Timing a motor by ear...

[GsxrMike]

How do you do it? I don't have a timing pointer and even if I did I don't think I would be able to see it. The motor runs great in the mud but on the road it lacks power at full throttle. I have to back off to about 3/4 throttle to get it into the higher rpm range. Any tips would be great! TIA

 

[supersize75k5]

Old school way was to advance the timing until it started pinging under load then retard it a few degrees.

Although that will work, it will be nowhere near to the best timing.

Base timing is just a base timing when the engine is idling and not under load. It's a starting point. Sometimes it's low, sometimes it's high. If too high, it makes it hard to start the engine.

Advance timing can be mechanical with vacuum and with computer controlled engines, electronic advance.

Electronic is all controlled by the computer and is based on where the base timing is set.

Mechanical advance controls how much and at what rpm the advance timing comes on. A good performance setup will be at full advance by 3000 rpm. The base timing plus the mechanical advance give a total timing. Changing the base timing will change the total timing. Playing with the weights and springs can change the mechanical advance.

Vacuum advance is only for part throttle operation.

Now, all you're concerned about is base and total. As I mentioned, total can be just about anywhere. Lets say you use 10* BTDC as a base timing. Engine starts and idles fine. Now the total timing is where the power is made.

Total timing depends a lot on the specific engine. Timing that one engine may like will not be the timing for another. Where an engine likes it's total timing can't be guessed at. The engine either needs to be on a dyno or by using dragstrip tuning to find the best timing which gives the best MPH. Being off by one degree can change the engine 10-20 hp. Once the best timing position is determined, no tuning changes to the engine such as jetting, plug gap, valve lash etc will affect where that engine wants it's timing.

Lets say you had a base timing of 10*. Checking the total timing gives you 32*. If you advance the timing to 16*, the total will be 38*. If you make more power at 38*, you may find the 16* base timing is now too much. 32-10 = 22* of mechanical advance. To maintain 10* base and 38* total, the mechanical advance needs to be changed to 28*

Now if your distributor is computer controlled, the best thing you can do is set the base timing to the factory specs and let the computer control the distributor. There has to be a mark somewhere on the balancer. If not then you'll never get a correct base timing. Change the balancer to one with a timing mark.


Before you bother with any of this, do you now for sure you have good fuel pressure and it is not a fuel related issue on any level? Maybe plumb in a fuel pressure gage and have a check. im also curious is your carb and dist. are the computer controlled versions?

 

[obijuan]

i just time it with the throttle at around 700 rpms to where the motor doesnt shake at all. if you put a nickel on the intake it shouldnt move.

 

[GsxrMike]

That was very informative. Any links on adjusting the mechanical advance? I think I may need adjustment at around 3000rpm and up but I don't know my base timing. I guess I will need to put in my pointer and get a mirror.

BTW: I think I have a HEI dizzy. There is no computer and it isn't point type so...what do you think? I tried to read a book on ignition systems but I think I learned more from your post than I did from the book. Thanks again!

EDIT: When I set my base timing I want to remove the vacuum advance and run the engine up to about 1000rpm right?

 

[GsxrMike]

Alright I just read an article on adjusting the timing curve of an HEI distributor. Sounds scary. What do they mean by more/less timing? It sounded backwards to me. I think they said more timing at idle will make the engine start easier and less timing at higher rpms will yield more performance. Does more mean closer to 0* timing? Sorry for all of the lame questions.

EDIT: here is a link to the article - http://www.pontiacstreetperformance.com/psp/distcurve.html

 

[onetonbb74]

What do they mean by more/less timing?http://www.pontiacstreetperformance.com/psp/distcurve.html

More timing means the number is higher for instance btdc is before top dead center so if my timing is reading 10 btdc on the gun and I want to add more timing, the number would get higher like 14 btdc for example. Less timing would be getting the number closer to 0 (easy to start).

from the article: However, the engine will idle better and be more responsive at very low rpm with more timing in the initial setting, and less in the mechanical advance.

This guy has an opinion on the way the timing is progressing. He is saying that more timing in the initial setting so you dont have to rely on the mechanical advance to do all the timing. Somehow your going from 10btdc or so at idle to 36/38btdc ish at 3k rpms.

btw, i use a white out pen and mark the line on the balancer so you can see it better. I suggest using a can of brake clean and a light and give it a shot.

 

[original balzer]

By ear is the only way I have ever timed a vehicle.

Heres my method.

start the engine and get it up to normal temp.

with the vacuume adv still attached I will hold the throttle so it runs near 1500RPM then advance it until it pings and back it of until it stops,
using very small adjustments and waiting for it to stabilize its self. I then give her a few full throttle blasts to listen for ping. If I get ping I lower the advance a tiny bit more. I keep doing this until I get NO ping at full throttle blasts.

I then take the vaccume adv off and run it up to around 1000RPM and adjust it till it runs the smoothest I can find. Again using VERY small adjustments.

This way (although is usually argued by everybody I know as wrong)I find the most adv under normal conditions with the vacuume adv attached. Then I fine tune it without the vacuume hooked up.

Ususally this gets me perfect timming in my oppinion. They start quick and I dont get any ping.

 

[GsxrMike]

Alright thanks guys! I still gotta find a way to set my inital timing. It is suppose to be close to 50*F today so maybe I will get out there.

 

[bp71k5]

Isn't a timing gun like $10? I know times are tough right now, but that's an important tool to have.

 

[GsxrMike]

I have a timing gun but I don't have a pointer on my motor and I can't figure out how to install one.

