Anyone explain camshaft grinding?

Onlybackroads

Onlybackroads

Senior Member
Hey everyone, I've heard of "ground cams" but never really knew what this meant exactly. I know it's changing the lobes to change valve timing/duration, but what is the actual process? Is material added then reshaped? I tried to search on google but there are so many crappy explanations, same with youtube. I'm sure someone experienced can tell me in a simple way. Thanks!
 
From Mike's HAMB link:
I think this is the part that troubles you:

"Just to restate what others have said, lift and duration are increased by grinding away the "base circle" of the cam. The lobe doesn't have material added to it, but the non-lobe part is ground away making the difference between highest part of the lobe and the lowest part of the base circle a greater distance"

So, they grind the tip and the heel both. The heel will often end up a smaller diameter than the main (principle) diameter of the shaft itself
 
Ah, gotcha, so the entire circumference of the lobe is ground down, then the height adjustment of the tappets makes up for the shrinkage of the lobe. That makes a lot of sense, thanks! I knew it had to be a simple procedure to explain, I just had no idea!
 
IF you're real lucky Jim Brierley or Pete will see this and give you a good explanation.
All I can do is bump it to the top.
Good Luck:)
 
Here's a copy of a handout I used to use at cam seminar's.

TEST YOUR CAMSHAFT GRINDING KNOWLEDGE.
QUESTION (1) How does a cam grinder know what shape to grind a cam lobe when they are all different from engine to engine?
ANSWER 1.
Cam grinding machines unlike cylindrical grinders use a master that automaticly controlls the grinding wheel or the work table to duplicate the profile of the master. These masters are produced from blanks and are ground to the profile of a new or unworn cam lobe. The operator keeps a series of masters in a library that allow selected profile grinding of worn camshafts. These masters can be factory purchased as computer ground finished masters or simply ground on the cam grinding machine using a new or good cam lobe and duplicating the profile onto the blank. They can also be generated on a milling machine from a set of lift figures that an engineer has designed for a specific purpose. These new masters are then cataloged for future grinding requirements.
QUESTION (2) What is the most common finish fault when re-grinding camshafts?
ANSWER 2.
Grinding chatter marks are often seen on the base circle and the sides of the lobe. Chatter marks can cause hydraulic lifter problems and premature wear. Pronounced chatter marks and eccentricity on the base circle can cause hydraulic lifter pump up and an engine miss on idle. Burn marks can be present when an operator trys to hurry the grinding process. Burn marks will almost always result in early failure of the cam lobe.
QUESTION (3) What causes these chatter marks?
ANSWER 3.
Due to the design of a cam grinder having a reciprocating grinding head or table that follows the master profile, any out of balance of the grinding wheel will cause a chattered finish. The camshaft has to be held rigid with a steady rest. This steady rest has to be adjusted correctly and positioned as close as possible to the lobe being ground. The chatter marks occur when the camshaft or grinding wheel are allowed to vibrate during the grinding process. Trying to finish grind at too high an rpm of the cam will cause chatter also.
QUESTION (4) Some cam designs require the lobe to be ground at an angle to assist in rotation of the lifter or follower. What three methods are used to achieve the desired angle when grinding?
ANSWER 4.
The face of the grinding wheel can be dressed at the required angle.The grinding head work table can be adjusted to the required angle. The camshaft table can be angled.
QUESTION (5) Apart from finish, accuracy and concentricity what other items have to be considered when grinding a camshaft?
ANSWER 5.
(a) The straightness of the cam before grinding. (.001 in. maximum allowable bend)
(b) The indexing of the camshaft to ensure the correct cam timing is maintained.
(c) The cam design can accommodate the passing of the conrods between the lobes and this clearance must be maintained when using new billets or cams of a different model from core stock. (Ford Falcons are examples) Ensure correct undercut between lobes.
(d) What effect the stock removal on a lobe will have on the rocker gear geometry or non- adjustable hydraulic tappets has to be considered.
(e) The hardness of the cam lobe after regrinding.



Here is a URL for cam info that explains it extremely well.
http://tildentechnologies.com/index.html
 
In common terms, valve adjustment is made on the heel of the lobe. When the heel of the lobe is ground down to the main shaft of the cam or below, this increases the lift. Being as valve adjustment is made on the heel of the lobe, lift will increase to the amount that was removed from the heel of the lobe. More lift increases torque or power that you can feel in the seat of your pants. Grinding the tip or toe of the lobe widens the lobe. widening the lobe increases duration or the length of time that the valves actually remains open. More duration gives more top speed at the cost of losing torque. With a low compression engine like the model A, if too much widening of the lobe tip and too much duration is added, horsepower and torque will be lost. The reason for this loss is because with low compression the engine won't have the omph or power to kick the RPMs up to the level where the duration will be of benefit. The best regrind cam will increase lift as much as possible while slightly increasing the duration.

The height of the Model A&B cams are only one thousant below the level of the cam bearings. If the actual height of the lobe was increased it wouldn't be possible for the lobes to pass through the cam bearings in the block. Being as lobe height can't be increased without boring out the cam bearings in the block and having a completely new cam made with larger bearings and lobes, the only way to increase lift in the model A&B engines is reduce the heel of the lobes.
 
Yes, great info here!

So, if you have a straight, original, Model A Cam, and you wish to get more lift (and thus power), is it financially most practical to send your used Ford cam off to an Experienced, Model A/B cam grinder? (and how much lift/duration should be specified)?

Or, is it more cost effective to just order a brand new performance cam from Bill Stype or some other high performance cam supplier?

Either way, what adjustable lifters are recommended for the Ford or aftermarket performance cam with the lower lobe heels?
 
