Hot Rod Forum : Hotrodders Bulletin Board - View Single Post - Camshaft Options for SBC 350
View Single Post
  #6 (permalink)  
Old 03-27-2008, 02:17 PM
techinspector1's Avatar
techinspector1 techinspector1 is offline
Last wiki edit: DynoSim combinations Last photo:
Join Date: Oct 2005
Location: Zephyrhills, Florida, USA
Age: 75
Posts: 15,341
Wiki Edits: 326

Thanks: 1,504
Thanked 2,024 Times in 1,564 Posts
Cam and head gaskets will be the two most important choices you will make for this motor. The cam must be chosen with the correct intake closing point to support the static compression ratio of the motor and the gasket thickness will determine the squish (piston crown to cylinder head clearance with the piston at TDC)

You are in the same position most guys are when building a motor, starting off choosing parts without knowing the particulars of the motor. To choose the correct cam, you must know the exact static compression ratio of the motor. To choose the correct gasket, you must know the piston deck height (distance from the piston crown to the block deck surface with the piston at TDC).

You'll need the piston deck height first, so measure the depth of the piston in the bore. This will tell you the correct gasket thickness to use so you can add the gasket cc's to your formula to find SCR. You'll be shooting for a squish (piston deck height added to gasket thickness) of 0.035" to 0.045".

To find the SCR, you'll need 5 values. Cylinder cc's, combustion chamber cc's, piston deck height cc's, gasket cc's and piston eyebrow or dish cc's. I'll start you off with the cylinder, 738 cc's.

This might be a good opportunity to clarify the difference in deck height nomenclature for some of you.
BLOCK DECK HEIGHT: the measurement from the centerline of the main bearing bore in the block to the block deck where the head gasket sits. As produced by the factory, the block deck height on all small block chevies is 9.025".
PISTON DECK HEIGHT: the measurement from the top of the piston crown (the tallest part of the crown, right next to the cylinder wall) to the block deck where the head gasket sits. This measurement can vary considerably depending on the true rod journal throw from centerline, the true center to center length of the rod, the true compression height of the piston (centerline of the wrist pin to the crown) and the true block deck height. Piston deck height on motors from the factory might range between 0.025" and 0.035" for instance.

Last edited by techinspector1; 03-27-2008 at 02:52 PM.
Reply With Quote