<VV> Re: sleeved valve guides, and bronze

[BobHelt@aol.com]

In a message dated 8/15/04 9:35:26 AM US Mountain Standard Time, 
pottsf@msn.com writes:

> I'd like to reqest some basic education, here. What is the idea of
> installing bronze sleeves in valve guides?
>    Is a bronze lining supposed to be superior to a "bare" guide?
>    Is a new guide either so expensive or so difficult to install that
> relining is cost-effective?
> 
Hi Joe,
Looks like no one else is going to answer, so I'll give you my opinion. To be 
sure there are others out there who may disagree.

First, I'd like to comment that your failure seems to be related to a 
cracking of the guide, and not to unusual wear or lack of lubrication. My guess is 
that the guide was cracked during the installation of the bronze insert. But who 
knows for sure? Strange things DO HAPPEN. And sometimes it's just impossible 
to determine a cause. Maybe even, the guide was defective all this 
time.....????

OK as to bronze inserts. When you have worn guides, there are only a few 
options available to you. You can ream and install oversize valves (stems). But 
this isn't often done because of the lack of these valves. Besides there is the 
expense of new valves. Similarly, you can replace the old guides with new 
ones. But there are potential problems here too. The head has to be heated to 300+ 
or so degrees to get the guides out. Also does the shop have a fixture and an 
appropriate press, or will the mechanic get a BF hammer and start banging on 
the guides? I doubt that all the banging is good for the seats and the 
stuctural integrity of the head (think warp...) Then there is the cost involved here. 
Labor, new guides, heating.......  Installing the new guides is tricky too. 
Got to get the right depth. Got to make sure the fit is tight because removing 
the old guides removes some material. Usually 0.001 in. oversize guides are 
installed. Do they go in easily...or are they a bear? Now that you've got new 
guides installed, you have to be sure that the stem hole is PERFECTLY concentric 
with the valve seat insert. If not, grinding the valves will be a problem. 
Often you will find the stem hole is not concentric and will require some work 
or another new guide. Anyhow there are potential problems and lots of costs 
here.

Lastly in the options list is the installation of an insert into the old 
guide. This is easy, cheap and highly satisfactory. Getting an insert installed 
into an old guide requires using a type of material that will work and will go 
in easily. Bronze is a good material for the stems to run in because it 
requires less oil than CI. Bronze installs easily with a minimum of fuss. No other 
material is quite so good. A CI insert isn't malleable, and easily cracks or 
breaks when you are trying to install it. There isn't much of any material that 
can be easily installed, fitted exactly, with no damage, and serves as a good 
bearing material for the valve stem. And is inexpensive.

Besides bronze inserts have been used for decades with highly satisfactory 
results. 

I hope that this helps.
Regards,
Bob Helt