Hello Guys and gals, I am looking for information on a /170 engine. This 63 Valiant will just be a good driver/road car, so
I want to raise the compression up for more get up and go. I am thinking stock compression is 7:1 and I want at least 8:1
compression. Do they make/have a piston available for this? How much can the stock head be milled safely? Thanks for
any and all responses! Dodge33

Het Dodge33!
Are you going to rebuild the engine?
A simple compression bump can be obtained with a 70-90 slice on the cylinder head.
High compression pistons will be much higher compression than your 8 to 1 number.
With the head shave all your parts can be used, push rods, etc.

_________________
Hyper_pak

Thanks for the reply hyper_pak.... yes, it will be a full and complete rebuild, everything new.
The block has been bored, rods checked, crank turned & polished, holes chamfered, etc. Thanks very much for your response! Dodge33

Measure what you currently have and then "run the numbers" on an on-line compression calculator.
I like the one at the United Engine & Machine website:
https://uempistons.com/p-27-compression ... lator.html

Here are the stock 170 numbers to get you started:
Head Chamber = 54 cc
Piston Head = 0
Gasket Thick = .04
Gasket Bore = 3.5
Bore = 3.400
Deck = 0
Stroke = 3.125
Rod = 5.7
Intake Close = 50

This gives an 8.7 static compression and 7.6 Effective Compression Ratio
3 of the above numbers have a big influence on the outcome"
Head Chamber is likely bigger then the 54 cc I used above.
Your Bore will be bigger if over-bored. (3.460 = .060 over-size)
Intake valve closing point is camshaft & cam phase specific (50 is a good guess on a stock cam)

Change the bore from 3.4 to 3.46 and you get a .2 of a point compression increase.
Change the head chamber number to 58 cc (more likely) and you loose .5

The point: a 170 is more sensitive to changes then the 225 so Measure AND Calculate carefully so you end-up with the results you want.
DD