327 Vortec Timing on 8746
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Supreme Member
Joined: Jan 2001
Posts: 1,047
Likes: 2
From: Lincoln, Nebraska
Car: 1988 Firebird, 2000 GTP
Engine: 327
Transmission: 700R4
Axle/Gears: 9" posi, 4.11
327 Vortec Timing on 8746
I'm still working on my tune for my 327 Vrotec heads, cam specs:
Duration@0.050" 224*/230*
LSA 110*
Lift w/ 1.5RR .477"/.480"
I started off my looking at some of the tables other guys have posted up with similar builds. That got things running much better. I have since then been adding timing until I get 2-3 counts at 50-75% throttle, then backing off by 1/2* until it is gone.
I've been doing that and am at almost 40* advanced down low, 36* at idle, and I drop off to around 15* at WOT.
I have not done a lot with timing and am still trying to drop idle down so I can get it to stay running when hot. I'm down to 775rpm, but am still fighting the converter, which is bringing up temp at idle.
I'm going to try and post up my timing table. Fuel is within 2-3 of 128 on the rich side all through the VE table.
I suppose I should post somewhere else, but I've already gone through vaccum. I guess I can drop in more fuel, add even more timing and try to drop rpm some more.
Duration@0.050" 224*/230*
LSA 110*
Lift w/ 1.5RR .477"/.480"
I started off my looking at some of the tables other guys have posted up with similar builds. That got things running much better. I have since then been adding timing until I get 2-3 counts at 50-75% throttle, then backing off by 1/2* until it is gone.
I've been doing that and am at almost 40* advanced down low, 36* at idle, and I drop off to around 15* at WOT.
I have not done a lot with timing and am still trying to drop idle down so I can get it to stay running when hot. I'm down to 775rpm, but am still fighting the converter, which is bringing up temp at idle.
I'm going to try and post up my timing table. Fuel is within 2-3 of 128 on the rich side all through the VE table.
I suppose I should post somewhere else, but I've already gone through vaccum. I guess I can drop in more fuel, add even more timing and try to drop rpm some more.
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From: Charles County, Maryland
Car: 2000 BMW M5
Re: 327 Vortec Timing on 8746
Are you mass air or SD? I have a good tune from my 327 which had a holley stealth ram on it, 64cc aftermarket iron heads, 224/230 0.462/0.482 camshaft. I had the timing pretty under control.
Thread Starter
Supreme Member
Joined: Jan 2001
Posts: 1,047
Likes: 2
From: Lincoln, Nebraska
Car: 1988 Firebird, 2000 GTP
Engine: 327
Transmission: 700R4
Axle/Gears: 9" posi, 4.11
Re: 327 Vortec Timing on 8746
I should have mentioned I'm running TBI and am trying to get it to work with the stock converter. Heads were milled to 62cc, and I'm running the thinnest head gasket I could find in stock.. it's only a sheetmetal gasket. Compression came out around 9.5, I should have wrote it down, but I was to excited to get the thing running.
I didn't get a timing table up, but by 3200 I am at 32* At idle I have it around 36*. I know my whole issue is with air velocity since I'm running the Performer RPM Air-Gap. Fuel has to be falling out when I drop idle causing a rich/lean/rich. I tried slowing idle and that increased the rich/lean surging. I was looking through Chevy High Performance and they suggested only abround 15-18* at idle to start. I'm wondering if dropping that way down will do anything but loose vaccum. I know as I've been adding timing I've been picking up more vaccum but I can't believe I should be this high. I know another converter is needed, but I just don't have the cash for it right now and was hoping to get by. I'm about ready to just settle with the overheating but I know that's not good on the trans by any means.
I didn't get a timing table up, but by 3200 I am at 32* At idle I have it around 36*. I know my whole issue is with air velocity since I'm running the Performer RPM Air-Gap. Fuel has to be falling out when I drop idle causing a rich/lean/rich. I tried slowing idle and that increased the rich/lean surging. I was looking through Chevy High Performance and they suggested only abround 15-18* at idle to start. I'm wondering if dropping that way down will do anything but loose vaccum. I know as I've been adding timing I've been picking up more vaccum but I can't believe I should be this high. I know another converter is needed, but I just don't have the cash for it right now and was hoping to get by. I'm about ready to just settle with the overheating but I know that's not good on the trans by any means.
