Loose Valve Guides

The exhaust valve guides are loose on a 1973 850 engine I'm building. First a little more detail, both intake and exhaust guides are cast iron (I thought all 850's had bronze guides). When I say loose, the exhaust guides are able to move up and down (but not wobble) at room temperature. One guide can move about 1/16" by pushing with my fingers. The other guide can be removed with a drift and light hammer taps. The I.D. wear is still within tolerance specified in the repair manual.

Here's the question, can the exhaust guides be re-installed with red Loctite? Red Loctite is supposedly good to 400 degrees F. That's the same temperature I normally use to install new guides. If I decide to install new guides, what is the recommended interference fit? Is it the same for cast iron and bronze guides?

Please enlighten me with your collective wisdom.

Oversize valve guides are usually available.

I can tell by the sound of your voice you are willing to drift in some over sized guides yourself and call it good.
Noble indeed.
Valves should be installed by someone who does it for a living so they can press in new valve guides, ream them to the stems which have been checked out.
then cut the valve seats so they are perpendicular to the valves.
It usually cost me about $500 for a complete job.

The head I have now is just one valve job away from a Full Auto head

mechanic matt said:

The exhaust valve guides are loose on a 1973 850 engine I'm building. First a little more detail, both intake and exhaust guides are cast iron (I thought all 850's had bronze guides). When I say loose, the exhaust guides are able to move up and down (but not wobble) at room temperature. One guide can move about 1/16" by pushing with my fingers. The other guide can be removed with a drift and light hammer taps. The I.D. wear is still within tolerance specified in the repair manual.

Here's the question, can the exhaust guides be re-installed with red Loctite? Red Loctite is supposedly good to 400 degrees F. That's the same temperature I normally use to install new guides. If I decide to install new guides, what is the recommended interference fit? Is it the same for cast iron and bronze guides?

Please enlighten me with your collective wisdom.

Click to expand...

No Commando motor used bronze guides as OEM.
The guides will need to be replaced with oversize guides after reaming the hole in the head for the correct interference fit.- .0015 except RH4 intake guides which should be .001 for bronze guides- they will need to be a little tighter for cast iron. It they are driven in too tight they will crack the head. Locktite will not hold. Jim

Jim, have you ever done dental implants? You wouldn't believe what my dentist wants to charge me.

No one has brought up the issue of heating the head during installation of guides.
installing-valve-guides-question-t9742.html

RennieK said:

Jim, have you ever done dental implants? You wouldn't believe what my dentist wants to charge me.

Click to expand...

No. but if you want to stop by I will give it a shot....

rx7171 said:

No one has brought up the issue of heating the head during installation of guides.
installing-valve-guides-question-t9742.html

Click to expand...

Absolutely. The head needs to be at 350-375 degrees before removing or installing the guides.

Actually the best way to remove the guides is to bore them out. It preserves the interference fit of the guide and will often let you re- install standard size guides.
Jim

Excellent advice from Jim on remvoing the guide by boring. I hear too many stories about oil leaking between the guide and the guide bore, which usually starts shortly after the guides are replaced by a "reputable" machine shops. They pound out the old guide cold, and pound in the new guide cold, scoring the bore, and creating a pathway for the oil to leak.

Check out this video. Not a boring operation, but a "core drilling" operation. Same idea, and should avoid the issue of scoring the guide bore:
http://www.youtube.com/watch?v=2ZtI9vN5iUI

Stephen Hill

I found this video on blacksmith style guide installing on Al twin head. It cuts off as he's about to deal with clearances.

[video]http://www.youtube.com/watch?v=GEg18pE0PHQ[/video]

Thanks for all of your input. I was trying to find an easy shortcut but you have convinced me otherwise. I'll be installing over-sized guides.

Guido suggested only a pro should tackle this job but I've seen too many botched jobs by so-called pros. I'm not without some experience (been building hot rods and motorcycles for nearly 50 years, Nortons for the past 14 years).

Again, thanks for your comments,
Matt

mechanic matt said:

Thanks for all of your input. I was trying to find an easy shortcut but you have convinced me otherwise. I'll be installing over-sized guides.

Guido suggested only a pro should tackle this job but I've seen too many botched jobs by so-called pros. I'm not without some experience (been building hot rods and motorcycles for nearly 50 years, Nortons for the past 14 years).

Again, thanks for your comments,
Matt

Click to expand...

Jim was right about that no one mentioned that you have to heat the head first before extraction and upon installation of the guides.
About that "only a pro should install them" comment, most people do not have a press, a reamer, an oven to heat the head or valve grinding equipment.
Now if you have all that stuff and have done this before then do it.
You're initial post asked if you could just glue them back in. To me that indicates a novice approach.

To me a pro is someone who specializes in a specific trade.
Didn't mean to offend you Matt.

Guido,

No offense taken, your comments were very appropriate. I just don't fit the normal Norton Owner category.

Matt

If you are really good with precision measuring tools that can do small bores, and the holes for the guides were not so loose they were hammering themselves out and leaking, then you may be able to mix and match oversize guides and get the head useable with a minimum of expense and work. Maybe even have someone grind the O.D. of some guides for a custom fit.

Once they are in and tight and reamed, the tell-tale will be how they line up with the old seats when you check them with some fine grinding powder or machinist blue. If they end up being non-concentric then it may be time to check the cost of replacing the head against sending it to a known expert with experience in fixing that sort of problem.

In this day and age a "virgin" head is a prize to be well taken care of. Do anything you have to do to keep the original guide bores and seats as long as you can before resorting to any machine work. The reason for this is because unless you can afford to pay the very best names in the business to do the work you can get into trouble. The general automotive machine shop that is not Norton specific in some way has a good chance at doing a lot more harm than good when he fits your Norton job in between Jimmy-Joe's stock-car head and surfacing someone's brake rotors....

I love to follow these threads. I'll throw in my .02.
I now do my own valve jobs and have also done several for local norton club members. This was after I also had "pros'" do one for me..."do" as in butcher...
IMO a pro is one who will take money for what they do or attempt to do. Being sucessful at doing a particular type of head is an entirely seperate issue...
Sometimes you learn the particulars of a certain casting like a norton head or a $3000 lotus twin cam the hard way. Therefore even a good shop for chevy or triumph is no assurance they know how to do a norton head. I have bought, acquired or made a whole range of head working tools for well over $3000, and in 2 decades it has easily paid for itself in 2 lotus and a half dozen norton valve jobs.

As Guido mentioned, If I do a head it is a majority of $500 and especially the 850's get cracked checked before I even touch it, as you may know that probably half of all RH4 850 heads are cracked... even frome new. Does your "shop" automatically crack check your head or even know the probelm exists? So if someone shows up at my door thinking a valve job is $150, they only get a blank stare from me... and get shown the door.

These days, If I am so unlucky to have head that need an OS guide I clean up the bore and measure. Well it's 2.5 over and I take an 10 OS guide and cut down to fit with the right interferance fit.

Unfortunately I don't get to do much bike or mechanic work for that matter... since these days I'm mostly doing "constuction " work on my new (very old) shop. :mrgreen:

THIS i'd love to see!! LOL... you guys crack me up. Cj


by comnoz » Wed Mar 14, 2012 6:41 pm

RennieK wrote:
Jim, have you ever done dental implants? You wouldn't believe what my dentist wants to charge me.

No. but if you want to stop by I will give it a shot....