Cam re-grind

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Princess Valiant

Princess Valiant

A.K.A. Rainy Day Auto
FABO Gold Member
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So I am still looking around for a new cam and lifters for my slant build up for a valiant wagon.

I almost went for a new Comp cams unit from Summit racing as they are readily available, but then I started hearing push back about the oil pump gear being too hard and eating up oil pump gears and causing engine failure.

A few people have told me to "regrind" an original cam for better results.

I started asking RRR about it but I am still not clear so I decided to bring it over to FABO in case anyone else has the same question. He mentioned something about putting a cam lobe on, so are the lobes removable?

Maybe my thinking is wrong but it seems to me that if you "regrind" or "grind" a piece of metal, less material exists than previously.

So if you have a worn cam and you grind material off, then you have a cam with specs worse than a worn cam.

I am sure there is something I am missing??

any Cam gurus out there who can explain this ?
 
When they regrind a lobe, they reduce the base circle.

Depending on the original lobes and LSA, you can only change the lobe a small amount.

For example, if you have a cam with say, 280 advertised duration, .480 lift (.320 at the lobe) on a 112 LSA, it would be difficult to make it much more lift or close up the LSA more than about 4-5 degrees. Or gain more than .050-.060 lift.

Ken from Oregon cams can give you more precise numbers.
 
I will try, so bear with me. I am not a genius, so all I can do is explain it in my own terms.

Imagine the cam lobe being a triangle. Now, imagine that triangle on the cam core. A cam grinder can grind that lobe to end up most anywhere on the core he wants it. This is why you can end up with more lift and duration while grinding AWAY a camshaft lobe, because while he grinds it away, he also RELOCATES it in relation to the cam core centerline, as viewed from the front of the camshaft. In other words, the grinder can move the lobe on the cam centerline so that it will give more lift than before, even though he ground some off the lobe, because he MOVED the lobe on the cam centerline. Generally, reground cams may require custom length pushrods, as the base circle becomes less than it was originally. Sometimes though, new pushrods are not required, because some engines have a great amount of adjustability in the valvetrain. The slant six is one of those engines. You may not even require new pushrods. It is simply something you will have to measure for yourself to see.
 
If you want to look Hughes Engines has slant cams.
Same as you I heard the Comp cam story. I've used them with no failure.
Just a thought.
 
I had a mopar slant cam nearly destroy a distributor gear. I found it by accident. It was nearly gone. Doug Dutra used to have his dist gears hardened to alleviate this problem. I got in on a group deal and had a 15 of them hardened through him about 10 or so years back. They have all been used or sold, but I mention it as another possibility. Maybe they guys over at slantsix.org could get another group hardening deal together with him.
 
Darter6 said:
If you want to look Hughes Engines has slant cams.
Same as you I heard the Comp cam story. I've used them with no failure.
Just a thought.
Click to expand...

I had a problem with Hughes and a roller cam, they intentionally sent me the wrong one that I told them not to...

I would go with Ken at Oregon Cams, he ground a nice one for my ex's slant and she was happy with it...
 
Rainy Day Auto said:
I started asking RRR about it but I am still not clear so I decided to bring it over to FABO in case anyone else has the same question. He mentioned something about putting a cam lobe on, so are the lobes removable?
Click to expand...

The cam grinder can move the center line of the lobe a little when he regrinds it... You may have gotten confused in some of the terminology when he first explained it...
 
First, please always state the engine . Guys here knew enough to figure it out. When grinding lowers the base circle, most engines need longer pushrods to match. But, your slant has adjustable rockers, so if within range should be OK.

Yes, they can add material to the lobes before grinding, but expensive. Wheeler Dealers did an episode for a rare engine. But, slant cams are easy to get.
 
Rainy Day Auto said:
So I am still looking around for a new cam and lifters for my slant build up for a valiant wagon.

I almost went for a new Comp cams unit from Summit racing as they are readily available, but then I started hearing push back about the oil pump gear being too hard and eating up oil pump gears and causing engine failure.

A few people have told me to "regrind" an original cam for better results.

I started asking RRR about it but I am still not clear so I decided to bring it over to FABO in case anyone else has the same question. He mentioned something about putting a cam lobe on, so are the lobes removable?

Maybe my thinking is wrong but it seems to me that if you "regrind" or "grind" a piece of metal, less material exists than previously.

So if you have a worn cam and you grind material off, then you have a cam with specs worse than a worn cam.

I am sure there is something I am missing??

any Cam gurus out there who can explain this ?
Click to expand...
Have you called Ken at Oregon Cam Grinders? Talk with him, to grind a cam is roughly 75 bucks, but for him to custom grind a brand new cam off a cam blank, is only 150 bucks. Which is what I am doing with my 440 as its pretty much a wash between prices for an off the shelf grind vs a custom grind. You can have one ground off of a used blank, it just reduces the overall cam circle diameter as mentioned above.
 
Add one more for Oregon cams, have the stock roller reground in my 360 magnum and it seems to run pretty damn good. And when they grind the base circle (round part on the bottom of the lobe) it increases the lift the valve sees from the same lobe. The lobe will be taller than before because the base circle will be ground down.

It all works in conjunction with taller pushrods too, but if you have adjustable rockers on that slant still you might be able to take up the slack I'm not sure about that. Like for example on my 360 I had to get longer pushrods because when the lifter was on the base circle of the cam the stock pushrods where all sloppy. So I had to order some longer pushrods. It was confusing me too when I first heard about it. The needing of a taller pushrod deal helped me understand.

Another way to explain would be because you have the base circle on cam, which is now shorter than stock, set as a neutral point (no lift going on). When the cam rotates around the lifter has to climb more up the lobe. Because the other side of the cam is shorter. Compared to how it was before when there was still more material on the bottom side of the lobe, which would make the lifter have to climb less up the same lobe.
 
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I have a 225, totally rebuilt but not quite stock. I read the horror stories about the /6 cam distributor drive gear on Slantsix and it spooked me enough that I decided to stay with the original cam and oil pump. I took the pump apart and checked it thoroughly against the specs in the FSM and it was good. I told Oregon Cams my engine mods and intended use and Ken recommended 2 grinds. I went with the milder as this car is a cruiser, not a street racer. The stock lift was a puny .375. Sent him my cam and got it back in less than 2 weeks. So my original cam is mated with the original oil pump and uses the original adj rockers and pushrods.

I'm using Lucas Hot Rod Oil available from Summit. It's approaching 2000 miles and everything is good so far.
 
Rani, explaining cams is hard to break down into easy to understand and terms sometimes. Getting "The picture" can be hard to develop.

The lobes are not removalable. When RRR said "Put a lobe on it." He was meaning to regrind the lobe shape differently. You will have less material but it will be better because it is a fresh surface not a wrecked one made worse. Like reboring a cylinder, there's less wall left but what is left is in great shape ready to use.

YR mentions what is done with the lobe and it is ground smaller. But it is the amount of ramp rise off the lobe which will determine the size even if physically smaller, it can be larger in lift and duration as measured at the valve.
Think like a magician, its all smoke and
mirrors that fool the eye but not the dyno. Little things can cause big effects just like big things can have little effect. Like gears in a clock.

Open up Comp Cams or Crane Cams website and look into there tech explanation & terms section. On cam tech. This should help out a bunch.
 
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