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Can we talk about good timing?

4K views 33 replies 15 participants last post by  PA_cob 
#1 ·
So, after fiddling with Pertronix, hard starting, and whatnot, I decided to to go with an HEI distributor. The simplicity and tune-ability of them won my heart. After a little bit of missteps, I've got it running really well right now. (My buddy literally pulled his out of his roadster and gave it to me. I gotta figure out how to repay him.) Anywho, the motor is a 289, edelbrock 1406, mild cam. I gapped the plugs to about .045". I'm getting about 12" of vacuum, which sound pretty good to me. When timing it, I started at 10 degrees, but it really didn't like it. It ran okay, but stumbling at idle, and a dead spot off idle. I increased to 12 degrees, and it's happy a lark. Seems like a lot of timing, so I figured I see what your opinions were.
 
#3 ·
12 was what I ran for years before my car was controlled via ECU. I think 10-12 is fairly normal for a 289/302.
 
#6 ·
jgrote, the 'end' timing is more important than where it starts. Ideally, you'll be somewhere between 28-36 degrees @2800, and all done. 28 = fast burn heads like the GT40P, which does better with the late spark.

Cam timing has a lot to do with this, as does compression ratio. Most 'stock' fords seem to like about 34. Whatever you can get away with on the gas you run, without ping.

If you advance so that your ignition is silky smooth, and it runs like a diesel at WOT, then it's really not going to to any good. Are you running vacuum advance? It's a feature that really helps street driven cars. Drag vehicles only care about whether they can idle (but not idle quality) and what happens at wide-open-throttle. Street cars usually enjoy better idle quality, part throttle, and economy.

Vac advance makes that possible, by advancing the spark when thin mix makes ignition take longer. That happens at idle and cruise. High vacuum conditions in the manifold. When you step on it, vac advance goes away.

So - time your mechanical advance, paying close attention to end timing, but getting your idle timing right too. Adjusting the RPM spread is different for every dizzy.

Once mechanical advance is set, you can hook up your vacuum to manifold vac, and that should smooth your idle out a lot. Then you can adjust idle bleeds and finally, set your idle RPMs on the carb.

Happy motoring.
 
#7 ·
Just noticed you’re in Denver-ish. Does that mean 5,000 ft-ish of elavation?

If so, that changes things. Air is thinner and thereby actual compression ratios are lower... and your engine will benefit from more (initial and total) timing. It’ll be some trial and error, listening carefully for pinging, detonation or engine run-on.
 
#9 ·
@bbmach, Yes, I'm at about 5500 ft. I'll check total timing later today. It snowed a little last night, so the car is once again tucked in, staying warm in the garage. It was 70 2 days ago! I WANT TO PLAY WITH MY CAR! @Grimbrand, Yes, I do have the vacuum advance hooked up, but to the carb. I was trying to learn more about how vacuum advance works in conjunction with mechanical advance, but still having a hard time wrapping my head around it. I may also need to learn how to adjust the mechanical advance. I know springs adjust when it comes in, but still need to learn how to set the end point.

I just want to stop a second to thank all of you who are taking the time to help me here. Part of the reason I still play with cars is that I love to try things out, learn new skills, and experiment with new ideas. Going into these endeavors with a little knowledge makes it 10 times more fun. I've been playing with old cars since a little before the internet existed, and hanging out at my local parts store was my only way then to get this info.
 
#10 ·
Its all a compromise, give and take and trial and error. Whatever your combo and climate likes the best.
As you go higher on a good initial * on throttle to get what you want for total * for you you might consider using a ported vacuum for advance. I like it for a nice low RPM at idle but instantly advances once the throttle cracks open.

I think you would be a prime candidate to use O2 sensors.
 
#11 ·
Think of it this way: The springs and limiters (and direction you have the dizzy clocked) come together to provide Mechanical advance. It only cares about how fast the engine's spinning.

Vac advance always seemed a bit backwards to me, when I was first trying to understand it. "Wait, when the engine's flat-out, it does nothing?"

But basically, that's it. Ignore vac advance, mostly, for setting your timing. Make sure it's disconnected, and that the hose (or vac nipple) is plugged so you have no leak. Vac advance is only an accessory. It does have a profound effect on how smoothly your engine idles, and on your gas mileage, but it will never affect full-throttle operation, and it won't keep your motor from running.

