A, B or "touring" cam?
 

I'm tearing into an engine and the camshaft looks to be in pretty good shape (the engine was rebuilt sometime in the past, well before I got the car). I want to rebuild it with a "touring" camshaft, but how do I tell what I have? I suppose I could compare it to the Burtz "touring" camshaft I have for my Burtz build, but are the differences between the various cams in lift height, lobe profile or cam timing? I'm not anxious to regrind a good cam if I don't need to.

Thanks, all.

JayJay

Re: A, B or "touring" cam?
 

Take it to a cam shop, assuming you have one close.

Re: A, B or "touring" cam?
 

The cam needs to be reground either as is or whatever you decide and no matter what, the lifters need to be refaced also.
If you decide to go cheap and not do this, the lifters absolutely need to be kept with the lobe they were running on before.

Re: A, B or "touring" cam?
 

Thanks, Pete, good point. One of the compelling reasons for this teardown was to refresh the valves and to replace the original lifters with adjustable (the gaps are way out of whack). Since I'll be changing the lifters I'll go ahead with a cam regrind as well.

The good news is, at first glance the babbit looks good. (Note: dictionary wants to replace "babbit" with "wabbit", as in "wascawwy wabbit".) Need to check the clearances still but I'm optimistic.

Re: A, B or "touring" cam?
 

I recommend the 1 inch dia. lifters with the pinch nut and have the cam reground for the 1 inch lifters.

Re: A, B or "touring" cam?
 

The bearing metal was invented by a guy named Babbett, so it is capitalized.

I personally don't like reground cams and would buy a new one. But that is my opinion and others disagree.

Re: A, B or "touring" cam?
 

The Model B camshaft profile, which is an improvement of the Model A grind, is used by some as a touring grind for the Model "A" camshaft. The Model B camshaft is distinguished by an extra lobe that drives a fuel pump. The Model B camshaft does fit into the Model A engine without any modification.
Camshaft lobes are case hardened to reduce their wear rate. Case hardening does not completely go through the camshaft, so it is considered more of a surface condition. Thus there is a concern the regrinding an existing camshaft may reduce the case hardening which affects the camshaft's life.
My preference would be to use a Model B camshaft, or buy a new camshaft with a touring grind. Perhaps the Burtz camshaft has a profile more suitable for touring, so you may want to consider getting a camshaft with the Burtz profile. I do not know if the Burtz camshaft will fit into a Model A block.

Re: A, B or "touring" cam?
 

Burtz cam will fit a stock Model A block.

Re: A, B or "touring" cam?
 

There were 3 Model B cams produced, the most common one had .302" of lobe lift. The best one had .339" but these are more rare. The Burtz cam is a little more radical, more lift and duration, and does put the power curve at a little higher RPM.

Original A/B cams are not case hardened, they are just made from really good steel, so re-grinding them does not change its hardness.

Re: A, B or "touring" cam?
 

Heat treat in model A/B cams is adequate as is for a hot rod regrind. They were NOT case hardened from the factory.
What works best for a mild street engine is more lift, LESS duration and MORE lift velocity.
You do not lose low end performance this way. You DO get a slight lopey idle sometimes though which can be offset by certain engine modifications.

Re: A, B or "touring" cam?
 

All very informative but to the original question: once I have the cam out and on the workbench, how do I tell what I have? I get that the B cam will have an extra lobe for the fuel pump, and I can check for that. But as between a stock (original or regrind) grind and a regrind to B (touring) specs, is there any way I can tell? I need to mic the journals and lobes to determine if it's suitable for a regrind anyhow, but other than those raw metrics, is there a way I can see what the cam is ground to? And where is there a listing of what the grind specs are?


Thanks.

Re: A, B or "touring" cam?
 

There is no way to tell what the grind is just by looking at it if you are not experinced in doing that.
If you had a KNOWN hot rod cam to sit alongside and compare or measure lobes then you could tell if it had been modified but not to what specs.
You could NOT tell what the specs were just by looking at it.
There are many websites that list specs for various cams and you can find them by searching "camshaft specs".
To find the specs of a cam without some special equipment the easiest way is put it in the block it is going to be run in and degree it. All this requires is a degree wheel and a dial indicator.

Re: A, B or "touring" cam?
 

Set the cam in the engine with one exhaust and one intake valve and adjustable lifters. Set the tappet gap to 0.010 inch on both valves. Set a degree wheel on the crankshaft with a pointer. Set a dial indicator on one valve and measure the degree duration and lift. Use 0.010 inch lift off the seat for the valves as the start and end of the duration. Do this for both valves. Then compare your results with the specs. Depending on how the specs are listed, whether by crankshaft degrees or by cam degrees, you may have to divide the duration by two.

Re: A, B or "touring" cam?
 

You are almost correct. His name was Isaac Babbitt.

Re: A, B or "touring" cam?
 

You can get a rough idea by measuring lobe lift. The best way is with a dial indicator, but on a stock or near stock cam you can mic the lobe across the nose (fully open) and at 90 degrees from that point, the difference will give you lift in inches. Most, but not all, touring cams have higher than stock lift. I grind a cam that I call a 'C'. It is just a .339" B cam that I've copied and rounded the nose a bit for longevity, it now has .320" of lobe lift, and it makes a great touring cam. It has slightly more duration than earlier B cams, idles like a stocker and performs very well in the RPM ranges that we tour in.

