Valve Clearance ???

[Pilotdave]

I've been reading various sources for valve clearance specifications and have observed:

Service Bulletins (p220): .013" - .015"
Les Andrews: intake at .013" and exhaust at .015"
Bratton's Catalog (p2): .010" - .012"

Which leads to several questions:

1. Why are there so many different "specs"?

2. Are the variations just another example of the (sometimes) delightful ambiguity that's a part of this hobby?

3. What might be the most appropriate spec?

Thanks!

[pat in Santa Cruz]

Just to add to your confusion, Service Bulletins page 338 says .010 and .013.

I like 'em at .013 and .015. on a standard Ford cam. I've seen a lot of ex valves burnt with a setting at .013. In fact I just repaired a guys valves that were set that close. He had burnt ex valves at cyls 4 and 2. Its not uncommon for #4 exhaust to burn at .013, especially if the exhaust system is restricted with a cheapo repo muffler or if the engine is running hot. As the valves hammer themselves down into the seat over time, the greater clearance gives a little more lattitude before they have to be re adjusted. The slight click of a looser valve is a minor price to pay for longevity.

All that being said, if you have a reground cam or a new one from Bill Stipe, follow the grinders instructions. There is more to valve lash than just clearance for expansion, it also takes into account time on the seat from the grind. The cam grinder knows best about what your lash should be.

[Patrick L.]

What Pat said, good info.. Valve clearance is for sealing, timing and cooling.. Seat/face contact is for sealing and cooling[valve].. Exhaust sealing contact area is/should be wider than on the intakes for cooling purposes.. That said, I like to leave a little extra clearance for wear, as Pat stated, and a little extra cooling time.. .012-.013" intake and .015-.016" exhaust seems to work well,, unless the supplier/builder states differently.. My 'A' valve clearances have been .015-.016" [for all of them]for the 36 years I've owned it, lifters are non-adjustable and the engine was done in 1961..

[Pilotdave]

Interesting! Right now mine are in the .012-.013" intake and .014-.016 exhaust. The lifters are adjustable if one has (a) very thin wrenches and (b) 3 hands, so I am reluctant to dive into minor adjustments for a .001+/-.

[Jim Brierley]

On a stock cam I set them at 12 &14. As Pat says, if it is a reground or performance cam, follow the grinder's recommendation.

[Benson]

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While we are on the subject, what clearances does one use on a stock (un-reground) Model B cam?

Thanks

[hardtimes]

Originally Posted by Pilotdave

I've been reading various sources for valve clearance specifications and have observed:

Service Bulletins (p220): .013" - .015"
Les Andrews: intake at .013" and exhaust at .015"
Bratton's Catalog (p2): .010" - .012"

Which leads to several questions:

1. Why are there so many different "specs"?

2. Are the variations just another example of the (sometimes) delightful ambiguity that's a part of this hobby?

3. What might be the most appropriate spec?

Thanks!

Dave,
RE: #3...interesting question, given all the 'different' input..clear as mud?
I might add that the type of engine 'build' is to be considered in figureing 'most appropriate' spec.
I have set my warmed B valves ALL at .012. It seems to like that setting at just over 1000 miles running..go figure.

[Purdy Swoft]

Originally Posted by Benson

While we are on the subject, what clearances does one use on a stock (un-reground) Model B cam?

Thanks

I remember that the exhaust gap was .022 and Henrys comment was, with a little noise it will keep its poise. I don't remember the intake gap but it is not as critical because the fuel air mix passing through the valve kept it cooler and less likely to burn.

[Benson]

Thanks Purdy,

[glenn in camino]

I've always set intake and exhaust at .013. Never had a problem.

[Randy in Illinois]

Purdy Swoft said it all with Henrys quote. I agree. I like to here them slightly when cold. We set adjust them cold. They expand when warm. and the valves will seat. I use .015 IN .020 EX Sometimes you have to experiment what works best with your engine.

[Jim Brierley]

Benson, On my reground to B spec cams I recommend .012" & .014", same as I set an original Ford B cam.

[Benson]

Originally Posted by Jim Brierley

Benson, On my reground to B spec cams I recommend .012" & .014", same as I set an original Ford B cam.

Thanks Jim,

I missed your response somehow!

[Kevin in NJ]

Isn't the valve clearance really dependent on the material the valve is made out of and the type of cam?

Also do you not have to be careful on the diameter of the push rod face that follows the cam?

I am just wondering if maybe there is more to setting valves then blindly saying a certain setting works fine. I wonder if more information needs to be included to account for valve type and cam type.


Something to consider......
In some of my comments on vapor lock I got back and email from a guy.
He had a vapor lock problem, well he could not figure out why his engine would sometimes stop when it got hot so he called it vapor lock.
He took the engine apart for another problem and found the valves to be set up wrong.
The engine stopped having vapor lock problems once the valves were adjusted properly.


Anyway, just a few thoughts.

[George Miller]

Originally Posted by Patrick L.

What Pat said, good info.. Valve clearance is for sealing, timing and cooling.. Seat/face contact is for sealing and cooling[valve].. Exhaust sealing contact area is/should be wider than on the intakes for cooling purposes.. That said, I like to leave a little extra clearance for wear, as Pat stated, and a little extra cooling time.. .012-.013" intake and .015-.016" exhaust seems to work well,, unless the supplier/builder states differently.. My 'A' valve clearances have been .015-.016" [for all of them]for the 36 years I've owned it, lifters are non-adjustable and the engine was done in 1961..

I' with Pat and you. If you can hear them they are not going to burn the valves. To close is bad, because they get much closer when the engine is hot and pulling hard.

[Glenn C.]

I had a supervisor once tell me..."Awh laddie, I want to hear them, Not smell them"