I see some Model T heads advertised as a high head. Does that mean high compression head or does it have something to do with the measurement of the head? Thanks for the education, you all are great!
Has to do with the height of the head, not compression. Some early low heads actually have a smaller chamber, thus a little higher compression, but lack the increased water cooling capacity of a high head.
As you noted, the height of the head.
The 'high' one on the left is later head. The low one is earlier.
Are they interchangeable? It seems the high head would be desirable for better cooling. However, does the "gooseneck" sit higher and cause alignment problems with the top radiator hose?
This is an easy way to raise the compression on the later T engines 'a little'. The higher head came out in 1921? May not be exact but close.
They work fine but you have to slightly modify the outlet neck or add a 1/2" spacer to the outlet to bring it under the outlet on the radiator for alignment.
I couldn't notice any difference as far as the cooling is concerned. A good radiator is the key for good cooling.
1917 is year of change from low to high head. As far as compression is concerned, if you don't want to change the head on your engine, either install high compression pistons or mill a stock head. I have a friend who has milled a high head as much as .125, he claims.
I've had several low heads milled .125". When used with pop-up pistons, the performance is similar to a high-compression aluminum head.
It looks like the slant of the high head is less of an incline where the water intake is. It doesn't look like the connection to the radiator hose would be different from what it looks like in the picture.
I believe the heads are interchangeable. The water outlet is different for a brass radiator and a black one. The '26-7 Model U cars are entirely different.
On a low head the bolt holes stand two inches high. On the high head they're 5/8" taller.