Mustang '65 200 to '70 200 swap

[4Mustangs]

Other than the heads, carburetor/distributor and 6 bolt bell mount are there any other differences between the two engines that I need to consider?

With the chamber differences in the head, why did Ford keep the compression the same?

Which way to raise compression, Pistons, head or both?

What would be a max compression for a mild to moderate street engine?

Thanks in advance.
Ron

 

[CoupeBoy]

The '70 motor should be a dual drilled bellhousing bolt block, so it should drop right in. You should be able to use your old carb and distributor (if you want to) if the newer engine has a carb and distributor you can use that one as well.

Best way to raise compression.. good question, that question depends on what compression you are talking about.. static or dynamic.. Most will say to use the thinnest head gasket you can find and mill the head to compensate.. which leads to your next question.

What is the max compression for a mild to moderate street build.
9.2 (max) anything higher than that and you start running into real problems with engine pinging..

If you are going to tear it apart, you may as well throw an after market cam in there also, something like a 256/256.

(another)
-ron

 

[CZLN6]

Howdy Back Ron:

Q- why did Ford keep the compression the same?
A- They Didn't. '65 200 is rated at 9.2:1. '70 is rated at 8.7:1. The more interesting factor is that it is possible that nothing changed between the two engine years. 1969 to 1973 was a period of change and the only way to know for sure what you have with a '70 200 is to disassemble and measure. It wasn't til about 1974 that it became predictable as to valve size, hardened seats, intake tract volume and chamber volume.

Q- Which way to raise compression, Pistons, head or both?
A- 1st establish a zero deck height by decking the block. That is typically about .025" in most 200s with stock pistons. To be most accurate deck height should be measured with new pistons, bearings and machining done. Next, is to mill head and/or reshape the combustion chambers. Pistons should be selected based on intended use and load levels. Choices are cast or forged, dished or flat-top. Large dish or small.

Q- What would be a max compression for a mild to moderate street engine?
A- The answer to this question would vary depending on your locale- specifically elevation, and your intended cam. Longer duration than stock cams reduce cylinder pressure allowing more static compression. The big generality frequently used is to aim goal CR at intended gas octane rating. ie- if you plan to use 92 octane then a cr of 9.2:1 is a good ballpark CR goal. With an optimized combustion chamber and more duration more CR is available.

Hope that helps.

Adios, David