75 5C-4 heads

[Formula1973]

Ok general question here. The engine I have in my 73 Formula has 5C-4 heads. The engine is a 400, 481988 code and 400 stamped underneath.
From everything I have read, these heads were originally for a 350 4bbl date code on these are December of 1974.
Can anyone speak on this, if I am correct or why someone would do this? Higher compression?
Thanks and Merry Christmas

 

[melsg5]

it would slightly raise the compression or it was the only pair they could find after damaging an original head

http://www.wallaceracing.com/head1.htm

 

[cammerjeff]

It was pretty common to put the 4bbl 350 heads onto 400's in the late 70's early 80's to increase the Compression Ratio just a bit, and still be able to run the garbage unleaded premium of the day of around 89 to 91 octane. They would up the CR from around 8 to 8.8 to 1. doesn't sound like much but it helped a lot.
This was much easier and cheaper than putting flat top pistons in your engine. I would suspect that is why they were swapped in. No difference other that the smaller combustion chambers. They still have the big 2.11" intake valves, and screw in rocker studs. So they are not bad heads, not great but not bad.
And December 74 sounds correct as 5C heads are listed as early 1975 model year heads, so mid to late 1974 would be correct build dates for them.