Projects Shade tree Model A speedster kind of thing

The needle modification seems to have helped. I went out this morning, and the car ran much better. It still doesn't want to take full throttle pulls without skipping and backfiring, but it will accelerate normally now, and cruise at a constant speed. I pulled the plugs and cleaned them before I went, ran it about 10 miles, then shut it off right away. Still looks like it could be a bit lean to me, but I don't have enough experience reading plugs to be real confident in that diagnosis. It's doesn't seem to be running rich, though. Comments and advice welcome.

 

Well, while I was waiting for it to cool off enough to pull the plugs, I worked on my reserve tank situation. Plumbed it:





It has to loop over the tank so it won't just gravity feed back into the main tank when I open it. I guess that would work, but then I'd have to shut it back off, and pump the main tank back up before I could go.

I also slapped together a linkage to control it. Sacrificed an old socket for the petcock connection (remember, I used a 3/8" u-joint to make that connection).

 

Well, shoot. I hit "post reply" instead of "upload file". Dang it. Anyway, let me just continue.







I had an old brass petcock with the threaded end busted off, so I sacrificed it's handle to finish up with. Didn't take any pictures of that process, but here's a little video:

 

Plugs look ok to me. Have you tried adjusting the nut on the bottom of the card a flat or two in either direction? I was told to set it initially at 12 flats open thngo from there. By flats I mean the straight part of the nut. Screw it in till it bottoms, then back it out by counting flats which seems to be about two full 360s if I am thinking straight. What oil are you using in your dash pot? Thinner will allow the slide to move up quicker for more enrichment with more throttle. I used atf but for my autocross car the throttle was mostly wot or closed so may not be good for out on the road.

 

Love the fuel-supply fix. Thanks for your usual level of detail. A solution that is elegant in its simplicty. I have a similar problem--absolutely no way to gauge how much fuel is in the tank. I was going to carry a reserve can. But now you have me thinking I should just plumb it into the sytsem. Heck, I already have three-way marine valve in there.

 

Thank you, Clark.
Plym, I have the mixture set with that big nut so that it's correct at idle. You do it by lifting the piston just a bit and listening to the change in idle. If it slows or dies, too lean, speeds up, too rich , speeds up then settles, just right. I'm doctoring the profile of the needle now, bit by bit, to get a good mixture when I'm on the throttle. I'm glad the plugs look ok. I wasn't sure.

 

Here's an idea. Remove the air filter. Rig up a gopro type camera so it is looking down the carb. Drive and get to the point where it feels lean. Check the footage to see how high the piston is. then you would know the exact part of the needle that needs richening up.
Just thinking out loud.

Mart.

 

Creamed coffee is a good color and that's about where you're at. Trouble is the plug is reading the mixture at the throttle position where you're running. Keep enriching the mixture until you get it to run happily at full throttle. Then run it a while at full throttle and read the plugs again. You can do that with multiple full throttle passes with only idle in between. Idle doesn't color the porcelain, just the outside bottom edge unless it's really over rich. They don't change instantly.

 

Mart,
I think I just need to work on the tip of that needle. It seems pretty good now, except at full throttle. That's an idea, though.

Fabber,
I'll try your trick after I get the tip down far enough to let me make full throttle passes.

Thank you both for the advice.

 

How many washers under the needle and seat...in the float chamber? if there is one thick one or more than one try a thinner stack...that raises the float level slightly and will enrichen the whole range a little, should help a bit at the top end. Also if the washer is too thick there is not enough range for the float to control so carb will tend to empty the bowl faster than the pump can fill it. Are you still using a hand pump pressure system? If so maybe you need to give it a bit more when you reach wide open throttle? Maybe a tank pressure gauge, probably pretty hard to keep even pressure/float level with a hand pump.

 

Good points. I checked the float level with the 1/8" drill bit method, but not the washers. I'll look at that. I'm able to keep it at 2 psi easily, but it runs the same at 3, so I think it's got enough flow. I forgot to shut the fuel off yesterday when I started pulling hoses for the reserve work, and it pissed like a racehorse.

 

Rain this morning, so no test drive. I did take another couple of thousandths off of the bottom end of the needle. Since I couldn't drive, I piddled. The plastic trailer taillight has been bothering me for awhile. It was always just a stop-gap. I bought an older metal one off of the classifieds here, decided to use it instead. It's not really "period correct", but it's a lot better than the box store special. Installation was pretty straightforward. I just made a little angled wood block to get it level. Some drilling and bolting and wiring and I was done. The first picture is the old one.







