I know I should probably be posting this in the chevy section but i prefer advice from cruiserheads as I am a cruiserhead.

So......

I put a new crate motor into my landcruiser and have gotten it running. Broke it in at 1600 rpm for about 15-20 minutes. Now I'm at the point where I need to time it properly. On my old block, I had a line on the harmonic balancer which I used to line up to degree 8 on the block. It was easy enough. Now, when I run the engine, I have a degree meter on the balancer which reads from 0-50. When the engine is running, the "timing teeth" (dont know the name of it, but its the little metal piece that bolts to the crank cover which has the teeth) are pointing at roughly 25-35 degrees on the balancer. When I accelerate, it goes even higher. I have no idea what it should be set at. Any help would be greatly appreciated. Thanks!

First, you need to unplug the vacuum advance hose and plug the port. That will remove the advanced timing. Make sure you are on Cyl #1 because the timing you are talking about sounds really high. That piece of metal is referred to as a "timing tab". I'm a chevy man and when setting up timing, usually run around 10* base timing (with the vacuum advance unhooked) and in the neighborhood of 30-35* IIRC (its been a while since I've done a dizzy install). I would suggest getting the adjustable vacuum advance kit they sell at any parts store, it is a new diaphragm that has an adjustable spring-rate/timing stop in it that allows you to taylor your timing to your engine and make the most power available. I used this method to setup a 350 in a friends 60 in B-Burg last year and he's had no problems (ignition module bit it, but that's non-related). I'll check my numbers on the timing today and verify the total is correct. I know that 10-12* base is what I usually run. Makes very good bottom end torque.

8-10 deg for base timing (with vac adv disconected) and around 33-38deg TOTAL advance. This is on most wedge shaped cast iron cylinder heads, more efficient head/piston design requires less total timing.

Total ign timing is measured with no vacume advance, engine revved up to where the mechanical advance is fully advanced, ususally around 3500rpms.

With vacume adv applied (8-12 inches of vacume applied)I usually look for 42-46deg advance. Remember, at WOT there is no vacume advance because manifold vacume is zero or close to it.

Alot of the GM dist Ive messed with usually dont advance ENOUGH from centrifugal to allow 8-10 deg of base timing to achieve the 33-38 deg of total timing. When I set timing I set TOTAL first, then check base timing. This will tell me how much tuning I have to do to the dist.

Fords are usually the opposite, they OVER advance and have to be modded to actually reduce the amount of centrifugal advance they allow.


Centrifugal advance is for power and throttle response.

Vacume advance is for mileage only.

Total advance is determined by the efficiency of the combustion chamber and piston, as well as fuel octane.

Higher compression, boost, NOS, 4-valve pent-roof chambers, high-swirl, heart shaped, angled plugs and others all require LESS ignition timing because by design they require less time to ignite and burn the fuel/air mix.

Wedge shaped, low compression, low octane fuel, hemispherical chambers, dished piston domes and others require MORE time to ignite and burn the air/fuel mix therefor you need to light it off SOONER. Hense, more timing needed to be put into the motor.

Lower octane fuel burns FASTER than high octane fuel BTW, which is why when you put high octane fuel into an engine that has been tuned for lower octane fuel you dont see a difference in power/mileage. You have to advance ignition timing to get the power gains from the higher octane.

The slower burning rate of the higher octane fuel is why its less prone to pre-ignition/detonation.

Tuning for max power can be done by watching your MPH in the 1/4 mile, dyno, or measureing top speed (fun but not the safest way)

Get an adjustable timing light to tune with and go for it.

Chris:cool2:

To simplify. The "0" on the scale on your new balancer is the same as the line on your old balancer. Use this mark and adjust like you did b4. OR you can use the #'s on balancer scale and use the TDC "0" mark on the stationary timing tag on the engine. If you want 8* make so the 8* mark on the balancer lines up w/the TDC "0" mark on the timing tab. This is what the earlier posts are about. They're looking at intial timing & total timing and trying to get the most out of your engine.

Thanks for all the input. This cruiser needs to pass smog so I guess i'll have to use the 0 mark. I'll put it at 10 and see how it runs. I tried 8 but it ran kinda sluggish. Throttle response was not good so there must be something else factoring in. Also, where does the vacuum advance on the distributor connect to? Just one of the vacuum ports on the carb or on the manifold. Thanks? This is my first engine swap so bear with as some of my questions may be dumb. :)

SBC's are notorious for the outer ring on the balancer "turning" on the inner ring. This causes retarded timing when you actually line up the marks correctly and WILL cause the motor to be "sluggish" even though the timing is set "to spec". Basically you set the timing to 8deg but because the balancer has turned the actual timing is -2deg. If the motor is old Id verify the balancer isnt "spun".


Setting the timing to 0 for smog will only fly if that is what the spec is.

Chris:cool2:

More advanced timing will eliminate sluggishness. You can advance timing in small increments till you get the response you want. More advance will make the engine more racey.If you start hearing pinging when you accelerate or apply a load, you've gone too far and the timing should be retatrded till ping goes away.

Timing should be set w/the vacum advance disconnected and the port blocked off on the engine/carb. GM hooks the vacum to a ported location on the carb above the throttle plate. Some people will hook the vacum as per GM others will use mainfold vacum(below the throttle plates) trying to make the throttle more responsive off the line.  You should do a search here or on other web sites and read up on the subject.,

Updates?



Chris:cool2:

I use to set timing on a small block i had by total timing at about 2500 rpm...36-38 range