02RedHawk

iTrader: (17)

Hey All....

I recently ordered a custom cam from a sponsor (224/224 .581" .581" 114LSA, 0 degrees advance) which was to be a Comp-Cam on XE-R lobes.

I just got my order from them, and instead my invoice shows a Lunati grind (224/224 .578" 114LSA). Here's the cam-card that came with the cam:



Sorry for being a bit naive when it comes to cams, but how does this Lunati cam differ from the one that I actually ordered? (aside from the obvious difference in lift - .581" vs .576") Am I reading the card correctly that it has 2-degrees advance ground in?

What is Lunati's equivalent to Comp's XE-R Lobe?

Thanks so much for helping me interpret this card.... I want to make sure I got what I ordered.... Its going into an LS1 with milled .020" LS6 heads, so P-to-V clearance is my biggest concern.... I don't want a "new" Lunati cam to upset my delicate clearance to my heads....

PREDATOR-Z

You should get exactly what you ordered. This cam is definately not the one you ordered. It will peak a little earlier due to the ground in advance and will idle a little rougher. Probably will not make as much power than the TRUE XE-R.
What I hate about LUNATI is that they do not give you the DUR at .006 so you can't really figure out the ramp rate variance between .006 and .050 which helps identify the XE-R lobe (49)
IMO return it and ask for what you ordered or get your money back.
Who sold it to you?

02RedHawk

iTrader: (17)

Texas Speed. They are of course a very reputable shop so I am sure they'll fix the error without hassle. I am surprised, though - when I ordered it I specifically verified with Jon that it was going to be the Comp-Cam on XE-R lobes. Then when I received my invoice / cam in the mail it was this Lunati grind.....

I appreciate the clarification, Predator-Z.

Steve - Race Eng

iTrader: (1)

I have calalogs listing the Comp and Lunati durations @.006" lift (advertised duration) for these grinds.

The Comp XER lobe duration @ .006" is 273 degrees.

Lunati @ .006" is 283 degrees. Therefore the Comp cam has 10 degrees less hydraulic intensity than the Lunati cam. Less is better in terms of performance.

As PreditorZ mentioned, the engine will idle smoother with the Comp grind and will produce more low end torque. The Lunati grind will however be easier on parts - the lifter acceleration rate is lower.

I would not pay too much attention to the 2 degree advance or any advance, retard ground in. One should always degree in a camshaft on installation. Never trust the sprockets to be marked correctly. Never trust the cam to be ground correctly. I've seen sprockets marked off two or three teeth and cams marked with incorrect lobe numbers, exhaust profiles ground on the intake lobes and visa versa. The cam can be advanced or retarded during installation to suit your needs.

Most aftermarket sprockets have provisions for advance, retard. The chain will stretch 2 degrees so it is common practice to install cams with 2 degrees advance to compensate for chain stretch.

Steve

PREDATOR-Z

Steve, would you say this is true with stock GM chains but i can hardly understand that fact with a double roller, which is what most of us use in aftermarket build ups.

Steve - Race Eng

iTrader: (1)

I never use stock chain sets in anything I build up here. I have used just about every brand of aftermarket chain set through the years. They are all consistently off.

You have to remember that there are tolerances at work here. Sometimes they add up, other times they cancel each other out. For instance, if the camshaft is indexed off a degree or two from the front locating dowel and the timing chain sprockets are off a bit in the same direction your camshaft installation could end up off a few degrees.

The roller chains will stretch roughly two degrees as I mentioned before. I always install the cams two degrees further advanced than desired to take care of the stretch or wear.

Another thing, when you degree in and check these hydraulic roller cams you should have a pair of lifters that are filled with epoxy so the pushrod seat stays in the full up position. That way it will act like a solid roller during the checking process. This will also make it much easier to check the valve train geometry. Remember, the engine sees the action at the valve not the lifter.

A lot of guys (most) are doing the geometry checking incorrectly. When I get some time I'll put up a post on how this should be done.

In regards to camshaft quality, I have a very high definition Cam Doctor here and specialized software to check camshafts. Camshaft quality varies from vendor to vendor and from machine to machine at the same company. The engineer at the cam company may have done a great job designing the lobe profile, but if the machine grinding the cam is worn out, grinding wheel is out of balance, operator is not having a good day, etc. the camshaft coming off that machine will not be very good. Some companies are better than others at checking cams before packaging and shipping. Some don't seem to care from what I have seen.

Steve