New one on me

J

JayJay

Well-known member
OK, Barners, here's the mystery (at least to me) of the day.

A couple of weeks ago I returned from a 3,400+ mile trip to Albuquerque (was going to the MAFCA convention in Ruidoso, but that didn't quite work out...). During the trip my car was plagued with very poor power going uphill (especially at altitude), and overheating. Part of the overheating was the 100+ we had all trip, part was undoubtedly the questionable radiator, and part may be due to the lack of power causing me to push the car harder than it might otherwise have been with a strong engine. Lack of power was there even at moderate temperatures.

Before we left I did a complete tuneup - points gapped to 0.020", set timing, and changed plugs. I did switch from Motorcraft TT10 to Autolite 3076 since the TT10 are getting harder to find. I checked and regapped the points halfway through, they weren't out much (0.015").

Mid-trip I pulled the plugs and found #1 and 2 look pretty normal to me (right plug in the photo attached) but #3 and #4 were developing a distinct orange tinge to the electrode. Got home and the orange tinge is much more pronounced (left plug in the photo). In addition, #4 seems a bit wet upon initial startup. These were not present with the TT10 before I set out on the trip. And I don't recall noticing the lack of power before, but I haven't pushed the car like we did on the trip.

Other than low power, the car seems to start and run pretty well. Clear cap shows spark at all four distributor terminals, and switching out the distributor body doesn't make a difference. New head gasket within the last year. Compression is consistent at 80-90 psi. It's not using any appreciable amount of water other than what spews out when it overheats. Oil consumption is nominal for an old engine, quart every 500-750 miles.

I'm running stock Zenith carb. I purchased the car a couple of years ago and I don't know much about the engine except that it's 0.080" over with a large lip at the top. Some of the valves are way open (0.025" or higher) but there aren't adjustable lifters, so I'm presuming the cam lobes may be quite worn. It just might be, in spite of the good compression, that I have Old Tired Engine Syndrome.

I have a reconditioned engine with newly reground Jim Brierly "C" cam, adjustable lifters, valves ground and new rings that I'm going to install. And I'm going to switch back to TT10. Relatively new Bergs HD radiator going in with the replacement engine.

But the plug color of the 3076 and the lack of power have me confused. Anyone have any ideas of what else I could check? I don't want to do a parts cannon type of thing.

Thanks a million.
 

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Having the cylinders bored out by 0.080 will not help with the cooling. But, as you say, it was probably a questionable radiator.

Power from an engine comes from having good compression and good breathing and good ignition. With the larger gap at the valves and, as you say, a possible worn cam, you are not going to get good breathing.

The large lip at the top of the cylinder means that the engine is worn.

Here is what I would advise, and you may not like my answer. Rebuild the engine by sleeving it or buy a Burtz kit. If you plan other long trips the Burtz kit will give you better service and will cost you less than a rebuild in the long run. Buy a new radiator from one of the suppliers. Buy a high compression head. If you don't already have one, buy an overdrive. If you have good mechanical skills, the Burtz engine is not hard to assemble. The instructions from Terry are excellent.

Regarding the orange plug. It looks like it may have gotten too hot and possibly with some oil consumption in that cylinder. It may be the wrong heat range. Going back to the TT10 or a different, colder, plug may help.
 
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nkaminar said:
Having the cylinders bored out by 0.080 will not help with the cooling. But, as you say, it was probably a questionable radiator.

Power from an engine comes from having good compression and good breathing and good ignition. With the larger gap at the valves and, as you say, a possible worn cam, you are not going to get good breathing.

The large lip at the top of the cylinder means that the engine is worn.

Here is what I would advise, and you may not like my answer. Rebuild the engine by sleeving it or buy a Burtz kit. If you plan other long trips the Burtz kit will give you better service and will cost you less than a rebuild in the long run. Buy a new radiator from one of the suppliers. Buy a high compression head. If you don't already have one, buy an overdrive. If you have good mechanical skills, the Burtz engine is not hard to assemble. The instructions from Terry are excellent.

