I probably could have posted in the Lobe Profile thread, but I didn't want to hijack WS6 TA's thread. My questions are a little different.

I'm working on picking my first cam, and I have found that I simply don't know enough. Anybody got any book recommendations?

When you have a cam "custom ground," how custom is it? Do you just pick which intake and exhaust lobes you want and specify the LSA, or can you nail down the exact intake and exhaust opening and closing points (assuming you know enough to pick them yourself)? Can you say "I want to hammer the valve off its seat as hard as possible without making the lifters edge-ride, but then set the valves down on their seats a little bit more gently" so as to reduce the risk of valve float? What is the purpose of asymmetrical lobes? What about lash ramps: can you specify if you want them to be agressive or gentle? (I'm thinking of solid flat-tappet cams.) Can you specify tight lash or regular lash? How much extra does it cost? I'm guessing many of these things depend on the company and who you get on the phone. Is it ever possible to talk to an actual engineer?

I realize these are pretty big questions, but this is what I think about as I lie awake at night. Then I get bothered that I don't know the answers and I have to post my questions online.

 

You can specify anything you want, but the way most people get a custom cam is that they either go directly to the grinder or to an intermediary like Lloyd, describe your specific combination and then get a cam tailored to your specific needs.

As I said, you could specify your own...

Say you have a Crane or CC grind and you have enough experience to know that you like duration and overlap, but you want more lift. You can begin with a "shelf-grind" cam spec, give that to the grinder and tell him; "Add another .015" lift to that cam. Or you could as for more exhaust duration... whatever.

Ultimately, your best bet is to work closely with your head porter and see what he has to say.

 

I have to say that if you think you will come up with something better than the people who do tons of simulation and testing, or even near as good, you aren't being realistic. Either buy an "off the shelf" grind or pay the extra $100-150 to have something specific to your needs (i.e. a "custom").

Rich

 

Getting the correct valve events and lift compatible with the rest of the engine "package" is Job One. The agressiveness of ramps,and flanks, etc. should then be tailored to your engine parts, rpm range, as well as vehicle and driver combination when designing a "custom" cam.

Along with the cam, the rest of the valvetrain parts are critical to achieving the performance you expect. Usually a package of parts is specified.

Float or loft is usually dependant on rpm, springs, part stiffness and mass as well as lobe profile near the nose. Bounce on the seat involves springs and closing ramps among other things.

I agree with having a custom cam specified by those who do that for a living. They don't necessarily work for a cam company. I agree that asking Lloyd Eliott for a recommendation is a good idea even if he didn't do your heads.

As far as getting to discuss your needs with the engineeers who design lobes, that's a long shot, but it depends on the company. The more specific you engine/vehicle combination is, the more time the "cam guy" will need to spend specing a cam. Usually the custom costs only a little more than a shelf grind especially if you buy it from the designer.

David Vizard has done some good atrticles and books about choosing cams. Try his "How to Build & modify Chevrolet Small Block V-8 Camshafts & Valvetrains" It's been around since 92 but it has a lot of good basic info in it.

 

Bret Bauer (who posts here) designs custom cams, and does a very good job of it. I am surprised he doen't charge more - they run maybe $100-150 more than an off the shelf grind.

Also, you haven't given any info on your combo. The more unusual it is, the more you might benefit from a custom spec cam. OTOH, if it's a pretty standard combo you won't gain much, if anything. For my Camaro, a custom cam was needed due to the combined use of blower/nitrous and the dual purpose use of the car. I wanted an HR cam with good street manners that I could also use effectively at the track with nitrous. OTOH, the motor currently in my race car is a basic carbed BBC alcohol motor and I use an off-the-shelf cam. People have been drag racing these things for decades and experiementing with various cams. Any gain from a custom wouldn't justify the cost. However, I am collecting parts for a new race motor that I will build over the winter. It's also going to be an alcohol BBC but will use EFI. I want to make big hp with it but keep the revs down to ~6,500. This is not typical of race cams, which are usually designed for higher revs and carbs. So, a custom is in order for that combo.

Rich

 

Yes, the key is knowing what lobes do what.... Basically what you described is one of the reasons for asymmetrical lobes. The opening and closing sides of the cam are not a mirror image of each other when you plot everything on a graph.

