Projects Shade tree Model A speedster kind of thing

Got to thinking. Seems to me two of the defining characteristics of hot rods are cutting weight and adding power. I got the weight cut, need to do something to hop up the motor a bit, if I'm going to feel like this is the real deal. In keeping with my "use what you got and what you know" theme, I'm going to replace the old Zenith with a 1 3/4" SU. It's running really well since I re-adjusted the timing (embarrassing story, but I had originally set it before I made the push rod for the advance lever, and had the arm on the distributor at full advance instead of full retard, so... No harm done, I hope). Anyway, I used a spare intake manifold so I could keep the set up that's working all together and ready to slap back on there. I'm going to run the new intake with the original carb mount blocked off. I think the pictures will be self-explanatory. I made my new pipe long to keep the SU away from the exhaust manifold heat, but I think its too long. I'll probably chop it off, shorten it, and re-braze it.

 

Also did a little playing around with the free video editing app I got. Just some drive-by stuff. Notice how I forgot where the phone was hiding in the bushes at the end? Left that in out of a sense of honesty, and because one of my girls says its her favorite part.

 

Man, you're having too much fun with that thing!

 

@Tim

 

Now that's what cell phones are for...

 

More piddling today. Trying to get to where I can try out that SU set-up I made. Salvaged a bellcrank off of an old bicycle frame that had pushrod brakes, of all things, and doctored the little brass vacuum nipple for it to pivot on. Really just had to drill out the hole and tap it. Here's a before picture:



And here's a little after video (sorry I forgot to film it landscape):

 

Here's a little start up video.

 

I'm going to secure that copper line, don't worry. It runs well with the SU, maybe a little hesitation if you romp on it, gets better if I advance it all the way. I might play around with the timing a bit more, I'll have to do some research. First I'll try a little thicker oil in the dashpot, for those of you familiar with SU's . I am also going to shorten the neck between the carb and the manifold. It's longer than it needs to be to keep the carb clear of the exhaust heat, and now my hood doesn't fit. Only needs to be about 1" shorter, but I might go a little more. It's probably just my imagination, but I feel like it runs smoother with the SU than it did with the old Zenith. One thing is for sure, though, the old Z ran rich, no matter what I tried. Black smoke and the rich, gas stink to the exhaust. The new carb is much better, which seems lucky to me. I was worried I would have to fool around with the needle, but so far, so good (knock on wood). I'll know more when I can get it out on the road again. This weekend is a big festival here, and the roads are pretty crowded. Still no insurance or tag on this deal.

 

Oh yeah, if you listen carefully, you can hear the decidedly non period correct electric fuel pump clattering away. It's stuck up under the inside of the starboard frame rail, just one of those little square jobs. I should probably have rigged one of those cute little brass hand pumps to pressurize my tank, but they are expensive, and I already had the electric one, so...

 

Thought I heard one, but thought, not on this car !

 

Yeah, but at least I didn't buy it. I traded for a 79 MG Midget with a Weber 45 DCOE on it years ago. Predictably, the engine had thrown a rod. The Midget is long gone, but I still have the carb, manifold, and that low pressure electric fuel pump. I'll just pretend its one of those pre-war Lucas ones. Haha. Anyway, onward we go. I have dedicated a lot of time to old Shade Tree this weekend, because next weekend I'll be in Cedar Key, FL at the annual small boat meet. This morning I finished my jack-legged dual exhaust. I think I've mentioned that I have been using my father's old left over Model A stuff a good bit on this build. Sacrificed his intake manifold for the SU job, and now I have used the ass-end of his old exhaust manifold and the one that came with the car to make a dual exhaust. I read somewhere that they used to do this from time to time in the old days, so i figured... I think the pictures pretty much tell the story. Video at the end.






It's a real hot rod, now. Hahahahaaaaaa

 

I wanted those pipes to come out over the frame rail, got a section of a 1940 torque tube that I wanted to use to make a lakes pipe, but I'll have to find some with a sharper bend, or use the flexible stuff. If I even do that. I'm kind of digging the side pipes. Might try some kind of baffles, though.

 

Very cool, as always.

 

This morning I shortened that SU intake. As the pictures show, it is much lower, and now the hood just clears it. Might have to notch a little when I decide on an air cleaner arrangement, but that's ok.



I also fooled around with the exhaust. See in that last picture how it has to pass below the frame rail? I want it above the rail, for a bunch of reasons, so I did some cutting and welding and brazing and came up with this:



I know those welds aren't the prettiest things. Had too much tip and not enough experience for that thin stuff, and I burned through in a couple of spots, had to fill back in. When it all turns rusty, it'll blend right in. Haha.

 

Neat job on the whole exhaust setup.

 

I know very little about SU's, so do they run OK not being level? Are they slide type like Mikuni motorcycle ones with no float?

