Projects Shade tree Model A speedster kind of thing

Alright, time for an update. The engine has been back in for a while. Got it started without much drama, set the idle pretty high to seat the rings, damn thing started to heat up, so I shut it down. Peered down into the radiator neck with a flashlight, some of the tubes look plugged. Felt the front of the radiator while it was running. Sure enough, about 25% of it was cold. I had poked around in the block while I had it all apart and loosened up a bunch of crud, thought I had gotten it all out. Guess not. Took the radiator off, boiled up about 5 gallons of soapy water in my turkey fryer, turned the radiator upside down, put the cap on and plugged the inlet, filled it up and let it soak for a few minutes, then flushed it with the rest of the still hot water. Things looked better. Slapped it back on, still overheating. Trotted up to the Ace Hardware and bought some wood bleach (oxalic acid) for $10. Mixed it up and filled the system with that. Started her up, and there was an immediate improvement. Still have a cool section of the radiator, but she's not overheating, at least with the yard driving I've been doing. I'm going to leave the acid in for a week, running it up to temp every day, then drain it and flush with baking soda. Anyway, the motor is running like a clock, so far. Still has the ticking from the #4 exhaust valve, but I'm not too worried about that. Seems to me I can really tell the flywheel is lightened, the throttle response seems much more crisp. No "seat of the pants" dyno on the new head from the little driving I have been able to do. I spent a lot of time with that B distributor, which came from a real nice guy on the classifieds here. I'm happy with the timing of it, and with my little pointer and pulley notches. Sorry for the long post, just catching us all up. Here's a video. You can compare it to the earlier one called "Shade Tree Worn Valve Guides?" in post 314. So far, the refresh seems like a success. (Knock on wood.)

 

be careful or you will end up w/ a pile of these engines from ups trks from all over the states-people sending them for reasonable priced o/hauls!!

 

What may be in the radiator is old water pump grease. Need to flush it with some Dawn or similar product. Just a cap full is all you need. Usually takes several flushes. Good luck!

 

Patsurf,
It's only a reasonably priced deal with my free labor. I wouldn't advise anybody sending me their engine, unless they mean it as a gift. Hahahahaaa

Steve,
Thank you, but I used soap in the hot water, didn't help. The acid seems to be working, at least somewhat. We'll see.

 

Not much to report. Still fiddling with the mixture on that SU. I've drained the acid mix out of the cooling system and flushed it real well, seems to be much better. Still a cool section in the radiator, but it's not as wide or as cool, and I don't seem to be overheating, but it's colder out now, so I don't know. I did make a cover for the battery hole in the floorboard (stock location). Eastern White Cedar in two layers glued up with epoxy.



Then this pile of junk:



And I've got this:



I was going to put a squishy gasket of some kind on it, but the little plastic handle on the modern, cheapo battery keeps the lid pressed up against those little toggles just right. I was getting worried something was going to rattle down there from inside (haha) the car and short my terminals. As soon as that gets weathered and dirty, it'll fit right in.

 

Looks like your shop floor is tracking into the car some, hahaha. Have a merry Christmas my friend.

 

Hahahaaa. Yeah, it does get in there from time to time. You too, man.

 

The overheating problem seems much better, but my carburetor issues are baffling me. The symptoms are that I have to set it as rich as it will go at idle, but at any constant rpm above idle the engine gradually stutters and dies, lots of exhaust backfiring. If I push the piston that controls the needle down with my finger, it solves the problem. Timing is correct, checked with a light. Fuel pump is working fine. I've adjusted the float level to specs, so that's not it. I noticed there was some wiggle in the throttle shaft, took it out and found this:

It's hard to see in the picture, but there are some pretty significant steps worn in each end. The bushings in the carb body seem fine. I scrounged around in my junkpile and found some thin-wall brass tubing that fit the bushings perfectly, so I turned down each end of the shaft so that the tubing was a tight, press fit, cut a couple of pieces to length, and soldered them on.