I guess the difference is pretty subtle, but I like the fact that it is older, metal, and I think the lens is a definite improvement. Plus, it's progress.

 

I am late to the party. But fantastic build. I am really digging it.


Sent from my iPhone using The H.A.M.B. mobile app

 

Plugs look fine, but it's hard to get a good reading on today's gasoline, plus you'd need to shut it down right at the time it's running rough and check them at that time, not after continuing to run it back to the shop.

 

Yes plugs readings are only good on some modern fuels ( most of them can barely be described as gasoline) and as Blues 4U says it needs to be a "plug cut" , i.e. declutch and switch ignition off at virtually the same time. Pull over and examine or change the plugs if you cant check them on the spot .
In saying all that it seems like you are heading in the right direction.

 

Thank you both for the advice. We still have non-ethanol fuel around here, which is what I run in this thing. Any chance it would work better for this than the regular pump grade?

 

Yeah the "cracked" synthetic fuel they make now for injected cars is a different animal to what we are all used to. Lower evaporation temperature etc etc , because the injected cars have a sealed fuel system and evap return etc....
As I said it is becoming more and more difficult to read plugs , alcohol readings are completely different and when the two are mixed there is no telling what you are seeing. It's easier these days to use a gas analyser, but they are expensive and temper mental damned things.. I am not sure if you can get one of the air/fuel gauges they sell for injected cars to work in an open (carb )system... I wouldn't worry too much if the plug readings are not perfect, just as long as it doesn't run lean and melt something, or be so rich that you lose power. That is a bit of a fine line with gas, but with alky you can be quite rich and not lose power...just ecomomy.
Personally , I think you are pretty close now , just keep chipping away at it. One of the great things about SUs, is that once you get it right , all else being the same it won't change much for a lot of miles. Even altitude is automatically compensated by the damper /needle system....IMO one of the best carbs ever made.

 

All right. Opportunity knocked in the form of a post in the classifieds by lake_harley for a pair of H6 SU carburetors from a Triumph TR4, so I bought them (thanks again). They appeal to me because there are two of them, and because my HS6 was introduced in the early 60's (as I recall, too lazy to Google it right now) and the H6 is the older version, dating back to the late 30's (again, too lazy...). They arrived in good shape, and I immediately snatched them off of the Triumph manifold and started figuring on how to fit them to my Model A block.



I bought a 1 3/4" id conduit elbow from the local big box store. Cut the mounting flanges off of an old stock banger manifold (I'm keeping the current carb/manifold intact, just in case) and chucked them in the lathe to turn a seat for the conduit.



I had to slice that end of the conduit and braze it back to reduce it, and I know I'll still have a big shoulder right there, which is far from ideal, but oh well. Brazing that thin conduit to the cast iron was pretty tricky. I eventually got them sealed up, (had to use a bit of JB Weld, shhhhh) but it's not too pretty. I measured carefully and clamped the flanges to a board to keep them lined up and fitted a 3/4" cross-pipe, then marked, un-clamped, and drilled holes in the main runners before re-clamping it all and brazing.



I've always heard dual carbs need that cross connection, and every stock dual SU intake I've ever seen has it, so I figured I'd better have one, too. Hope it's big enough in diameter. Next I made the plates to bolt the carbs to.



Nothing special, just hacksaw, holesaw, drill bits, and the edge sander. I clamped them to a piece of angle iron and brazed the rest of the mess to them.



Sanded the JB Weld almost all back off, painted it up and called it a day. It's drying now. I'll take the carbs apart this afternoon and make sure everything is ok inside. Lots of piddling around to get the throttle linkage and all, but hopefully I'll be able to see something next weekend? Knock on wood. Thank you for looking.

 

If you need parts for the carbs, here is a supplier; http://www.gowerlee.dircon.co.uk/

 

I like your manifold, and yes the H series carbs are really fitting for the era...That is the direction I have gone too. I particularly like the bronze choke/enrichment levers and linkages etc...they look great all polished up. Did you consider using the Triumph manifold with some small modifications? I have a MG manifold here I was going to look at with the idea of cutting it in half along the balance tube and then reshaping the flanges at the head/block end to fit the Model A. Just lengthen the linkages with new connecting tubes and use a piece of hose to join the balance tube until I was sure it would work, then maybe welding in a piece if new alloy tube....or making a copper tube or ? to press fit after some more machining.

