JAKEJR

This has been kicked around on another Forum for a few weeks now, and so far, I've only found two guys who've degreed-in their LT1 cam. I'm surprised that so few have done so, but that's an issue for another day.

For starters, I've degreed-in many, many camshafts over the years on both Big and Small block Chevys (so I know how to do it) and I have all the necessary equipment. But, I've never tackled a LT1 before, that is, I've never moved a LT1 cam from how it checked dot to dot.

I'm planning to advance my son's CompCams shaft another 2 degrees from how I degreed it in when I installed his new cam several weeks ago. The issue that's arisen has to do with the IGNITION timing being altered at the same time - which I know happens when earlier engines with distributors (back of block) are the type being run. I plan to use an offset bushing installed in the camshaft gear

I'd like to hear from guys who have degreed-in their LT1 camshaft on engines running an Opti-Spark, to find out what, if any, steps were taken to address the Opti rotor movement issue.

Thanks,

Jake

West Point ROCKS!

ss.slp.ls1

iTrader: (36)

First of all you can't change anything when you degree your cam, degreeing the cam is just to ensure that the valve events are happening when they are supposed to. You can degree it to ensure that your cam was ground to your specs properly. If not, you need a new cam.
What makes you think that advancing the already installed cam by 2* is beneficial?
Not to many people advance retard their cams because you can just get your cam ground with the desired timing and timing is not manually adjustable, you have to alter the computer to change the timing, aka tune the car.

JAKEJR

First, the specs on the cam card are only a recommended starting point, not etched in stone. A cam can and should be moved, (fine tuned) to hit the sweet-spot depending on what the installer is looking for.

Second, a cam doesn't always check according to the info on the cam card. As a dramatic example, Karl Ellwein degreed in his 383 cam and found it was 8 degrees advance, four more that the cam card recommended as the stating point. He then installed and degreed-in a known good cam and found it checked the same way. So his problem was with the engine itself, not the cam. Probably due to the broaching location of the keyway in the crank snout.

Third, GMHIGHTECHPERFORMANCE degreed-in a cam in a 355 they were builiding.

Fourth, if, when degreeing-in a new cam and it doesn't check to the recommended starting point shown on the cam card, the cam should be moved, but also if more low end or more top end power is sought.

Fifth, back to back dyno results show a significant difference in power when a cam is advanced or retarded.

But, with all due respect, all of the above is off-topic. I didn't ask whether or not I SHOULD do it but, instead, how the ignition timing issue was addressed. See what I mean?

Jake

West Point ROCKS!

Wicked94Z

iTrader: (26)

with timing marks on a balancer, pointer obviously, and an msd opti.

96capricemgr

iTrader: (1)

Engine should be tuned to what it likes the number displayed in Datamaster or tunercat is irrelevant.

JAKEJR

Right, Kirby (on another Forum) already recommended that procedure, to use a MSD Opti with it's adjustable timing feature. Of course, I'd need to know what the ignition timing was supposed to be in order to move it the correct amount. Only other option I can see would be the trial and error method.

Wondering what others, who have actually moved their LT1 cam, did other than the above.

Thanks for your response.

Jake

West Point ROCKS!

ss.slp.ls1

iTrader: (36)

It would be better to change the timing and fuel (injector pulse) throughout the entire power band. You need a tune to get the most out of a cam, not just adjust the timing on the opti. I say you should degree your cam, make sure that the valve events are happening when they are supposed to on the cam card. If so, leave it alone and get a tune.

JAKEJR

You're assuming that the PCM hasn't been re-programmed. Bryan Herter already re-programmed the PCM.

As another point of reference, depending on the RPM checked and the amount/direction of cam movement, recent dyno tests showed as much as 23fl/lbs of torque and 17 HP difference. There's a lot to be gained by fine tuning the intake centerline. I already degreed in the cam when I installed it, using the Intake Centerline Method. It hit right on the cam card specs, but I want to tweak it.

The cam card specs are ONLY a recommended starting point. Recommended starting point is what needs to sink in here. I thought most guys already knew that.

So, please, please, don't continue to make such recommendations. I know they're well-intended, but actually they aren't particularly helpful. Please try to stay on topic. Re-read what I asked in my original post. If that post needs clarification, let me know and I'll edit it.

I'm beginning to suspect that no one, or very few ever degree-in a LT1 cam; resorting to merely using the dot to dot method.

Doesn't anyone degree-in their LT1 cams?

Think I'll see what the guys on CorvetteActionCenter have to say. Sooner or later I'm bound to find someone who's degreed in their LT1 cam.

Jake

West Point ROCKS!

ss.slp.ls1

iTrader: (36)

FYI, Cloyes 3145 DR timing sets have three keyways for 4* adv, 4* rtd, 0*.

http://www.summitracing.com/parts/CLO-9-3145/

Just another option besides the offset bushing.

As stated, MSD has an adjustable timing feature as well.

Did you also consider that the tune has already be altered and may not be optimal after you adjust the intake centerline? Don't know if it was dynotuned or not.

Wicked94Z

iTrader: (26)

what info are you actually looking for besides a pat on the back for wanting to degree your cam? i already suggested the msd opti, and 96caprice suggested just redoing the whole timing curve to what the motor likes, not what the numbers read on the tables. i dont think there any other options.

96capricemgr

iTrader: (1)

Jake does not understand the difference between a book and the real world, therefore EVERYTHING seems to always be much harder for him. Over analyze and underperform will be all he ever accomplishes.

Whyrun

iTrader: (1)

Hell I'm confused?

I'd be degreeing that cam in with the @.50 method. Using the centerline- method only on todays cam profiles with the funky lobes they have ain't much better than, the "old" dot to dot

aboatguy

Jake,

I degreed my cam....It checked out according to the cam card. Since it was a custom cam I left it as is. If it didn't check out I would either move the timing set to the correct key way and/or use offset bushings. (I used a comp adjustable timing set)

However, I would not sweat the timing since Ed Wright adjusts the timing,fuel curves etc IAW with what the engine actually needs during the tuning process.



So this time I agree with Dwayne and the others, degree the cam to where you want it, install the opti.........run the sucker and either datalog it and get it tuned or get it on a dyno and get it tuned.


Mike