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From: Kansas City, MO
Car: 83 Z28
Engine: 406
Transmission: T56
Axle/Gears: 9" with 4.10s
Re: 327 Vortec Timing on 8746
Code:
20 30 40 50 60 70 75 80 85 90 95 100 6375 29.88 34.1 34.1 34.1 28.83 24.96 22.85 21.09 20.04 20.04 20.04 18.98 6000 29.88 34.1 34.1 34.1 28.83 24.96 22.85 21.09 20.04 20.04 20.04 18.98 5600 29.88 34.1 34.1 34.1 28.83 24.96 22.85 21.09 20.04 20.04 20.04 18.98 5200 29.88 34.1 34.1 34.1 28.83 24.96 22.85 21.09 20.04 20.04 20.04 18.98 4800 29.88 34.1 34.1 34.1 28.83 24.96 22.85 21.09 20.04 20.04 20.04 18.98 4800 29.88 34.1 34.1 34.1 28.83 24.96 22.85 21.09 20.04 20.04 20.04 18.98 4400 29.88 34.1 34.1 34.1 30.94 26.02 23.91 21.09 20.04 20.04 20.04 18.98 4000 29.88 34.1 35.16 35.16 31.99 28.13 26.02 22.85 21.09 21.09 21.09 18.98 3600 29.88 34.1 35.86 35.86 33.05 29.88 28.48 24.96 23.91 22.15 21.09 19.34 3200 29.88 34.1 35.86 35.86 33.05 29.88 28.83 27.07 24.96 22.85 21.09 20.04 2800 29.88 34.1 35.86 35.16 34.1 30.94 29.88 28.13 24.96 22.15 22.15 21.09 2400 28.83 31.99 35.86 34.1 33.05 28.83 28.13 26.02 22.85 22.15 20.39 19.34 2200 28.48 30.94 35.16 33.4 31.99 28.13 26.37 24.61 22.15 18.98 18.63 17.93 2000 28.13 29.88 34.1 33.05 30.94 27.07 24.96 22.85 21.45 18.98 17.58 16.17 1800 27.42 28.83 33.05 32.34 29.53 24.96 22.5 19.69 17.93 16.17 14.06 12.66 1600 27.07 28.13 31.99 31.99 28.13 22.85 20.04 16.88 15.47 14.06 11.95 10.55 1400 26.02 27.07 29.88 29.88 24.96 21.09 18.63 14.06 13.01 11.95 10.9 9.14 1200 24.96 26.02 28.13 28.13 23.2 19.34 17.93 13.01 11.95 10.9 9.84 8.09 1000 23.91 24.61 22.85 22.85 22.85 17.93 14.06 9.84 9.14 8.09 7.03 7.03 800 22.85 22.85 22.85 21.09 21.09 14.06 9.84 9.14 8.09 7.03 5.98 5.98 600 22.85 22.85 22.85 20.04 20.04 14.06 9.84 9.14 8.09 7.03 5.98 5.98 400 20.04 20.04 20.04 20.04 20.04 14.06 9.84 9.14 8.09 7.03 5.98 5.98
Are you running underdrive pulleys? I'm surprised that your overheating, but I guess like you said the converter could be causing it. I'm just running a 3 core brass rad and a single fan and never had overheating issues yet.
What fuel psi and injectors are you using? Do ya have a WB or are you just tuning of the BLMs?
I think that I was getting better vacuum with less timing. A couple times I actually got 15+ and 18 cruising.
Another tip I found somewhere was to use the same SA and VE values where the car likes to idle. This helped me much at keeping a smooth idle.
Last edited by graebz28; Jul 22, 2009 at 12:45 AM.
Re: 327 Vortec Timing on 8746
I am not Vortec but have the later version Edel RPM heads with supposed improved chamber design. I had idle as low as 16 and as high as 24. 24 seems OK. Did anyone suggest 36? Seems awfully high.
