|03-20-2006 05:34 PM|
Thanks for all the replies. Lots of good ideas.
I think Ill give them another chance.
Use chrome stem valves, have them honed to final size, & polish the stems.
Ill check the runout but would be pretty disappointed if it was greater
|03-20-2006 04:15 PM|
|machine shop tom||
MOST aluminum OEM production heads have cast iron guides. I see very few worn guides, and the heads I see usually have 125,000 + miles on them.
My experience with bronze guides is extensive. I personally used bronze guides for most of my guide replacement between 1985 and 1995 or so.
I found that they work best with a chrome-plated valve stem. An unchromed stem will wear rapidly both the valve and the guide.
Bronze guides CAN be sized tighter than cast iron, but there are some caveats involved. First, the valve seating equipment must be able to seat the valves to within the guide's tightness parameters. If your valve seats have .003-.004"" run-out, a guide sized to .0012" clearance won't work very well. Also, for a guide to be fit very tight, it must be straight and round. Typically, the best way to accomplish this is with a Sunnen valve guide hone.
The latest wrinkle in guide liner sizing is ball-broaching. It has supplanted sprialing and reaming as the more desirable way to size guides, in part because it provides a more intimate liner to parent-bore fit. Final sizing is still done with a hone.
Solid bronze guides (thick wall) are still sized by reaming and honing.
The bronze liners must be finished with a slight chamfer and with a honed finish. As was said by others, good installation techniques are needed for good service life from bronze (or any other) guides.
At this point I install more cast-iron guides than bronze liners. I feel that cast guides are more cost-effective and, for most applications, longer lived.
Most hot-rod type engines are not expected to last as long as a stock type of rebuild. I think that if hot-rod heads were to be checked after 60,000-80,000 miles, the mystique of the bronze guide may be a little dimmed.
|03-20-2006 02:33 PM|
|baddbob||what materials are the oem alluminum headed engines using for guides nowadays?|
|03-20-2006 10:16 AM|
But that was not the topic of this thread, was it?????
NAIRB and I agree.
|03-20-2006 08:05 AM|
|03-20-2006 06:13 AM|
The wear in the original guide is usually not a problem as long as the boring tool will straighten the guide ID. Unless the guide is really shot (over .015 wear). Then replacement with solid guides is done.
Iron guides are used only because they are INEXPENSIVE!! Check most aftermkt heads you will not see iron guides in anything above base line..
If you are getting "Gold" you have an abrading problem. This is an installer problem not the product.
|03-19-2006 10:07 PM|
My years of experience and that of my friend who is the best head-man I have ever seen says......... gray iron guides only. Drill them out, press in new ones, and go for the gold.
Factory heads are all gray iron and guides regularly last 100,000 plus miles under horrible maintenance conditions, so why fight the battle.
|03-19-2006 08:54 PM|
I worked with a guy who swore by them I just swore at them.
But he also polished the valve stems and claimed to never have any problems.
I guess they have their place but reman builders are probably more apt to go oversize stem. Maybe.
On a 502 big block with good oil pressure, brand new valves(unpolished), and the small stock umbrella seals. After 50 hour test the exhaust side had little "gold mines" on top of guides. Not good.
Do you have a wear limit that you automatically go to a thick wall guide?
How about straightness of the liner banana shaped guides ever a problem?
|03-19-2006 08:21 PM|
I have used the K-liners since 1994 with very few problems. The spiral grooving keeps oil in the guide and close clearances can be maintained. The secret is proper installation and trim, good valve stems (polished) assembly lube and snug initial fit.
I have pulled some of these heads with 250+thousand miles on them and had little wear problems.
I use them in my own engines.
|03-19-2006 07:00 PM|
Here is a link to what some of the benefits they claim it has.
|03-19-2006 06:30 PM|
Bronze liners are used in high production shops. They are fast to install, and they do follow the original guide geometry, keeping the seat concentric with the guide. However, they are thin, and the sizing balls used to swedge them into place is a little hokey in my mind.
I don't think you have enough material there for a sturdy bearing surface. Personally, I think a hardened 1/2 inch guide insert is the way to go.
Bronze must be honed in my mind to leave a cross hatch for a little oil to lubricate.
|03-19-2006 06:21 PM|
I have heard them referred as K Liners and the shop that installed them swore they were the hottest item, well 15,000 miles later they were worn out.
I would not recommend them unless you are on a very tight budget or enjoy replacing things with short miles on it.
|03-19-2006 06:05 PM|
Bronze guide liners
Since we have all hopefully put in our 2 cents on grooved cylinder heads I thought I would bring up a different topic. Thin wall bronze valve guide liners.
My own experience with them is not good. They seem to wear out too fast.
Does anybody have any tricks they would be willing to share about getting them to last?
Or pros and cons of why they would or would never use them?