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Old 10-03-2009, 03:24 PM
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what timing for sbc

I finally got a timing light and plan to set the timing on the 355 in my mustang. It has dome top pistons, 492 heads, big cam, team g intake, 650 holley dp, accell distributor. It is an 1/8 mile racecar only. I am wondering what I should set the timing on. I will be running 110 octane race gas

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Old 10-03-2009, 06:58 PM
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40-42 degrees TOTAL



Quote:
Originally Posted by old fords
I finally got a timing light and plan to set the timing on the 355 in my mustang. It has dome top pistons, 492 heads, big cam, team g intake, 650 holley dp, accell distributor. It is an 1/8 mile racecar only. I am wondering what I should set the timing on. I will be running 110 octane race gas
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Old 10-03-2009, 10:28 PM
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40 to 42 is way too much. the engine will make max power when the timng is set at 32 to 38deg. Usually 36deg is best.

If the cam is big you can benefit from recurving the distributor to allow more timing at idle, yet 36ish timing at full advance.
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Old 10-04-2009, 07:10 AM
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What I did was use the lightest springs in a recurve kit, set the total at 36 degrees and let the idle timing fall where it may.With a race only car idle quality is not really a concern nor is low speed driveability.With doing it this way it starts easy(no kickback) and by the time I am up on the converter the timing is all in any way like it would be with it locked out.
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Old 10-04-2009, 11:49 AM
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I guess I was lucky then, I ran my Small Blocks at 40-42 total. Crank trigger,multi step retard box for cranking. Done it for 20 years.Now on a 447 stroker I ran 36-38 total.


Quote:
Originally Posted by F-BIRD'88
40 to 42 is way too much. the engine will make max power when the timng is set at 32 to 38deg. Usually 36deg is best.

If the cam is big you can benefit from recurving the distributor to allow more timing at idle, yet 36ish timing at full advance.
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Old 10-04-2009, 12:33 PM
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Total timing depends on what heads you have, what pistons, and deck height.

Dome tops and old smogger heads (492's) need lots of total timing. I think 40 degrees should do it. Domes slow flame speed and 492's have slow flame travel chambers so you need a good amount of timing. Try different amounts at the track and let us know what works best. Are you sure the timing tab is at true TDC?

If you had flat top and fast burn heads and a good quench area then you would need much less timing, say 34 or 35 degrees.

Big cams require lots of initial timing. low timing will make the headers glow red and the carb run rich. I would run 20 to 25 degrees at 1000 rpms.

If the cam has 290 degrees of duration then you should be able to run up to 10.75:1 with 93 octane with out any issues. 300 degrees duration could run 11:1 on 93 octane.
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Old 10-04-2009, 01:27 PM
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Quote:
Originally Posted by dgcantrellsr
I guess I was lucky then, I ran my Small Blocks at 40-42 total. Crank trigger,multi step retard box for cranking. Done it for 20 years.Now on a 447 stroker I ran 36-38 total.
If your motor requires that much timing you need to address why. Some older leaded type race fuels slow the fuel burn rate down too much requiring more timing.
Modern unleaded race gas has a quicker burn rate more like pump gas and does not need so much timing. (and it makes more power as a result.)
High piston dome creates a convoluted combustion chamber, slowing and upsetting flame travel speed and efficientcy, again requireing more timing.
Fixing the dome contour solves this, restoring the flame travel and efficientcy.
less timing and more power.
excessively rich fuel mix AFR's sometimes used to ward off detonation and preignition slows the burn speed, requiring more timing.
correct full power AFR uses less timing and makes more power.

If you do not use the proper idle timing then jacking up the timing to compensate can fool you into thinking the motor needs this much timing to run best.
The car will leave the hardest if you stage near idle just off idle and shock the converter
to maximize converter flash stall and torque multiplication and chassis reaction at launch.
On a racey big cammed motor, locked out timing allows this by maximizing low rpm throttle responce.
When the proper amount of idle timing is employed you do not need to stage loading the engine rpm up against the converter at the line to get the spark timing up as you do with an advance curve.
Try it.
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Old 10-04-2009, 05:42 PM
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I had most all the bells and whistles on my dragster, ran Q/R and some Top Dragster. Best ET W/stroker motor 5.08 134 MPH @ 1800lbs.
355's and 377 Ci went like 5.49-5.70
We also used an item they call a transbrake, stall converters around 5000-5600 leaving around 4500 on full tree and on the wood on Pro-Tree.

Quote:
Originally Posted by F-BIRD'88
If your motor requires that much timing you need to address why. Some older leaded type race fuels slow the fuel burn rate down too much requiring more timing.
Modern unleaded race gas has a quicker burn rate more like pump gas and does not need so much timing. (and it makes more power as a result.)
High piston dome creates a convoluted combustion chamber, slowing and upsetting flame travel speed and efficientcy, again requireing more timing.
Fixing the dome contour solves this, restoring the flame travel and efficientcy.
less timing and more power.
excessively rich fuel mix AFR's sometimes used to ward off detonation and preignition slows the burn speed, requiring more timing.
correct full power AFR uses less timing and makes more power.

If you do not use the proper idle timing then jacking up the timing to compensate can fool you into thinking the motor needs this much timing to run best.
The car will leave the hardest if you stage near idle just off idle and shock the converter
to maximize converter flash stall and torque multiplication and chassis reaction at launch.
On a racey big cammed motor, locked out timing allows this by maximizing low rpm throttle responce.
When the proper amount of idle timing is employed you do not need to stage loading the engine rpm up against the converter at the line to get the spark timing up as you do with an advance curve.
Try it.
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