Model A and B valve lifter difference

[Randall]

Did a little checking on the differences of model A adjustable and original B lifters today.https://youtu.be/9_rZUfRFBtU?si=V_m19xZUTvi6y80u

[Pete]

Originally Posted by Randall

Did a little checking on the differences of model A adjustable and original B lifters today.https://youtu.be/9_rZUfRFBtU?si=V_m19xZUTvi6y80u

And?

[Randall]

Sorry Pete try clicking link ,think it will work now.

[alexiskai]

Randall, I don't think this video gets at the concerns about A vs B tappets. The issue was about the width of the tappet at the base, not the height of the tappet. There used to be a page on FordGarage that covered this question; an archived version is here.

[The Master Cylinder]

Originally Posted by alexiskai

Randall, I don't think this video gets at the concerns about A vs B tappets. The issue was about the width of the tappet at the base, not the height of the tappet. There used to be a page on FordGarage that covered this question; an archived version is here.

It is unfortunate that some of Vince's most excellent articles on Ford Garage are not available. If you search for the article on Model A and B "push rods, you get a Tom Petty song.

[alexiskai]

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Originally Posted by The Master Cylinder

It is unfortunate that some of Vince's most excellent articles on Ford Garage are not available. If you search for the article on Model A and B "push rods, you get a Tom Petty song.

It's really an invaluable community resource. Since it hasn't been updated for years, I made a local copy on my computer using the Internet Archive. Much easier searching and I have access to pages that are no longer linked.

[Bob C]

Here is a link to Vince's comparison of A and B lifters.
https://web.archive.org/web/20150118...comparison.htm


More Vince's cam info.

https://www.fordgarage.com/pages/camshaftspecs.htm

[BRENT in 10-uh-C]

Originally Posted by alexiskai

Randall, I don't think this video gets at the concerns about A vs B tappets. The issue was about the width of the tappet at the base, not the height of the tappet. There used to be a page on FordGarage that covered this question; an archived version is here.

Colin, this was debated many years ago here on Fordbarn (-back when Shelly owned the website) and yesterday when Randall called me to discuss this, I gave him my recollection on how that debate went, and suggested he make a video. His findings basically corroborated what we discovered back then. Likely, Vince made a webpage about that time as a way to share his research on the topic. Even Marco drew some visuals to help Fordbarners understand his opinion(s) on the subject. I have posted a couple of those below. I do think Randall's video may share some insight on this. So now to discuss the size differences.

There were many theories discussed back then such as the extra width was necessary to make use of the full width of the camshaft lobe, and others suggested the wider foot allowed the valve to open earlier allowing for more duration. I think over time, some (most??) of those theories have been debunked. Basically in a nutshell, when you look at the crown on the face of the Valve Push Rod (-Ford's nomenclature) you will see enough of an arc or crown where the pressure is lifting in the center of the camshaft lobe, -and not at the perimeter of the foot of the Push Rod (-Tappet). With the quality of today's oils, -and based on the longevity some people have been able to drive their Model-A/B engines while using the smaller foot Push Rod, it appears the information that was found in the Svc. Bulletins was either flawed, or not applicable to those using the Colony adjustable tappets that many rebuilders use today. IMO, Randall's video confirms what was discussed back then, and it would have been nice to have been able to show a video such as Randall's to prove some people's opinions were not reality.


.

[The Master Cylinder]

Think I will stick with Bill Stipe's recommendation and continue to use the push rods (lifters) with the larger base, 1.117".

I agree with alexiskai, Randall's video doesn't address the wear concerns about the width of the tappet base and the cam.

[BRENT in 10-uh-C]

Originally Posted by The Master Cylinder

Think I will stick with Bill Stipe's recommendation and continue to use the push rods (lifters) with the larger base, 1.117".

I agree with alexiskai, Randall's video doesn't address the wear concerns about the width of the tappet base and the cam.

Fair enough, how do you propose to 'address this' to prove the smaller tappets are an issue?

I have been around this game for a long, long time and I honestly have yet to hear someone speak of a camshaft failure, ...especially a Stipe IB series camshaft. There are many Model-A owners that have 50k plus miles on their engine that have worn-out the bottom end yet during the rebuild, the camshaft was re-used. So, can you cite some examples where there was premature cam failure due to the smaller tappet foot??

I will even take this a step further. Imagine how many new Stipe cams, Winfield Cams, Crane Cams, and all of the other reground Model-A/B camshafts that Effingham, Brierly, Pete, and others have produced over the years. I am going to throw out a number (-I'm sure my estimate is very conservative!!) but for the sake of a good discussion, lets just use an arbitrary number of 25,000 Model-A camshafts have been used in Model-A/B engine rebuilds, ...and lets say that ½ of them (12,500 camshafts) were used with the smaller Tappets. Now, lets say that you/someone can show that 25 of those camshafts had a premature failure because of the smaller foot. That correlates to 'two-tenths' of ONE percent (0.200%) failure rate because of the smaller footprint. Even if someone could document 100 camshaft failures, that still does not equal to a 1% failure rate.

