Modern Valve Guides

R

Ron/IA

Well-known member
Went to my local Model A parts supplier today, and bought a complete valve train. Stainless steel valves, one-piece guides, keepers, and springs. When I looked at the valve guides, they didn't look like the illustration in the catalog. They are straight, and called "modern" valve guides. Call me dumb, but how in the world are they held in the block? Friction, Loc-Tite, or magic?? Here is what Bratton's catalog states:

MODERN VALVE GUIDES - This is a one piece straight guide. To install, insert the under cut end into the block first. The top domed end extends above the bottom of the dished hole about .030" use a 5/16 bolt about 3” long to tap the guide in. After the guide is in place, use a countersink with 1 degree angle to clean up any burrs, or hone the hole. The guide is longer then the stock ones, but there is no need to shorten them. Tappet clearence is .010" - .013" on a cold engine. Can only be used with moden style valves (9180), keepers (9310) and retainers (9330).

Can anyone enlighten me?

Thanks, Ron/IA
 
I bought my kit from Snyders and the valve guides looked pretty much like the split ones, except that they were all one piece. And they are inserted from the bottom and held in place by the bottom flange pushed up by the valve springs.
 
Ron/IA said:
Went to my local Model A parts supplier today, and bought a complete valve train. Stainless steel valves, one-piece guides, keepers, and springs. When I looked at the valve guides, they didn't look like the illustration in the catalog. They are straight, and called "modern" valve guides. Call me dumb, but how in the world are they held in the block? Friction, Loc-Tite, or magic?? Here is what Bratton's catalog states:

MODERN VALVE GUIDES - This is a one piece straight guide. To install, insert the under cut end into the block first. The top domed end extends above the bottom of the dished hole about .030" use a 5/16 bolt about 3” long to tap the guide in. After the guide is in place, use a countersink with 1 degree angle to clean up any burrs, or hone the hole. The guide is longer then the stock ones, but there is no need to shorten them. Tappet clearence is .010" - .013" on a cold engine. Can only be used with moden style valves (9180), keepers (9310) and retainers (9330).

Can anyone enlighten me?

Thanks, Ron/IA
Click to expand...
The highlighted quote is a misnomer as a general rule. Most of the guides I install need to be driven in with some force. Once in a while I find some that are a bit loose, those I locktite in, but most need to be driven in with a 2/3 pound hammer. I have a driver that is used on an air hammer but even find this won't work at times. When this happens I use a 5/16 bolt and a brass drift with a 3# hammer and this is pretty tough.
 
Gentlemen, thank you for your answers. What threw me was the illustration in the Birdhaven catalog is as CarlG discribes, but upon opening the package found the straight guides. I am not so sure I like this arrangement, and may return them for the more standard style.

James - You state using the 5/16" bolt and a brass drift. I am guessing the shaft of the bolt is inside the guide, with the head resting against the top of the guide. Why do the Bratton's instructions specifically state the bolt should be 3" long? I am still not 100% sure of the proper method for installing these guides.

Thanks, Ron/IA
 
I suspect the reason a 3" bolt is specified is that it will have a shoulder without threads ---that is what I look for when I am using a bolt instead of the proper driver. ---this is for support and to help prevent a burr , sometimes I will chuck the bolt in the drill press and dress the radius under the head with a file also ---depending on how the bolt fits the guide.
 
Will the old freezer trick work on valve guides as it does on other things like wrist pins and flywheels?
 
MrTube said:
Will the old freezer trick work on valve guides as it does on other things like wrist pins and flywheels?
Click to expand...

The thermal coefficient for steel is 0.0000065/oF If the guide is 0.750 in diameter and you cool it 75F from 75 room temp to 0F, it will shrink about 3 1/2 tenths, (0.000365") not really enough to help much. If you use dry ice (-109F) it will shrink about .00084, still less than a thousanth of an inch. That may not be enough. Liquid nitrogen (-320F) will shrink it 0.0019, almost two thousanths. Unfortunately, at -320F steel will shatter like glass. If it doesn't drop in, you can't help it with hammer taps. If it were 6" in diameter, 0F would shrink it three thousanths, liquid nitrogen fifteen thousanths, almost 1/64th of an inch!

When you do press fit type piston pins you heat the rod small end to about 550F, (below the manufacturing temper temp. so you do not further anneal the rod). A one inch rod hole will open up over three thousanths.

The bearing hole in a flywheel is over 1", heating the wheel to a safe from warpage 200F + freezing the bearing will give you almost two thousanths (0.0017)

If a guide is too tight to go in at room temp with a smartly tapped 1 lb hammer I would recommend taking it down a little with emery and crocus in a lathe or drill press. Clean out the block hole with a stick and fine emery, too. Cast iron will crack if you have too tight of a press fit.
 
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With "modern guides" without a shoulder (they are also made with a shoulder-one piece) you have to remember to adjust for installed spring height. Not only does the lack of a shoulder effect this but the lenght of "new" valves and retainers as compared to the original. The last set I installed would have ended up with only 35# assembled on the seat pressure. The good books call for 60-65# of pressure on the seat. The average shim I had to use was around .435 thick, without correct spring pressure you will have a built in governor.
 
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First picture is the tool I used to drive out the old guides

Second picture is valve set I bought that shows the one piece valve guide with the flange.
 

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Ron,they're held in the same way the guides are held in your modern car.You don't worry about them because you have never had a reason to give it a thought.How often have you seen a modern guide fall out?It has happened before,but in almost 40 years of being a mechanic I would have to think hard to remember where I saw it.
 
d.j. moordigian said:
Carl,

Did you purchase the kit from Snyder's? If yes, is the valve SS?

Thanks, Dudley
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Yes, the kit came from Snyders and the valves are listed as SS. Haven't tried a magnet on them, but that's the way they are advertised. Real neat kit, went together very well. Block already had hard seats, and there was very little (if any) lapping required.
 
Ive never had a problem with original style valves & guides.Just one of many *modern* upgrades that are realy not needed-in my opinion.The mushroom stem gives a much larger surface area,along with the original lifters than the modern replacements & would keep the adj for a very long time.SS valves may require more clearance than stock valves.
 
I agree with columbiA, and it seems like the cushion of oil between the larger foot would make for quieter valve lash.
 
When removing very tight guide ( even ones not so tight)it can work better to tap the guide and screw in a bolt, then use a drift punch to drive the guide out ---this way you don't mushroom the guide and damage the bore in the block or head
 
As "callcoy" (Steve-Santa Rosa) mentioned yeserday, I too wondered about the spring tension when using a straight guide without a shoulder versus a standard guide with a shoulder. He stated having to use .435" shim to compensate.

I am not questioning his measurements, but my first thought was the difference 65# to 35# seemed like a whole lot for only .435" of height. Then I thought the shim measurement is nearly 1/2", and the book states the spring free height is 2-15/16"; that is approximately a 15% change.

Now my questions are: Do the springs that come with the modern straight guides adjusted for no shoulder? Would engine performance be effected if the spring pressure were reduced that much?

Thanks, Ron/IA
 
Ron: I'm sure that performance and reliability would be affected by less spring tension. I've seen lots of numbers thrown around for seat pressure, but I haven't seen or heard anything about what Ford recommended. The service bulletins aren't much help, can anyone give a definitive spring pressure with the spring compressed to the original installed height with the valve closed? The 65 lbs quoted above seems high to me...
 
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