 

[onetonbb74]

there are 2 different ones for the 350 that ive noticed, one that is directly 12 position on the balancer or there is one at 2:00/2:30 position. Find top dead center by removing the number 1 spark plug, have a buddy put his finger over the spark plug hole until it blows his finger off the hole(compression stroke) then look where the line is in relation to the damper and buy the proper timing tab, the most common ive seen are the kind that bolt on to the timing cover with 2 bolts but the factory ones are welded to the timing cover itself. Once you bolt it on, line it up with 0 and your all ready to go.

You can also measure the circumference of the damper and get the correct timing tape that has number readings on it that make it easier to read.

 

[original balzer]

Isn't a timing gun like $10? I know times are tough right now, but that's an important tool to have.

Never owned one. I come from the other school of thought I guess. I belive no 2 engines are the same. Meaning You could build 2 identical 350 chevy small blocks yet they would require differnt timming to run at perfect. They would require differnt carb adjustments too. Some things like timming, you just cant do by the number or from a book.
Of course this is just my own personal oppinion.


GSXRMIKE, What do you mean by initial timming? If it runs great in the mud and not on the street I would think your timming is retareded too far. while under power like in the mud the mechanical and/or vacuum advance would advance the timming to run good. But under normal driving, it isnt advancing it far enough.

Loosen the hold down so you can move it, but it doesnt move freely.
Like I said to do it by ear you warm up the engine. With the vacuum advance still hooked up, run it up to around 1500 rpm advance it until you hear it ping. Then back it off until its gone. Then give it full throttle a few times, this makes the vaccume/mechanical advance to advance as far as they will. if you hear ping when you give it full throttle burst retard the timming a bit more. Once you have no ping what-so-ever that will be close to where you need to be(is this what you mean by initial timming?). Now you disconect the vacuume advance and run the engine to 1000 rpm and fine tune untill it runs the smoothest.

Oh then tighten the hold down and your done.

 

[GsxrMike]

I just got done with my build http://coloradok5.com/forums/showthread.php?t=229252&highlight=gsxrmike%27s+build and I never actually set the timing. It runs great in the mud but on the highway it leaves something to be desired at WOT. I've got my timing tab mounted now and I just have to set the timing and take it for a spin.
Questions:
The mark on my balancer is TDC correct?
When I set my timing would leaving it idle with the vacuum advance disconnected and setting that way be correct?

 

[Randy92782]

By ear is the only way I have ever timed a vehicle.

I'm the same way. My methods is kinda hard to explain but i just have someone inside the cab start it and determine whether i have to advance or retard it. Keep starting it til it starts with no hesitation.

This method has always worked for me and i've never had a problem with sparkknock or such on heavy loads. Plus it turns on pretty good if ya got a good carb.

 

[Hogback Fabrication]

Isn't a timing gun like $10? I know times are tough right now, but that's an important tool to have.

X2

Never owned one. I come from the other school of thought I guess. I belive no 2 engines are the same. Meaning You could build 2 identical 350 chevy small blocks yet they would require differnt timming to run at perfect. They would require differnt carb adjustments too. Some things like timming, you just cant do by the number or from a book.
Of course this is just my own personal oppinion.

Absolutely true that no two motors are the same (well, once they leave the factory and have 100K+ on them).

But timing by ear is hokey IMO. If you use a timing light and set the timing at 8 deg. and it doesn't ping at idle or running down the road then you can try more. This way, you will know that maybe 10 or 12 is right, maybe 13 is too much.

Setting timing by ear, you have no idea. You might set the timing to 15 deg and get ping so you end up turning it back to 5 deg to get rid of the ping. There's no way of knowing where you're at.


IMO, this kind of timing tuning (and carburetor tuning for that matter) is why so many people with K5's get single digit gas mileage.

 

[GsxrMike]

Alright I just went and set my timing to about 14* btdc (it was at like 18*) with the vacuum line off at about 600rpm. I took if for a test drive and it drove better but I still had a hickup about 3000rpm and then it picked back up and had enough power to kick the tcase out of 2H. Any advice? Should I set it and 12* initial and see what happens? Thanks for the help guys!

 

[Randy92782]

IMO, this kind of timing tuning (and carburetor tuning for that matter) is why so many people with K5's get single digit gas mileage.

I'd say it probably has to do alot with how heavy their foot is on the skinny pedal. I set my 83 truck up just like this and get 13mpg. Granted it probaly gets a quart of oil to every 200 miles but that's just cause the motor likes oil and it's 11 or more years old

 

[BlazerBud]

guess. Just move it about 1mm increments in one direction until it pulls hardest running up hill. You may be advancing it or retarding it. But going up hill will be a better indicator because it is under load at all RPM.

 

[Blue85]

Technically, total timing is initial + mechanical + vacuum. Some don't believe that this is ever seen (probably becaue it is such a large number), but it is what you experience when you close the throttle from high load, high rpm conditions.

First things first - figure out where you're at and make sure each part of the dizzy is working correctly. It is pretty common for the mechanical advance to be stuck so that it doesn't even work.

While I agree that useable timing can be achieved by ear, it is silly to try to optimize it without the light. How do you know what your mechanical advance is doing (if anything)? How do you know how much the vacuum can is pulling in? If you don't have the tab, timing tape works great and is only about $10 from Summit. You just need to find TDC once (spark plug hole or drop the oil pan)

If you want to change anything more than initial timing, you'll need a curve kit. These are cheap and good to have since the factory springs are usually too stiff. Then you'll have to experiment to see if the engine (or maybe you?) prefer ported or manifold vacuum.

 

[GsxrMike]

Could anybody describe engine "ping"? Is it like a miss? I've never heard it and I've had some f'ed up timing before. I've timed my engine to run like piss but never heard a "ping"

The way my engine is timed now it sounds like it has a miss about half throttle under no load but I have less initial timing that I did before I timed it. What gives?