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A65 valve guide replacement #318559
06/15/10 12:38 pm
06/15/10 12:38 pm
Joined: Sep 2004
Posts: 798
Farnham, Surrey, UK
gunner Offline OP
BritBike Forum member
gunner  Offline OP
BritBike Forum member
Joined: Sep 2004
Posts: 798
Farnham, Surrey, UK
Ive been inspecting the valve guides on my 68 Firebird head and have noticed that the valves can be rocked back and forth slightly, indicating worn guides.

So IM now looking at my options for replacing the guides and am considering doing it myself.

I have some questions:-

- how easy it it to fit new guides? The BSA manual suggests that a suitably sized drift can be used to knock them out but what about refitting?

- how do you ensure the new guides are concetric with the seats?

- do the new guides need reaming to fit the valve stems?

- what type of guides are best, iron or bronze?

- do the seats need to be recut and is this a diy job?

All info welcome


1968 A65 Firebird
1967 B44 Shooting Star
1972 Norton Commando
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Re: A65 valve guide replacement [Re: gunner] #318572
06/15/10 1:30 pm
06/15/10 1:30 pm
Joined: Sep 2002
Posts: 7,813
Seattle
Alex Offline

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Alex  Offline

BritBike Forum member
Joined: Sep 2002
Posts: 7,813
Seattle
Originally Posted By: gunner
- how easy it it to fit new guides? The BSA manual suggests that a suitably sized drift can be used to knock them out but what about refitting?


It really depends on your level of experience and confidence. Replacing the guides themselves is really very straightforward as you have stated. All you really need is a suitable drift and some way to heat the head.

Quote:
- how do you ensure the new guides are concetric with the seats?


You don't. Replacing the guides almost guarantees that the seats need to be cut. Since the cutter uses the guide as a pilot, concentricity is guaranteed in this way.

Quote:
- do the new guides need reaming to fit the valve stems?


IME, most Bronze ones do, most iron guides don't.

Quote:
- what type of guides are best, iron or bronze?


This really can open up a can of worms, particularly when it comes to which brand of bronze guides to use. Cast iron guides are often more durable and generally don't have problems with sticking...and they usually don't have to be reamed and honed as stated above.

Quote:
- do the seats need to be recut and is this a diy job?


I would never replace guides without cutting the seats. NewWay makes a relatively inexpensive ($400 US) cutter set for a three-angle valve cut that leaves a superior valve seat with a bit of practice and care. Worth it if you're going to do this a few times...


A smattering:
'53 Gold Flash
'67 Royal Star
'71 Rickman Metisse
'40 Silver Star
'37 Rudge Special
sixtyseventy Lightboltrocket road racer...and many more.
Re: A65 valve guide replacement [Re: Alex] #318581
06/15/10 2:26 pm
06/15/10 2:26 pm
Joined: Sep 2004
Posts: 798
Farnham, Surrey, UK
gunner Offline OP
BritBike Forum member
gunner  Offline OP
BritBike Forum member
Joined: Sep 2004
Posts: 798
Farnham, Surrey, UK
Thanks for the info, looks like iron guides then.

Next question, (and I know this is an age old issue), do you heat the head to remove/replace the guides or do it cold?


1968 A65 Firebird
1967 B44 Shooting Star
1972 Norton Commando
Re: A65 valve guide replacement [Re: gunner] #318613
06/15/10 5:53 pm
06/15/10 5:53 pm
Joined: Jul 2009
Posts: 3,549
Vic. Australia
P
Pete R - R.I.P. Offline
In Remembrance
Pete R - R.I.P.  Offline
In Remembrance
P
Joined: Jul 2009
Posts: 3,549
Vic. Australia
The first thing you do is clean ALL the carbon off the guides,inside the ports.The best way is by soda-blasting.

If you want to minimize damage to the head,and also make the guides easier to remove then drill them part-way through.Starting from inside the port,drill the guide bore bigger,but not all the way through.Core them out until the wall thickness is 0.040" or less on any part of the guide that has an interference fit in the head.

Find or make a punch that will fit in cored-out section of the guide and stop against the un-drilled section.The advantage of this (besides reducing the wall thickness of the guide)is that the guides are removed in tension,so they are drawn thinner when you punch them.
Put the punch in the freezer,and heat the head in an oven to 150-160 C.Each time you punch out a guide,put the punch back in the freezer and the head back in the oven.

When the old guides are out and the head has cooled,measure the guide holes in the head.The new guides should have 0.001"-0.0015" interference if they are bronze;not less than 0.0015" interference if they are iron.
Before you fit the guides,coat them with moly grease and put them in plastic bags in the freezer.The punch you use should also go in the freezer.If this punch locates in the guide bore,make sure the corner radius is under-cut to avoid flaring the top of the guide.Heat the head again to 150-160 C.
When the guides are fitted and the head has cooled,you must measure valve-stem clearance in the guides (measure the stems,and measure the guide-bores).Before you do any reaming,the tightest part of the guide will be close to the centre.
Iron guides can run about 0.001" tighter than bronze guides.

