I have an aluminum head and blew a head gasket after 15 years. The head was warped at about .030" due to the heat generated after we ran out of water at highway speed.
We found that the radiator shell rubbed a crack into the front side of the top tank and water leaked through the thin crack caused by the vibration. Why the engine has vibration is unknown to me . . . ;~) perhaps the very radical cam grind is part of the cause.
We all know that .030" is about a 1/32 of an inch and so now the cylinder head must be giving different compression ratios in each cylinder.
It still runs smoothly and I am wondering if the difference between cylinders is going to affect anything down the road.
I did not recently take a compression test after re-assembly but before the incident we had 92 pounds in each cylinder which gave us a compression ratio of 6.25 to one.
At this time the two end cylinders have had .030" removed and I am wondering how much higher their compression ratio is at this time.
I have a good compression tester with a full set of spark plug adaptors, the long hose and the gauge.
I am wondering if anyone could guess what the difference is between one and four and two and three and if it is a serious condition.
I will take compression readings when I take the car out of the trailer but right now I am not well enough to get to it and am lazily asking for opinions.
I am tinkering with the idea of adding a little bit of welded aluminum to the lower compression chambers in order to equalize all of the chambers. I think it best to modify the head than the pistons which would change the reciprocating mass.
Any input is welcome, even from my enemies who like to tease me.
The picture below was taken on one of Tony Bowker's fun filled San Diego Speedster runs at the beautiful Borego Springs in the California Borego Desert. We popped a soft plug and had a contest to purchase the oldest nickel in the crowd in order to keep the car period correct, note the period correct electric fan which obviates the need for a water pump but does not rob engine power to turn the fan. lol.
Frank, If you are concerned about the head giving different compression in each cylinder you should "cc" the head and that will let you know what size / compression you are working with in the head.
In my primitive shade tree world there are two test of significance - does it run smooth? You already answered that with a yes, and are the compression readings within 10% between the highest and lowest readings. You can run that test when you feel up to it or when a friendly T mechanic comes by.
If it runs smooth and well, I probably wouldn't get worried about it but the readings would give better info.
Hope you start feeling better soon.
I'm betting that it's negligible, but I would be real interested to see the results of your compression test.
BTW, I'm thinking an electric fan will rob just as much hp as a belt driven one. That's assuming you have a charging system. The additional load on the generator/alternator results in additional torque to spin it. First Law of Thermodynamics. Conservation of energy. You don't get something for nothing.
the volume of the .030 "thick" area in less than one hundredth of the cylinder volume.
If the volume of the head combustion chambers was exactly the same before milling (probably not) and the compression ratio was 6.25 to 1, then milling 0.030" of two cylinders would increase the compression ratio in those two cylinders to 6.47 to 1.
If the bore is 3.75", then the milling would decrease the volume by 0.331 inches cubed.
I guess that the head volume of each cylinder could be measured then adjust as needed to make them equal. I don't know if it would make any difference. Warped heads are milled every day and probably none have the volume adjusted to compensate for the milling. Also a compression ratio of 6.25 or 6.5 is very low by today's standards and I bet no change in performance would be noticed.
Frank, fine tuning is good, but I wouldn't worry about the difference.
Hal, the reason for using an electric fan is you can choose the effect and top rpm of the fan as needed, you don't need to follow the engine rpm.
I guess a fan connected to the engine needs to be designed for a certain cooling effect needed when the engine idles and the car stands still, then when the rpm increases at road speed and the car moves the fan uses much more engine hp without doing anything useful. The electric fan doesn't run faster at road speed, instead it might even be turned off, so a lot less energy from the battery needed than a belt driven fan robs from the engine.
About 40 years ago some engines (Volvo 164 comes to mind) used a hydraulic converter style of fan hub to lessen the fan drag at higher engine speeds - still not as energy efficient as an electric fan.
Some food for thought. I have done this before, as
to plumb a remote (from a school bus) heater core
underneath with a small electric circulator and
a fan. This can be controlled with either a manual
switch or thermostic switch. More coolant capacity,
I suppose even a short length of a home base board
section would work. The circulator I made from a
simple boat bilge pump, takes hardly no current it
only moves fluid. And then I think of a damper door
for inside heat for the winter.
I only turn the fan on when at a long traffic signal or climbing a long hill. The rest of the time it rests.
I had a VW Dasher that if I was going to be in heavy traffic I would stop get out and lift the hood and plug the fan in! Never did get around to replacing the thermal switch.
That makes sense.
Frank, I run a Z head on my '27 (yours looks like a Z). A bunch of years ago I blew a head gasket and my Z got hot and warped. I had it milled until flat could be obtained, but I don't remember how much. I found that when running the engine I got a knock. What I found is that with the head gasket removed #1 and #4 kissed (hit) the head. By using Dychem (blue bearing marking fluid) I found and ground away all the piston strikes. Then I put a gasket in there and checked to make sure no interference remained.
After that it ran fine... has for many years. You don't have to be concerned about the negligible volumetric differences in these chambers, but you better check to be sure that no metal to metal contact occurs between the aluminum of the pistons and the aluminum of the head!
The loss of volume due to the warpage and milling is insignificant compared to the volume of carbon crap which can build up on top of your pistons in normal use. The carbon coating of head and piston will not be identical from cylinder to cylinder. The way I see it the differences between cylinders introduced by milling is a mere speck compared to the log introduced by combustion debris build-up.
We have information on milling at our Tulsa website. If you trace the shape of the combustion chamber or a head gasket, you will get about 18 sq. in. You can use the to determine there is about 3 cc decrease in volume for each 0.010 removed from the head. 0.030 would amount to 9 cc or 0.2 to 0.3 change in compression ratio. I doubt this would have much effect.