Engine timing adjustment without timing light.

blackbird307 · Veteran Member

Engine timing adjustment without timing light.

427carl · A Poncho Legend!

Go into Winnipeg and get a fire extinguisher Then call Carl 1

4SPEED427 · A Poncho Legend!

Blake, are you trying to start it and it won't start, or does it run and you're trying to fine tune it?

Typically, if you have backfiring through the carb and it's timing related it would mean it's retarded.

And, typically, if it's too far advanced, as you are cranking, you will notice it almost "seize up" momentarily because what's happening is, it fires too soon, the explosion in the chamber tries to push the piston down as the piston is trying to come up.

I would say if it's not seizing, keep advancing it until it does that, then back up a bit.

And again, when I ask this, I am assuming it won't start. Do you know for sure you have the distributor in correctly located, not 180 degrees out?

4SPEED427 · A Poncho Legend!

Oh, and if it's not starting, do you know for sure you have the wires on in the correct sequence?

blackbird307 · Veteran Member

When I first found top dead center using a piston stop, matched the rotor up with #1, the engine would not start, or barely would. When it did start I would have to hold the gas to keep it running, very choppy, low rpm, some backfires. But I was confused because I was approximately at top dead center, no valves open, within no more than 5 - 10 degrees, and it seemed to be having a hard time starting. By turning the distributor counterclockwise I advanced the timing, and I didn't have this problem anymore. Maybe I was off way more than I thought after I put the cap back on.

It's starting, and running now, so I guess I'm tuning at this point. It idles fine, just the occasional backfire. It seems to backfire at lower rpms, ie when the engine starts. At higher rpms I hear popping too. When I turn it off, and advance it a little more, I hear less pops at higher rpm, so I figure I need to advance it some more until I don't hear pops anymore. However since I don't know what too far advance looks like, id rather not find out the hard way. From what ive read around the web, it sounded like I was too far advanced to begin with, or maybe I wasn't.

I still get fire shooting up when starting, but not all the time, sometimes I just see smoke shoot up. I am not too sure if its because it's too lean (I installed manual choke carb I am still getting used to). Maybe I just need to advance it a little more.

If I was off by 180 degrees, would I see any improvement in such small changes? I don't think I am but, you never know. Being off by 180 degrees would be like putting #1 spark plug at the opposite end of the rotor while at TDC right?

Thanks!

-- Edited by blackbird307 on Tuesday 20th of October 2015 09:26:16 PM

4SPEED427 · A Poncho Legend!

If you are off 180 it won't start so you are safe to say you have it dropped in correctly.

Make SURE you double check your wires to see if they are on correctly. Often guys will swear they have them on right, it runs like crap and when they double check they have at least 2 mixed up!

I would suggest more advance if you still get backfires. (assuming the plugs and wires are all in good shape and installed correctly) Keep advancing until it fights itself when cranking to start.

What is the history on this? Rebuilt engine, used engine, changed carb and intake, or......?

seventy2plus2 · Canadian Poncho Superstar!

When you found TDC with a piston stop, did you only hit the stop by turning the motor one direction? To find TDC properly, you need to hit the piston stop by going both ways, and TDC is between the two. That's because the piston stays at the top for a time while the crank is turning.

Either way, I suggest you get yourself a timing light, as right now you're flying blind. You haven't mentioned if you've disconnected and plugged the vacuum line to the vacuum advance, etc. Keep in mind things like air/fuel mixture will also influence things like backfires.

koolconvertible · Poncho Master!

Did you use a degree wheel when using a piston stop? That is not always TDC Where it stops. You can mark the balancer using the timing mark then reverse to stop again and mark. Half way between is TDC abouts, hopefully matching the timing mark if th balancer hasn't spun...make sure rockers are doing the right thing, drop in dist ensuring the mark on dist for number 1 is clear and correct. and make sure as Carl says the plug leads are correct.

koolconvertible · Poncho Master!

seventy2plus2 wrote:
When you found TDC with a piston stop, did you only hit the stop by turning the motor one direction? To find TDC properly, you need to hit the piston stop by going both ways, and TDC is between the two. That's because the piston stays at the top for a time while the crank is turning.
Either way, I suggest you get yourself a timing light, as right now you're flying blind. You haven't mentioned if you've disconnected and plugged the vacuum line to the vacuum advance, etc. Keep in mind things like air/fuel mixture will also influence things like backfires.

Good advice! you must have been posting hile I was writing!

blackbird307 · Veteran Member

Carl Stevenson wrote:

If you are off 180 it won't start so you are safe to say you have it dropped in correctly.

Make SURE you double check your wires to see if they are on correctly. Often guys will swear they have them on right, it runs like crap and when they double check they have at least 2 mixed up!

I would suggest more advance if you still get backfires. (assuming the plugs and wires are all in good shape and installed correctly) Keep advancing until it fights itself when cranking to start.

What is the history on this? Rebuilt engine, used engine, changed carb and intake, or......?

Checked the wiring 3 times, all looks good.

