When my motor was assembled I chose an XE268 and a Comp Cams double roller timing chain, part #3100. I didn't supply the bushing set, so the builder used Comp Cams degree bushing set, part # 4760.
As luck would have it, I forgot to leave the cam card when dropping of the cam. By the time I realized my mistake, he had already installed the cam "straight-up". The builder said he degreed the cam from the numbers on the cam box.
The bushing kit has four remaining colored bushings:
Copper - noticable offset
Green - noticable offset
Grey - Noticable offset
Black - no noticable offset
My question is this, What color is the bushing he used? (assuming the kit had five bushings) But more importantly does that bushing have any offset ?
I just want to have that "peace of mind" before buttoning up the bottom end.
Thanks, Steve.
The gold, 6*, bushing is missing from your "inventory". Not to be confused with the copper (4*) you say you still have. I would expect the box and the card to coincide, but I would check to be sure. Six degrees is a lot. It almost sounds like he took a cam with 4* advanced ground into it and retarded it to be "straight up". Good luck, and...
I took off the french lock, it's the silver one. I plan on taking the engine to 5000 regularly, 5500 occationally, 6000 once in awhile and 6200 rarely. Mods are in my signature.
Thanks again, Steve.
http://www.mikejh.com/snb73a.htm
73 L-82, 4 speed, 3:55 rear, AC, Leather, Power steering, windows and brakes, K&N air filter, Stock Q-Jet, Edlebrock performer intake, Hooker Comp Headers, Vette Brakes 1-1/4 sway bar and 550lbs coils in front, 7/8 sway bar and 360 lbs fiberglass in the rear, KYB GR-2 shocks all around, but they are too soft.
In the process of rebuilding the engine; A Lars rebuilt Q-Jet and distributor, RPM intake, Trick Flow 23* heads, 1.6 ratio roller rockers, Comps XE 268 cam, Speed Pro forged pistons, Hooker Super comps
Ok, I called Comp today. They said if I install the XE268 with the black bushing (0 advance or retard) the cam is ground 4 degrees advance. This will give me a power band in the 1600-5800 rpm range. Does this sound right?
Theoretically, yes. But if it was moved 2* (advanced or retarded?) why is it now "straight up"? It was ground with 4* advance, it was "corrected" with 2*.
Quote:
The bushing kit has four remaining colored bushings:
Copper - noticable offset...4*
Green - noticable offset...N/A (my catalog)
Grey - Noticable offset...(dark grey)...8*
Black - no noticable offset...0*
My 2000 Comp Cams catalog does not show a "green". Not listed above, my book shows a "silver", like in your engine, @ 2*, and a "gold", @ 6*
I guess the question, now is, is the cam at split overlap (truely straight up)? Or is it "straight up" as per the specs on the box? A bushing (2* or otherwise) can be installed to advance or retard. Any clue where you're at? You may just have to do it yourself, to know for sure. Somewhere, there are two degrees in limbo. Either the cam was ground two degrees off of spec, or it isn't at split overlap. Maybe a combination of each. Installed as intended (advanced 4*) the rpm range will be as stated. If it is any comfort, 2* won't make a world of difference. You may want to try it before you fiddle with it. But it would be nice to know where you are. Good luck, and...
By straight-up, I dont't mean theoretical straight-up. I mean cam and crank gear "0's" at 6:00 and 12:00 repectively, with no offset bushing installed.
If I the cam is installed; #1 TDC, cam gear with the "0" at 6:00, crank gear "0" at 12:00, and the black (no offset bushing) in the cam gear. Is this correct. Is this how comp intended the cam to be installed?
Is this a safe bet. I don't have a degree wheel. (or the confidence to degree my cam)
I know I'm beating a dead horse, I just want to have that peace of mind that it's correct. Thanks for your input guys.
I don't think you are trying to beat a dead horse. You just want to thoroughly understand what is happening. I don't blame you.
Quote:
By straight-up, I dont't mean theoretical straight-up. I mean cam and crank gear "0's" at 6:00 and 12:00 repectively, with no offset bushing installed.
If I the cam is installed; #1 TDC, cam gear with the "0" at 6:00, crank gear "0" at 12:00, and the black (no offset bushing) in the cam gear. Is this correct. Is this how comp intended the cam to be installed?
Is this a safe bet. I don't have a degree wheel. (or the confidence to degree my cam.
That is how they are always installed. The "dots" get lined up and the cam is either advanced or retarded by the bushing. My question comes from the fact that a 2* bushing was used, and why? Did it take two degrees to get it to spec (advanced 4*)? If so either the cam or the crank (keyway) is two degrees off. Or did it take 2* to get it to split overlap? If so, again, something is 2* off because it should take 4* to negate the 4* ground into the cam. The timing set could, also be the culprit. Or a combination of tolerences in all three items.
You are correct; however, in that this is how Comp intended it to be installed. But! This is also, why cam get degreed. Good luck, and...
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HELP!!!! Comps XE268, cam degree bushing kit question