 

Ok, that split exhaust is pretty cool. Nice job on the build.

Cliff Ramsdell

 

Thank you for the comments. I like the exhaust, too. Working on a side pipe right now, trying to taper an old drive shaft. SUs are slide type, I think Mikuni kind of copied/improved (?) the idea. They have been around forever. That one is designed to sit at that angle. The little vertical barrel is the float chamber. The piston you can see just inside the venturi is vacuum operated, rises when the throttle plate opens. The jet needle is attached to it and rises, as well, so that one action opens the venturi and adds gas. It's a neat system. Scroll to about 1:25 in the Shade Tree SU Start video a couple of posts up, and you can kind of see it. They get a bad rap in some corners because they were most common on imported sports cars, mostly British, and were usually set up as duals. If you don't know how to synchronize them, they can be a pain. I like them, though.

 

I tapered an old driveshaft,cut a long vee section out and welded the edges back, pretty standard stuff. I wish I could have started with something a little larger diameter, so the taper would be more dramatic, but I used what I had, in the spirit of this whole build. Trying to work out the geometry of those two exhaust pipes and the angle of the new side pipe was pretty frustrating, so I got some of that flex-pipe from the 'Zone and used that. It's all brazed. We'll see. I really can't get excited about how it looks. Maybe it will grow on me. The real problem is that, since I started this exhaust work, it runs like crap. Extra lean, which I attributed to the short, open exhaust. I tried baffling it with my hand over the end of the new pipe, but that doesn't seem to make a difference. The new carb was working really well with the stock exhaust.

 

Keep a close eye on that flex pipe if you keep it, in my experience it disintigrates quite quickly.

 

To tell the truth, I don't think I'll keep any of it from the flex pipe out. I'm not happy with the side pipe proportions, but I was anxious to get something on there so I could see if it would help the lean issue out any.

 

@rwrj is there a chance that the 90 degree direct angle in 2 directions before flow to exit could be contributing to the problem.

On my hotrod I have a lakes style header that does have a 90 degree in the flow but further down the line.

The one after stock setup with the 2 under the frame had smooth flow. You did say it ran crap with all three but was the underframe better for performance than the latter 2 with the sharper 90s?

I'm no exhaust, engine performance specialist...but was just thinking how generally exhaust has smooth transitions for flow.

 

Lots of rodders run shorties but they are generally baffled. You could fab up some they are rings with a series of holes and a piece of pipe also with perforation. Obviously they are made through research but many concoct their own through disection of old mufflers and such. This would give you that back pressure...again just thinking out loud.

 

Stogy,
I see what you are saying, but it's been lean since I went to the dual exhaust. I'm thinking it is just evacuating the exhaust so easily that it's pulling in more air than the carb can keep up with, fuel-wise. I was actually hoping the 90's would help create some back pressure. I tried putting my hand over the end of that side pipe to create back pressure, but it didn't seem to help. Something in this carb/exhaust combination is just way off. I can always go back to stock, but where's the fun in that? We're getting the first effects of Alberto here now, so I'm not sure when I'll get back to it. Gives me time to do some research, I guess.

 

Cool project , i like it.
Less is more.

Hennie

 

The SU carb fuel mix is adjustable. The nut under the spring beneath the slide functions to move the tapered needle up and down within the set jet orifice. This effects the amount of fuel introduced to the air flow. On my Austin 1098 engine, with dual SU 1 1/2 diameter carbs, They are both at 9 flats out from closed. Turn the nut till it is closed (leanest setting) the screw it out counting flat parts of the nut as they face you. For an initial setting go with about 12/13. If its lean and bogs open up a couple more at a time till the bog goes away. If its rich, close a couple at a time till the raw gas smell goes away. Difficult to say where it might end when comparing dual smaller ones on a smaller engine vs a single larger one on a large engine. But you should be able to get it close with some fiddling. As for oil in the dashpot, I've used every thing from Marvell mystery oil to 50 weight.

 

Tie it down and stay safe...hope its not going to be to nasty.

 

When you close the nut,count the flats so if this adjustment doesn't do any thing you can at least return to w g ere you are now.

 

Yeah, I know about the mixture adjustment, but thank you for the suggestion. I unscrewed it until the spring was loose, still lean. You check it by raising the piston about 1/32" and listening to the engine. Revs fall, lean. Revs increase and settle back, mixture is good. Revs rise and stay up, rich. I'm still lean at max adjustment. They don't really have a choke, as such, but a mechanism that moves the jet down, providing an extra rich mixture. Even at full adjustment and full choke, I'm still lean. I've checked for vacuum leaks with carb cleaner and propane, including the throttle shaft (which is notorious for wearing on these), but I can't find one. I'll take the carb off and apart tomorrow.

 

Stogy,
Thank you. Right now, looks like more of a rain event than anything. Knock on wood.