Has anyone ever tried JB Weld or other products to seal valve guides on 427 heads? Machine shop has tried three time to fix but the new exhaust guides leak water into the exhaust chamber.

Jim

 

Find a new machine shop! Sounds like that machine shop may have already destroyed your heads.

 

Yep. They tried to make them 'purty'...and over-machined them. Glue isn't the answer....it won't hold up in that vibrating, hot, oily environment.

 

 

My machine shop had to freeze the last set of guides before pressing them in the heads to keep them from leaking. I think he used a lot of red loctite too!

 

Let me say this first, you should avoid changing these guides whenever possible. There are so many other ways to do a repair without removing the originals, it's not worth the "risk".

If you're not familiar with the procedure you WILL ruin the heads.

The exhaust guides specifically are "stepped" and MUST be removed from the bottom in the chamber area and pressed/driven out towards the rocker arm side. You CANNOT remove them by laying the head on a bench, chamber down, and driving them "downwards", the wider (upper) "stepped" section of the guide causes the smaller lower section of the casting itself to crack.

If you have the opportunity to see the casting with the guide removed you will notice these exhaust's go directly through the water passages. They are "water-cooled" at the center of the guide. The "upper & lower" lands are 2 different sizes, not noticeable by eye! Upon reinstalling the "new" guides they must be installed in the same direction! From the top, rocker arm side, down toward the chamber!

(Add) If it turns out that your heads aren't cracked, the guides may just be improperly installed, but the chances are they're "split" on the bottoms!

Thanks, Gary in N.Y.

P.S. There really is no way of repairing the castings once they've been damaged from this procedure! The heat from the exhaust running actually "spreads" the cracks open!

 

My heads off ebay have this same problem. What are the ,"other" ways to repair this?

 

James:

Beating out the guides three times has pretty much negated the possibility of obtaining a good installation with stock guides at this point.

IMHO, your'e going to need to find a "real" machinist (not just the local automotive machine shop) to do this job. He is problably going to need to MAKE oversized O.D. guides to fit the enlarged bores in the head. This assumes that the heads have NOT been cracked or severely scored by improper removal of the guides (three times).

Goodson has cast iron "universal" valve guides that can be machined to fit. See link...

http://www.goodson.com/Universal-Cas...-Valve-Guides/

IN ADDITION.. Whoever is going to do this job will need to hone out the valve guide bores in the head with a precision small-bore hone to get them properly "cleaned up" and finished to accept the new oversized O.D. guides.

This will require someone who can utilize precision tools properly. Not just Bubba with a hammer and a guide driver.

Each end of each guide bore will need to be cleaned up with the hone and miked for size. Then, a properly sized new guide will have to be turned down on a lathe to provide the needed interference fit on BOTH ends of the guide.

Once prepared the new guide should be PRESSED in with a press with the head in a holding fixture. Chill the guide, use thread sealant on both the inside of the bores and the outside of the guide and press them into the head to just the proper depth.

IMHO I wouldn't try JBWeld, Locktite etc. Not in this situation.

And, when all that is done, Knurl and ream all the guides I.D. and re-grind the valve seats...

Good luck.

P.S. Hey everyone... quit trying to change guides with a hammer and a guide punch... Yea, yea, I know... It can be done... but none the less IMHO it's "just wrong"...

 

Google QMPracing in Chatsworth Ca. They can get it right the first time.
May have to try a few times they are pretty busy
818-576-0816 Mike or Brad
JB weld turns to liquid when it gets too hot fwiw