View Full Version : Automotive head?

04-15-2005, 02:24 PM
So my local MC dealer tells me he thinks the previous owner put an automotive had on one side of the engine. Skidim tells me I can check the head casting number to verify and that simply looking at the outside (without removing the valve cover) won't tell you. So where can I find the casting number, and how long a number should I expect? The only thing I can see is either a "15A" or "20A" on either head.

'85 S&S......PCM/Ford 351.

04-15-2005, 02:50 PM
Aside from using brass freeze plugs, there is no difference between the 2. Do you have a problem with your engine? I have what would be considered "automotive" heads on my 84 S&S. I had a pair of GT-40 heads laying around that came off of my Cobra. I took the heads to a machine shop and asked to have them resurfaced, valve job and brass freeze plugs installed. They work perfect and I have no issues. What has your dealer told you specifically about the "automotive" head?

04-15-2005, 04:02 PM
I'm a little skeptical as he based his opinion on a quick visual of the outside and Skidim said that wasn't possible. Skidim mentioned the size of the exhaust valves may vary a little. They too talked about the brass vs steel plugs but haven't had a chance to double check. The dealer said his only worry is the EGR that looks like it was crimped shut. When I compare heads, both have the same bolt at the EGR, one simply has what looks to be a copper pipe crimped over, the other does not.

I replaced the automotive carb with a marine unit from Skidim and the dealer claims it doesn't run perfect; there is an intermittent miss at the low end and it struggles to get to max RPM. Sent the carb back to skidim (as it was missing the linkage for the secondaries) but they tested it and said it's running flawless. We'll see what the dealer says when I get the carb back.

Thanks for the input.....doesn't sound like I have anything to worry about.

04-15-2005, 04:15 PM
To continue on this path. The marine head should have a plug threaded into the port on the back where your EGR piping exits, as you have described. If you want to know what it should look like, check out the front of either head you have. I bet you there will be a threaded insert in those 2 spots. Ford heads can be used on either side of the engine, there is no left and right side, so there will be thermactor/egr holes in the front and back. You can get these plugs at any machine shop or you can go to a Ford dealer. As I said before, there is no difference. Your dealer was probably right in describing the head as automotive just by the piece of crimped pipe you said was extending out the back, that's understandable. I would have the correct threaded plug installed and be sure they check for vacuum leaks.