408 ignition curver advice

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mbaird

mbaird

mbaird
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The 408 in my Swinger seems pretty lazy at lower rpms and I am thinking its my timing curve . I had the engine dynoed but that only covers 3000 - 7000 rpms .

The build is as follows
W2 heads ported
246/250 @ .050 / .648 lift on 108 solid roller
W2 Victor intake
9.5:1 compression
850 Pro Systems carb
Daytona Sensors CD-1 programmable ignition
TTI 1 7/8 headers with 3” exhaust and crossover all the way back .

My current curve is 18 intial and 32 total . Would 25 by 1200 be too much ?

Looking for more torque in the 1500-2000 rpm range . This thing should melt drag radial tires at will when I roll into the throttle . IMO .

IMG_0446.jpeg
 
It's the cam...
My last cam had a long duration low ls and wasn't worth crap under three grand but after three grand hold on for dear life...
Had the cam reground and a different animal...
 
32 is low for a total on a small block. Should have 34-36 give or take.
 
mbaird said:
My W2s are closed chamber race heads with .040ish quench .
Anything more than 32 yeilded nothing on the dyno . Surprised the dyno guy as well .
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Well all I can say is, the dyno ain't the car. Carry on and good luck!
 
j par said:
It's the cam...
My last cam had a long duration low ls and wasn't worth crap under three grand but after three grand hold on for dear life...
Had the cam reground and a different animal...
Click to expand...
I don’t consider 246/250 to be a long duration for a 4” crank but maybe your right .
 
RustyRatRod said:
Well all I can say is, the dyno ain't the car. Carry on and good luck!
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True for many aspects of tuning but wouldn’t wide open throttle at max rpms under load be similar in both cases ? In the car engine bay heat would become a factor but that would call for less timing I would think .
 
mbaird said:
True for many aspects of tuning but wouldn’t wide open throttle at max rpms under load be similar in both cases ? In the car engine bay heat would become a factor but that would call for less timing I would think .
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There are more aspects to a power curve than wide open. I can certainly see the added timing not making a difference in peak numbers. What about in the car and under the true load of the car at lower RPMS? It's entirely possible it could pick up elsewhere. Do you happen to know the cranking PSI, Michael?
 
4 speed 3.55 gears although I just picked up a set of 3.91s with clutch style sure grip .
 
RustyRatRod said:
There are more aspects to a power curve than wide open. I can certainly see the added timing not making a difference in peak numbers. What about in the car and under the true load of the car at lower RPMS? It's entirely possible it could pick up elsewhere. Do you happen to know the cranking PSI, Michael?
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185 cranking
 
But the total timing really is a reflection of and determined at high rpm performance. If the engine doesnt perform any better at 34 than 32 why use 34. Unless you are suggesting the engine might want 34-36* at 4000 but 32* at 6500…. Which would be possible with my digital ignition . That would be interesting!
 
mbaird said:
But the total timing really is a reflection of and determined at high rpm performance. If the engine doesnt perform any better at 34 than 32 why use 34. Unless you are suggesting the engine might want 34-36* at 4000 but 32* at 6500…. Which would be possible with my digital ignition . That would be interesting!
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No, I'm suggesting the engine might want 34-36 "somewhere else" besides 6500. Since it didn't make a difference at 6500, it "might" make a difference elsewhere. I mean dang. It might not. But dammit man, it's free to try. lol
 
mbaird said:
The 408 in my Swinger seems pretty lazy at lower rpms and I am thinking its my timing curve . I had the engine dynoed but that only covers 3000 - 7000 rpms .

The build is as follows
W2 heads ported
246/250 @ .050 / .648 lift on 108 solid roller
W2 Victor intake
9.5:1 compression
850 Pro Systems carb
Daytona Sensors CD-1 programmable ignition
TTI 1 7/8 headers with 3” exhaust and crossover all the way back .

My current curve is 18 intial and 32 total . Would 25 by 1200 be too much ?

Looking for more torque in the 1500-2000 rpm range . This thing should melt drag radial tires at will when I roll into the throttle . IMO .