Let the experts cut the seats if they can guarantee less than 0.001" runout.

Re: A65 valve guide replacement [Re: Pete R - R.I.P.] #318635
06/15/10 8:42 pm
06/15/10 8:42 pm
Joined: Sep 2002
Posts: 7,813
Seattle
Alex Offline

BritBike Forum member
Alex  Offline

BritBike Forum member
Joined: Sep 2002
Posts: 7,813
Seattle
FYI, I never heat the head to drive out the guides. There's just not enough difference in CTE for the guides to loosen significantly. Never had a problem yet. I always heat the head and freeze guides to drive them in.


A smattering:
'53 Gold Flash
'67 Royal Star
'71 Rickman Metisse
'40 Silver Star
'37 Rudge Special
sixtyseventy Lightboltrocket road racer...and many more.
Re: A65 valve guide replacement [Re: gunner] #318657
06/16/10 12:00 am
06/16/10 12:00 am
Joined: Sep 2004
Posts: 798
Farnham, Surrey, UK
gunner Offline OP
BritBike Forum member
gunner  Offline OP
BritBike Forum member
Joined: Sep 2004
Posts: 798
Farnham, Surrey, UK
Great answers guys, thanks


1968 A65 Firebird
1967 B44 Shooting Star
1972 Norton Commando
Re: A65 valve guide replacement [Re: gunner] #318696
06/16/10 7:13 am
06/16/10 7:13 am
Joined: Jan 2004
Posts: 3,727
ca, us
D
DMadigan Offline
BritBike Forum member
DMadigan  Offline
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D
Joined: Jan 2004
Posts: 3,727
ca, us
The factory had a tool for installing guides reasonably centered to the existing seat. I made one by cutting a 45 degree taper on an alloy plug that will sit in the seat and a 1/4" coarse threaded rod in the port end of the plug that goes through the guide hole. The new guide is put on the rod with an old guide as a pusher and a coupling nut. Wind the coupling nut down the rod and push the guide in place. Less chance of whacking in the guide crooked with a hammer. For removal, I use a long 3/8" Allen head bolt with the threads turned down to 5/16" to fit in the guide.

Re: A65 valve guide replacement [Re: DMadigan] #318700
06/16/10 8:36 am
06/16/10 8:36 am
Joined: May 2004
Posts: 3,743
Sydney Australia
B
BSA_WM20 Offline
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BSA_WM20  Offline
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B
Joined: May 2004
Posts: 3,743
Sydney Australia
I bought a removal tool nearly 40 years ago.
A stepped ball shaped head ( locates on the seat ) with a long threaded rod through it.
The remover is a threaded sleeve that screws down the shaft and bears against the guide.
Bog simple , works a treat.
Never thought of boring out the guide but I can see the logic in it ( one to add to the list)


Bike Beesa
Trevor
Re: A65 valve guide replacement [Re: BSA_WM20] #318705
06/16/10 9:33 am
06/16/10 9:33 am
Joined: Feb 2010
Posts: 448
Au
M
markoz Offline
BritBike Forum member
markoz  Offline
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M
Joined: Feb 2010
Posts: 448
Au
This can be one of the cheapest jobs to get done by a pro get them to clean the head for you at the same time and it will look good and save you a lot of grief. Mark

Re: A65 valve guide replacement [Re: markoz] #318718
06/16/10 11:56 am
06/16/10 11:56 am
Joined: Apr 2005
Posts: 2,383
Bega NSW Australia
Mark Parker Offline
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Mark Parker  Offline
BritBike Forum member
Joined: Apr 2005
Posts: 2,383
Bega NSW Australia
Rather than replacing the guides why not have them K/lined the guides are bored a liner pressed in and sized. They can run quite tight clearances esp with a Nitrided valve. Usually they are pretty well aligned but doing a three angle seat is well worth the effort. Ever since useing some grinding stones I'm converted to that method. What you don't want is a head shop cutting the seats deep using a 3 angle cutter in a machine. The little hemi head needs the top cut to blend with the chamber not be down a step. If the valves are sunk into the head; using O/size valves or seat inserts can get the valve back up where it should be. Head shops can do seat inserts quite cheaply.


mark
Re: A65 valve guide replacement [Re: Mark Parker] #318833
06/16/10 11:40 pm
06/16/10 11:40 pm
Joined: Dec 2006
Posts: 259
Jerseyville, Illinois
L
ljm Offline
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ljm  Offline
BritBike Forum member
L
Joined: Dec 2006
Posts: 259
Jerseyville, Illinois
I just had a total rebuild on my 65 Hornet head. Like Mark Parker said I opted for the K/line insert. Turned out perfect. The seats were cut just like using the old guides. The line up is darn near perfect. I used Ed V's valve springs and NOS valves.
ljm


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