Setting the timing on a 383

[trumpetcharger]

Ok guys...I am ready to attempt to time my 1969 383. Currently, it has a 750 Edelbrock that is leaking vacuum (going to replace it soon...I hope), an MSD Blaster coil, and a standard distributor. I'm at about 6,000 feet above sea level in Colorado. I'm using an advanced timing light.

I've looked around a little bit on the net, and I've seen a few comments regarding where to set the timing, but am curious about a couple of things from you guys:

1) Do I set the time at idle or at a certain RPM?
2) Given the first question. what time should I aim for?

Thanks much guys...I am really new to this...never attempted it before...so want to make sure I don't louse anything up before I mess around with the thing.

Pete

 

[ChgrSteve67]

at idle you should be around 12 deg btdc
by 2000 rpm your dist should be fully advanced to around 32 deg btdc.
If your higher than that you should look into changing the advance stops in your dist.

Of course this is with a stock or mild cam.

Don't forget to plug the vac advance pod on the distributor while your timing your motor.

As for your carb 750 is a bit much for a 383.
I run a 650 and works really well for my 383 with a mild drag cam.
You would probably need to replace the jets and rods from the ones that come with the carb to adjust for the 6,000 feet elevation.
I really like the Edelbrock Thunder AVS carbs. I'm running model 1806.

I also recomend taking it to a tuner with a chassis dyno and having them adjust your carb, timing and choke properly to get the correct afr for your altitude.

Just my 2cents
-Steve

 

[Manifold]

I prefer using a vacuum gauge to find out what timing the motor wants. Since you're new to doing this, I'd say start conservative as Steve suggested with 12 BTDC at idle.

I'm at ~5640 feet and have a 383 in my '68. Slightly lumpy cam (unknown specs), unknown compression ratio, 516 heads, Holley Street Dominator single plane intake, 1" phenolic adapter, Holley Street Avenger 770cfm (which the motor loves!), Mallory Unilite with vacuum secondary, Mallory Promaster coil, and Hooker headers (probably 1 5/8"). When using Fugly's white paper to find timing (http://www.diamondbackengines.com/technical-white-papers/vacuum-gauges/), I ended up with 24 degrees at idle, 42 degrees all in by 3000 rpms, and 10 degrees in the vacuum advance.

At altitude, the engines like a bit more initial timing, but you have to make sure you are limiting the amount of timing added by the mechanical advance (for example, my Mallory came stock/pre-set to 24 degrees mechanical advance; I had to adjust it down to 18 once I found my numbers). Like I said, if you're not familiar or comfortable with doing this, then stay conservative on the timing.

 

[Cranky]

Also, your compression ratio will usually dictate how much total it likes.....the lower the compression, the more timing. What's your psi on a compression test? I've never had two engines that liked the same timing curve.

 

[Manifold]

On a side note, many people find that dial-back timing lights are inaccurate. It's better to use a standard timing light (or the dial-back light set to 0) with a degreed balancer or timing tape (don't expect it to stay there forever though).

 

[Cranky]

On a side note, many people find that dial-back timing lights are inaccurate. It's better to use a standard timing light (or the dial-back light set to 0) with a degreed balancer or timing tape (don't expect it to stay there forever though).

I like to lay out my balancer and then use a cold chisel to mark the lines. It's not '0' perfect but it doesn't have to be. You can also use the timing tape to lay it out with. Just make punch marks through the lines then cold chisel the punch marks and you don't have to waylay it with the hammer either. As for timing lights....you just need to do some research for what ones are on the money vs the ones that are not. I have a 30+ year old light that is on the money and have used it to check my dial back light and they are both together. There are both that are good and then there are the ones that are junk. So far I haven't found any good about things like that from Harbor Freight etc. Mac tools is mentioned and so is MSD and Ferret. The MSD is going to be around 200+ and the Ferret is more. Craftsman has had some good lights but they also have had some bad ones. My old one is a Craftsman and I've checked it against some of the better known brands and it right with them. I suppose I could post the model number but I doubt you'd find one on the net but maybe.....?

 

[trumpetcharger]

Hey guys...thank you so much for all of your help and advice! I ended up having to return the first light that I bought, as it had a short in it. I finally had a chance to try the new one out tonight.

I have it dialed in to about 10-12 BTDC now. It's running *better*, but methinks there are more issues afoot that I will have to get after over the winter, not the least of which is the aforementioned carb.

Dumb noob question here...as I mentioned, the timing is pretty well where it's supposed to be. However, the timing mark does tend to flit 5 degrees either way...either at idle or at increased RPMs. In other words, the timing mark/line is by no means "standing still" under the light. Should it be?

I've currently got Accel resistance plug wires and (mostly new but still carbon fouled) Champion RJ12YC plugs in there. Bad combination maybe? I'm just trying to click thru different things in my head, trying to determine why this car isn't running like it's supposed to.

Thanks again for all of the help guys!!

Pete

 

[Meep-Meep]

With the vac advance disconnected and the carb port plugged you should have about 36-38 deg all in by 2200-2500. Initial setting can be 12-15 deg. 6000 ft will affect how the engine runs because of the lower pressure so you may find yourself leaning it out to correct the mixture. Do a compression test as recommended above because that will answer a lot of questions. No matter what the 6000 ft will hurt you as compared to what you will do at sea level, but you can always put a lung on it to compensate for the loss of ATM pressure!!!

