VCCA Home Forums TECHNICAL - 1945 AND NEWER 1949-1954 Radiator bubbles

I mentioned this before - 1949 Chevy 4400 (ton and a half grain bed) - the compression in all 6 cylinders is the same. It measures at 75 psi, which is a little low but could be due to a number of things. The point is that the compression is the same in all 6 cylinders.

When the engine is running there are occasionally tiny bubbles in the radiator. It is not a steady stream. The bubbles are not large. They are smaller than half a pea, but they are there.

At first I believed that this could be some air in the cooling system that the waterpump is stirring out. But it hasn't quit in 150 miles.

I am running without a thermostat.

My mechanic friend last week didn't believe it was serious. Certainly not serious enough to cause the engine to miss.

It seems to me that these bubbles have to be an indication of a 'compression leak'. I re-torqued the head bolts last week. They're all good now to 80 ft. lbs.

Am I just worrying too much about this? If it is a compression leak, will it necessarily get worse and cause a head gasket failure? I would rather avoid pulling the head again.....

Lee Prairie

Though much more prevalent in earlier Chevys drawing air in along the water pump shaft could be the cause of the bubbles. Go to your local auto parts place and get an exhaust gas detection kit. If the bubbles are exhaust gas it will detect it but if air not. Once you know where the bubbles are coming you can take steps to fix it. Ignoring a problem will only let it get worse.

Some things need to be considered here.
(1) Why is the compression as low as it reads? Have you tried ANOTHER gauge ...is it a faulty gauge? Do a wet and dry compression test, that'll give you insight. Because the cylinders all read "the same" ..... on the low side does not make the problem any less of a concern.
(2) The bubbles could be air bubbles, but getting the exhaust kit, as mentioned, once again ... will eliminate any erroneous diagnosis.
(3) Prior to doing the valve job, was the cylinder head magnifluxed? Once again, any telltale signs back then could point to a correct diagnosis now.

I would also install a thermostat (like it should have) and see what happens.

Everytime I had seen this it was a cracked head or a head gasket
John

Thanks to all for comments.

FIrst of all, I don't believe anyone would do a valve job on a cracked head, so the magnaflux of the head (should be) is automatic. Pay tuition on that lesson once and you'll never do it again. But, on all the overhauls I do (mostly Allis) the heads get magnafluxed without exception.

Secondly, I disagree with the comment about the compression being the same ... Certainly if the compression were NOT all the same and the variation were significant, that would be stronger evidence of a problem. I've used a single guage and not while the engine was running - the starter motor was turning the crankshaft.

I'm inclined to tear it down again, replace head and manifold gaskets and re-do the adjustments to see if I can get improvemenmts, but the engine runs fine now as is. I am just suspicious of the (very few) radiator bubbles and the gas mileage is way low. (The local expert and guru doesn't believe the radiator bubbles are a cause for concern...)

Lee Prairie

None of the auto parts stores here have even heard of an 'exhaust gas detection kit'. These are Sturdevant's, CarQuest, Napa and Advance Auto Parts.

I don't know how these places stay in business. The only advantage nowadays to a physical store as compared to an internet store is that you can go to a physical store, buy it, and take it home.... you don't have to wait a week for shipping. If they don't have a good inventory, then they're useless.

Lee Prairie

I had intended to post this earlier. When you first start up an engine there is almost always some air disolved in the coolant. It comes from various sources one is the interface between air and coolant. As the coolant is heated the dissolved air is forced out forming small bubbles. It is the same bubbles that you see in the pan of water on the stove before actual boiling occurs. It can take a while for that dissolved air to come out.

I as well as your expert (guru) don't expect a few bubbles are any cause for concern unless they increase with time.

Any modern well equipped repair shop will have one. It will cost less to have them test the coolant than to buy one.
I could sell you one but not sure about mailing a liquid.

NAPA has its "block check kit" for $50 which is, I believe, what earlier posters were referring to.