Re: A, B or "touring" cam?
 

I get it that lift means the valve travels higher, and gets more breathing. But what is the duration (in plain english)?

Re: A, B or "touring" cam?
 

Duration is how long the valve is off of it's seat, Usually measured after a certain amount of initial movement of the valve, like .050 after opening to .050 before fully closing. Measured in degrees of crankshaft rotation.

Re: A, B or "touring" cam?
 

ddweave, Thanks for the correction. Babbitt. My spell checker even likes that one.

Re: A, B or "touring" cam?
 

Makes perfect sense, other than ... I don't have adjustable lifters, which is the primary reason for getting into the valve train in the first place (to install them). I'll just assume that the cam is a stock A cam unless I find the extra lobe, in which case I'll assume it's a B cam. Either way, a regrind is in my future.

Thanks a million to everyone who responded. I have learned a lot, which is usually the case when I go on the Barn.

Re: A, B or "touring" cam?
 

still not quite there ...

The front of all knowledge wiki says:

"the term babbitt metal is frequently styled in lowercase."

Re: A, B or "touring" cam?
 

Seat-to-seat duration is about 254 crankshaft degrees on a stock B cam, 260* on the .339" lift cam. Duration on a 260* performance cam will out perform the same duration on a stock cam because the rate of lift is greater. The .050" figure is a random figure used by many grinders because the rate of lift may vary as done by different grinders, .050" tends to give a better idea of how the cam will run under racing conditions. Too much cam in a stock or near stock engine can actually hurt low-end power, so stay on the mild side for street (touring) use.

Re: A, B or "touring" cam?
 

Everything about camshafts can be found here: https://www.tildentechnologies.com/index.html. Thank you Terry.

Re: A, B or "touring" cam?
 

Thanks

Re: A, B or "touring" cam?
 

Thanks

Re: A, B or "touring" cam?
 

Well, after all that, it appears I have a stock Model A camshaft. three bearings (as is the block), eight lobes, not nine. Before I pulled it out of the engine I put a dial indicator on it and found the lobe lift is 0.284"-0.291". Since a Model A cam starts out at 0.302" and a Model B starts out at 0.334" (see https://www.fordgarage.com/pages/camshaftspecs.htm), I suspect I have a stock Model A shaft that has worn lobes. I'm going to do some more detailed measurements tomorrow before I send it off to be reground, but at first blush this appears to be a good shaft.

And the babbitt (isn't this how we decided to spell it) appears to be in excellent shape, both rods and mains. Interestingly, there were no shims on the mains, so it will be interesting to plastigage it to see what the clearance is.

Re: A, B or "touring" cam?
 

My late 30 engine had an early 5 bearing cam in it when I got it and it was a screaming machine. Got it to 70 once for a very short burst on the freeway.

Re: A, B or "touring" cam?
 

I'm curious about that because I was told that the original 5-bearing cams gave slightly more power than the later 3 bearing cams, but with a less smooth idle.

I wonder how well the shorter 5 bearing cam bearings (especially the center bearing) hold up in a later engine block?

Re: A, B or "touring" cam?
 

I think there was more power, It definatly wanted to go faster than otheres I have driven. It was very happy at 55MPH.

Re: A, B or "touring" cam?
 

Depending on the cam, the power may be produced at a higher rpm. Even the "touring cams." An engine with Babbitt bearings and unbalanced crank may not be able to stand the higher rpm, like 3,000. (I like to capitalize his name in honor of the early work that he did that enabled the production of many engines and accessories. Plus my spell checker seems to like it that way.)

Re: A, B or "touring" cam?
 

Spoiler alert: most spell checkers will let anything with a capitalized first letter pass as a name. Mine likes "Babbitt" but not "babbitt", seems to still have the latter confused with "rabbit".

Re: A, B or "touring" cam?
 

Rabbit bearings sound like the would go "Lickity split"!

Re: A, B or "touring" cam?
 

Wabbitt bearings. “Kill the Wabbit! Kill the Wabbit! — Elmer Fudd

Re: A, B or "touring" cam?
 

Well, we know they will last at least 500 miles at 6500 rpm twice a lap. They were crudely balanced though.

Re: A, B or "touring" cam?
 

2900 rpm is no problem with a properly rebuilt babbitt engine.


My friend drove his car regularly on long tours at 65 MPH (that is about 2900 RPM).


At 35,000 he pulled one shim (one rod/main cap at a time) on each main and rod bearing.


Each time the crank was locked.


He replaced all the shims and put another 35,000 miles on it and no problems at 70,000 miles.


The same re-builder did my engine and at 25,000 it is still working just fine.

Re: A, B or "touring" cam?
 

It seems that early cams don't wear as much, but are ground to the same dimensions. There were three 5 brg cams, the first had all 5 ground to the same size, #2 had #2 and #4 ground smaller to ease assembly in the 3 brg block, #3 had them just rough turned on a lathe.