advancing cam 4 degrees [Archive] - Team Camaro Tech

: advancing cam 4 degrees


sbcBill
Apr 8th, 10, 08:09 PM
I have read here and on other forums that the engine performance can be significantly increased by advancing the cam by 4* when using the L-79 cam (327/350 HP engine). Is there any truth to this claim? Has anyone done this with this cam in a 327? How did this change affect the cars performance, idle, etc? Is it woth doing or not? Thanks in advance,
Bill

Melrose RS
Apr 8th, 10, 08:43 PM
Do you know if the cam is ground advanced or ?

If it is supposed to be advanced and you install it retarded it is going to run like, well, not so good.

We once accidentally installed a 30/30 cam in my Dad's 327 vette "straight up" and it felt horrible. No low end, fouled plugs, poor idle, pinging, gas mileage... Took it apart, added 4 degrees advance and bam! back to it's old self.

I've messed with adjustable timing gears on Toyotas too. I don't have any hard data to show you and I don't recommend randomly advancing cams without knowing what you are getting into, but advancing it 4 gave it better low end response. Felt lighter and snappier.

I don't know if the factory performance cams like L-79, 30/30 are ground advanced or got advanced by the specific timing chainsets, though. Somebody else may know.

hhott71
Apr 9th, 10, 04:46 AM
Try it, the cam advance kit is cheap, as are the gaskets.

BUT test performance at the strip before you do it. Also your MPG on the street.

If it helps you have proof instead of it "feels" better hopefullness.

69z28boy
Apr 9th, 10, 06:44 AM
unless it is a GM NOS L79 cam, then it most likely has 4 degrees advance ground into it already.

i always install my cams an additional 2-4 degrees advanced...

for instance, my 30-30 and 140 offroad cam were installed 7 degrees advanced in my engines... and they ran great that way.

the general rule is that advancing the cam picks up the low end at the expense of the top end,
and retarding the cam has the opposite effect.

most cam manufacturers grind advance in simply to take up the slack in the timing chain as it wears and stretches.

THanks

Aaron

zdld17
Apr 9th, 10, 03:58 PM
This is a basic stock GM cam 3896929, if you are sure what you have. Should run well as it is but usually guys try to move 2 or 4 advance and it runs better but at the expense of the top end. If thats not an issue, then go for it as this cam is probably ground a 112 or 114 lsa. Unless you are adding additional above stock stuff to the motor, I would install it dot-dot. If you want to find out if its off some, put a degree wheel on it and check it out against its specs. If you have them.

sbcBill
Apr 11th, 10, 11:56 AM
The cam is a new NOS in the box 151 GM cam. I know Chevy never ground an advance in their cams, I will keep it the way it is and use it dot to dot when installed. Thanks for the comments.
Bill

69z28boy
Apr 11th, 10, 12:48 PM
The cam is a new NOS in the box 151 GM cam. I know Chevy never ground an advance in their cams, I will keep it the way it is and use it dot to dot when installed. Thanks for the comments.
Bill

i'd urge you to consider advancing it... especially if it has no advance ground in..

the advance is ground in to eliminate a retarded cam when the chain stretches..

advancing 4 degrees will indeed put a bit more bottom end in the cam, and as the chain wears or stretches, the cam will not retard in the process.

A

Z15CAM
Apr 11th, 10, 01:29 PM
To install a cam in the position you want you need the Mfgr's Cam Specs and a Degree Wheel. After you have Determined TDC using the Positive Stop Method, the Location at which the Intake Valve Opens and Closes at .050" is generally used to Locate the Cam. The built in 4 degree advance really means nothing when Degreeing but does indicate a cam with a 110 ICL and 110 LSA is generally installed at 106 Degrees which is 4 degrees advanced relative to Crank Rotation. Remember the Cam turns at 1/2 cycles to the Crank. To increase Dynamic Stroke and Dynamic Compression, I have often installed a cam which calls for a 108 Degree ICL at 104 Degrees which is 6 Degrees advanced relative to the Crank. You should always do a Valve to Piston Clearance Check after degreeing a Hi-Perf cam where generally for every 2 degrees advanced the Intake Valve Clearance to Piston shortens by approx .010" and the Exhaust lengthens by approx .010".

Valve to Piston Clearances are closest when the the Valves 1st Open and Close. Advancing a Cam tends to improve Torque at Lower and Mid range; however, you should compare the results with a DCR Calculator in attempt not to foul the recommended 8.2 DCR Dynamic Stroke Ratio for Pump Gas Octane. It is important to know your Static Compression ratio when Selecting a Cam.