Questions about timing and 750DP.
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Car: '91 Firebird
Engine: 305 TBI
Transmission: 700r4
Questions about timing and 750DP.
I'm trying to set up my carbed setup, but I need to know a few things. I've heard that carburetors need a different timing curve than EFI. What I want to know is how my timing affects the carburetor tuning. I have a MSD setup so I can set my timing curve to anything I want. I don't have any vacuum advance at all. It's just set as 12* at startup and 32* all in by 2800rpms. I have a 3500 stall, and I usually take off at 3000. I have 456 gears with 28" slicks and a TH350 trans. It all weighs 3500 with me in it. I initially had a bit of a bog with this carburetor whenever the secondaries would open[after stalling it up on the line]. I'm thinking my timing may have something to do with it and possibly a vacuum leak at the brake booster.
I'd like to know this:
1. What would it hurt to have all my timing come in at 1000rpm? I usually idle around 850-900.
2. If I run it and find it's slightly lean, will it help to remove some timing or should I just jet up and not touch the timing?
3. I don't run powervalves(I only race it). Do the jets need to be squared? or can I have like 76 primary and 80 secondary?
I'd like to know this:
1. What would it hurt to have all my timing come in at 1000rpm? I usually idle around 850-900.
2. If I run it and find it's slightly lean, will it help to remove some timing or should I just jet up and not touch the timing?
3. I don't run powervalves(I only race it). Do the jets need to be squared? or can I have like 76 primary and 80 secondary?
#2
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Car: 82 Berlinetta/57 Bel Air
Engine: LS1/LQ4
Transmission: 4L60E/4L80E
Axle/Gears: 12B-3.73/9"-3.89
Cam? Intake?
You're basically running locked-out advance. Might as well lock it out.
What heads? SBC's usually like more on the order of 36 degrees, although Vortec heads typically use a little less. Try different setting and see what it likes best.
Jetting is whatever makes the engine run best. But, you can't do anything until you know you don't have any vacuum leaks.
You're basically running locked-out advance. Might as well lock it out.
What heads? SBC's usually like more on the order of 36 degrees, although Vortec heads typically use a little less. Try different setting and see what it likes best.
Jetting is whatever makes the engine run best. But, you can't do anything until you know you don't have any vacuum leaks.
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Car: '91 Firebird
Engine: 305 TBI
Transmission: 700r4
Re: Questions about timing and 750DP.
It's a 6.0 with a 226 cam and a victor jr. intake. Stock coils fired by the MSD box. I wouldn't know what it likes best, I'm usually just happy if it takes off hard and doesn't bog or backfire. I don't know what pinging sounds like and I've tried reading the plugs, but that has never worked out for me.
Last edited by gunz4life2; 06-14-2008 at 12:41 AM.
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Car: '91 Firebird
Engine: 305 TBI
Transmission: 700r4
Re: Questions about timing and 750DP.
Yes. It's in my truck for now, until we can find another 3rd gen to put it in(I lost mine to a friend a while back).
Last edited by gunz4life2; 06-14-2008 at 12:46 PM.
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Car: 82 Berlinetta/57 Bel Air
Engine: LS1/LQ4
Transmission: 4L60E/4L80E
Axle/Gears: 12B-3.73/9"-3.89
You're pretty much in uncharted territory from what I've been seeing as far as members on this Board go.
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Car: '91 Firebird
Engine: 305 TBI
Transmission: 700r4
Re: Questions about timing and 750DP.
Well can you atleast tell me what it would do if I had all the timing in by 1000rpms(32* total).
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#8
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Car: 82 Berlinetta/57 Bel Air
Engine: LS1/LQ4
Transmission: 4L60E/4L80E
Axle/Gears: 12B-3.73/9"-3.89
Since you stall up at 3000 RPMs, it wouldn't be any different than having a curve that brings it in by 3000 RPMs.
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Car: 1987 IROC
Engine: 350 vortec
Transmission: TH350 3500 stall
Axle/Gears: 3.73 10 bolt grenade
Re: Questions about timing and 750DP.
if you're starting at 3K then you won't change anything if you change where the timing comes in if it's still under where you stall it to. sounds like you need to make good friends with someone who knows their way around a holley pretty well and someone who can read plugs and tune the carb. ls1tech.com may have some help as well on the timing though
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