Regrind or not to Regrind

[talonted_one]

Me and some friends were thinking about having some cams reground to HKS specs....


I just wanted to know what were you opinions about doing so.

Pros of doing it?
cons of doing it?

over all is saving a lil money now going to hurt longevity and potential in the long run?

 

[BoostinAWD]

The stock cams don't have near the lift as hks cams, so how are you gonna do it?

 

[HighPsi91]

Yes you can have the factory cams reground to HKS specs provided you find a place to do it for you. The benefit is pretty much only cost. The downside is you may have to shim the HLA's if they overextend. I have run regrinds in the past with no problems and they were ground much larger than any HKS cams.

 

[talonted_one]

sweet thanx for the replies...

Well my crew have a very reliable and very good machine shop do pretty much of our custom work.

from my research the shims can be made from none other than pentiful and high quality Dimes... true or false..anyother suggestions?

 

[BoostinAWD]

How does it work? Do they weld onto the lobes then grind them to spec?

I'm curious How much does it normally cost for this?

 

[talonted_one]

yep thats exactly it...

as far as price I'm not exactly sure. We are getting a hook up supposedly

 

[cait sith]

I wouldn't do it personally. 600 bucks for the assurance that my valvetrain was going to be PERFECT is better than going the cheap route.

Mod cheaply, mod twice.

 

[talonted_one]

so far the only quote on price I have is around $150 give or take. I'll be sure to keep everyone updated.

 

[HighPsi91]

Typically regrinds do not require welding of the lobes. The base circle is cut down.... this is how you get more lift, etc. Stay away from welded cams. DSM cams do not need to be welding. Depending on the size of the profile you want you may need 1st gen C/D cams. They have the most meat to work with.

 

[GSX_Dan]

Typically regrinds do not require welding of the lobes. The base circle is cut down.... this is how you get more lift, etc. Stay away from welded cams. DSM cams do not need to be welding. Depending on the size of the profile you want you may need 1st gen C/D cams. They have the most meat to work with.

Sorry to bring this back from the dead, but I've been trying to figure this out as to exactly how they manage to get more lift out of a cam by cuting down the base circle and not using welding to add more material to it....? What is the base circle, because as I understand it is the smallest circle from the cam center through the cam profile curve.

 

[drivemusicnow]

Okay think about it this way:

The cam rotates in a line as centered by the "bearing" surfaces and cam caps.

The valve moves a distance as defined by the distance between the radius of the base circle as compared to the highest point along the cam profile. If you make sure that your decreased radius "base circle" (which is the shortest radius along the cam profile) does not over extend the lifter, the valve will be opened and closed properly. If you have to, you can add shims to the lifter so that the lifter is at an acceptable height when the valve is closed.


The cam profile defines a lot of things such as how fast the valve opens (valve acceleration) how far the valve opens (lift) and for what length of time the valve is open (duration). There is an unlimited number of possible combinations between those three parameters that define how the cam will run. As long as you make sure that those three things are correct, and that the lifter is not over extending, you're set.

Since this thread was made 4 years ago, I'm guessing it never really happened though. By the way, DKS cams are re-grinds, as well as Web cams I believe (not sure on the web cams).

 

[GSX_Dan]

I don't understand how cuting down the base circle actually increases lift. All I can see that is happening is the part of the cam lobe that doesn't actuate the valve at all is getting cut down, then a shim is added under the lifter to make the rocker come back into contact with the lobe(if necessary).

Also how can duration and ramp speed (valve acceleration) be increased with regrinds without the process of welding? From what I understand(or trying to) after a regrind you're left with the same OEM cam profile, just with more lift. Is this all the HKS 264/272 are?

 

[drivemusicnow]

no, the bearing surface stays exactly the same, as the axial rotation of the cam stays on the exact same line.

When grinding the cam for instance recreating an HKS 272, you will grind down the the portion of the lobe (the surface that directly opens and closes the valve) that would be the "closed" position of the valve. When a valve is closed, the lifter is at full extension, and is following what we have referred to as the "base" circle. If we grind down ONLY the part of the cam that is in contact with the lifter when the valve is closed, than the DIFFERENCE in the radius between the base circle and the outermost point on that cams profile (the tip of the lob) increases. This effectively INCREASES lift, would slowly but surely increase duration, but keeps the same ramp rate or valve acceleration rate. If we want to make that stock cam into a 272, you need to grind the lobe as well, to get the right shape.