Regarding the orange plug. It looks like it may have gotten too hot and possibly with some oil consumption in that cylinder. It may be the wrong heat range. Going back to the TT10 or a different, colder, plug may help.
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Thanks, NK. All good suggestions. I had already thought about the bore, plus I’m not sure just how crudded up the water jackets and radiator are. Already have a Mitchell O/D in it.

I have a Burtz already but it is going into the ‘30 Town Sedan I’m building (as will the Mitchell O/D). I took the engine that came out of the ‘30 (0.040” over, ran good when I took it out, all measurements within or just out of spec), put a new cam in it and that’s the one I’m putting in the ‘31. I have a 5.2 head that will go on it, and a relatively new Bergs high capacity radiator. That will hopefully get me by until the ‘30 is done, which is intended to be the keeper. Then I’ll sell the ‘31.

Oh, talk about DOH! After I posted this, I went for a drive and noticed the ammeter was discharging. Turns out the fan belt was loose. The same fan belt that turns the water pump…
 
I have found that opening the GAV a bit in higher altitudes gives a little power boost. Haven’t driven in hot weather at higher alts, though, so I can’t provide any data there on GAV affects.
 
700rpm said:
I have found that opening the GAV a bit in higher altitudes gives a little power boost. Haven’t driven in hot weather at higher alts, though, so I can’t provide any data there on GAV affects.
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Thanks. On this trip we had recurring 90-100+ F at 5K feet and above. Highest point was 9600 ft (Sonora Pass, California Sierra Nevada range), many 7000 ft climbs coming across US 50. I’ll try opening up the GAV next time.
 
Hi temperature will cause lower atmospheric pressure like higher altitude. The combination will definitely cause lower performance.

Your loose fan belt may be a partial cause for over heating. But the Model A water pump is over sized so maybe not. Some people cut down the impellers to reduce coolant flow.

Did you ride the train in Durango?
 
nkaminar said:
Hi temperature will cause lower atmospheric pressure like higher altitude. The combination will definitely cause lower performance.

Your loose fan belt may be a partial cause for over heating. But the Model A water pump is over sized so maybe not. Some people cut down the impellers to reduce coolant flow.

Did you ride the train in Durango?
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We did ride the train. Rains the previous week caused a huge rockslide and closed the upper part of the track, but it had been cleared in time for us to make the full trip. Then the night after our trip another rockslide, so we lucked out. We had a beautiful day on the train between the storms, until we got back to the hotel and I found a flat tire on the Model A. That’s another story, though.

Car was running too hot today in just modest temps, so loose fan belt wasn’t it. I’ll try flushing the engine but since the new engine is ready to go in I’m not going to spend too much time chasing it down.
 
Have you retorqued the head since encountering overheating and high altitudes? You might have a small localized gasket water leak between 3&4 even though the gasket is 1 year old. The tinge might be a residual of burned coolant.
 
JayJay said:
Thanks. On this trip we had recurring 90-100+ F at 5K feet and above. Highest point was 9600 ft (Sonora Pass, California Sierra Nevada range), many 7000 ft climbs coming across US 50. I’ll try opening up the GAV next time.
Click to expand...

It’s the opposite, higher altitudes have “thinner air”, which will cause the car to run rich. You should lean out the GAV if you spend significant time at higher elevations. Remember, high elevation is all relative to the elevation you live and drive at. 7000 ft isn’t high if you live at 6000ft, vs 7000 ft and live at 600ft.
 
Hitman said:
It’s the opposite, higher altitudes have “thinner air”, which will cause the car to run rich. You should lean out the GAV if you spend significant time at higher elevations. Remember, high elevation is all relative to the elevation you live and drive at. 7000 ft isn’t high if you live at 6000ft, vs 7000 ft and live at 600ft.
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I think the altitude of my house is on the order of 80 ft MSL. So yeah, 7000 ft is significant. 8900 ft is even more significant.
 