A and B cams can't be reground to achieve original lift and duration from the available metal.It can restore either lift or duration or some compromise,but not both.
 
Not so My original cam ground by Bill Stipe has more lift and slightly more duration. Just any cam can't be ground for better lift and duration. If the core is too badly worn the results won't be the best. I talked to Bill over the phone and he gave me the specs to look for and I measured several of my used cams before I found one that met the core specs that Bill requested. Lobe diameter of the core needs to be at least 1.225 and center bearing size needs to be 1.557 . I chose the Winfield super street 3/4 race grind. The large base single lock lifters was recommended for this cam
 
Purdy Swoft said:
Not so My original cam ground by Bill Stipe has more lift and slightly more duration. Just any cam can't be ground for better lift and duration. If the core is too badly worn the results won't be the best. I talked to Bill over the phone and he gave me the specs to look for and I measured several of my used cams before I found one that met the core specs that Bill requested. Lobe diameter of the core needs to be at least 1.225 and center bearing size needs to be 1.557 . I chose the Winfield super street 3/4 race grind. The large base single lock lifters was recommended for this cam
Click to expand...

Sorry Purdy but rocket1 is correct in post 12.
 
southfork said:
Yes, great info here!

So, if you have a straight, original, Model A Cam, and you wish to get more lift (and thus power), is it financially most practical to send your used Ford cam off to an Experienced, Model A/B cam grinder? (and how much lift/duration should be specified)?

Or, is it more cost effective to just order a brand new performance cam from Bill Stype or some other high performance cam supplier?

Either way, what adjustable lifters are recommended for the Ford or aftermarket performance cam with the lower lobe heels?
Click to expand...

It was most practical for me to have my cam reground. I sent mine to Bill Stipe for a regrind. Suitable cores are getting scarce. I chose the Windfield 3/4 race grind. The lift is 317 intake, duration 255 ,lash .016 . exhaust lift 310 , duration 252 , lash .016 . The cost was only $125.00 . The large base single lock lifters from Brattons were used. Snyders sells the same lifters. The double lock lifters have a small base and are not recommended for the new or reground cams like I use. Lobe height is the same on model A and B cams. Both cams when new , the lobe height is .001 less than the height of the cam bearing. model B cams used a longer lifter with a larger base. without going out and measuring one of my cams, I believe that the heel of the B cam was less than the A cam and this and the longer lifter gave the B cam more lift. There is some disagreement about model B cam lift. Jim Brierley has said that there are three different lifts used on various model B cams. Jim says that Model B lifts were 302 , 315 and 339 .Vince says that all B cams had a lift of 339. I have never seen a quote from Bill about what The lift was on the model B cams. I have seen model B cams advertised with a lift of 302 so I mostly agree with Jim Brierly that there was more than likely a variety of lifts for the B cams depending on the application. I haven't found my notes on original model A lift and duration but I believe that my 3/4 race cam is much better than original model A specs. Of course a new cam would be better and the tip of the lobe wouldn't have to be reduced by grinding to increase duration and the heel could be machined to give more lift. Same for a new old stock cam, the heel could be ground for added lift and the B cam already had more duration than the model A . A reground model A cam if it meets core specs can give more lift and duration than a stock model A cam and give better performance while saving a great deal of money. The new cams can give more but cost nearly four times more.

I haven't seen any dyno tests showing the gains with the different grind cams new or regrind on a stock engine. Piranio has dyno tests showing horsepower and torque on stock engines with various heads and compression ratios as well as different manifold and carburetor variations. The model B engine in all its glory had only 50 horsepower while the model A had only 40. Piranios dyno sheets show that the stock model A engine gains nearly seven horsepower with the stock C head that had only 4.6 compression but an improved combustion chamber over the model A. If there is only a 10 horsepower increase between the model A and the model B engine this means that the model B cam, larger intake and larger carburetor only added around three horsepower. Acording to my experience I believe that model B grind cams are highly over rated.
 
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Vince, People have used regrind cams for added performance since the model T days. Regrind performance cams can boost performance If the cam grinder knows what he is doing and the core meets certain specs, this is just a fact of life. This is not to say that all of the touring cams that are offered by some will actually help. Its good that Bill is offering new cams and most want to help him sell them. Don't sweat it he is doing all right and selling plenty cams. Bill,Pete,Jim brierley and many others have ground and sold performance cams for years. If these cams didn't improve performance they would have went out of business a long time ago. I'm not surprised that you and Pete are disagreeing with my comments, That is pretty much the norm. It hasn't been that long and I'm sure others will remember when Pete was boasting about a model A cam that he has on display that some guy ground on a bench grinder that had won some speed record . This cam that was ground on the bench grinder was just copied by looking at a cam that someone else had ground and the bench grinder guy had no special cam grinding equipment. I guess that the cams that pete grinds are good but the ones that I've mentioned are just no good because I'm not a cam grinder by profession and don't know what iI'm talking about. I listed the specs on the cam that I run in my roadster and the profiles, lift and duration is different on both intake and exhaust . I have experience with cams and lifters. Sure you've got theory but you are not a cam grinder either. I don't have BS credentials nor do I need any. I do have a lifetime with model A's that includes actually working on and building them. The question was asked about cam grinding. I have experience with model B and other performance cams used with model A's. I have actually installed and used them. I just answered some questions that have been shrouded in mystery. I don't claim to know it all like some but don't hesitate to answer questions in common terms.
 
Hey Pete,
HMM, thanks for that..I think:) ! This is why some guys grind them (YOU), and why some guys run them (ME). And, I'm soon going to test out your knowledge on the NOS B cam that you did for me..thanks :cool:
 
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