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Discussion Starter #1
Hey car is a 93 fox hatch weighing 2980 with a sbc 383 11.5 comp and a .630 .630 solid roller with ported 2.08 1.60 world products sportsman 2's and a Vic jr intake th350 3800 stall and 3.73 gears with 26 tall tire. Now installed the cam straight up and checked the balancer with a piston stop and adjusted the timing pointer so everything is correct, we double and triple checked the cam timing and the balancer tab was at TDC, when we brought the car to the track with 36 degrees timing it ran a 11.66 at 118mph with 38 it ran 11.40 at 119 and at 42 it ran 11.11 at 121.8mph, I have now advanced the cam 3 degrees and the car still wants high 40+ degrees to get it back where it was at the cam installed straight up at its 106lc, why I'm confused is this top end was on a 406 and on the dyno it didn't want anymore than 37 degrees timing then power started dropping off, so why does it want so much timing with the 383??? it's making mph so it loving it but why?? Lol someone please help me
 

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what type of timing gun are you using? i have seen some guns with auto advance be wrong, i have also seen a car that was so rich that the only way it would run was with 45 degrees of timing in it..
 

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What are the cam specs? That sounds like a lot of cam given the rest of the combination; especially converter and gear ratio. That could be why it likes timing.
 

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Discussion Starter #4
The plugs look like a nice toasty color not too lean or too rich, we have tried a digital gun, a dial back gun and a old sears craftsman chrome gun and there all reading the same, carb is a 950 Holley hp and the cam is 268/270dur @ .50 Lol too flustered to remember everything I've been pulling my hair out all night on this, the compression is 180psi across all cylinders, when I advanced the cam I was hoping it was going to raise the cranking compression but it didn't do much I gained 2psi
 

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Timing as I've been told is directly related to the effieciency of the cylinder head chamber. It is what it is on this motor. I've had small inch motors that liked 50 + degress of timing, as long as your watching the plugs and it contiues to like what your giving it go for it. . JMO.
 

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if your timing gun shows it runs best at 42, then 42 is what it is, so what's the problem?

we also don't race dynos.;)
 

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One of my combos kept making more and more power on the chassis dyno, went up to 44* of timing, 23* SBC. I never tried that at the track, kept it at 40* all the time. I only saw 10hp change at the tires between 38* and 44*. You are seeing way more than that.
 

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Timing as I've been told is directly related to the effieciency of the cylinder head chamber. It is what it is on this motor. I've had small inch motors that liked 50 + degress of timing, as long as your watching the plugs and it contiues to like what your giving it go for it. . JMO.
so true so true^^^^^^^^^^^^^^^^^^ if my car went faster with 60 degrees thats where id have it....jus-sayn!!!
 

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Agree with more timing if it's happy... keep an eye on the plugs though before you make a dontation to Alcoa's scrap pile. But in a larger motor like that it's an indication of an underlying issue be it a mismarked timing pointer or mechanical mismatch. I've run 48-50 before but in a 3" stroke SBC with a dome that had to be ugly to get any compression ratio with a normal 23 degree chamber. Generally with lower compression and a bigger engine you won't have a ratty looking dome to deal with thus the indication something isn't marked right or isn't happy when it likes so much timing.
 

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Required timing is related to the efficiency of combustion as a whole. Compression ratio, piston top design, combustion chamber design, induction velocity, equality of distribution to the cylinders, how well the fuel is atomized and mixed with the incoming air, vaporization characteristics of the fuel, ignition quality, heat retention by the plugs, heat in the engine, reversion characteristics due to cam and induction design... all these and probably a few more factor in.

Find ways to improve vaporization, use fuel that vaporizes sufficiently for the combination, use a plug with a sufficient heat range... things like this will lower timing needs and usually make more power in the process.
 

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Discussion Starter #16
Did t see it mentioned but what fuel are you running ?
94 octane chevron pump gas with this 11.5 to 1 motor the 406 was 12.5 to 1 and I ran vp c16. I was going to try a 94/100ll av gas 50/50 mix next time out a couple guys were saying the plugs look good but the timing mark on the ground strap was back where the strap bends maybe ill try a lil hotter plug and it seems to be a trend forming here with guys sayin lower compression will result in higher timing.. Back to the drawing board to review this combo, thank you guys very much
 

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Hey car is a 93 fox hatch weighing 2980 with a sbc 383 11.5 comp and a .630 .630 solid roller with ported 2.08 1.60 world products sportsman 2's and a Vic jr intake th350 3800 stall and 3.73 gears with 26 tall tire. Now installed the cam straight up and checked the balancer with a piston stop and adjusted the timing pointer so everything is correct, we double and triple checked the cam timing and the balancer tab was at TDC, when we brought the car to the track with 36 degrees timing it ran a 11.66 at 118mph with 38 it ran 11.40 at 119 and at 42 it ran 11.11 at 121.8mph, I have now advanced the cam 3 degrees and the car still wants high 40+ degrees to get it back where it was at the cam installed straight up at its 106lc, why I'm confused is this top end was on a 406 and on the dyno it didn't want anymore than 37 degrees timing then power started dropping off, so why does it want so much timing with the 383??? it's making mph so it loving it but why?? Lol someone please help me
Distributor or crank trigger? What RPM are you checking timing at?
 

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OP,

In regard to the engine liking less timing on the dyno vs. the track.

What was the weather on the dyno vs. the weather at the track? ;)

42 deg. is not all that abnormal for a "low compression" 23 deg. SBC with a cam more suited to "high compression".

As mentioned - efficiency.

Jason G.
 

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Discussion Starter #20
OP,

In regard to the engine liking less timing on the dyno vs. the track.

What was the weather on the dyno vs. the weather at the track? ;)

42 deg. is not all that abnormal for a "low compression" 23 deg. SBC with a cam more suited to "high compression".

As mentioned - efficiency.

Jason G.
Understandable, the dyno was a different short block with more compression I think that made a big difference.
 
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