E31 head value

[CEgg11]

Hi all. I bought an E 31 a few years ago for a project, and frankly forgot I had it. What do they sell for now?

[LeonV]

Last one I sold went for $150.

[CEgg11]

Thanks. I looked on ebay and there are two - one that is dirty, untested for 400.00 and one that is ready to bolt on for 700. Asking is different than getting though.

[LeonV]

Thanks. I looked on ebay and there are two - one that is dirty, untested for 400.00 and one that is ready to bolt on for 700. Asking is different than getting though.

There's a rebuilt one locally that hasn't sold for years. I think he's down to $275 now. There really isn't anything special about the E31, the reason they were popular was because racers needed them. They have smaller valves, not bad but not great combustion chambers, and they're usually very corroded from age and poor maintenance. There were over 30,000 made, so they're not really rare either...

[Walter Moore]

The combustion chamber is smaller than the later heads, in part because the engine was smaller. Some people also talk about the head being a "quench" design, but I have never been able to track down what that means, or why it is a good thing.

Apparently if you are building a 2.8L full race motor for racing gas you can get crazy compression ratios with the E31. In a stock L24 the E31 gives you around 9.5:1 or something like that.

The down side, besides the valves being smaller than on the L26 or L28 heads is that the intake valve seats were brass, and didn't hold up well. When the intake seats go bad you have to have them cut out, and then you have to replace both the intake valves and seats with larger L28 intake valves. (Not that anyone minds, but the cost is higher than reworking later heads because there is more labor and parts.) If you install the larger exhaust valves, you have to either use it exclusively on an L28 motor, or on either a L24 or L26 you have to "eyebrow" the cylinder walls to create clearance for the valves. (Which seems like it ought to lower the compression ratio.)

If you have the head in a fully rebuilt condition, with larger valves ready to install it might be desirable. Otherwise it is pretty much just a core.

[conedodger]

Dave Rebello will be building a motor for me over the winter. I gave him the choice of several different heads. He wants to use my E31 on flat-top pistons in an L28 block. It will have really high static compression which I believe he plans on taking care of with duration on the cam...

[pbarcher]

Rob,

Can you provide more info on why Dave Rebello will use your E31 on an L28? Has your head been modified already, and if so what did you do?

Peter