View attachment 1716251492
Click to expand...
Nice ride!. The cam is not the problem since my buddy has a 246/250 on a 108 ls flat tappet cam, ported victor, 10.1 compression in a 408 and it doesn't suffer from lack of low end in a heavy short bed dodge. His engine made 500hp/500tq and he has 4.56s with 30" tires, I think the 3.91s would be better for you. As far as the timing curve on the few 408s that went across our dyno @Newbomb Turk found all of them wanted around 24-26 degrees timing at idle with nothing more until just after peak torque then an additional few degrees. This type of curve made the most overall power and added 15 or so hp at peak.
 
You have a high rpm intake & wondering where the low end went? Use an RPM intake.
9.5 CR is not helping either. You need a HEAP more initial timing, 30* plus.

img267.jpg
 
lead69 said:
Nice ride!. The cam is not the problem since my buddy has a 246/250 on a 108 ls flat tappet cam, ported victor, 10.1 compression in a 408 and it doesn't suffer from lack of low end in a heavy short bed dodge. His engine made 500hp/500tq and he has 4.56s with 30" tires, I think the 3.91s would be better for you. As far as the timing curve on the few 408s that went across our dyno @Newbomb Turk found all of them wanted around 24-26 degrees timing at idle with nothing more until just after peak torque then an additional few degrees. This type of curve made the most overall power and added 15 or so hp at peak.
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That’s good info .
The engine can idle around 750 but I set it at 950 to keep solid rollers happy .
It’s easy enough to change my curve I just haven’t had the time and wanted some feedback before diving into it .
 
Can you show a plot of the curve? Need idle, 1500 2300 3000 etct 25 at say 3500 does not tell me anything at all, and do not use a dial back timing light iot will prob be off.
 
halifaxhops said:
Can you show a plot of the curve? Need idle, 1500 2300 3000 etct 25 at say 3500 does not tell me anything at all, and do not use a dial back timing light iot will prob be off.
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Yes . I will need to break out my laptop when I get home later today .
 
mbaird said:
The 408 in my Swinger seems pretty lazy at lower rpms and I am thinking its my timing curve . I had the engine dynoed but that only covers 3000 - 7000 rpms .

The build is as follows
W2 heads ported
246/250 @ .050 / .648 lift on 108 solid roller
W2 Victor intake
9.5:1 compression
850 Pro Systems carb
Daytona Sensors CD-1 programmable ignition
TTI 1 7/8 headers with 3” exhaust and crossover all the way back .

My current curve is 18 intial and 32 total . Would 25 by 1200 be too much ?

Looking for more torque in the 1500-2000 rpm range . This thing should melt drag radial tires at will when I roll into the throttle . IMO .

View attachment 1716251492
Click to expand...
I'm running virtually the same cam with just a touch less lift. One motor's cam has a 108 LSA, and goes through an 2004R and a 3800 rpm lock-up converter.

The other motor has an identically sized cam, but it has 115 LSA, because its boosted. The builder says that will tame the cam significantly, but I haven't installed the motor, as I'm waiting for a transmission.

Both motors have EFI which might help at lower rpm

20240510_181759.jpg
 
RustyRatRod said:
Well all I can say is, the dyno ain't the car. Carry on and good luck!
Click to expand...
My W2 408 also peaks at 32 total on the dyno. The combination of long stroke and closed chamber doesn't require a lot of total timing.
 
mbaird said:
The 408 in my Swinger seems pretty lazy at lower rpms and I am thinking its my timing curve . I had the engine dynoed but that only covers 3000 - 7000 rpms .

The build is as follows
W2 heads ported
246/250 @ .050 / .648 lift on 108 solid roller
W2 Victor intake
9.5:1 compression
850 Pro Systems carb
Daytona Sensors CD-1 programmable ignition
TTI 1 7/8 headers with 3” exhaust and crossover all the way back .

My current curve is 18 intial and 32 total . Would 25 by 1200 be too much ?

Looking for more torque in the 1500-2000 rpm range . This thing should melt drag radial tires at will when I roll into the throttle . IMO .

View attachment 1716251492
Click to expand...
I had a custom curve distributor done at FBO last season. After removing the Firecore that I did myself, the custom curved FBO was an absolute dog. It was 18 initial, with mechanical to 32, all in by 3000. It was like I lost 100hp. I pulled it and made adjustments to mimic my previous Firecore, the performance was back instantly. 22 initial, 32 total, all in by 2400. You may wish to give something similar a try.
 
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