 

Mine may not actually be a Triumph manifold, that's just what the little paper tag wired onto it says. The runners on it split into two ports each after the balance tube, which made using it too much of a challenge. I also can't weld aluminum, all I have is an OA torch. Thank you, 97, for complimenting the manifold. Too bad it won't work. I've gone to some effort on this thread to own up to and describe my mistakes, so here goes nothing.

As soon as the paint was set up enough, I couldn't resist holding it up to the motor. Dammit. That balance tube won't clear my home-made dual exhaust manifold, so I ran back to the store and picked up a couple of 3/4" conduit elbows. Modified it like so:



I'm not going to lie, I was pretty proud of myself for figuring out all those angles. Almost made up for not checking the fit the first time, before I brazed it up. I brazed the new work up and dashed outside again. Damn if I hadn't put the bend in backwards, sticking in TOWARD the exhaust manifold. Kind of lost that good feeling. Oh well, at least I knew myself well enough to have bought two elbows. Third time's the charm:






At least I feel like I'm getting a little bit better at brazing, with all this extra practice. Hahaha. I think I'll have a beer.

 

Couldn't resist. Who cares if I smudge the paint a little? Not me. You can see from these mock-ups what the issue with the straight balance tube was. One problem with this rig is going to be that the little helmet piece will now be between the two air cleaners, doing nothing useful. I'll have to puzzle on that one a bit.

 

You sure do like to tinker! I love it.

 

I got an unexpected day off from work because of the weather, and put it to good use. I had already torn the carbs down and cleaned them up. These carbs use an adjustable throttle connection so that you can set each idle independently, then lock it down. Trouble is, mine are now farther apart than they were, so I sawed the middle rod of the assembly in half and soldered each end into a 1/8" brass pipe.



There's a video below that shows how that thing works. I also made a brass plate (that you can see in the video, as well) to hold the stock Triumph throttle bell-crank (forgot to take a picture of that, you can kind of see it in the video, too), and reversed the orientation of the choke/enrichment linkage. I still have to make a longer rod to connect the two levers for that system, and run a longer choke cable down to it. Anyway, I got it all installed before the rain hit, and she started right up. I won't go into the ritual of adjusting dual SU carburetors here, Google and Youtube will take care of that, if you're interested, but I have it pretty close, and I'm pretty happy with it. Won't be able to get on the road until the weekend, but I'm hopeful. Here's the proof:



Thank you for looking.

 

Somebody with sharp eyes and a working knowledge of Mode A's will probably notice that I had the accelerator bell-crank set up to pull instead of push. Just had it on the wrong end of the manifold. Shouldn't be a surprise to anybody by this point in the action. It was a matter of moments to move it to the back carb. Took a bit longer to shorten both the Triumph and Ford rods to fit. I need to do a little bending on the part inside the car, it's bottoming out on the floorboard before I quite get to full throttle, but here it is:



Hopefully I'll be ready for a road run Friday afternoon or Saturday morning, if the weather and the world co-operate.

Oh, yeah. Sorry about the little bit of Phillips head slot in the little bolt that keeps the bell-crank bracket from moving around. It was what I had on hand. It'll fill up with grease and dirt soon enough. Hahaha.

 

You are one creative dude. I can't wait to see you take it for a run.

 

I love it. So on your hood can you take the bottom part off and rebuild what you already have? Or my other thought would be a two into one air cleaner.

 

It's looking good.

Sounds pretty throaty. Nice.

Mart.

 

looking forward to the road test report

 

Thank you all.

Rusty,
I'm thinking of the 2 in one option, just because I like my little helmet. I might go with a longer version of the helmet piece, though, that covers two separate air cleaners.

Mart,
You were right, all along. The old HS6 just wasn't enough carb for this set up. Doesn't make sense to me, because of the flow rating. I think it potentially flows enough air, but just not enough fuel. I was getting closer with my needle adjustments, but then the dual option showed up at a price I could afford (thank you again, lake_harley). I took it out this morning, and man is it running better. Which brings me to:

Blackbob,
Here you go. I apologize for the aggravating rattling sound. It's some part of my jackleg camera mount. I didn't realize it was there until I got the card out of the camera and watched it on the computer. I'll try to eliminate it and make another video. The little waterproof case for the camera also started fogging up on the way back. Honestly, its a pretty crappy video all around. Oh well. Hopefully you all can hear enough past the rattling to tell something about how its running. I was cruising around 55 most of the run. I'm pretty happy, for the time being.