Sealing Valve guide bores

rx7171 · Jun 6, 2014

Torontonian said:
Probably the inlet valve guide seals. Once put my head into a reputable shop ( you can easily guess which city..) , mild smoking ,pulled head to find NO seals ! Found several teenageres doing work to learn owner had teamed up with a college and a gov't apprenticeship program. Next time HE does the work only. :!:

My guess seals too.
I had an experienced shop that specialized in old English bikes rebuild my head.
Had smoking problem one side that had me replace rings, then new pistons and rings and still smoke.
Took head back to shop and found one of new valve seals on intakes was split! Probably from installation.
If smoke only one side I'd suspect the seal but not so much if both sides.

I'd want to confirm your shop heated head prior to installing guides and correct oversize for guides used.
Does your receipt indicate oversize?

pommie john · Jun 7, 2014

I don't think it's the seals.

I've replaced them twice. The exhaust guides are obviously leaking, and they don't have seals, so I need to address that somehow, also it seems likely that the oil on the inlet guide is coming from the guide bore, not down the valve stem , so I really don't think it's the seals.

rx7171 · Jun 7, 2014

pommie john said:
I don't think it's the seals.

I've replaced them twice. The exhaust guides are obviously leaking, and they don't have seals, so I need to address that somehow, also it seems likely that the oil on the inlet guide is coming from the guide bore, not down the valve stem , so I really don't think it's the seals.

Yes your pictures are clear on that, including the exhaust guides that usually don't need seals anyway.
Since it appears all are the problem it appears a faulty installation.
A correct installation requires oversized guides and correctly heated head during installation.
Were oversized guides used?
Was the head heated?
I would have the work redone with correct size guides and heat and I'd want to watch them do it.

pommie john · Jun 7, 2014

rx7171 said:
pommie john said:

Yes your pictures are clear on that, including the exhaust guides that usually don't need seals anyway.
Since it appears all are the problem it appears a faulty installation.
A correct installation requires oversized guides and correctly heated head during installation.
Were oversized guides used?
Was the head heated?
I would have the work redone with correct size guides and heat and I'd want to watch them do it.

Click to expand...

There's a question

They claimed that they use liquid nitrogen so the guides just drop in with no heating. However, they obviously used a torch because the rocker arms showed signs o scorching where they've obviously been exposed to a flame:

The guides are oversize, but I forget how much. Kibbewhite guides go up to 6 thou over and they were too small so I had a pair made to order.

I'm asking locals where I can get good work done on the head, but last time I did that , I ended up at the place that did this stuff-up.

john robert bould · Jun 7, 2014

The problem is due to the guides being removed with a carbon build up encrusted around the old guide...ALWAYS drill off the guide that sticks into the port....Drill the guide off untill it just touchs the head...then drift out the remaining "stubb" this ensures a carbon deposite will not broach the guide bore..sounds a bit to late...but better than compounding the problem.

Stillreel · Jun 7, 2014

.... or learn to live with a little smoke.

Nice thread on character of Norton's here.

BCV

Hobot · Jun 7, 2014

Ring job may still be part the problem d/t extra blow by case pressure over whelming case ventilator device and intake guide. Only the intake guides should ever feel chamber suction as exht valve is seated on intake and hi pressure when exhausting.

john robert bould · Jun 7, 2014

We all assume the exhaust port is positive pressure...but is it?

hobot said:
Ring job may still be part the problem d/t extra blow by case pressure over whelming case ventilator device and intake guide. Only the intake guides should ever feel chamber suction as exht valve is seated on intake and hi pressure when exhausting.

Matt Spencer · Jun 7, 2014

Carefully drifting them out , head heated , and a big measure up and under the microscope .

some spaceage loctite if the clearance / head to guide is satisfactory , after thinning the in port portion
particularly on the intakes .

If the scourings on the load line , a top line machineists needed , to avoid ill angled valve heads requireing
excessive seat recutting & recession . To make custom guide . :x

Pay to size both fore & aft pairs matching dimns .

Let the head heat through to remove them , or fit . dont hurry it .

Get the Drift.

:lol: :x :wink:

Hobot · Jun 7, 2014

We all assume the exhaust port is positive pressure...but is it?

