MTFCA Forum

Question : Can a 'low' head be used on an improved 26-27 with the water outlet mounted fan, without causing interference problems for the fan due to a slightly lower mounting position ?

There is almost no difference in the front neck mounting position. There may be some variation due to heads having been milled, some variation to minor casting shifts from the factory, however, I have yet to see a significant variation based upon early low heads versus the more common high heads.
About ten years ago, this subject came up. I had three late brass era low heads, loose, not on an engine. And I had three common later high heads, one a no script head (either replacement or I am told used by the factory in 1927?).
I put all six heads on a cleared off smooth work table, and slid them around butting the outlets against each other in every conceivable combination.
I had one low head that was about 1/8 lower than any other, however, it clearly had been milled excessively. And I had one low head that was a tiny amount higher than any of the high heads (less than a 1/16 higher).
On a few occasions since, I have double-checked myself, because this idea keeps coming around. All mine are still all very close to the same height.

The low head water jacket may be "lower", however, the hump running up to the outlet on a low head is much higher than that is on the high heads.

Here is a side by side comparison. The low head has been milled at some point in the past. Just as Wayne said, there really is no difference in the mounting position of the outlet.

Terry,
A high head is to provide more volume for coolant, why would you want to put on a low head?

High head is 3.97-1. Low head is 4.2-1. That little bit of difference is not worth the using when factoring the lower cooling capacity IMHO.
I would strongly recommend spending the money for a Prus head if you want a noticeable power/speed difference.
26-7 heads were slightly less compression than earlier high heads due to poor fuel quality @ the time.

The low head would require shorter head bolts. Weren't the earlier head bolts smaller than the later ones?

TXGOAT2 wrote: ↑

Sat Sep 20, 2025 1:13 pm

The low head would require shorter head bolts. Weren't the earlier head bolts smaller than the later ones?

Only very early like 1909/09 (3/8"?) then were standardized to 7/16". Length was changed when the high head came out.

A shaved head and the overbores typical today would probably get you about the same compression increase. Modern rings would probably help gain some compression pressure by reason of better sealing over a wider operating range. Modern oil might help a little, too. Back in the day, many Ts ran with heavy carbon deposits, and some may have achieved pretty good compression pressures at lower operating speeds.

Not much difference in the later stock heads 4.0 vs 3.8.

On one of the T's I have came with a low head when I bought it. Still on it. It also has a low radiator. I have had no overheating problem. If the water passages inside the head and block are kept clean and you run antifreeze all year around, even in Southern California, don't have any problems with it. I always use 50=50 antifreeze and or distilled water, because of hard water from our well which will fill things with lime and calcium deposits.
Norm

Humblej wrote: ↑

Sat Sep 20, 2025 12:11 pm

Terry,
A high head is to provide more volume for coolant, why would you want to put on a low head?

Jeff, John, Pat, Mark, and Frank, I was asking because I have a high compression REEDER aluminum low head I wanted to try. I know I'll have to use 'low' head bolts.

OK, good to know, because everyone has been addressing the fit of a Ford stock low head.