Lee

Napa should have it or order it for you. it's called block tester kit also known as a combustion leak tester kit. napa number # 700-1006 for under $50.00 bucks.
:vcca:

OK - guys, I did the NAPA "Block Test Kit" thing. If you believe that $49.99 is "below $50" THEN YOU ARE A NAPA EMPLOYEE.

Customers will equate anything close to $5O with $50 ... amazing that "retail" people don't understand that.

So, the NAPA "Block Tester Kit" ($50 minus one cent ... so NAPA can claim it is "under $50" like the above poster who must be a NAPA employee) indicates there are no exhaust vapors in the cooling system.....

I did this test several times. First... I followed the directions to the letter. I got a negative result. I cleaned the aparatus (remember, I am a Ph.D. Chemist), and started the test again. For two hours. Still a negative result.

I don't believe there is any exhaust gas in the cooling system.

This is not a "head gasket / cracked head" issue.

It is a timing / fuel system issue.

Lee Prairie

Couple of questions:

when testing compression, did you do a leak down test?

did you check the oil for signs of coolant (looks milky)?

Is the coolant level going down?

Is something plugged and you re getting cavitation at the water pump?

The timing/fuel mixture would not cause bubbles....perhaps I have lost track of the original question.
A 216 will run fine with the timing advanced an extra 10 Deg or retarded an extra 10 Deg, although the power and fuel consumption will be greatly reduced at the retatded position.
Just try every thing inbetween and see where it runs the best.
Don't be afraid to experiment with the timing.
I would suspect the real culprit is the carburetor.

Good question, what are we trying to diagnose, the bubbles or the misfire?

Well, after all the good, experienced, seasoned advise you've received, it seems you have now diagnosed your own problem, timing and or fuel. How does timing and or fuel relate to 70 pounds compression, Mr PHD Chemist?

The poor fuel milage ad the fact that it requires little chocking still leads me to believe that there is something amiss with the vacuum power piston in the carburetor ( I believe it has a Rochester)
Either no vacuum is reaching the piston, the piston is stuck, or, the spring is incorrect, The check ball is missing (depending on year) or ?????

I'm not sure what your point is, bobg1951chevy. "Dr." would be correct rather than "Mr.", but when people say "Dr." I look around to see if my father is standing behind me. So, normally I don't press that issue.

My comment about being a Ph.D. chemist was just to say that I am familiar (very) with washing / preparing apparati for repeat measurements. It was nothing more than that, although some took it the wrong way, obviously.

Regarding other comments (many thanks to all!), I too am suspecting a vacuum problem. There is no miss-fire now the way I have it timed (as Gene or Ray advised, #1 fires on the ball as slow as it will go), but the gas mileage is about 65% of what it should be.

The compression test I did was a "dry" one and the engine was cold and I gave no thought to the position of the throttle. I may re-do that (test on a hot engine and with a squirt or two of oil in the cylinder for the "wet" test) and I may not. The fact that every cylinder gives the same reading (under identical conditions) is the important thing (this is well-known but it can also be seen in the stovebolt tech tips).

I started this thread out of concern for the tiny bubbles in the radiator. There is very little bubbling, the bubbles that are there are extremely small, and the NAPA $50 minus one cent Block Test Kit indicates there is no exhaust gas in the engine coolant.... and I am skeptical of that test result, which confirms nothing more than there is not enough exhaust in the engine coolant to detect. OK, I accept that and go on to something else.

To make the engine run properly (definition: run with no miss and does not die when the accelerator is "punched"), I have to pull the choke out some. When the engine is hot and I'm in 4th gear, I push the choke all the way in and cruise there. But, when I stop and start again, the choke has to come out some. Pulling out the choke does more than change the fuel/air mix. It also causes a spark advance and so on. I adjusted the octane setting at the vacuum advance, but decided against a setting other than zero, since the same timing can be had several ways.

The manifold "heat valve" is stuck, but from previous posts, this should not affect a warm / hot engine ... the heat valve is stuck in such a way that it is correct for a warm engine (the weight is at an angle). So, I discount this as a problem.

