Anyone Degree a Cam on an LT1?

[Torque]

Anybody ever degree a cam on an LT1? I just put my new Cam in, it has a 108degree centerline, the Cam went in at 105degrees so I used a bushing kit to get it to 108 degrees. My thoughts are this messed up the optispark timing (not revving very well) and this might be the symptom of my having degreed my cam.

Any thoughts?

So far, the results are as follows:

Craig at GTP says- Degree the Cam
Ed Wright programming says- put it in striaght up, it will impact timing, even though when they explained it, the computer still uses the knock sensor and O2 sensors to adust timing on the fly so you woudl think it would compensate

Going to ask the Cam guys now.....

[BAS]

Re: Anyone Degree a Cam on an LT1?

I put my CC extreme 218/224 cam
in straight up.


12.5 @ 109

Originally posted by Torque
Anybody ever degree a cam on an LT1? I just put my new Cam in, it has a 108degree centerline, the Cam went in at 105degrees so I used a bushing kit to get it to 108 degrees. My thoughts are this messed up the optispark timing (not revving very well) and this might be the symptom of my having degreed my cam.

Any thoughts?

So far, the results are as follows:

Craig at GTP says- Degree the Cam
Ed Wright programming says- put it in striaght up, it will impact timing, even though when they explained it, the computer still uses the knock sensor and O2 sensors to adust timing on the fly so you woudl think it would compensate

Going to ask the Cam guys now.....

[Rob B (shoebox)]

If the camshaft position in relation to the crank is changed from stock, the position the opti is sensing is going to be off. Perhaps it could be allowed for by making changes in the complete spark map, but I am not sure if that would work or if that is the only thing that would have to be done.

[Torque]

The last time I put this same model cam in, I put it in straight up and was in the 12's at 118mph. Trying to get every last bit of power out of this car so I figured the right thing to do is degree it and get it right. The custom cam shop tells me to, Craig at GTP tells me to, and now a local tuner tells me to. Ed Wright/Fastchips is the only one that is now telling me not to. I am thinking I will replace the optispark (I think it's bad, tried my backup and it was worse) and then throw in the towel and put it back in straight up. Such a pain in the rear! The things we do for HP!

[Torque]

I like your sites Rob B (Shoebox). We have the exact same car, black on black, I have the same rims, almost got the black, ended up with the chrome. I love the way the black looks.

So you think degreeing the cam is going to confuse the computer? I thought degreeing was to make up for machining tolerances in the timing chain and cam so in essence it was bringing it back to where it is supposed to be stock? Make sense? Everyone seems to have a different oppinion on this?

[N20LT4Bird]

Originally posted by Torque
I thought degreeing was to make up for machining tolerances in the timing chain and cam so in essence it was bringing it back to where it is supposed to be stock? Make sense? Everyone seems to have a different oppinion on this?

Thats what actually degreeing a cam is. Your matching it to what is on the cam card. Then, if for some reason, you want to advance or retard valve timing, you can. But, degreeing is almost like double checking the manufacturer, which I would imagine you could do, just like any other engine. Now, if you want to ADVANCE valve timing, I believe you could run into problems with the OPTI/PCM.

[wolfdogs]

we did my LT4hot cam straight us.....as per Ed Wrights instructions... never a prob to date....and that was 4 yrs ago.

[N20LT4Bird]

My hot cam is installed straight up too, but I did not degree it to check it out either. Seems to run real nice though.

[Torque]

What timing sets are you guys running? I am running the GM performance parts sets. Wondering if this might be playing a factor?

[Rob B (shoebox)]

Originally posted by Torque
I like your sites Rob B (Shoebox). We have the exact same car, black on black, I have the same rims, almost got the black, ended up with the chrome. I love the way the black looks.

So you think degreeing the cam is going to confuse the computer? I thought degreeing was to make up for machining tolerances in the timing chain and cam so in essence it was bringing it back to where it is supposed to be stock? Make sense? Everyone seems to have a different oppinion on this?

Thanks, I like the black, too.

It's a little different for the LT1 as compared to an SBC. The opti can only be mounted in one position, so initial timing or cylinder reference location cannot be changed (like turning the distributor housing on an SBC). If the position of the dowel pin is changed, then initial timing will be altered. The pcm gets crank and cam position info through the opti and assumes everything is mechanically "staight up", then all timing is done elctronically.

[Torque]

So if the cam went in straight up at 105 degrees and it is supposed to be 108 degrees, the computer would have been programmed off of 108 degrees, so correcting this should have been the right thing to do correct?

Also, if for some reason it was not, I only retarded the cam by 3 degrees which is measured from the crank, the cam turns half the speed, so the actual timing retard would only be 1.5 degrees right? This would not be that bad?

[Rob B (shoebox)]

There has to be someone that knows more about this than me.

If you do your own programming, maybe you could experiment by globally advancing/retarding (whichever you need) the timing (1.5º or whatever you determine) in the spark tables and see if that does not take care of it.

[Torque]

I am 90% sure my opti is crap so I just ordered a new one to see if this could actually be the culprit of my problems. Will post the results on this.

As for the timing, I will try the new opti, if it acts exactly the same, I will give a local tuner a shot at re-programming. I am not so worried about the timing of the spark as much as the timing of the fuel injection which is also timed off of the "optical eye" which acts as the cam position sensor. I also think this could be programmed around because when you change cams, you have to change this as well to compensate.

Anyway, will try these two things and if I get nowhere, I will just put it back in straight up!

[Joe 1320]

Boy is this thread a potential can of worms. Everything that has been discussed so far is right on the money. The big problem as you already know is the timing cannot be changed mechanically, it must be done via a new program. (except of course the change when the cam is retarded or advanced). My advice is to set the cam according to manufacturer specks and get a new program for the spark advance flashed. The cam timing is going to be important as it affects cylinder pressure, rpm power peak along with a few other things that cannot be "band-aided" by a simple timing change. This is why a dyno tune session is the best idea after a major internal swap.

[Torque]

I totally agree. I learned a bunch of new info on the Advanced Tech message board on the CamaroZ28.com site. Unfortunately, there is still a bunch of conflicting data out there and a ton of speculation. I think many peole run into this problem, ask a ton of questions, get a bunch of advice, eventually figure it out, and then don't post the results. I am going to be sure to post my results so that hopefully others don't have to run a one man R&D shop like I seem to be doing.

One thing I have learned for certain, different timing sets out there give you different Cam degrees even if you put them in straight up. For example the Cloyes (sp?) set comes 4 degrees advanced out of the box, I am running a GM Performance parts roller which should be same as stock but for those running these other sets there is a ton fo variance.

Also I have found out the GTP-6 Cam is known for a ton of variance and there are many others out there that have experienced this problem.

The last thing I learned is that Ed Wright locks down his ECMs when he programs them which really screws you when you need to do fine tuning like in this scenario. I have also heard some bad things about his tuning, not trying to slam him, his program worked great for my car the first time around, just hearsay but what I have heard about the programming was not too good and the fact that I am locked in irritates me.

Anyone out there using LT1 edit? Looks like this might be my best option at this point. Not sure if I want to spring for it though, heard it's pricey!