All Small Six Distance from the top of the piston to the deck of the block with a piston at TDC.

[100_2023]

Hi fellow Ford 6 fanatics. I have a short block 200 that was built with flat top pistons with no valve reliefs or dishes in the top. I guess I need to measure the distance from the top of the piston to the deck of the block with a piston at TDC. It is a .030" overbore from the 3.68" dia original bore, making it a 3.710" bore. One of our members is looking at using this with his Classic Inlines head. He measured his combustion chambers at 46 cc's. I'm thinking the compression distance with the pistons was .035" below deck. Tell me what to do & how to calculate the compression ratio.

Thank you,

 

[Bill56]

Quick guess.
200 cu in = 3.3 liters. ( the overbore will add just a little)
3,300 CCs divided by 6 CCs = 550. (displacement of one cylinder)
550 divided by 46 = 11 ( do NOT go cheap on the gas! )
The displacement of the distance of the piston below the deck will drop that some, not much.

With no valve relief, it might be wise to mock up the head with no gasket and only one set of pushrods.
Put modeling clay on the top of the one piston where the pushrods are and hand turn the crack two turns.
This should leave imprints from the valves in the clay.
Slice across them to be able to measure the thickness of the un squished clay and that gives you the amount of valve clearance.
Add the thickness of the compressed head gasket you plan to use for real life clearance.

 

[bubba22349]

If the Pistons are at .035 below the block deck it would have a 10.00 to 1 Static Compression Ratio with 46 CC Combustion Chamber's. With the Camshaft info you could also find out the Dynamic Compression Ratio and know what grade of Fuel it would need.

 

[fast64ranchero]

Diamond Pistons has a nice Compression Calculator https://diamondracing.net/p-10-compression-calculator.html
But you would be about 9.9 to 1 static compression.

 

[100_2023]

Thank you guys. It has a Clay Smith camshaft (H-264-0-B). The single pattern 110 LC 264/264 Ad Dur cam; 214/214 Dur @ .050" lift. It is a 435/435 lift with stock 1.5 ratio; 464/464 lift with 1.6 ratio & 480/480 with 1.65 ratio rocker arms. It is one of the earlier profile camshafts from about 4 or 5 years ago, before they changed them recently. I will make for sure on the piston tops to block deck. I will measure. I can't find the paperwork on it. I found the paperwork on everything else except this short block.

Thank you again!!!

 

[bubba22349]

On the camshaft info you would also need to know the Intake Centerline or else when the Intake Valve Closes ABDC

 

[hodaka100]

Does anyone know of or willing to make a compression ratio calculator for the ford straight six? Where it is easy that you put in your stock engine and the fields are automatically filled and then you can change numbers for your modifications.

 

[rocklord]

It's easy to make a compression ratio calculator in Excel, or any spreadsheet program.
You have to make sure to include all of the volumes (combustion chamber, head gasket, deck recess, piston recess, piston stroke) all converted into the same values (cc's or cu.in). Add all of these volumes up, then divide by all of the volumes minus the piston stroke. This will give you the static compression ratio.

Hope this helps