Thread Starter
Supreme Member
Joined: Jan 2001
Posts: 1,047
Likes: 2
From: Lincoln, Nebraska
Car: 1988 Firebird, 2000 GTP
Engine: 327
Transmission: 700R4
Axle/Gears: 9" posi, 4.11
Re: 327 Vortec Timing on 8746
I heard that about Vortecs as well, which is why I wanted to get this figured out. I'm going to pick up a new Ingnition Module because the one I have is from a salvage yard a few years ago. It could be that that is what is doing all this.
I'm running 13psi with the 65lb 350 injectors. I have a set of 80lb 454 injectors but I wanted to get everything really close before I switch over if I need to.
I'm tuning off BLMs but want make it to the Dyno when I get most of these issues squared away.
I think tomorrow I'll try a tune with less timing around idle. I might have it so high because I was WAY rich when I first started tuning. I tried tuning out a vaccum leak in the beginning and things just kept getting better with more timing in the beginning.
I mainly made this post just to get an idea of how much timing most engines use. I'll try backing it off again and hopefully it'll make a difference. If not I think I'm having problems.
I'm running 13psi with the 65lb 350 injectors. I have a set of 80lb 454 injectors but I wanted to get everything really close before I switch over if I need to.
I'm tuning off BLMs but want make it to the Dyno when I get most of these issues squared away.
I think tomorrow I'll try a tune with less timing around idle. I might have it so high because I was WAY rich when I first started tuning. I tried tuning out a vaccum leak in the beginning and things just kept getting better with more timing in the beginning.
I mainly made this post just to get an idea of how much timing most engines use. I'll try backing it off again and hopefully it'll make a difference. If not I think I'm having problems.
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Joined: Oct 2005
Posts: 330
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From: Dyer, In
Car: 91 Camaro RS
Engine: 355 Vortec
Transmission: 700r4
Axle/Gears: 3.42
Re: 327 Vortec Timing on 8746
I also think 36 degrees is too much advance at idle. From my experience a cammed vortec engine will typically need about 25-27 degrees at idle. Excessive timing or lean will cause excess heat, I doubt the TC is causing the problem. Idle around 850rpm should be possible with your setup.
I do not agree with setting timing to the most advance before knock. Set timing to the lowest value that provides good driveability and performance. If setting it this way does result in knock in certain areas then decease timing for those areas only. One exception may be to increase the timing slightly in cruise areas to increase mileage.
I do not agree with setting timing to the most advance before knock. Set timing to the lowest value that provides good driveability and performance. If setting it this way does result in knock in certain areas then decease timing for those areas only. One exception may be to increase the timing slightly in cruise areas to increase mileage.
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Thread Starter
Supreme Member
Joined: Jan 2001
Posts: 1,047
Likes: 2
From: Lincoln, Nebraska
Car: 1988 Firebird, 2000 GTP
Engine: 327
Transmission: 700R4
Axle/Gears: 9" posi, 4.11
Re: 327 Vortec Timing on 8746
Well, I pulled timing down low so I have 32* up at 3200rpm and am at 18* at 800rpm. I am loosing vacuum at idle in gear, but I have some work to do with VE again. SO... as far as temp goes it did not seem to make a difference as far as how quickly heat came up. Still slowly creeps as I sit. I did notice that just off idle even I picked up nearly 10Kpa. So it may just be a fuel issue that needs addressed now.
I also was thinking about that timing offset that is added to account for any advance done mechanicaly with the distributor. If that does infact affect injector firing. Would it be possible to get that set so that there is limited time during idle for fuel to fall out of suspension? Advance or retard the injector by a few degrees so it could possibly fire at a time with more air velocity? Just a thought though.
I also was thinking about that timing offset that is added to account for any advance done mechanicaly with the distributor. If that does infact affect injector firing. Would it be possible to get that set so that there is limited time during idle for fuel to fall out of suspension? Advance or retard the injector by a few degrees so it could possibly fire at a time with more air velocity? Just a thought though.
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