How much is too much

[Dick Steinkamp]

Originally Posted by Tom Wesenberg

NO cam can be reground and match original specs. Either the lift or duration has to change.

Not so. The base circle (heal) is reduced in order to have enough "new" material on the other end to grind the stock profile. Here's a good thread on that...

http://www.jalopyjournal.com/forum/t...am-work.36558/

You do have to make up the difference in the slightly shorter total cam lobe. Usually done with adjustable lifters/rockers. With a stock model a valve train you would need new valves so that you have long enough stems to obtain the proper clearance.

I agree with Mitch to leave it alone since it runs fine now.
BTW, I have a Studebaker V8 and the spec calls for .024" valve clearance. I thought this would make the engine sound like a rear bumper dragging tin cans at a wedding ceremony, but it's quiet.

I have owned many Studebaker V8s and agree they are quiet engines when the valves are adjusted correctly. It is a function of the "ramp" on the cam from the lobe to the heal letting the valve down gently to it's seat. Contrast with a high performance Chevy V8 solid lifter cam that has so much duration that it has to literally "dump" the valve on to the seat. They make a pretty neat hot rod clatter .

[Tom Wesenberg]

"You do have to make up the difference in the slightly shorter total cam lobe."

And that's why I still stand by my statement that the original specs can't be in a reground cam.
Either the lift or duration will have to be changed.
Actually I need to add a third parameter to this to be accurate, and that is valve opening to piston position. So, if you have a reground cam you can't have the same degree for engine cam timing and the same lift and dwell as original factory specs.

[Mitch//pa]

Agree with Toms post #22

The reground cam will not spec out as original unless you add metal and machine it.

Of course youll need an adjustable valve train to compensate....

Most of us will never notice the difference on our stock 40 horse machines

[Dick Steinkamp]

Originally Posted by Tom Wesenberg

"You do have to make up the difference in the slightly shorter total cam lobe."

And that's why I still stand by my statement that the original specs can't be in a reground cam.
Either the lift or duration will have to be changed.

Yea, I said that wrong. The total cam height would be the same (nose to heal). You would still have the same lift, the same duration, the same cam profile. The lobe heal is just closer to the cam shaft base circle which would make the valve clearances greater. This is usually easily made up with adjustable lifters/rockers.

[Tom Wesenberg]

Originally Posted by Dick Steinkamp

Yea, I said that wrong. The total cam height would be the same (nose to heal). You would still have the same lift, the same duration, the same cam profile. The lobe heal is just closer to the cam shaft base circle which would make the valve clearances greater. This is usually easily made up with adjustable lifters/rockers.

I think it was Marco who posted a good overlay picture showing how you can't grind an original cam and have it spec out the same. Anyway he did a good post showing why it can't be done, but I don't have time to find it now.

[Synchro909]

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Originally Posted by Dick Steinkamp

In order for the valve clearance to INCREASE with wear, it would have to be that the HEAL of the cam (not the nose) wore faster than the valve receded into the seat.

Having the NOSE of the cam wear would reduce valve lift but would not affect valve stem to lifter clearance.

I think it is unlikely that the heal of the cam wears to the point of affecting clearance in these low valve spring pressure engines.

X2.
Valve clearances are measured when the cam follower is on the heel of the cam. That is, when the valve is closed. The cam follower is only on the lobe when the valve is open.
To the OP, too much clearance will only cause noise and reduce the amount the valve opens. It will have a MINOR effect on the engine's breathing but not so much you need to worry. IF your clearances were set correctly when the motor was assembled, I'd guess it has done lots of miles by now for them to be that big. I think I'd let it run till it needs a rebuild and be confident your clerances are not going to cause a burnt valve.

[George Miller]

Originally Posted by Tom Wesenberg

"You do have to make up the difference in the slightly shorter total cam lobe."

