IH SV/4 Popper combustion chamber volume

[Robert Kenney]

I have been collecting data on IH sv related cylinder head volumes while rebuilding various versions of IH engines. As part on the redo I take the time to cc (bouret) the combustion chambers of the heads that have not been milled. I will begin logging the data hear as I get it along with the proper method to cc your own.


I am currently building a non ic 392 for a local club member. The engine is .030 over so along with the data used to calculate compression ratios the new displacement needs to be taken into account. @ .030 over bore the 392 becomes a 396.

The chambers in these particular (stamped # 434515 c92) heads are = 85 cc
note that heads have had the chambers cleaned up a bit adding maybe 1/2 - 1 cc

Head gasket volume @.040 compressed thickness = 9 cc

volume associated with the piston being .033 below the deck = 7.332 cc

piston d shaped notch volume = 10 cc Corrected to measurement

Each cylinder's swept volume is 49.576 cu/in (812.4 cc)

add all volumes up and you get 923.732 cc
divide that number by the non swept volume which is 111.332 and the compression ratio is = 8.29 -1

we will be milling the deck of the block .033 (zero decking) so remove the 7.332 cc from the calculations and you get

total volume of 916.4cc

divided by the new non swept volume =104cc

for a new compression ratio of 8.81-1
if we can remove 2 more cc we can achieve 9.0-1 this will probably come from the heads milling .015 from them.

I recommend leaving it at 8.8 - 1.

 

[Robert Kenney]

A quick note on the above setup.

Before machining the deck the engine will be mocked to verify for sure that the piston is .033 in the hole.

Silvolite pistons with a compression height of = 1.907

stock unmolested connecting rods ctoc distance = 6.753

cylinder block deck height = 10.521

crank stroke = 3.65625

 

[Robert Kenney]

Finished mocking and rechecking piston notch volume.

I first measureed it at 12 cc, but today I checked it the correct way and find it to be 10 cc. I updated the data in the first post and recalculated the compression ratios.