Think more on this why Norton only used intake guide seals and then only after 6 star oil pump and rocker spindles installed to block oil flow.

rx7171 · Jun 7, 2014

>>There's a question They claimed that they use liquid nitrogen so the guides just drop in with no heating. However, they obviously used a torch because the rocker arms showed signs o scorching where they've obviously been exposed to a flame:<<

The smear of aluminum on the guide in one of your pictures indicates just "dropping in" didn't happen.
And did they apply torch to head prior to removing old guides but were the holes still made oversize by forcing out the old ones because the head wasn't heated properly. Repair manual calls for 150-200 degree F "evenly".
Don't know if this helps but since all the guides are leaking around their bodies it has to be an installation problem.
Even though aluminum smear indicates tightness is it possible the guides OD weren't large enough for an oil tight interference fit?

pommie john · Jun 7, 2014

Local forum member Ashman has a recommendation of someone who knows what the are doing. I think the head just needs to be given to a competent engineer who can look at what's happened and find a fix. It might be an expensive cure, but if I work out how many man hours I've spent playing with carbs, rocker spindles gaskets and god knows what, I think it makes sense to get an expert to check everything.

Hobot · Jun 7, 2014

The smear of aluminum on the guide in one of your pictures indicates just "dropping in" didn't happen.

A recent interference fitting fail a short way in I was able to pull back out left Al grey on bronze bush which my machinist said was evidence of shearing Al not just slipping in. So had a bit of bush OD removed to try again.

72Combat · Jun 8, 2014

After 2 years of racing the BMW quite happy with k liners for the valves.

the 900 bores were borderline but the motor ran mint for 50 races.
New motor also runs K lines, I was sceptical but now a convert.
BMW's don't run valve guide seals.
Might be worth a look?

batrider · Jun 8, 2014

rx7171 said:
>>There's a question They claimed that they use liquid nitrogen so the guides just drop in with no heating. However, they obviously used a torch because the rocker arms showed signs o scorching where they've obviously been exposed to a flame:<<

The smear of aluminum on the guide in one of your pictures indicates just "dropping in" didn't happen.
And did they apply torch to head prior to removing old guides but were the holes still made oversize by forcing out the old ones because the head wasn't heated properly.

.......Repair manual calls for 150-200 degree F "evenly".

No it's 150-200 degrees C in the manual. Or hot enough to fry spit.

Hobot · Jun 8, 2014

BTW the mc-engine email list of world class builders calms nothing works as well for tight interference fit pressing as good ole fashioned caster bean oil which both avoids galling and then glue seals with heat.

Stillreel · Jun 8, 2014

Just had a look inside the valve covers and I'm thinking now the plug fouling issue is oil/valve guides rather than a carb issue. Significant pooling around the intake valve springs. Is there an oil return port beside the intake valves? This may be plugged? I think oil return on the exhaust side is the push rod opening.

BC

Hobot · Jun 8, 2014

tiny hidden intake box drain is at rear RH corner mostly over the oil hole of barrel drain. Its possible some sealant plugged barrel drain hole to back up but think the passage out-down head is not straight enough to reliable probe with a wire and may just jam swarf more so off with its head again eh. Could pull TS cover and fill oil in rocker to see if flows down well enough or not. Once in a while we hear of simple short cuts working as hoped.

pommie john · Jun 8, 2014

Well, I've found why oil drips down the left intake guide.

What a dreadful bit of bodging. It had some loctite under the flange too.

rx7171 · Jun 9, 2014

batrider said:
rx7171 said:

>>There's a question They claimed that they use liquid nitrogen so the guides just drop in with no heating. However, they obviously used a torch because the rocker arms showed signs o scorching where they've obviously been exposed to a flame:<<

The smear of aluminum on the guide in one of your pictures indicates just "dropping in" didn't happen.
And did they apply torch to head prior to removing old guides but were the holes still made oversize by forcing out the old ones because the head wasn't heated properly.

.......Repair manual calls for 150-200 degree F "evenly".

Click to expand...

No it's 150-200 degrees C in the manual. Or hot enough to fry spit.

Batrider
You are absolutely right.
Funny I looked it up in the manual and when I was typing it in I thought I was being careful.
A real brain fart on my side.
However I'm guessing that applying a torch to head to get it "evenly" heated to that temperature could be problematic including warping the head.

Sealing Valve guide bores

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