The remaining things are vacuum, timing and fuel adjustments. I'm an antique tractor guy and these considerations are not so important on low RPM engines (often the difference in power (tractors) comes from governing the engine at 1800 or 2000 RPMs... easy to change - see the specs for Allis WD and WD45).

So, I have a lovely 1949 Chevy 4400 (which probably has a 1950 216 engine that has been bored to 236) that runs very well (no misses), gets awful gas mileage and has to be choked partly to perform well. **Deleted Joke about First Wife regarding choking and performance** I should have had that idea 20 years ago.

The vacuum is 18 inches mercury (Hg). The distributor turns like it is supposed to when the accelerator is depressed. But, I really need to understand where the fuel economy is going. :-(

Lee Prairie

I'm a little curious as to what set up is installed on your truck that would have the choke altering the timing.


One method not yet mentioned for adjusting timing is by ear. I've heard this method used since I was a pup. Easiest to do with a manual trans.

Vehicle at normal operationg temp, a straight stretch of road preferably a slight incline, traveling at a low speed in high gear, advance the timing until a very slight ping is heard upon acceleration. This engine speed should be a the lowest limit normally operated in high gear. If the distributor is in the ball park the octane selector might make the adjustment. Otherwise a little twisting of the distributor will be necessary. If you plan on doing some heavy hauling, a few degrees of timing will have to be removed.

I'm thinking there might be a problem with the enrichment circuit of your carb. A transfer slot could be obstructed. These are primarily for off idle performance but might be keeping the carb from keeping up with demand. They work in conjuction with the accelerator pump.

When you did the compression test, how did the plugs look? Any of them look different from the others? Any much cleaner than the others or have unusual deposits?

The less than $50.00 trick largely originated with J.C. : Penny who priced almost every thing at 0.02 less than the whole dollar.

Well Lee, I’ve been workin’ on this reply on and off since this morning. Just so ya don’t feel like the Lone Ranger, let me tell ya bout my version of the hesitation dance.
When I was a young man, I eat, slept, and drank cars. That was my life and that was the crowd that I hung with. I worked in the auto business up until I went in the service at 21 and I’ve always worked on all of my cars and many of my friends. I’ve always managed to keep them running well even before I got a drivers license which was way back in July of 1957. Me Pop was a journeyman auto mechanic trained back in the 20’s when they actually had apprenticeships for the trade, so my older brother and myself have worked on and built cars ever since we were little kids. My four years of high school was a breeze for me, because I spent four years in auto shop mostly helping the instructor because of my background. Later we ran midgets in the 60’s thru the 80’s. When I got bored with the racing I learned to fly and completely scratch built two aircraft with no help. One of them, a Pitts biplane, I flew in aerobatic competition for several years. I made my own engine mounts, which are a lot more complicated than those for an auto engine, built the devices for the inverted fuel and oil systems, adapted my own version of the Bendix fuel injection for the 320cu.in. Lycoming engine. Point here is I’ve always done all of my own work, chassis and engine and it’s always been reliable, I’m still here to tell about it is a testimonial to that.
Dad taught both of us to be very thorough, in our work. I’ve applied this same attitude to the restoration of my 1950, 3604. Before a the tires ever hit the road, the complete drive line, and brake system was totally disassembled brought down to bare metal anything that needed to be replaced was replaced with new or else re-machined by my self. The engine got the same treatment. Now all this narrative was just so you don’t think that I’m a newbe that has never twisted a wrench before. I taint the best in the world, but I’m a half assed good mechanic.

Now about that problem. My truck was 95% original when I got it and what was not correct is being put back the way it was from the factory. From the get go, everything that would come off the engine was taken off and rebuilt, meticulously that is. The head was completely gone over new seats and valves and resurfaced. All of the settings and adjustments have been made to the factory specs. The timing is on the ball and the fuel system is as clean and filtered as one can make it. The original carburetor, the Rochester ”˜B’, was the first model that was introduced in ’50. As I’ve said a dozen times on this forum it was all rebuilt with much care and special attention to make sure that all the passages were completely clear. Lead plugs were removed to gain complete access to the passages. New lead plugs were made; I machined molds that I poured new plugs into like one would do for a musket ball. In other words I know all the passages are clean and clear.
There has been a hesitation or a better description would be a stumble in this 216 from the day that I brought it home. It does it with the original Rochester, it did it with other Rochester’s that I have rebuilt and switched out and right now it has a Carter W-1 on it that I have been experimenting with for the last thousand miles or so. http://www.pbase.com/dennygraham/image/112012225/large .