Put it all back together with the highest of hopes, but nothing has changed. It's like the mixture is changing over time at any constant throttle setting above idle. I'm going to get a cheap fuel pressure regulator and try that, although it doesn't make sense to me that I would have to set it rich at idle if the pump is overpowering the needle? Seems like that would give me a rich situation. Any suggestions?

 

I have messed with some SU’s before and found that most of the rich idle issues were caused my the end of the mixture needle was worn and the only way I was able to properly tune mine was with a gauge pin installed in the top as a reference to the needle position during a rich or lean mixture. Then I have to remove the needle and modify that position on the needle to get the correct mixtures. I do know the oil in the top damper can also cause fuel to be inconsistent as well. I probably confused the heck out of you and nothing I just said made any sense at all to you. But I get it in my head. ;-)

 

I'm far from an expert on SU's brittish stuff...
The A Engine is 3.3L ... MGA etc was ~ 1.5 1.6L and they used 2 SU's...as far as i know...
I'm gonna try a deuce 1-1/4 setup on my model A...
....If that's not enough...???

We're way of the B.H.P. curve!

Here some research i found on SU's...
Used to hate these buggers on my Volvo...
https://www.minimania.com/Carburation___Initial_Considerations_and_Manifolds
https://www.howacarworks.com/fuel-systems/adjusting-an-su-carburettor
http://www.mossmotoring.com/su-carb-very-fine-tuning/
http://www.sucarbs.com/?page_id=20
https://sucarb.co.uk/technical-su-carburetters

 

12, I think I kind of see what you are saying. I think my needle profile is just all wrong, but I'm not sure where to go from here. 30, I have seen that chart. I think the hp side of it is more useful to us, because Model A engines turn so slow compared to more modern ones. I think that makes the displacement side of the chart misleading. My carb is the 1 3/4" version, came off of a 1800cc Volvo b18, but there were two of them on that motor. A single one is right for about 50 hp, according to that chart, and so are the twin 1 1/4" ones that you are planning on using. I've been messing with them for decades, and I have had good luck, but this application is not working out, so far. I can adjust it at idle by raising the slide slightly and turning the big mixture nut on the bottom and get that ticking over really nice, but when I open the throttle and just hold it steady, it gradually loses rpm, then spits or backfires through the carb and dies. The exhaust is getting a good bit hotter than it used to, also. It all seems like a severe lean situation to me. I've checked for vacuum leaks with a water bottle, can't find any. The only thing I've changed since it was running before is the rings and the head. I'm sure it has a lot more compression than it did. I have to admit, right now I'm stumped.

 

If it's lean then wouldn't that mean that is is under carbureted? (Trying to learn here)

 

I picked up this setup for a ford A/B motor someone made. Though I have not used it was real cheap and if I ever get to build my speedster someday it is what it will get. The gentlemen I got them from made the manifold and linkage, there is a couple more brackets that go with it for the linkage. But is was to well thought out and he said it ran awesome on a A. So I bought them! They are off a MGB and are 1 1/2” SU’s if that helps. I have tuned dual SU’s on my Datsun 510 and they being a variable Venturi carb worked well even with a large cam on my Datsun L20B which was a 2.0L and the head flowed way better than a A motor and made 3 times the HP.

 

Cactus, I think it's enough carburetor. If memory serves, a 1 3/4" SU flows something over 200 cfm, which has got to be way more than a stock Zenith, and they work fine. The problem (I think) is that the needle isn't letting enough fuel in for the air. Maybe something to do with being tuned for a dual set up on a much smaller engine? Anyway, since I bought this carb with it's partner, I have a spare, so I yanked the needle out of it and tried modifying it. At first I just chucked it in the lathe and filed/sanded it down "by guess and by God". That helped, but it was still lean at open throttle, so I just filed a flat into it.

It's hard to see in the picture, and hard to explain, but basically what I am doing is the equivalent of trying a larger jet. Of course, I have the original needle set aside, so I can always go back. It seems better, not bogging near as bad and the lean/rich adjuster is back up in the middle of it's travel. I think I'll keep fiddling with it. I also did a compression test, since I imagine the rings must have seated during all of this. It's jumped from around 60# on all four to just over 80#. Those worn rings and huge ring gaps couldn't have been helping, and the new (to me) head pushes it from 4.22 to 5.22/1. Reckon that explains why the exhaust system seems hotter? Ha.

