327 Vortec Timing on 8746 - Third Generation F-Body Message Boards

TZFBird · 07-20-2009, 11:46 PM

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.

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327_TPI_77_Maro · 07-21-2009, 09:04 AM

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.

TZFBird · 07-21-2009, 09:29 PM

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.

graebz28 · 07-22-2009, 01:42 AM

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

Here is the vortec timing table that I am using right now. I still need to work with it a bit, but the car is able to idle at 850ish. I have not tried to get it lower yet. Make sure that your idle SA is actually what it says it is. I never tried to push the idle timing that high, but I can give it a try although i have stick so it is more forgiving. Bottom line on vortec heads supposedly is that they need less timing than regular heads.

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.

Ronny · 07-22-2009, 04:39 PM

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.

TZFBird · 07-22-2009, 10:39 PM

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.

alvanwie · 07-22-2009, 11:39 PM

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.

TZFBird · 07-23-2009, 04:29 PM

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.