Again, setting theories and hypothetical 'what-ifs' aside, at some point during the past 15 years or so that this topic has been debated here, if the failures were indeed as Colin has suggested, then wouldn't we have seen/experienced/read-about hobbyists with some greater level of cam failure rate? Real world statistics with the smaller tappets just do not align with the hypothetical theories people are trying to argue with.

[Pete]

There are a few things that are etched in stone about cams.
Each grind is designed to run with certain diameter lifters.
Most modern cams with a polidyne curve design are made to run with a 1 inch diameter lifter face.
The original model A and B cams were designed with the 3 curve method. This got by for operating parameters the engine was designed for. It was also FAR cheaper to scribe 3 curves than to spend days figuring variable lift velocities by long hand math which was all they had in the twenties.
Bill Stipe told me that ALL of his cams were designed to run with a 1 inch diameter lifter face.
All of mine are likewise.
That means usually running the so called double lock lifters.
HOWEVER, running a larger lifter face on a cam designed for a 1 inch lifter will not hurt anything.
Running a smaller lifter face than the cam was designed for will definitely shorten cam and lifter life.

Basically, if you are going to run an original model A/B cam, use original lifters. They can easily be refaced and improved in the process by taper grinding. Original lifters were flat faced.
If you are going to run an after market or reground cam, ask the grinder what diameter lifters it is supposed to run with. If he doesn't know, find another cam grinder.

[alexiskai]

OK, I think I understand now.

The belief that Randall's video is attempting to prove or disprove is that, because the base (or foot, or head) of the original B tappet is slightly wider than the Colony tappet, this causes the cam to engage the tappets at different crankshaft degrees, which would affect the performance of the cam.

The video shows that the cam in fact engages both tappets at the same point, presumably because, as Brent notes, there's a very slight crown on the face of the tappet there.

I will say, I don't think the information about what hypothesis is being tested comes across well in the video. But I appreciate it now that I understand what's going on.

[Y-Blockhead]

Originally Posted by BRENT in 10-uh-C

I have been around this game for a long, long time and I honestly have yet to hear someone speak of a camshaft failure, ....

Well, here is one for ya, I surely believe it is failing. Can't tell you why but here ya go...

[Pete]

Yup, it is failing....LOL
Rust problem from some time in it's life.
It will probably run that way for another 10 years at least though.

[BRENT in 10-uh-C]

Originally Posted by Y-Blockhead

Well, here is one for ya, I surely believe it is failing. Can't tell you why but here ya go...

Yes, I also agree with 'Mr. S' that it is failing ...but it does make you wonder just how long it will last 'as-is'.

So, Pete does add a lot of value to this debate, but it does make me wonder just how many original Model-A or B camshafts have been used with adjustable Tappets over the past 50+ years in restorations. So how many of those original non-reground cams have failed due to the smaller Push Rod foot?

BTW, so when we add 1 failed camshaft to that 12,500 hypothetical number, that now puts us at a failure rate of around 0.008%. Is that 8-thousandths of 1 percent??

[johnneilson]

Honestly the Model A/B cam lifter combination is not loaded heavily enough to be a problem if properly manufactured

The issue of face diameter really only comes into focus if the cam opening ramp contact point reaches the edge of the lifter face

In very aggressive cams the face of the lifter cam be ground to a very large convex radius and this will help

In the motors with very large cams it is customary to use lifters with face diameters of 1.2”
And at this point clearance must be verified and mitigated

Aviation has had issues with cam and lifters
Search cam/lifter spalling on Continental O320 engines

John

[Pete]

Originally Posted by johnneilson

In very aggressive cams the face of the lifter cam be ground to a very large convex radius and this will help.John

Here is a pic of a radius face lifter used with a cam that has .515 lift.
It has a 2 inch radius. Note the slot to keep it in alignment. A "key" is installed in the lifter bore that runs in the slot.
The cam line in the block is bored oversize and insert bearings installed for this type of cam.

[SAJ]

Here is a link to a cam lobe picture that I found in a members car in 2014. At the time Jim Brierly commented in the second post that it did look like too small a followed foot for the lobe grind. Any more opinions?
Not a Model A or B grind though but an English Ford 10 regrind.
I once installed a radical high lift grind in an English Jowett Jupiter with a small follower foot. The edge caught and chattered the cam lobe very quickly. I mushroom-ground the followers and alleviated the problem temporarily, but then got rid of that cam and went to a different set up.
https://fordbarn.com/forum/showthread.php?t=156760
Oops, I cannot seem to make this a clickable link. It works if you "open" it. I used the paperclip icon to post.
Advice please.
SAJ in NZ

[BRENT in 10-uh-C]

Originally Posted by SAJ

Here is a link to a cam lobe picture that I found in a members car in 2014. At the time Jim Brierly commented in the second post that it did look like too small a followed foot for the lobe grind. Any more opinions?
Not a Model A or B grind though but an English Ford 10 regrind.
I once installed a radical high lift grind in an English Jowett Jupiter with a small follower foot. The edge caught and chattered the cam lobe very quickly. I mushroom-ground the followers and alleviated the problem temporarily, but then got rid of that cam and went to a different set up.
https://fordbarn.com/forum/showthread.php?t=156760
Oops, I cannot seem to make this a clickable link. It works if you "open" it. I used the paperclip icon to post.
Advice please.
SAJ in NZ

The keyword in this!!