TheSamba.com :: View topic

Mon Jun 26, 2017 9:14 pm

Hi, I have been a visitor to this Samba Vanagon forum for years but this is my first post. Today I ran into a surprise by a used pair of AMC head I have collected for years.

I did a measurement of the valves on the AMC heads. I also measured the valves of a used pair of VW OEM heads that I am trying to determine if they are still good. The AMC heads were pulled from a 1.9 and the OEM heads were from a 2.1. I believe they are interchangeable anyway.

The valve stems on the OEM heads measured as the specs listed: intake .314" and exhaust .351". However, the valves on the AMC valves are surprising: intake .311" and exhaust .311" as well.

My micometer isn't a high precision one so these numbers probably do not reflect the wear on the valve stems but the numbers do tell me what they probably were when new. So I think the thought of getting the OEM valves that seem to be in excellent shape from the OEM heads and install and replace the MAC valves on the AMC heads is simply a no go. The OEM valve stems of the intake valves will be slightly too fat and the exhaust valves will be way too fat to fit into the AMC heads.

Has anyone found out about this before? Or I simply have a pair of AMC heads with wrong valves and guides done by someone before? The heads are in very decent shape. I measured the stems near the tip where there is no possible wear to them.

By the way, I am working on the bottom end of a 2.1 WBX right now. I will post questions on a different post later.

Tue Jun 27, 2017 12:59 am

AMC heads have well documented valve failures. I recommend you to replace both of them.

I've never done it myself, so my advice stops here :lol:

Tue Jun 27, 2017 4:28 pm

Thank you. Yes, I am aware of the talks about AMC valves. That's why I have the thought of replacing them with those from my VW heads. But for some reason I don't seem able to do so because of size differences, meaning they are incompatible. This is quite a surprise. I never heard of such differences between AMC and VW heads. The only explanation maybe my AMC heads were rebuilt by some one prior to my acquisition. The valves were not of correct (although close) specification. The heads do look in excellent shape though. I guess I can have the valve guides machined for OEM valves to fit.

Tue Jun 27, 2017 6:10 pm

As I recall the valve stem sizes on a Vanagon engine were 8mm (.314) intake and 9mm (.354) exhaust. Could be wrong.

The AMC heads sounds like they have 7.9mm (.311) valves installed. Must be a vendor spec thing..for sure the exhaust valves are not exotic or sodium filled..the larger valve stem would of been used to help dissipate heat from the exhaust valve head.

The good news is your AMC valve guides are usually reamed to fit the valves..so if you use your 7.9mm inside diameter AMC valve guides and fit NEW VW Vanagon valves..the machine shop will be able to ream and fit your new valves to the AMC valve guides as there is plenty of meat on those valve guides to work with.