Who has installed Comp Cams 07-503-8 (xr276hr-12)

[96'bowtie]

I've installed the cam and used the extreme duty timing set which does not have provisions for advancing or retarding the cam on install.

I a curious if anyone has installed this cam and confirmed install with a degree wheel or has made adjustments on the install via a a keyed sprocket?

I red a GM high te h article where they installed the same cam and they said comp suggested to advance cam 4 degrees.

Just looking for feedback.

Thanks

[96lt1m6]

Competition Cams puts 4° into the cam dot to dot right off the bat so I could not see adding 4° more... to be honest I have always put my Cams in dot to dot when using Comp. Great off the shelf cam!

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[96'bowtie]

Thanks for the reply.

that is what I thought, I've always installed them dot to dot. I have an interesting problem. With my idle timing above 20 degree, the cats are glowing red I presume form the overlap and unturned fuel? Lowing the spark advance at idle to 12-15 causes the headers to glow.

There fore I was wondering if missed something. I cannot seem to figure this one out. I don't appear to have any air leaks. The egr system is removed. Really comfusedon this one.

[firebird_1995]

Timing too retarded will cause the fuel mixture to be still burning after the valves open. Try advancing the timing at idle. Mine idles around 48°

[96'bowtie]

Just to confirm, you closed throttle idle advance is 48. I did not think to go that high. I am having a problem when I advance the idle, cats begin to get cherry hot, however the is at 20 degree, the more I advance the hotter the cats get, I presume it is from the unburned fuel from the overlap.

I can try to advance the idle to 30-40 degree.

[firebird_1995]

I use tunercat so the terminology may be different but looking at the "main spark advance vs. Rpm vs. Map" at idle (1000) and at 35 kpa im at 48. At 40 kpa,47. At 45 kpa, 46. At 50 kpa, 44. Not sure what kind of kpa you have at idle but I would find that out first, then tweak that cell

[joelster]

It's too rich. Lean the mixture out a bit and see what happens.

[96'bowtie]

I know it sounds basic, how do you lean it out a idle though lt1 edit? The PCM is targeting 14.7 and all the tables for fueling are pe related and don't effect idle fueling. It was suggested to advance timing, however that is not necessarily removing fuel and the cat problem gets worse through the overlap.

If you offset the Maf table at the idle flow numbers would the 02's try to compensate and PCM just ad injector pw?