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Discussion Starter #1
Hey guys,

I have been running locked out timing (34*) with no curve whatsoever. The car made best power there on the chassis dyno, however, that is WOT tuning essentially. The car is 100% street driven for fun (no cruising the coast- talking about some poundings). I am running a Billet eCurve (no vac adv- See setup pictures attached). I notice down low it sounds like it is missing and or loaded up.

Should I be running an advance curve? If so why and what base timing?

Specs on my motor are:

  • 383, 3.75 Stroke, 5.7 Rods, 4.040, SCAT4340 Crank
  • -5cc SRP Flat top pistons: 10.3 SCR, 8.11 DCR
  • 233/240 .583/ .550 108 LSA 104 ICL (Running 1.6 Rockers)
  • Brodix Aluminum IK 67cc Chamber, 193cc Runner, 2.02, 1.60 Valves
  • Holley 650 Double Pumper, Down Leg Boosters, 900cfm Baseplate
  • 26" Tire, 3.55 Gear, 200-4R, 3200 Stall

I was thinking 19* Base, 15* Advance all in @ 3000


If it helps, I removed my distributor cap and it seems very fouled for only 350 miles.
 

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Discussion Starter #2
So if you see attached. I am running a "Q" configuration. With the circuits being 1 and 7 on the pot dials. With the car running I am seeing 34*
 

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Not so sure that's fouling ,looks more like the rotor phase is advanced due to your 34° locked advance.
I'd try a curve as you described and see how it feels.
 

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Discussion Starter #4
Not so sure that's fouling ,looks more like the rotor phase is advanced due to your 34° locked advance.
I'd try a curve as you described and see how it feels.
Thanks, the contacts look really dirty with build up and don't know if that would really affect much
 

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Discussion Starter #5
So I'm running a 20* advance @2500. This gives me a 14* base and 34 total. All in all it starts up much easier and behaves better at idle. This is the "G" configuration.

I'm idling and cruising around 11.6-12.4. Heavy acceleration is in the 14-16:1 range


I still seem to have a bad miss up top and from a dead still stomp. Also had a teenie backfire, could barely hear it when I shut the car off.
 

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Discussion Starter #6
Will the mixture screws affect bad bogs/misses when stomping to WOT?

Thanks for the help guys, appreciate it
 

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Travis

If indeed you are loading up at idle, then as much initial as you can get will help, dont go backward.

I would say for your set up this would be great and would noticed hardly any difference in a change of a curve.

18* to 22* of initial and a 16* to 18* mechanical curve. Total at 34* between 2500 and 3000 rpms.

IF you were able to add a vacuum can that add between 12* and 14* of timing at idle, then that would be the hot ticket. This would give you 46* to 48* of timing at cruise.

You did have this tuned on the chassis dyno right? I would not change what they did.

They only way I would is if I had something like a LM2 installed with 02 sensors in the headers so you could data logger your different set ups.
 

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Will the mixture screws affect bad bogs/misses when stomping to WOT?

Thanks for the help guys, appreciate it
No.

Bogs should be tune with pump cams and or squirters.

Misses are ignition realated, but dont come from your curve.

If you have black tracking, you might have a cracked distributor housing and or rotor.

Are you running a MSD box?
 

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Mixture screws affect idle richness and leaness.
 

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Discussion Starter #10
No.

Bogs should be tune with pump cams and or squirters.

Misses are ignition realated, but dont come from your curve.

If you have black tracking, you might have a cracked distributor housing and or rotor.

Are you running a MSD box?
Yes I'm running a box. Man lots of trial and error
 

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Boldly procrastrinating
66 El Camino 57 Chevy pickup 2004 Tahoe
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I would be trying the G or F curve with 16 or 18 intial.

Does that thing have any place to plug in a vacuum hose? if not, how does it compensate for load? cruising at 2200 and WOT/heavy load at 2200 don't call for the same advance at all.
 

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Boldly procrastrinating
66 El Camino 57 Chevy pickup 2004 Tahoe
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scrape that gunk off the contacts with a pocket knife or something and see if it does better with a curve. phasing of the rotor to the cap can be an issue with locked advance.
 

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Discussion Starter #15
What is phasing of the rotor mean?

I tried many curves but like I was talking to Aaron on the phone I have a strange miss/major bog when sudden WOT bursts. During these times my AFR reads 22.4 and it's almost like the car dies but because it's still rotating and let off the gas, it draws fuel back in and continues to run. On the highway it does it but not as bad, the engine gets loaded up but it's like it's not hauling butt
 

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If your air/fuel ratio goes up to the 22 range AND you have a bog, you just found your problem. Right? Try a bigger rear squirter and jet the secondaries up 2 sizes until bog goes away. WOT AFR should be around 12.5:1 for best power.

What do you guys think of my advise?

Btw, I have a 454 10.4:1, Hydrolic flat tappet cam, 244/260 @ .050", 108 lsa 108 icl. My timing is 25* at idle and 35* All in about 2000. I'm using an HEI that I made my own advance limiter. Because my idle vacuum changes from 10 in/hg in park 1050 RPM to 6 in/hg in drive 850 RPM, I use ported vacuum to my vacuum can that adds 10* while cruising or light accel. 35* total + 10* vacuum has been working well. Throttle response is crisp, runs great at cruising rpms. My engine likes timing. I don't think your timing is a problem.
 
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Travis,
You say the engine gets 'loaded up' on the h'way. What do you mean by that? It misfires, or you suspect it is running rich? What does it do when it loads up, misfire, surge? What heat range are the plugs? Common mistake is fitting plugs that are too cold, which then foul with low speed running, & then misfire when the #10 hits the pedal....

Also, your locked timing will be helping, not hurting your performance. In fact at cruise, you could use MORE timing, up to 50-55* in total.
 

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Discussion Starter #18
I'm running a heat range 7 NGK plug.

I have tried bigger squirters but I can smell that they are too large at WOT. Remember my cat was chassis dyno tuned. The issue is at transition
 

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I'm idling and cruising around 11.6-12.4. Heavy acceleration is in the 14-16:1 range


I still seem to have a bad miss up top and from a dead still stomp. Also had a teenie backfire, could barely hear it when I shut the car off.
If you are really 14-16 wot, that is way lean. Have you looked at a plug? You should have wot around 12.5 range. Idle Im gonna say mid 13's and cruise around mid 14's.

Your bogs are also due to being lean most likely. You need to make sure your pump arms are adjusted correctly. If it still bogs start increasing the sqiurters.

If you really are 14-16 wot, thats probably gonna hurt something at some point.
 
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