installing an air/fuel ration gauge.

I guess this puts closure on the matter, it was fun, I got to ask a lot of questions and receive great responses here and I mostly did it because I had the carb kit in my attic. Next time I would try twin IDFs because that's my comfort zone, I love IDFs, but I would have to hunt down an X IDF manifold and I don't think there are any in the US for sale.

When I get my jetting dialed in I'll report back in a separate post but that may be months from now.
 
Hi Carl,

I was hoping for at least a pic with the carbs and air filters installed on the car. On my side, I'm quiet since I have lost power to the fuel pump, but working instead on refitting the pedal box under the dash. I will work on the fuel pump after.

And winter is here in Québec. We are actually in a midlle of the first snowstorm of the winter. Many schools are closed. Perfect time to work in the garage!
 
So Carl, now that you've tried an X1/9 with a well sorted 34DMTR, and two DCOEs, what's you're preference? One carb, or two?
 
Daniel, I'll post pics of the finished set up tomorrow. I just painted the panel that goes between the engine bay and the trunk but it should be dry tomorrow.
Mike, no one is supposed to ask that question! I'd have to do some runs on the DCOEs and then swap out everything and do it again with the DMTR and I'm too lazy to do that at the moment. From a clinical standpoint, the 34 DMTR is probably just as good as the DCOEs on my motor, only a dyno would know for sure. The DCOEs are more.....fun. They are loud (probably too loud when you have a gutted interior like mine). Like most dual carb setups on Fiats, they give instant throttle response, more so than a single carb or FI and this makes the car feel more powerful. I already admitted I did this just because it was available but I had been thinking of going the dual DCNF route till I remembered I had these carbs. All my 124s had or have dual IDFs.
Pain in the ass, sure....the idle is never constant and my IDFs are always getting idle jets dirty but these are my fun cars. The 34 DMTR frankly amazed me once I had it jetted right. Smooth idle, no hassle, great power and just not as much fun. As most of my friends know, my Fiats are never stock, I get totally bored with stock Fiats....it's a problem I have. A lot depends on how you use the car. My X is for local cobweb clearing, going out for a 30 minute buzz. My spider is for longer club drives or going to Carlisle. If your X is to be a daily driver or shopping cart and you have low tolerance for things not being wonderful then you might not like dual carbs.

Not sure if I answered your question but I tried1
 
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Final pics. I made the closure panel between the engine bay and rear trunk with 26 gauge sheet metal, pretty thin stuff but it's not meant to be structural.
 
Thanks Carl, I'll take your answer as you prefer two carbs. Of course the only way to know for sure is to see if you take them off.
 
Thanks for the pics Carl. Now I understand why you made the opening so big. You could hide a lot of things in these air cleaners.
 
The top of the filters pretty much match the top edge of the carbs so the only special clearance considerations I had for the filters was side to side fit. They are huge but what came with the carbs.

Mike, you are a sharp feller, always wait at least six months to see if a guy's modifications are in fact a good idea. Kind of like thinking the heater assembly is not really needed and a waste of weight...in August...and then realizing in November I could extend my driving season but adding it back in!
 
Carl, those Project Binky online courses are really paying off ;) Looks great, man! Those plug welds can be tricky to fill completely when you're welding in awkward areas. I had a few on the coupe that needed a 2nd round.
 
Court, those silly plug welds have been bothering me ever since I did them. The holes were too big and clearly they were not filled. Either I go back and weld some more or more probably just fill the holes with bondo or JB weld since it's just a cometic fix at this point.

Project Binky makes me feel totally inadequate! But thanks for the pat on the back.
 
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