Disadvantages of a reground cam
 

After reading a different thread about cams I started wondering what the disadvantages were to the reground cam. The advantage would probably be price. Also what are the advantages and disadvantages of a reground cam?

Re: Disadvantages of a reground cam
 

Disadvantages of a reground cam: When compared to a newly manufactured
1) Worn bearing surfaces creating a loose fit between the block
2) Worn distributor drive gear teeth causing sloppy distributor timing
3) More duration when ground to restore lift (changed ...thanks Marco!)

Advantages of a reground cam: When compared to a newly manufactured
1) Less cost

Disadvantages of a reground cam: When compared to an unrestored original
1) You really need to measure the overall lift of the original cam and compare it to the specs of a reground. A really good original could be as good as a reground cam if the lift is very close because the duration will be better.

Advantages of a reground cam: When compared to an unrestored original
1) The lift will be back to spec but again, you need to measure all aspects of one cam to the other.

If you have more than .004" clearance between the block and the cam journals, you could notice a nock.

Re: Disadvantages of a reground cam
 

Great answer to K zoo`s question,i too are now just a little bit wiser thanks ...ken

Re: Disadvantages of a reground cam
 

Thanks for the very complete reply. I'm not there yet but I when the time comes I want to know what direction to go.

Re: Disadvantages of a reground cam
 

That should be: 3) More duration when ground to restore lift

Re: Disadvantages of a reground cam
 

One other thing to add to this list is something that Bill Stipe, James Rogers, and I have discussed in our chats, is that all reground cams on the market are not equal in quality either. If one is truly concerned with performance, then a degree wheel and a dial indicator should be used on all four tappets to verify lobe uniformity between each valve not only in lift, but in valve timing. Just as Marco pointed out, less duration is what is needed to get the 'I' valve closed faster so it can start building static compression on the compression stroke. Hypothetically having one lobe ground where it opens & closes later in relationship to the others will potentially not allow it to build as much compression in that cylinder as compared to the others, thus creating a cylinder imbalance. Think about how this can affect the smoothness and the overall power of the engine.

.

Re: Disadvantages of a reground cam
 

Any disadvantage would be very negligible in a 40 HP Model A. Advantages are price and availability. Most re-grinders suggest a minimum diameter on the bearings, the center main wears the most.

Re: Disadvantages of a reground cam
 

Another advantage to a new cam from Bill Stipe is that you can order one with an oversize center bearing and bore your block to match. When I went through this years ago I had the center cam bearing metal sprayed to build it up. Check your block for wear in the center cam bearing (which is the block itself). Just one of the small details that will result in a better engine

Charlie Stephens

Re: Disadvantages of a reground cam
 

Very true, but you must have at least two larger bearing journals--the front bore must be as large as the center journal or you can't get the cam into the block. Might as well do all three. Or have the block bored for standard-ID cam bearings instead of oversized cam journals.

Joe

Re: Disadvantages of a reground cam
 

Isn't it amazing the only bearing in the A that is pressurized, the center cam bearing, and it is more worn then the ends.

While we are on the cam bearing discussion, how about some details from experience.

What is considered too worn, actual dimensions, and the best ways to measure the block? When can one expect extra noise from loose cam bearings?

Some added details would help others learn how to evaluate their blocks.

I have to admit I am just learning the techniques for high accuracy measuring. My brother has been helping me. I have learned the low quality inside snap gauges may be made of brass and will not be accurate. I have some Central Machinery steel gauges, I got them recently cheap, that do an adequate job. The Starrett tools are much better.

Re: Disadvantages of a reground cam
 

Some of you machinists can make go-no go gauges be turning a bar with step increments of a thousandth or two.

Re: Disadvantages of a reground cam
 

I have a Stipe regrind "touring " cam. I have often wondered whether or not I made the right choice for my application.The engine has new cam bearings,Brumfield 5.9 head,standard valves,but new style with keepers,counterbalanced crankshaft,bearing shells. I encounter lots of long hills on tours,shifting made easier with a F150 tranny which I love.I think it should pull better on the hills. Any thoughts?