Ported vacuum (the weirdo port on your carb that takes off just above your closed throttle plates) is confusing to a lot of people. It has zero vacuum with the blades closed, but kicks up to full manifold vacuum as soon as they begin to open. A lot of 70s smog engines use this to keep the exhaust hot and make the catalytic converters function better. (Genius! Let's dump more unburnt fuel out the tailpipe in order to reduce emissions!) It's also useful for some cars with a lot of overlap on the cam, because the fluctuations in manifold vacuum can be strong enough to cause surging and stalling from the vac advance while it's just trying to idle.

There are a lot of very knowledgeable people that swear you should always use ported vacuum. It's an ongoing argument that may never be resolved. But to my thinking, it makes no sense to have "zero vacuum" and adjust idle to be perfect running on straight mechanical advance, then transition to a whole bunch of vacuum advance for cruise timing. Such a situation would work fine at full throttle, but not for everyday driving. I believe the best compromise you'll ever get with ported vacuum is an idle that's a bit retarded, and cruise that's probably just a bit over-advanced.

For most cars straight up manifold vacuum works best. If you have it all set right, what works best at idle will also work best at low-throttle cruise, giving you smooth idle, crisp throttle response, and best possible mileage. Under full throttle, the additional advance 'goes away', leaving you with a base mechanical curve that won't ping or detonate, allowing best possible throttle response, safely.
 
#12 · (Edited)
"........ I increased to 12 degrees, and it's happy a lark. Seems like a lot of timing, so I figured I see what your opinions were.
12 degrees BTDC isn't that much. That is the stock specification for the 289 K code (HiPo) engine. Total timing is 40 for the HiPo.

That said, my 289 engines have run best with 16 - 18 degrees BTDC, and total timing limited to 37-38 degrees... A stock distributor has 2 reluctors of different degree ratings, usually the 14L slot (the larger numbered slot) is the factory original setting , switching that for the 10L slot will let you run more initial timing and not have too much total timing.

I don't know if your current distributor has that adjustability.

Z

PS:
At idle, if you can advance the distributor and the rpm goes up, that tells you one thing : the retarded ignition setting is not giving your engine enough time to burn all the gas in the combustion chamber / cylinder. Advancing the timing is giving your engine more time to completely burn the fuel / air mixture, so the rpm goes up because more gas is being combusted (sp ?). Think about it.
 
#13 ·
Yep, same experience as Zray.

I run 16* initial but mine likes 18* better. I just was trying to limit total advance to 40* so I had to back it off a bit. It's a 289 with a bit of a rowdy cam and it doesn't like to idle at lower than 16.
 
#14 · (Edited)
+1 on on Z and Kelly. I too am running on the 10L reluctor. I added two pieces of shrink tubing to the arm in the slot to mimick the original sleeve, and I get 18 initial and 38 total. I run ported vacuum and tuned my vacuum canister down to account for the extra initial timing. If you run on manifold vacuum with the reluctor on 10L you will probably have way to much initial advance.
 
#15 ·
Thank you so much everyone! I played a little bit with it when I settled on 12, but it did seem to want a little more. I was just afraid to go any further. I'll go to 16 and then check my total and see where I'm at. I assume lighter springs will bring on advance sooner. I may go ahead and order some just to have them. I still need to figure out how to limit the total. I know it's all adjustable on an HEI. I just need to learn how.
 
#16 ·
Well, I thought I should wrap this up in case anyone ever wants to follow me down this road. First, I bought a distributor in Amazon for $48. This one: https://www.amazon.com/gp/product/B075M3T6RP/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1 It started out bad, and only got worse. I ended up returning it. What I learned is that most of these are coming from the same place, and they have a 2 piece shaft. The purpose of this shaft is to make these things a little more universal. If you're looking to go down this road, stay away from these. After that, my buddy pulled his disty out of his roadster to let me try it. He bought it from Jegs for $137. It worked perfectly. While I was trying his out, I decided to do a little more shopping and found this one. https://www.amazon.com/gp/product/B00S75G3BU/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1 This one is a 1 piece shaft unit. What was REALLY interesting was how much it had in common with my buddy's. There are the letter "JG" cast into the bottom of both housings. The shaft looked identical. The module had the same part #s and mfg name on it. I got it installed this morning, and everything went perfect. However, on his disty, the car was happy at 12 degrees of timing. It liked 14 degrees on this new one. Meh, we'll call that good enough. Now time to go and get some icecream...
 
#17 ·
Those GM distributors look horrible in a Ford. There are much better options .
Just my opinion and the opinion of most Ford owners .
 
