VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1912-1928 Heat Stove

I got my 28 motor running last week. This is the one I've written about previously. It came with my 26 Touring I'm working on and was the subject of my "Resurrecting a motor" article. I could only keep it running with the choke out and I understand from other posts that it needs a heat stove. Today I set about manufacturing one. A very helpful fellow at the local muffler shop provided me with the parts: a 6" piece of 3" pipe, a 20" piece of 2" pipe, a short piece of 1.5" pipe, and 24" of 1.25" flex. He also expanded a couple of pieces of 2" pipe to fit inside the 3" pipe. With some welding and grinding, I think I have my "poor man's" version of a heat stove. I have pictures of the parts and the finished product. The fitting at the carburator end of the flex pipe is for the crankcase breather pipe since I have an RXO carburator. Tomorrow I need to go back and get him to expand the inlet a bit so that the air cleaner will slip on. Total cost thus far - $32.

That arrangement looks like it is for the 1927 single port exhaust manifold.

The hot air take off from the stove for the 1928 engine will be parrallel with the engine. The 1927 is vertical.

Will the engine not run properly without one of these? i am rebuilding my car and wasn't going to bother with this because it looked a bit like one of those unnecessary additions you get on a early car (and a lot of work). I don't intend to use the car in winter due to all the salt on our roads so it will only be used in the warm (ish) and damp British summer.

This should be interesting. I look forward to the replies. I have seen 28 Chevs with just an air filter but I know for sure with my "28" that I have driven for 17 years that if the car runs badly or worse then the connection tube to the heat sink has slipped off the carby.
Let us see a photo or two of your car. I saw one in 2007 in England that used to live a couple of miles away from me in Australia.

The early updraft carburetors up to and including '28 did not totally vaporize the gas. A little heat from the exhaust does the trick. In very hot weather the heat tube can be removed. The carbs can be setup to run better without the tube but will run a bit rich (due to particulate gas in the combustion chamber which does not completely burn).

For that matter the early 6 cylinders up to about 1990 or so also used a little exhaust heat to warm the carb gas/air mixture to help insure total vaporization.

I don't know about driving our 28 in cold weather air (no cabin heater) but I have driven it in summer heat of 105 degrees F and it runs fine with the heat box hooked up, never have driven it without the carb heat.

Mine runs rough w/o it at lower speeds. I haven't run it enough to form an over all opinion but at lower speeds it's rough enough that I definitely want the heat box hooked up.

I hooked up the heat stove today and ran the motor hoping to see a big improvement. Unfortunately it still needs the choke out most of the way in order to keep it running even after it warms up. I took the carburator apart and adjusted the float level but no improvement. I'm not sure where to go from here. Any suggestions? I've included some pictures.

That heat stove looks better than I anticipated. Nice job.

Perhaps you problem is caused by the idle circuit. I'm sure you have adjusted the air mixture screw on the carburetor.

Likely the carburetor has buildup of gum or varnish. As a first step, take the idle mixture screw out, squirt some carburetor cleaner into the hole several times then blow out with air. Put it back together screwing the mixture screw all the way in and start the engine. If that does not improve or cure the idle problem then a thorough cleaning and inspection or rebuild is in order. If it does help but you still need to have the choke pulled out to run correctly then clean the rest of the carb. If that does not solve the problem then have an experienced person look over the carb. Taking to the local mechanic may not be the best option if he does not have experience with these carbs.

Would it help to spray starter fluid around the carburetor mount and intake manifold maybe is pulling more air from some where else and the idle would increase when hit with starting fluid

On a similar topic, has anyone done a comparative test where the daisy shaped sheet metal "flow straighteners(?)" were installed/ removed from the head ports? I took them out of my engine, a 27 block with a 3 port head and never regretted it, but the engine is far from stock. I cant see that they would do anything except restrict the flow- they certainly are not going to help the fuel get around the square corners in the head ports.

Herb Kephart

Actually I'm missing one of those daisy shaped items in the intake manifold. I don't know if that makes a difference. I had the engine running again for awhile today and still can't get it to run without the choke almost all the way out. I checked compression and they were all around 75 - 80 lbs. The spark plugs are pretty black so it's running way too rich. I checked the vacuum and it was around 15 inches of hg. but fluttered a lot. Turning the needle valves in or out has absolutely no effect. I had the carburator completely apart and cleaned everything well. I cannot find any air leaks. I'm fresh out of ideas.

Does the engine run better at higher speeds than idle? At higher rpm can you push in the choke? If so then check for a vacuum leak.

Have you checked the valve timing? Most 4 cylinder aftermarket timing gears are mismarked so it is common to have the cam timing ~ 15-20 deg. off when engine is rebuilt. You may need to mark top center as determined by a wire or screwdriver into the spark plug hole in # 1 cylinder. Then check to be sure that the valves open at the proper angle.

Don't give up we will get this figured out.

Hi,
Check the vacuum tank out.The valve could be leaking or the vacuum tank float full of fuel alowing fuel to enter the manifold via the suction line from the vac tank.
Easy check is to unhook line from manifold and plug it and see if it solves the problem,remembering the car will only run for a short while till the vac tank is empty of fuel.
Cheers
Rusted

I was on a 4-cylinder tour and my vacuum tank dropped the inlet valve. I would let it run until the raw gas was being sucked into the intake manifold. Disconnected the vacuum line and plugged it. With that full vacuum tank I could easily do 5 miles before I needed to fill it again.

If the inlet valve brass seat drops out, it can be glued in place with super glue. Works well, done it several times. Just make sure you get the seat fully seated before the glue sets. Once it sets it is there!

