What do the L98 heads like as far as timing? I have cast heads with stock roller cam. How much timing did the 350TPI's come with? Would 34-38 degrees be my best bet? ------------------ 1986 CAMARO Z28 -> 151,000 original miles, 43,000 on 89' vette 350 block, Holley 650 DP, Weiand intake, 1.6 rockers, 1 5/8" headers, no cat, 2 1/2" Flowmaster catback, Mallory coil, March pulleys, T5 with 3.35 1st gear and 0 miles, 90% Centerforce clutch, 3.73 posi, Eibach 1" drop springs, Spohn LCA's, Spohn adjustable panhard rod, Subframes connectors, polyurethane swaybar bushings/endlinks, 2 12" Sound Streams, 2 Infinity 6X9's, 2 Pioneer 6X9's, 800 watt Lanzar Vibe amp. ET 13.22@ 106.4MPH Next mods-> Homemade ram air, B&M shifter, Extreme Energy 230/236 cam.

I usually start with a base timing of 8 to 10 degrees with a total of about 34.

This is a setting that you will need to play with and see what your personal engine likes.

There is a good article on timing in the December Hot Rod. Pg. 30.

Each engine will respond different to timing settings. ( I'm running 15 degrees base timing on my carbed 86 chevy pick up, and it loves it )

Whatever you pick, listen for pinging. This would be the death of a nice motor.


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ASE Mechanic/Machinist/Smog Tech

1999 NBM Trans Am
1986 Chevy 3/4 ton pick up
1981 corvette
1995 Kawi ZX6R

GO #3

JDM,

I presume you're talking about total ignition advance, not valve timing.

If you are using the ECM, timing can be changed in two ways - move the base timing and reprogram the advance curve/offsets. Stock parameters allow up to about 40-42° at 2,300 RPM in highway spark mode and optimal coolant and intake air temperatures, but that falls rapidly with larger throttle openings.

If you are setting up a mechanicla distributor for your engine, are you using a vacuum unit as well? The vacuum will net an extra 15-18° depending upon the distributor and diaphragm used, so you'll have to calculate that in as well. You shold be able to get by with at least 35° on the centrifugal advance alone but it will have to be curved to come in at higher RPMs instead of full advance at 2,000 RPM.

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Later,
Vader
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"No matter how hard you try you can't stop us now"
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I am using the stock computer advanced system. Somebody told me to unplug one of the plugs on the back of the distibutor and then do my initial timing changes. Is this correct? What is the factory settings for initial and total advance? Thanks.

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1986 CAMARO Z28 -> 151,000 original miles, 43,000 on 89' vette 350 block, Holley 650 DP, Weiand intake, 1.6 rockers, 1 5/8" headers, no cat, 2 1/2" Flowmaster catback, Mallory coil, March pulleys, T5 with 3.35 1st gear and 0 miles, 90% Centerforce clutch, 3.73 posi, Eibach 1" drop springs, Spohn LCA's, Spohn adjustable panhard rod, Subframes connectors, polyurethane swaybar bushings/endlinks, 2 12" Sound Streams, 2 Infinity 6X9's, 2 Pioneer 6X9's, 800 watt Lanzar Vibe amp. ET 13.22@ 106.4MPH Next mods-> Homemade ram air, B&M shifter, Extreme Energy 230/236 cam.