Just like above.... The one thing to think about on a aggressive flat tappet cam is the costs to pulling it off.

#1 You have to have excellent lifter bore location in the blocks, because if they are off on angle or on location, that's one sure fire way to wipe out a lobe. The aggressiveness also correlates to the size of the flat tappet. A .904" Mopar Tappet works much better than a .842 GM tappet when you want lots of lift or lots of area in a very small duration range. Figure $500 to have the lifter bores bushed in the block.

#2 You should have good lifters, like EDM oiling hole versions from Comp or Crower. Schubecks lifters are also really nice for this. $80 for a standard set of flat tappet lifters, can grow to 3 times that for EDM lifters and up to $640 for flat tappet Schubecks.

#3 Breakin Rockers would also be really helpfull, but a set of Schubeck lifters elminate the need for this as well. Figure $250-$275 for break in rockers, or lots of time swaping springs on the motor.

So in the end, a solid roller setup can cost a lot less, have MUCH less chance of burning a lobe off the cam and give you the aggressiveness that you are looking for in terms of valve opening.

#4 Custom Flat Tappet cams are usually $100 more than an off the shelf cam, your not going to find a $84 Custom Cam special flat tappet cam. Figure $225+ You don't even want to know the cost of a NASCAR spec stellite welded flat tappet core. Well maybe you do... $850+

OldSStroker never mentioned it, but yes some people can. He gets along with one of Comps Engineers very well. Mostly due to the reason that they can talk the same talk and understand each other. This is not something the average guy can do. The best thing to do is talk to someone who does this for a living and understands what's going on with the whole system.

BTW Rich, Thanks for the compliment.

Bret

 

Thanks for the great responses.

I didn't list my combination because I'm probably just going to run an off-the-shelf cam, but thinking about which one to pick got me to thinking about custom cams and just how specific you can be.

BUT since you asked, this all started when I bought a lightly used 1987 LS6 454 crate motor last fall. It appears that it has never been apart, so I'm basically going to swap on an old Edelbrock TR2X tunnel ram, put in a cam to match, and throw in a new oil pump for peace of mind. Here are the specifics:
10.2:1 compression (unless someone has info to refute that)
Iron rectangular port heads (990s) that flow like this
The heads are equipped with screw-in studs and long-slot stamped rockers that are good to 0.600" lift
Edelbrock TR2X tunnel ram with 1200 to 1320 cfm of carburetion (runner length is 7 inches)
I plan on using Howard's Direct-Lube lifters (0.021" hole in the bottom)
It will be run with open headers at the track
Trans will be a Muncie M21 4-speed (2.20:1 First), which only drops the RPMs about 25% on shifts
Rear is a 4.10:1 12-bolt. I'll almost certainly need more gear, but I'll get a baseline with the 4.10 and go from there
Tires will be between 26" and 29" diameter (12" max section width), whatever works
Car is 3485# with me in it and a half tank of gas (SBC/TH350 combo)

Stipulations and notes:
I don't want to shift at more than 7000rpm, mainly because of the knurled-shank bolts Chevy put in the rods
Vacuum is not a concern (the only vacuum line will be the one to the distributor)
Please notice that the rockers won't take more than 0.600" lift
The cam must be a solid flat-tappet design
This is a dragstrip car that will only be driven to and from the track. I like to think that I don't care about "driveability" because I'm so hard-core, and now is the perfect time to test that.

 

A Comp cam to consider would be the 11-611-5 295B-8.
260/270 .629/.638 on 108 lobe sep. Lash is .028/.030 so you'd take that off your lift.
The CompetionProducts Howards lifters are great and anything is a good idea on a BBC as they are fairly hard on valvetrain. Comp has a comparable lifter, 800-16 with the edm .012" hole, though supply has been sparse for a while.
Another lifter to consider is Crane's solid 99250-16, they are a higher crown and rotate faster in their bore, lowering the wear potential. Lunati may also source their's from Crane, not sure.

SStrokerAce I didn't know mopar lifters would fit in a sbc and clear the adjacent cam lobes. Ford lifters are a common swap in CT, but that cuts it pretty close.