Thanks but I know it's not the vacuum tank because I didn't have the vacuum line hooked up to vacuum tank, the inlet on top of the manifold was just plugged. I'll check the valve timing tomorrow.

I do have one more question about the RXO carb. All the instructions say that this carb has only one adjustment. However my carb clearly has two needles that can be turned in and out, the idling adjustment screw close to the top and a bigger one at the back. What is back one for?

You have a dual adjustment RX-0. The one on the back side sets the "high speed" mixture. Those carburetors were installed on high altitude vehicles. I have a few of them but have never tried one. Took one on a 4 cylinder tour to Santa Fe, NM at the request of a '26 owner. He was concerned about how well his car would run at that high an altitude. Ran fine with the 33S
RX-0 so never tried the 34S dual adjustment.

I suspect those Dasiy air straighteners have a reason for being in there or chevy wouldn't have bothered with them, but it would show up if it was a problem on the two cylinders that side feeds with plug color once you get it running closer to right.My guess is they either transfer more heat from the head to further vaporise the fuel or they help blend the spinning air from the round intake to the more square intake passages. My gut tells me it is the heat thing. If your carb adjustments don't affect anything, then there is most certainly an air leak on the intake side or a fuel delivery problem. It looks like your engine is recently rebuilt so I have to ask this, Did you go back and retorque the head and intake after you ran it the first time? Any engine with the old style copper/steel asbestos (or modern equivalent)composite gaskets has to be retorqued. Be sure to readjust the valves after doing the head. The plugs are black because the choke is out that far and the engine what the "needs" change with load and speed which the choke can't do unless adjusted every time speed and load changes. If the retorquing dosen't do the trick , start chasing something in the carb not letting the fuel flow normally. Check the jets and filter screens for anything, even rag lint will mess them up. I worked on a zenith O4B last spring that had "reformulated" California gas sitting it it for a while and pulled out little bitty tiny chunks of green brass corrosion from out of the jets from caused by an oxygenated fuel and brass carb reaction. After cleaning the jets, lines, vac tank etc several times it ran like new. And yes I even found rag lint in there from a red shop rag. Your fluttering vac readings may be caused by the engine just being a low rpm 4 cyl but may also be from valve timing off like someone else mentioned. 4 cyls flutter more than 8s but shouldn't flutter a lot. Another thing to check may be the float setting too low and not letting the fuel be at the level where the suction can pull enough up unless the choke is part way closed. A couple rules that help me are "backfiring through the carb is a lean condition", "black smoke is rich". An engine likes to run at just past lean at the point where all speeds and loads perform well. If you do have a high altitude carb, one of those needle valves may make it run too lean at lower altitude. The higher you go, the less air you get and the less fuel you want so screw in the one that doesn't show up in your book and see what happens. If it is letting in too much air then you have the culpret. Hope you get it going good, Looks like a neat project!

Thanks again for the good advice. I checked the valve timing this morning. As near as I can determine, using the angle of the crank handle as the reference points, the intake valve begins to open at 22 degrees after TDC (#1 cylinder). I only have the manual for the Superior K and V and if I interpret the Fig. 50 diagram (p. 64) correctly, the intake valve should begin to open at 16 degrees after TDC. I'm assuming that the '28 motor is the same. Should I pull out the camshaft and move it over a tooth? Which way?

I checked the torque on the headbolts and they are tight. I also tightened the intake manifold bolts and the carb to manifold bolts. I don't think they are leaking. I'm just using 1/16" cork gaskets. I know that this head has been cracked and substantially repaired sometime in its past. There is in fact a whole new piece of steel welded in on the exhaust manifold side. There is still a small crack that leaks water. Is it possible that there is another break somewhere inside the head that is allowing air in? Is there a way to find out?

I reset the tappets to .008". I can take the high altitude needle on the back of the carb right out and it still runs the same. It does seem to repond somewhat to the idle mixture screw. Even if I rev the motor it still will die if I push in the choke. Moving the choke even slightly will change the way the motor runs.

I did discover that the #4 cylinder was not firing even though it was getting good spark. I replaced the spark plug and now it definately fires on all four. I think this was probably causing the flutter on the vacuum but I haven't checked if it's now steady.

I do not have a muffler yet. Would this make any difference? Does anyone know what the correct outlet pipe size is for the muffler. I know I need a round one to fit the muffler holder which I do have.

Here is a link to a chart that may help with the valve timing. http://chevy.oldcarmanualproject.com/chevyresto/2807.htm

Thanks. I just checked that valve timing again. For the #1 intake, from UDC to when the tappet starts to tighten up is 16 degrees. Yesterday I was measuring from when I could actually see it move. I think valve timing is dead on.

This sounds like a situation where you need a buddy with a car that works well. I have a car that runs well and friends that are building cars. They give me bits and pieces like carbs and I put them on my car and run it. I then report on how well it works. In your case I would swap carbs with someone who has a working car and see if the problem transfers across.
I have found that some carbs have had badly worn spindles which allows excess air to be sucked in so that the choke has to be left out to compensate.
My car starts on full choke and once it fires, even just one cylinder, I immediately push the choke full in and it will sit and idle.

Well, I finally solved the problem of the car (1928 motor with RXO carb) not wanting to idle without the choke out. It was a matter of finding the right person to ask. Earlier this week I visited the "Carburetor Doctor"(http://www.carburetor.ca/)in Stony Plain to look into buying a kit. When I explained the problem I had, he immediately told me that I had "a plugged idle circuit". He printed off a diagram and pointed out where the blockage should be. I went home and took the carb apart and cleaned that passage and now it idles like it's supposed too.