Late Model 170 Head

[kukm66]

Does anyone know if there were improvements on the 170 head later on in the years? Larger log, carb bore?

 

[mustang6]

Yes, the 1969 1/2 - 1972 170 heads had the larger 1.75" intake carb bore, the bigger intake log, 1.649" intake valves, 1.38 exhaust valves, and 52 cc. combustion chambers. Until the larger valved 200/250 heads came along in the late 70's, the later 170 heads were the best for performance and compression.

 

[mustang6]

Here's some pictures of one I had that fits the description:

 

[CZLN6]

Howdy:

Note the rounding of the corners of the chamber opposite the spark plug hole. That is a tip off of the smaller 52 cc chambers. The larger 62 cc chambers are much more squared off. This Kidney shaped chamber gives a slightly higher quench to bore ratio. Valve shrouding is still a limitation.

Thanks for the great photos mustang6.

Adios, David

 

[mustang6]

For comparison purposes (and to further David's description) here's a couple of photos of a '79 250 head that I recently had milled down to 50 cc. combustion chambers for use on a 200 (new valves came from Mike). I was cc:ing the chamber in the photo just to make sure after I got it back- that 2 cc. per .010" rule of thumb worked perfectly!

David, just by looking at the comparison it would appear that the intake valve on the 250 head is more severely shrouded than the smaller intake in the 170 head. Comments?

 

[CZLN6]

Howdy Back:

That is entirely possible and it may vary from head to head. As has been said before, Quality control on the casting process was not very precice. The biggest difference is the size of the intake valves.

Adios, David