 

[Cranky]

The timing 'bounce' is common at idle. How many miles does it have on it? The older the engine is, it'll probably have more. The bounce probably isn't as noticeable at higher rpm?

 

[Manifold]

The timing 'bounce' is common at idle. How many miles does it have on it? The older the engine is, it'll probably have more. The bounce probably isn't as noticeable at higher rpm?

Cranky - Is the bounce specific to points distributors, or is this a distributor shaft/bearing/bushing wear issue that could affect all distributors?

I haven't played with a points distributor in 15 years, so I'm rusty on them and can't remember if there was bounce or not. I simply put in electronic ones and ditch the points.

 

[Cranky]

The distributor could be worn and probably is if it's an original unit but things can stack up like a sloppy timing chain, or worn cam drive/intermediate shaft or all of it. How did it run with the 24/42? Unilite with vacuum secondary? You mean vacuum advance, right? Vac hose disconnected it's running at 24 degrees and then goes to what when you hook it up? Your Unilite is a points unit?

 

[Manifold]

How did it run with the 24/42? Unilite with vacuum secondary? You mean vacuum advance, right? Vac hose disconnected it's running at 24 degrees and then goes to what when you hook it up? Your Unilite is a points unit?

It runs great with 24* initial, 42* total. Yep, meant Unilite with vacuum advance. Probably still had the Holley on the brain when I typed that!

Yes, 24* with vacuum advance disconnected. When I was running the Carter AFB 625cfm, I did what I'm used to doing which is plug the vacuum advance into the timed spark port. So, no advance at idle. After doing some reading on the use of full manifold vacuum as the vacuum advance source (since the Holley I was putting on no longer had the timed spark port due to the race calibration Proform primary metering block), I felt it could do me some good to try it (and I had no choice other than to not run the vacuum advance at all, which I didn't want to do). The timing does jump up some at idle when using full manifold vacuum, but I don't have the exact number handy. It wasn't much and a quick idle adjustment brought it back down to where I wanted the idle. I had the can adjusted to only provide ~10* when I set up the timing and didn't touch that adjustment when I went from the ported to manifold vacuum source. IIRC the vacuum advance doesn't advance at under 10" of vacuum.

My Unilite has the optical trigger. Like I said, I haven't played with points in a long time! Still have my feeler gauges and dwell tool though. ;)

 

[skudkino]

I might be a little late to the thread, but...
I also have a 383. I tore out the points distributer and replaced it with a electric ignition. I tore the electric one out of an old broken Dodge truck with a 400. I didn't notice any big differance when I did the switch, but I am also having a difficult time being happy with my timing. Is the differant distributer with differant vac advance messing me up, or does it even matter?

 

[1968_Roadrunner]

I know this is an older thread but I am having timing isssues right now and hopefully I can get some advice. I have a Pertronix Flamethrower distributor in my 383. Stealth heads with domed KB pistons (KB400). Holley 830 and Torker intake. Voodoo Cam. I finally got my timing tape on it yesterday and got to look at it quickly before it flew off! The problem I am having is that the car runs perfect set at 20 initial and about high 40's full. Everything I am reading says this is too much but if I back it down to 12-14 and about high 30's it doesn't run as good. Any ideas???

 

[rlsbee]

I know this is an older thread but I am having timing isssues right now and hopefully I can get some advice. I have a Pertronix Flamethrower distributor in my 383. Stealth heads with domed KB pistons (KB400). Holley 830 and Torker intake. Voodoo Cam. I finally got my timing tape on it yesterday and got to look at it quickly before it flew off! The problem I am having is that the car runs perfect set at 20 initial and about high 40's full. Everything I am reading says this is too much but if I back it down to 12-14 and about high 30's it doesn't run as good. Any ideas???

Your Pertronix distributor should have have come with advance limiters.
( I use the same distributor)
There will be a 12, 16, and 20 degree limiters. The ones that come on it are 24 degrees. If you want to keep the initial at 20 degrees try installing the 16 degree limiters. This would give you a total of 36 (vacuum disconnected). If it runs ok, fine. Another option would be to back off the initial by a degree or two and try the 20 degree limiters. I had to play around a lot with initial and total to get my 383 where I was happy with it and where I could run it on available gas. I highly recommend reading the Diamonback Engines 'white paper' noted in another post

 

[Onit]

With the vac advance disconnected and the carb port plugged you should have about 36-38 deg all in by 2200-2500. Initial setting can be 12-15 deg. 6000 ft will affect how the engine runs because of the lower pressure so you may find yourself leaning it out to correct the mixture. Do a compression test as recommended above because that will answer a lot of questions. No matter what the 6000 ft will hurt you as compared to what you will do at sea level, but you can always put a lung on it to compensate for the loss of ATM pressure!!!

 

[Onit]

Ok so I'm reading on this forum about timing I'm new to all this timing stuff as well I know this is an older thread but I am having timing isssues right now and hopefully I can get some advice. I have a Pertronix Flamethrower distributor in my 383 but I don't under stand when u guys say it should say With the vac advance disconnected and the carb port plugged you should have about 36-38 deg all in by 2200-2500. Initial setting can be 12-15 deg.so I have The volume plugged And my needle is jumping all over the place I put the different Springs in the distributor the gold ones or copper I'm just looking for a little bit help very new to the office it was my dad's car and he passed away so I'm just trying to keep his memories alive by keeping this Dang car running good Oh By the way I have an elder block intake manifold and an elderbrock and an elderBrock 600 carburetor