CT Jack said:
Have you retorqued the head since encountering overheating and high altitudes? You might have a small localized gasket water leak between 3&4 even though the gasket is 1 year old. The tinge might be a residual of burned coolant.
Click to expand...

Good point, Jack, thanks for the reminder. And the stud between #3 and #4 is that pesky one that you have to take loose to remove the clamp from the ignition cable.
 
You might want to also check that you have the polarity of your coil correct. It is an easy check with one of these polarity checkers from just about any Model A parts vendors:

547286


Brad in Maryland




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I agree with the point that altitude change causes a pressure differential but why didn't 1&2 tinge the same as 3&4?
 
My guess is 1&2 are burning leaner than 3&4 , you have adjusted richer to compensate the leaner mixture on 1&2 so 3&4 are running richer? A wild hair guess
 
If it was my A, I'd check for an intake manifold leaking slightly, that'd explain the color difference in the plugs. Also important, make sure your timing is set so that when you pull it all the way down you hear some definite ping. Then lift just enough so the ping goes away. Then, no matter the settings otherwise, you know your timing is optimal. You CAN'T beat your ear to set timing, no if's and's or but's required.
 
I think that your problem is, for the most part, the altitude. Performance of a gasoline engine at altitude is a direct function of compression (obviously there are other factors as well that would be the same as at sea level). With a Model A’s low, low compression ratio power will drop off dramatically as altitude increases. Regarding the adjustment of the GAV, it makes sense that leaning out the mixture (clockwise on the GAV) would be what was required but ya never know and it certainly is not difficult to tinker with. If RPM got better performance by richening up the mixture, I’m not going to argue with him, it may have worked for his car. The compression is so low on a banger that anything could work, who knows? Not enough spark advance can cause overheating too. I don’t recall if this has already been covered but the rubbing block on “modern” points can wear down in a hurry (few people know how to properly lubricate them) which will retard the timing as well as limit the coil saturation. If performance returned to “normal” after returning home then I would write it off to the altitude and forget about it. You could spend years trying to find a problem that doesn’t exist . Just my 2 cents
 
jeepguy1948 said:
I think that your problem is, for the most part, the altitude. Performance of a gasoline engine at altitude is a direct function of compression (obviously there are other factors as well that would be the same as at sea level). With a Model A’s low, low compression ratio power will drop off dramatically as altitude increases. Regarding the adjustment of the GAV, it makes sense that leaning out the mixture (clockwise on the GAV) would be what was required but ya never know and it certainly is not difficult to tinker with. If RPM got better performance by richening up the mixture, I’m not going to argue with him, it may have worked for his car. The compression is so low on a banger that anything could work, who knows? Not enough spark advance can cause overheating too. I don’t recall if this has already been covered but the rubbing block on “modern” points can wear down in a hurry (few people know how to properly lubricate them) which will retard the timing as well as limit the coil saturation. If performance returned to “normal” after returning home then I would write it off to the altitude and forget about it. You could spend years trying to find a problem that doesn’t exist . Just my 2 cents
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Good thoughts. No question that altitude was a factor. What I haven't mentioned is that I was on a tour with five other Model As, and they kept passing me like I was standing still, especially on the climbs. Some of them were running Weber carbs, but otherwise pretty stock engines. Whenever I would come to the slightest uphill I would just fade, while the others would power on through. So I think that there is something remarkably different about my car compared to the others. Thank heavens I had the Mitchell O/D so I was able to drop down into second over for the climbs, otherwise I would have been toast. On a couple of the climbs I was down into second under and even first over.

I already have another refurbished engine I was going to put in anyhow, so I'm not going to spend a whole lot of time chasing this one down. As suggested I'll check head torque, coil polarity and manifold leakage the next time I have it at the shop, but otherwise I'm going to just pull the engine, replace it with the refurbished one, install the better radiator and get back to driving.

Thanks all for your most helpful suggestions.
 
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