Re: Disadvantages of a reground cam
 

Many diff tranny ratios. What ratio in the rear end?
Paul in CT

Re: Disadvantages of a reground cam
 

That is what I noticed also.

I drove several Model A engines with original (un-reground) cams for 40,000 miles, 50 years ago. All engines have been installed in the same Sport Coupe. These were well worn engines. The only modification to all of these engines was a head "with the large B" (5.2 ratio).

These old engines would pull hills at low RPM (Added to clearify: 35 to 40 MPH in 3rd gear) MUCH better than my present rebuilt Model B engine with the reground cam. The reground cam engine has to be run at a higher RPM to pull most hills ... down shifting or getting a running start to keep RPMs high enough.

A reground cam with its longer duration will raise the max torque and HP to a higher RPM and from the torque curves I seen, will result in a much more narrow RPM range where the max torque occurs.

Instead of having good flat torque curve over a wide RPM range starting at low RPM like the stock cam, the regrind cam has a sharp peak over a limited range and at a higher RPM.

As a result it is necessary to have a 4.11 rearend and to shift more frequently (hard to do with a 3 speed!) in order to keep within the narrow RPM range where the engine has enough torque to pull a hill.

Maybe these reground cams work at sealevel. But at 6000 feet and above they do not seem to work too well on steep mountain roads where there are curves, switch backs and motor homes that slow you down on a regular basis.

Re: Disadvantages of a reground cam
 

Everything is a compromise! Touring cams give more power but at a slightly higher RPM, with slightly less torque at low speeds. You may be lugging the engine on hills if you are in OD. High performance cams are even worse at low speeds, but more than make up for it at high RPM's provided you have more carburetion. Compression helps all across the spectrum.

Re: Disadvantages of a reground cam
 

Sorry for the long response time. The rear end is standard 3.78 to 1.The tranny is a 4 speed with 4th being 26% od. I have a good matching set of 4.11 gears,but not sure if it is worth the work of the RE and Re.Thanks for your input

Re: Disadvantages of a reground cam
 

Jim, suppose you take a standard available reground cam and advance the valve timing by, let's say 7 degrees, how would that affect bottom end and hill climbing in a standard rebuild.

Re: Disadvantages of a reground cam
 

There seems to be a lot of talk about cam problems but no one really talks about the numbers and facts, timing, lift, etc.
I notice many reground cams are not timed correctly for a stock engine when I degree them on my engine stand. They generally have the intake opening too soon and closing late losing the static pressure for these low compression engines.

I Ask the guys here on this web site and the regrinders out there what timing they have for opening and closing seat to seat both intake and exhaust. My guess would be most don't know because they never degree the cam when they installed it and the regrinders don't know ether or more likely will not tell you because they don't want you to check there work.

It seems when ever a person is not getting the performance they feel there engine should deliver the cams are the first thing to blame. And they may be correct but you need to know the facts first.

With that said ask your regrinder what valve timing he is going to grind on your cam.
Ask for valve lift, lobe separation, and openings and closing of the exhaust and intake.

Then if you want to get deeper in to it ask him what degree of intensity he has on that regrind?
If he can not answer all your questions move on to a different grinder because he does not know CAMS!!!!!

He is selling you something you most likey will regret installing.

Happy motoring!!

Bill Stipe

www.stipemachine.com

Re: Disadvantages of a reground cam
 

This thread kinda got away from the original question. I got the touring cam from Bill Stipe,complete with the technical information He provided. With the engine described in my earlier post,is the touring cam the best option,or should the 3.78 rear gears be changed to 4.11,or better carburation?Highway speed is no problem,it is just that long hills will slow her down to 30-35 or so in 3rd gear. Thanks again

Re: Disadvantages of a reground cam
 

James Rogers, the theory is that an advanced cam will provide more low-end power while a retarded cam will provide more at the top end. I usually set them "straight-up", with equal overlap. I suspect all engine types are different and only dyno or other testing would really tell you. Bill Stipe does a lot of dyno work and is usually willing to share his findings.