#18 ·
While I agree with you every one is entitled to their own opinion. And when doing any type of restomod you can't really argue with function and performance over looks. While I went with an original distributor and a pertronix 3 which was super easy to install, I have heard that the HEI style is very easy and hassle free. @jgrote if you ever decide to go for an original look in the future I highly recommend that you take a look at pertronix. They make a drop in distributor with all electronics and cap already installed.
 
#20 ·
And this is why I love this forum so much. You guys aren't shy, are you. Most Ford owners, eh? Got any polling to support that? I believe that if this was true, this thing wouldn't be for sale in about a hundred different places. As you can see, I'm not shy either. Be that as it may, this thing purrs now. Even my wife noticed how much better it idled. And FWIW, I was not going from points to this. I was going from Pertronix to this. @MrFlash, I do agree that the flat top duraspark looks more at home though. I may go that route If I ever get the hair up my rear to learn how to wire it. This was the easiest way.
 
#21 ·
I'm not saying they don't work . They just scream GM HEI . They are readily available because they work and they are reasonable or cheaply priced . I have been a counterman selling parts for over 30 years and that IS a GM distributor cap . Just not my cup of tea .
 
#23 ·
@c6fastback, I totally agree with everything you just said. You are correct that it is a GM style cap, cheap, easy, and ugly. I even said the same thing to my buddy who talked me into trying it. He told me to close the damn hood and go enjoy driving my car. Everyone has a different use for their car. Mine is to enjoy a trip to the Dairy Queen with the wife and kid. I don't drive fast. I don't drive far. But I do need it to be reliable and safe enough to feel comfortable putting my family in it. So, even though I came across quite snarky in my previous post, I really do appreciate your view, and willingness to give it. I enjoy the banter back and forth almost as much as I enjoy driving my toy car.
 
#24 ·
If your dizzy is set up right, it'll work right, be it HEI, Ford, or some cobbled-together experimental monstrosity.

I like the Ford units because they fit better with a lot of air cleaners and Monte Carlo bars. They also have the benefit of looking stock.

I dislike the HEI because they are bulky and cause fitment problems. I dislike the ones with the in-cap coil because that's a crummy design. But if you have one and it works for your application, and you like it, then fine!

I freely admit I kind of turn up my nose whenever I see one of those big honkers in the front of a Ford, but it's not because they really suck or anything. Except for the coil-in-cap thing. They aren't better than the Ford units, nor worse, from what I've seen. They're just big and ugly to me.
 
#28 ·
I am all about Ford products or parts that are designed to work with Ford products. I personally was running an off the shelf new distributor that was from a local parts house. I didn't like the way it worked and the internals were not similar to an original Ford unit. I was able to source an original distributor and took it apart measured for tolerance, cleaned it up, put it back together, and installed a pertronix ignitor 3 which is literally drop in. It replaces the base plate and top plate and is just one unit. Once installed my car runs great and I still have a stock looking distributor. But there are those out there that will tell me I should just run points. That maybe I didn't learn enough about points and that I can make my car run just as smooth. I ran points before. The car ran fine. I do however see that the pertronix is an improvement over stock. And when I can improve on stock and make my care run better I will do so.
 
#31 ·
. The car ran fine. I do however see that the pertronix is an improvement over stock. And when I can improve on stock and make my care run better I will do so.
If I can ever find my bulletproof vest I'd be very tempted to break in to your garage and secretly install a decent set of points and condenser. I think years would pass before you noticed any difference, assuming of course that I made my escape without getting drilled.

Z
 
#29 ·
Would this be a bad time to mention an LS swap? J/K! So far I've been told that my car is ugly and I don't know what I'm doing. For those of you who don't bother to follow my build, let me remind you that I also run a 1 wire alt, electric fan, and even a brake light switch from a 74 Nova. Basically, every time my car leaves me stranded, I fix it with a Chevy part. Believe it or not, I'm not trying to be a troll here, but I'm building my car my way, with parts that I know and have experience with. I have to admit though, it's a little bit fun to post stuff up here to see what you guys think. Just know that you'll never hurt my feelings, so feel free to speak your mind. ;) And sometimes, you guys have even changed my mind. (I do have the CSRP disc brake kit.)
 
#30 ·
Thank you for taking this ribbing in the spirit intended. I write posts like I'm talking to a group of old friends over a table littered with empty beer bottles. On the internet, there's always the likelyhood of loosing the humorous side of things, which is too bad.

Z
 
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