And that's why I still stand by my statement that the original specs can't be in a reground cam.
Either the lift or duration will have to be changed.
Actually I need to add a third parameter to this to be accurate, and that is valve opening to piston position. So, if you have a reground cam you can't have the same degree for engine cam timing and the same lift and dwell as original factory specs.

I agree with Tom. There is no free lunch. Something has to give.

[Dick Steinkamp]

Originally Posted by Tom Wesenberg

I think it was Marco who posted a good overlay picture showing how you can't grind an original cam and have it spec out the same. Anyway he did a good post showing why it can't be done, but I don't have time to find it now.

Here's just a few cam regrinders that say that they will grind the stock cam profile on your stock cam...

http://www.elgincams.com/

If your camshaft is pitted, chipped, or worn, send it to us and we will grind it to either stock specifications or to a performance grind that meets your requirements.



http://www.oregoncamshaft.com/regrinding.html

we perform custom camshaft grinding to factory or performance profiles.



http://deltacam.com/

Custom camshaft grinding to factory or performance profiles.


Here's a diagram that may help. In this case, the grinder has actually increased the lift and duration of a stock cam. Notice that it is done by reducing the base circle. The same principal is applied when grinding a stock profile back on a stock cam.



One more...



It's tough to debate opinions or theories. If there are cam grinders that say it's impossible to put a stock grind back on a stock cam, or a profile with even MORE lift and duration onto a stock cam, please post links.

[forever4]

Originally Posted by Dick Steinkamp

Not so. The base circle (heal) is reduced in order to have enough "new" material on the other end to grind the stock profile. Here's a good thread on that...

http://www.jalopyjournal.com/forum/t...am-work.36558/

You do have to make up the difference in the slightly shorter total cam lobe. Usually done with adjustable lifters/rockers. With a stock model a valve train you would need new valves so that you have long enough stems to obtain the proper clearance.

I think Tom and George are the only guys on this thread who understands the facts and is correct.

You cannot regrind the cam and get the original lift and duration back back. People make the mistake of thinking it is a simple lift geometry problem. It is not, and it has nothing to do with making the push rods longer.

The cam profile plot of lift versus angle duration represents the time and opening of the valve, which affects the amount of air fuel mixture entering the cylinder. This is directly related to the power capable of being produced. If you integrate the area under the curve, it is profoundly different (less) for a reground cam.

Depending on the regrind, you can bias the torque and power a little, but overall you are at a loss compared to stock.

Many people here seem incapable of grasping this, or unwilling to believe it.

and so it goes...

[Dick Steinkamp]

Originally Posted by forever4

...You cannot regrind the cam and get the original lift and duration back...

...Depending on the regrind, you can bias the torque and power a little, but overall you are at a loss compared to stock...

I respect and admire all you have done for the hobby and have often used the information you have spent a lot of time putting together. Thanks. I'm sure you have forgotten more about Model A's than I'll ever know.

However, I try to deal with facts whenever possible. I supplied links to quality cam grinders who claim they can regrind a stock cam to the same stock profile...and that they can even grind a higher lift and longer duration than stock on a stock cam. I also provided illustrations of how this is done by reducing the base circle.

Is there anything you can link to that would substantiate your opinion that it can't be done?

[forever4]

Originally Posted by Dick Steinkamp

I supplied links to quality cam grinders who claim they can regrind a stock cam to the same stock profile...and that they can even grind a higher lift and longer duration than stock on a stock cam. I also provided illustrations of how this is done by reducing the base circle.

This conversation has been on fordbarn and ahooga 25 times over the years, and the facts are still unchanged.

Your illustrations from Marco / Bob Johnson are correct. Your understanding of them is not.

"OR", versus "AND" and the limits of the physics are key points. This is real life, not a theoretical abstraction.

Also what really matters is the integration of the area under the curve representing valve height and duration off seat, which is the real life breathing and the charge.

Based on the many discussions preceding on the boards, I don't expect to convince you of anything. That is your job. Or not.

