Question about new valve guides.......
 

I recently received a set (12 pcs.) of polybronze valve guides (930-104-321-50-M230) from PP for my 3.0 SC engine rebuild. Six (6) are lighter in color and the other six (6) in darker color. Obviously they came from two (2) different materials or production batches. I've never used before different color valve guides in a particular engine rebuild. Would it be prudent to use the valve guides from a single batch/color?

http://forums.pelicanparts.com/uploa...1421202000.jpg

Looking at the above picture of the valve guides, you'll see darker colored valve guides on top and the lighter color below. The picture was not able to capture the distinct color difference between these valve guides probably due to lighting or my cheap camera. Any comment, advise, etc. highly appreciated. Thanks.

Tony

This would be my guess: The guides are made from phosphor bronze - which has a very considerable copper content (90% or more) Due to this the bronze will discolor pretty quickly after manufacture - typically it will get gradually darker. The difference that you are seeing is probably due to some of the guides having been manufactured at different times. Remember also that valve guides are not electroplated - they are simply raw (untreated) material.

I happen manufacture using bronze and I have had specific bronze alloys produced to actually extend the raw finish color. We use up to 5% sterling silver - this helps keep the color a little more stable. We manufacture jewelry.

Discoloration process.......
 

Conda Green,

I've been using these poly bronze valves guides in the past and never had a set with mixed color. This was the first time I got a set of valve guides with different color and wanted to know if I should be concerned about this observation. Your information is well considered specially from someone working with precious metals. Thanks.

Tony

if you have a way to check hardness, the PB will be much softer, you will notice when reaming the guides after installed.

Or you could use the PB (darker color) guides in the exhaust and the others on the intake which many do when two different types of guides are used.

A very disappointed long time customer.........
 

Craig,

Will consider your suggestion about the two (2) different batches (lot) of valve guides. Pelican Parts won't pay for the return postage of these two different batches of valve guides if I decided to send them back (?). And PP sales rep suggested to order another twelve (12) valve guides and choose 12 of the same color and return the extra valve guides at my own expense. The fact that I have ordered parts in the $K plus amount already is very disappointing. My first reaction was to email Wayne Dempsey but decided to delay it. I've been buying parts from them since Tom Gould was handling the sales dept. and that was a long time ago. What were your recent experience with them? Never had any problem before with PP until the different colored valve guides arrived.

Tony

Take a light and dark. Put a drop of ketchup on the side and leave it for 2 days. Remove drop of ketchup and compare color. This will give you a raw view of both materials without oxidation/age considerations.

I think you are making a big deal about nothing. I wouldn't expect PP to accept them for a return unless you could prove they were the wrong material (i.e. the wrong part number).

Too say the least,glad I don't sell Porsche parts :eek::eek: can't see an issue here bronze can tarnish over time and thats the only difference I can see.
Return freight thats up to you,but surely its not that much????;)

Just checked and it's not April 1st so you must be serious.