12secvx, I like that set up. I was thinking about running both of mine, but one of them had been dropped, so I am using it for spare parts. I have another complete set on a Volvo b18, but that's another (off topic) story.

 

Happy Christmas Eve, everybody. Stole a few minutes from Santa Clausing to re-make my exhaust clamp. The copper tubing and self-tappers wasn't speaking to me.

 

Madfish,
I like that, especially the b/w. I'm going to keep my eyes peeled for one of those little brass hand pumps, that knocking electric pump is an intrusive, out-of-place sound.

In other news, I wasn't happy with my throttle linkage. I had the bell crank screwed into the vacuum outlet on the stock part of the manifold with a modified brass vac fitting, but the actuating rod was awkwardly angled, just seemed like a high wear or potential binding situation, plus I wasn't quite getting full throttle, which seems like a cardinal sin of hot-rodding. I find that fiddling around on stuff like this sometimes helps me process what to do about bigger problems, like my carb mixture issue. Anyway, I turned/drilled/sanded/threaded up a 45 degree fitting this morning.


Popped it on there, did a little bending and twisting on the bell crank, and it seems much better.

 

You can make one out of a beer keg pump.

 

This is one of the coolest builds I have seen.Keep up the good work.

 

Thank you. I'm making progress on the carburetor issue. It still tends to skip a bit, doesn't take fuel well sometimes, either. I felt like it was dialed in enough to make a quick road run this morning, though. It seemed to run better with a little bit of load on it, much better at constant speeds, still tends to buck and hesitate a bit taking fuel, though. I think my needle experiments just went a litttle too far, and it's consistently a little rich. I might try a thinner oil in the piston damper, let it rise a little faster under acceleration. Anyway, here's a quick video from the driver's seat. By the way, if any of you come to Georgia, it's now illegal to have your phone in your hand while driving. Just a heads up. I approve of that law, even though I broke it.

 

Looks like you are getting it dialed in. I have used 3in1 oil in the damper and it seemed to help it at the time and used a Air fuel ratio gauge later to verify.

 

The dangers of shade treeing.

That big limb behind the front tire is the culprit. Ain't no big deal. It'll glue back.

 

Bummer. An ironic end to 2018. But sounds like you're taking it in stride. I enjoyed the video, by the way.

 

Carb sizing: Using cubic inches can get you close but better thinking is horse power. The carbs you are using came off a motor making 100+ hp. Think about your A at maybe 60. Fuel pump/ pressure: I use exhaust gas pressure off the exhaust pipe ahead of the muffler- gives about 3 psi of silent pressure.

 

Tell anyone that asks, your hood got busted by some jerk at the track last week that tried to go by on the inside and bounced his right rear wheel in there. Maybe take a soft shoe sole and make some rubber marks in the area, haha.

 

Steve,
I agree on the carb sizing and HP thing. Remember, though, that the Volvo had two of those. If you look at the chart 340Hilborn posted up in #430, one 1 3/4" SU is just about right for 60 hp. I think 60 is probably a little optimistic for my setup, but I should be able to get it working. That's an interesting idea on using the exhaust pressure. How do you plumb that?

Got some glue spreading done. Epoxy thickened with colloidal silica. It'll definitely need some filling and sanding, but hopefully I can avoid having to make another hood. We'll see.

Happy New Year, by the way.

 

I tell you I sure as heck am glad you weren't involved in that hood kerfuffle...you cannot be duplicated...

 

Progress.

 

I'm interested in your exhaust pressure hook up as well. I ran a line from the exhaust pipe ahead of the megaphone to the nipple on the diaphragm snowmobile carb on my BSA single cylinder MC. The pulses worked real well for several runs on the short course at Bonneville in '71. I was apprehensive about running it on the street, wondered how much heat might be getting to the diaphragm and affecting it's longevity.

Ed

 

That's how model airplane engines get fuel pressure. They have a nipple on the exhaust that has a hose run from it to the fuel tank. Works great.

Dave