The heads are all nicely painted with POR 15 gloss black. The chambers are cc’d. It should be time to install the valves. But I have a nagging bug in my ear.
Why are the combustion chambers that are listed in the manuals from Studebaker as being 54.5 cc consistently coming in at 5+ cc over that. Here is a nice chamber from one of the bad heads. This from an unmodified ’63 R1 engine with a 1557570.
I decided to check one to see if it was about the same as the heads that got a valve job and .005 removed from the head surface. What I measured was between 58.9 and 58.6 cc. Five of my chambers in the restored heads are within 1 cc of these numbers.
So what is going wrong. Time to send off the details to the Studebaker gurus in the Turning Wheels Co-operator . I have worked with Jim Pepper on my earlier projects and so I sent the note to him.
His reply was an insight into the way things were done by manufacturers back in the day. Apparently manufacturers including Studebaker left a little extra ‘meat’ on the head surfaces which resulted in the combustion chambers being somewhat over the stated cc. This was usually in the range of 2-3 cc. They did this so that if a head needed to be planed it wouldn’t result in chambers that were too small. My heads may have had valve jobs in the past without planing to compensate. This likely why mine seem to be up wards of 5 cc over after my valve job. But then again maybe Studebaker meant for the chambers to be 3-5 cc over – who knows!
So now things begin to make sense. As I said earlier I had thrown enough canaries at that cat so I’m not going to plane the heads any more for now. I should have no problems with detonation at 8.1:1 which is good. I can always pull the heads and plane them if I feel the engine isn’t performing as I like.
So onward I go – getting the valves installed.