Cam Lobe Width !
 

I am working on rebuilding a 400 and ordered a Melling 068 from butler. It wasn't in stock so for an upcharge sent their version they offer with Comp Cams. While it was being shipped i found a Melling cam local spc-7. I did have a used 068 from years ago and lined them up for the heck of it. I can't believe the difference in Lobe Width on the new cams vs the older one. The new 068 and butler 068 are a lot narrower than the old 068 from melling. Any thoughts?

You’re not the only one questioning this because this is something a noticed decades in an auto parts store I use to work in which was also a speed shop.

If I recall right I think it was with a Cam Dynamics cam that I noticed this .

Really makes me want to find out what the minimum lobe width is to have the lifter spin properly.

I am half tempted to return the new cams and use the older one.

If your concerned about lobe width, you could send your old, OE 068 to Bulllet/Ultradyne and they can regrind/dress/polish it for you. Less expensive than a new cam and you get a nice new surface to break in a new set of lifters. That's an option. I too have noticed the lobes being more narrow the last 20-25 years on many cams. Can't say if that's a problem or not, but millions of cams have been made that way.

When they regrind a cam I’m assuming the original parameters / specs cannot be kept?

You can also see the lifter path does not use the entire lobe width so the additional lobe material is moot. Cam break in issues has a lot of moving parts.

Unless your cam is badly warn they should be able to regrind it to original specs. The only thing is you will now have a smaller base circle diameter, and will need to check if your push rod length is OK or you need new push rods.

Stan

Wonder why the older cams have the wider lobes if it was unneeded, I'd imagine they had the technology back then to understand it was unused.

Might be more in play than we realize. Larger lobes might play some part in the manufacturing process, perhaps easier to get an accurate lobe taper etc.

In operation ... maybe a larger lobe drags more oil to the center of the lobe.

Back in the day, just like today, they were pretty good at shaving off pennies, makes me think there may have been a reason for wider lobes.

Or I guess it might be as simple as back then a wider lobed casting could be used for more different applications.

I bought the Butlers' Johnson lifters and when ordering the cam basically said its a 50/50 shot making it past break in and another crap shoot getting the 500 mile mark. I just opened up the 400 I took out, been running this engine 20 years, bottom end getting real tired, but the cam in it is a Crane 878 with whatever lifters and it looks great. Fingers crossed when I get to the break in process. Thanks for the replies.

Cams back in early 80s late 70s were showing up with both size lobes..

I noticed the difference back then but nobody seemed to care or talk about it..

My old HO .. HC-03 cam is a fatty and my Comp AH294-8

For stock cams like a 066 or 068 I do not think the lobe width will make any difference in longevity. On stock type cams I think the narrower lobe is easier to break in, and the lifter machining doesn’t have to be quite as perfect. Some of the original factory Pontiac stock cams were ground on the narrower lobes, they were not all wide lobes. On bigger cams where the profile is using more of the lifter face the lobe width is a lot more important. A big profile on a narrow lobe there ends up with less footprint where the lifter has the highest acceleration. That is why most mechanical cams use the wider lobes and the EPC cores are EP-2 instead of the standard cores. What I have seen on the narrower lobes and bigger profiles is the lifter digs into the base circle the closing side of the base circle, and the taper gets removed quicker on the opening ramp.

Comp cams and generally uses narrower cam cores from EPC. Crower uses the narrow lobes also. The letter EP-1 or EP should be cast into on the core somewhere between the lobes on EPC cores. Melling always uses CMC cores and has a little wider lobes with the letters CWC cast into the core. Both EPC and CMC cores are cast at CWC though.

Probably because cams and lifters worked 99% of the time back then. I never had a failure, and didn't know anybody who had one, personally.

Catastrophic cam and lifter failure is a 21st century phenomenon.

If you have a good used Crane 96878 068 copy with lifters matched up to the cam I would pick that over any thing new.

Bulter’s new warm and fuzzy HFT disclaimer!

Interesting that Butler has that disclaimer. Well it’s been discussed on this forum dozens of times times , take your chances . When I went to the stroker route had a chat with Dave Bishopp from SD Performance back in 09 . He said nothing will be built in his shop other than a roller set-up. I ordered the Old Faithfull then. My go to guy has the same sentiment. It’s the world we live in now.

I wanna go back to the 80s. Lube it up, stick it in, and drive it!

Yes Bill …was never an issue then .

Not entirely true. Chebbies in the '80s ate a bunch of
cams. Neighbor dropped a lifter into the oil pan, LOL.
But I never had trouble with Pontiac cams (including
a used one) in the before times.

Fingers crossed ! Getting closer to putting it together. So between the new comp/butler 068 and Melling 068, which do you feel is the better way to go? Thanks

The melling might be safer. I would want to know more about the Bulter cam to decide though. It might be fine too. Personally I would return the HLJ lifters and try the DLC face coated Comp High energies.

I don’t know what profiles Bulter use’s, whether it is a close copy or their own version. Can also look at the Bulter version for letters like EP or CWC. There are some cams from Comp that have narrow lobes and have a CWC logo that I think are very poor quality cores.