When you look at the regrind compared to the real thing, you'll notice that the regrind has a small inner radius, but the same difference in radius from the "base circle' to the tip of the lobe. The re-grind is NOT just a proportionately smaller image of the larger.

So in summary:
Increase lift by grinding the base circle
Increase duration by grinding the base circle down
Increase valve accleration by making the slopes of the cam lobe steeper. (grinding the lobe)

You have to realize that this takes very precise machining, because very very small differences are significant. I drew a picture but I don't really feel like scanning it in. Take a look at http://www.opeltuners.com/rollerlifters/hydrprofile.jpg and pretend it is our stock cam profile. Then think about what would happen if you were to grind the "base circle" down further.


Then read here LINK
and compare the two profiles. It is an extreme case, but does a good job with the pictures.

 

[GSX_Dan]

Now it makes perfect sense. I was missing the fact that the lifter is at full extension when the base circle part of the cam profile comes around and it's this additional extension of the lifter that increases lift when the lobe spins around to open the valve.

Thank you for that awesome explanation

 

[Bohrn]

a good proven regrinder who knows what he/she is doing can make very nice custom cams, different than just 264/272.

And they will last a long time if done correctly.

as for cost, less than half price.

As well, no one has to know you have hotter cams in, if you get a stage 1 style cam, its still gonna idle well, have good vacuum and look just like a stock cam, but it will not fall off up top like a stocker.

 

[2gAWDTalon]

First of all, thank you drivemusicnow! I have always wondered this same thing... "How the hell do they get more lift if they take away from the lobe". Now, Thanks to you, I understand perfectly! Thanks!

By the way, DKS cams are re-grinds, as well as Web cams I believe (not sure on the web cams).

Web Cams are not regrinds, they are made from brand new cores... They had regrinds a LONG time ago before new cores were availible, but have not been regrinds for many y e a r s...

 

[Defiant]

Web Cams are not regrinds, they are made from brand new cores... They had regrinds a LONG time ago before new cores were availible, but have not been regrinds for many y e a r s...

If they're cut from stock camshafts, they're "regrinds". They'd have to get non-ground blanks for them to not be regrinds. The common trouble with reground cams is that too many grinders didn't do a proper heat treating and re-hardening of their work- I had a regrind on my 2000 start to flatten its lobes back in '81, and haven't gone near a regrind since. I have no idea how nor how well current cams are being re-done these days, but so many other procedures and methods have taken such large technological leaps in those years that I'd not be surprised to find out those days are long gone.

 

[Elvenhome21]

If they're cut from stock camshafts, they're "regrinds". They'd have to get non-ground blanks for them to not be regrinds. The common trouble with reground cams is that too many grinders didn't do a proper heat treating and re-hardening of their work- I had a regrind on my 2000 start to flatten its lobes back in '81, and haven't gone near a regrind since. I have no idea how nor how well current cams are being re-done these days, but so many other procedures and methods have taken such large technological leaps in those years that I'd not be surprised to find out those days are long gone.

The only time you run into problems with regrinds is when you run flat tappet lifters, when you run roller lifters there is zero friction on the lobes themselves hense the reason for rollers. Almost all roller cams aren't hardened very much if any. They normally they are just case hardened a couple thousandths deep. A guy on ebay sells Nippon regrinds and claims a stock mitz cam is case hardened .060 deep, and when he grinds they he takes off like .016 off the base circle so there iis plenty of hardened material left. On a chevy certain racing roller cams are billet steel the main reason they are hardened is to prevent the cam from twisting into two pieces.

 

[2gAWDTalon]

If they're cut from stock camshafts, they're "regrinds". They'd have to get non-ground blanks for them to not be regrinds. The common trouble with reground cams is that too many grinders didn't do a proper heat treating and re-hardening of their work- I had a regrind on my 2000 start to flatten its lobes back in '81, and haven't gone near a regrind since. I have no idea how nor how well current cams are being re-done these days, but so many other procedures and methods have taken such large technological leaps in those years that I'd not be surprised to find out those days are long gone.

Just to make sure we have the right info for anyone searching... Web cams are made from brand new blanks the same as HKS, Forced Performance, Brian Crower, Comp Cams, ect... They are not regrinds like DKS cams...
Fell free to check out there Mitsu Page
www.webcamshafts.com