Compression question

[Titleist16]

I am planning a rebuild and I am wondering about compression. I can get a set of pistons that are advertised as 9.2:1 for the 200. Hopefully I will be using a 78 head if I buy it, a moderate cam like 264, headers, 3 angle valve job, balanced. I was wondering if the 9.2:1 would be a good ratio for me? I live in Huntington Beach which is about 5 miles from the ocean but it can get hot in the summer (90-95). How much compression would it take off if I didn't have them plane the head to compensate for the thicker head gasket? Also, what is the stock compression ratio of the 200? Forged pistons are only a little more expensive, would you guys recommend those?

 

[CobraSix]

Try this link:

http://falconperformance.sundog.net/compcalculator.asp

It can get that hot in New England, I live and work right by the water. Well, use to live by the water, but still work by it. Anyways, I'm running 9.5:1 and I have absolutely no issues running 91-93 octance in the car.

Slade

 

[CZLN6]

Howdy Titleist:

The 9.2 pistons are the small dished replacement cast pistons and are a good choice. They will not give you a 9.2:1 compression ratio. They are identical to the pistons used in the '66 200s which had an advertized CR of 9.2.

9:1 to 9.2:1 should be a good CR goal for you given your elevation.

Know that the head will need to be milled to bring the '78 combusion chambers of 62 cc down to about 52 ccs and to compensate for the difference in the stock steel shim head gasket thickness of .025" and the aftermarket, composite replacement head gasket at .050".

That adds up to a mill cut of about .075". Be sure to use washers under the head bolts on reassembling. Measure twice and cut once!

Adios, David

 

[Titleist16]

What kind of compression can I get using the pistons for a 170?

 

[CZLN6]

Howdy Titlest:

The 170 pistons are not compatible with a 200 block. They have a smaller bore diameter. They are flat top.

I you want to go to a flat-top piston use Tempo 2.5 HSC. Same pin height and pin dimensions.

Other than increasing compression there is no advantage to a flat-top piston over the small dished. All things being equal, in a wedge type combustion chamber engine, the dished pistons will generate more power and be more resistant to Knock.

Adios, David