It starts fine, it idles fine, it carries a solid steady 20 inches of mercury, it has a solid 110-120lbs compression and runs along at 55 … 60 mph just fine, point here, no fuel starvation. With all the carburetors that I have had on it, the acceleration is sluggish and it has a hesitation when you hit the accelerator. I’ve advanced the timing up to 10° above the ball, which doesn’t make any difference, and the only thing that seems to get rid of the stumble and give it a little more pep is to pull the choke out a bit when I’m accelerating.

Ignition you say, like maybe the distributor? Here are a few pics of the work on the distributor. http://www.pbase.com/dennygraham/image/112011732/original and it has a new coil.

I’m really at a loss on this one and still can’t find any one that has come up with an answer. So Lee, don’t feel like you’re alone Ke-mo sah-bee, there are others out here with the same stumper that you’ve got.

Bubbles you say???? That one I have no ideas for either!
Denny Graham
Sandwich, IL

Wow!!!

Yeah jyd, I know, that’s the way I felt after proof reading it, I'm all outta breath me self, I had to get my frustration out of my system some how yesterday.
But come on man, don't "hesitate", all this effort deserves some fresh ideas, I know Lee and I aren’t the only ones that experience these finicky engine problems.
I’m kind of disappointed cuz this is well into my third year of owning the truck and the only other person that I have met with an old Chevy is my buddy that I’m helping get his ’50 truck on the road. I thought I would find some VCCA activity around my area where I could meet some other guys and discuss the problems that I’ve encountered but I taint seen a thing except for this group on the forum since I joined you guys. I did meet one guy at a hot rod show that was supposed to be the leader of the VCCA local group but really got what seemed like the cold shoulder and seemed to lack interest in anyone new joining in.
I would love nothing better than to have a whiz-bang Chevy expert take a ride in the truck and say simply, “just fix the whatzit and it should run a smooth as silk.” But I just haven’t run into that guy yet. To bad ya live two thousand miles away jyd, you might just be that guy I’ve been waiting to meet.

DG

I don't have any recent experience on the later 216 engines. So take my suggestions for what they might be worth.

First I wonder what a slight increase in the bore of the main jet would do? The specification I have shows the Metering Rod Jet at 0.093" (a 42 drill bit is 0.0935"). Assuming that the drill is accurate it will increase the bore area ~ 1% which might not be enough to tell anything. If fuel starvation is the problem at higher speeds then either that or a substitution of another metering rod should help. Will not likely help fuel mileage but might make it run better.

I also wonder what changing the metering rod coordination would do? Never tried it but you can bend the linkage rod on a W-1 a little to change the mixture at a given throttle position. It is easy to set back if it does not help.

The other thought which is a stretch is cam timing. Don't have the passenger versus truck cam specs at hand so don't know if there is much difference. I do know that some truck cams have different duration and lift plus are degreed differently from passenger. It is because of slower operational speeds, more torque and to get better fuel economy.

The truck and car 216 engine uses the same cam. Actually is no difference in the engines.
If using a Rochester I would go to the next larger (more rich) main jet. Not knowing what you have may be a #52.
For the Rochester would also check for lost movement in the accelerator pump link. I think this was mentioned before but is the ball of the correct material in the pump circuit.
Seeing the problem exists with all carburetors I would suspect its an engine/ign. problem.
I had this problem with my 1950 and discovered the slider bar on the wiper motor had a vacuum leak. Also made the idle a little shakey.
Also try seting the idle mixture screw to the rich side (1/2 turn farther out).