As a practical matter, why do you suppose that new repro stock cams outperform all the 'stock/touring' regrinds available for the last 50 years, and that everyone wants to use and recommend a Stipe 330 or clone, when a regrind is a third the cost?

[Dick Steinkamp]

Originally Posted by Dick Steinkamp

Is there anything you can link to that would substantiate your opinion that it can't be done?

I didn't think so.

[George Miller]

The total distance the lifter travels on a reground cam is less. So you have to change some thing. less lift,or less dwell or open and close the vales at a different time. You just can not get the same work done in a shorter distance.

[H. L. Chauvin]

Hmmmm. The dead horse from years ago seems to have risen.

Sounds like we are beginning to lean on individual opinions in Soap Opera Style where :

Oh, I agree with Mrs. Pertunia and Mrs. Fanny; but Mrs. Appleskin is not far off.

But, only Mrs. Pooh really understands what is going on!

Then Mrs. Pooh has to brag on Mrs. Pfinella because she complimented Mrs. Appleskin and Mr. Fanny, plus told Mrs. Lollypop she is full of B. S.

Seems if one wants to dig deeply in any type of cam modification, why not just go online where there is enough mechanical cam engineering terminology and can technical information to study the function of varying cams to any depth desired.

[GPierce]

Post 31.
Also what really matters is the integration of the area under the curve representing valve height and duration off seat, which is the real life breathing and the charge.

This is the key and illustrates why you can't have the original lift and duration.

[Mike V. Florida]

Help me out here,

[Kevin in NJ]

With a regrind the width at the base of the lobe gets smaller.

You do not get something for nothing. There is always a trade off.

You end up with a more aggressive lift on the side as the ramp has to 'increase' due to the reduced base diameter. It is like moving a handicapped ramp closer to the house, the angle has to get higher. So you have to lose something.

You also have to trust the guy sets things up right.

Really the cam is the heart of the engine. You need to spend the $$$ if you want things to be right. I spent the $$$ for a NOS B cam.

[Patrick L.]

You can regrind for more lift, duration, different center line,etc. Thats what cam grinders do. But you won't end up with a profile exactly the same as original if thats what wanted.

[Dick Steinkamp]

I realize that it is counter intuitive to think that you can put a stock profile on a stock cam by removing material. I also doubted that it could be done even though all cam makers say they can do it. I spent a lot of time doing research with the intent of proving the cam makers wrong. Something HAD to give.

What I found was that something DID give. Valve clearance had to be adjusted. Most commonly done with adjustable lifters on our flatheads and with adjustable rockers on overheads (sometimes with longer push rods and sometimes by machining down rocker stands if so equipped). That's it.

Here's one more try at an explanation...

In this image you can see the effects that a worn camshaft has on lift, if it is worn by 0.020" then it will have that much less total lift. To calculate the lift you measure the width of the lobe and subtract that from the height. By removing that same 0.020" from the entire perimeter of the lobe, keeping the same centerline, the entire lobe is smaller but the effective lift is restored to 0.400". That 0.020" now can be made up with the extra preload the factory gives hydraulic lifters, or on a solid lifter valve train you just reset your clearances.



http://www.coltcams.com/html/tech_tips/

I think it's healthy to doubt. I do...all the time. I did on this subject. The bottom line, however, is your opinion must be supported by facts in order to be substantiated (well, at least on engineering subjects ). Making it true by saying it's true doesn't work. If you believe that a stock profile can not be ground on a stock cam (like I believed at one time), then do some research and link to some facts from credible sources that support your belief. Your opinions and thoughts are interesting, but won't win debates.

[Tom Wesenberg]

Dick, true that you can grind back the same lift, but now lay a degree wheel over the blueprint of the reground cam and see if you can also maintain the same specs.

I never gave the subject much thought until about 10 years ago when a couple guys were debating the same subject. Marco had a nice drawing showing why it can't be done. Something has to change, just as Marco's drawing pointed out. I'll try searching for Marco's picture, but I don't always have luck finding old posts.