The engine I have in there is:
400 CID
280h Magnum camshaft
AFR 227 Eliminator cylinder heads
1.6 Ratio roller rocker arms, with 1/2 turn pre-load
800cfm edelbrock carb with manual choke
Edelbrock performer dual plane intake

My carb might be a little big, too lean causing it to backfire. I was divided on just going with a 700cfm. I went with the 800 because of my aftermarket heads.

koolconvertible wrote:

Did you use a degree wheel when using a piston stop? That is not always TDC Where it stops. You can mark the balancer using the timing mark then reverse to stop again and mark. Half way between is TDC abouts, hopefully matching the timing mark if th balancer hasn't spun...make sure rockers are doing the right thing, drop in dist ensuring the mark on dist for number 1 is clear and correct. and make sure as Carl says the plug leads are correct.

Unfortunately, I broke a bolt in my engine block. I then broke an easy out trying to remove it. Had to smash it out. In order to re-thread it, I had to remove the harmonic balancer. So the timing mark wasn't valid anymore. I had to find TDC again using the method Carl described.

Ill advance the timing a little more and see if that makes a difference.

-- Edited by blackbird307 on Tuesday 20th of October 2015 10:56:25 PM

-- Edited by blackbird307 on Tuesday 20th of October 2015 11:20:04 PM

4SPEED427 · A Poncho Legend!

We're talking a Chevy 400, not a 400 Pontiac engine?

4SPEED427 · A Poncho Legend!

Never mind, I googled the the heads and see it's a small block Chevy!

I was concerned it was a Pontiac 400 which has a reverse rotation on the distributor. I thought that might be messing you up.

seventy2plus2 · Canadian Poncho Superstar!

blackbird307 wrote:

Unfortunately, I broke a bolt in my engine block. I then broke an easy out trying to remove it. Had to smash it out. In order to re-thread it, I had to remove the harmonic balancer. So the timing mark wasn't valid anymore. I had to find TDC again using the method Carl described.

Ill advance the timing a little more and see if that makes a difference.

-- Edited by blackbird307 on Tuesday 20th of October 2015 10:56:25 PM

You've really lost me re the broken bolt, removing the harmonic balancer, and timing mark not being valid anymore.

If you've found TDC, mark it on your harmonic balancer (presuming it's been reinstalled) with some type of timing tab so you have a reference point.

GLHS60 · Poncho Master!

blackbird307 wrote:
I am trying to adjust the timing on my engine, but I need to find out if I am too far advanced or too far retarded. Are there any signs of knowing if I am either?

I see occasional puffs of smoke rise of through my carb, I even sometimes see a quick burst of fire. Which would mean either I am firing while the intake valve is open, or intake valve is open till after ignition, thus exhausting coming out through the carb. But I have seen both fire and smoke.

Could anyone help me?

-- Edited by blackbird307 on Tuesday 20th of October 2015 08:39:21 PM

To recap:

Retarded ignition timing will cause the engine to idle slower with less vacuum and will have a tendency to pop or backfire out the carb when the throttle is opened quickly.

My opinion, when checking, adjusting, setting ignition timing you want the engine warm and idling smooth, vacuum line disconnected.

If the engine is running rough, mixed plug wires, valve too tight, cracked cap, etc, etc, will make it much more difficult to time by ear.

Timing by ear is perfectly O.K. to establish a baseline that can result in a fine running engine.

With the engine warm and idling you can feel and hear the difference between early and late timing.

With the engine warm and idling, rotate the distributor CW, retarding the timing and the engine will idle slower with reduced vacuum and sound labored, like a dump truck.

From there rotate the distributor CCW, advancing the timing and the engine will idle faster with increased vacuum and sound relaxed and composed, like it should.

From there, over advancing, the engine will begin to idle erratic, almost dancing like when having to pee..

I encourage folks to get the feel of your engine by advancing and retarding their warm and idling engine to feel the effects of ignition timing.

From there you want to verify your effort, hard to start and pinging under load indicates too much advance.

The hotter the engine runs, the more tendency to ping under load or have starting problems. eg: grunt, grunt while cranking.

Good Luck !!

Thanks

Randy

-- Edited by GLHS60 on Wednesday 21st of October 2015 02:51:40 PM

whiskeydog · Addicted!

I bought a new (new to me) publication a few months back and read an interesting article you might make use of.

I hope the link works,

www.carsandparts.com/en/tech/performance/2015/08/tuning_for_todays_fuel.html

4SPEED427 · A Poncho Legend!

One thing I should add about timing by ear.

Years ago I had a pretty much stock 427 in my Acadian. I'd never put a timing light on it. It started to have a funny sort of surge when I was on the highway. I figured maybe it was time to put a light on because I had just set it where it ran the nicest. I was WAY too far advanced with my initial timing. I forget the number but I am thinking it was close to 20 degrees, and was supposed to be single digits. Because I had lowered the compression on the engine slightly so I would not have pinging problems, it never pinged no matter how much timing I put into it, but I'm sure such a huge initial advance was not the most efficient.

So yes, a correct setting is important I would say.

blackbird307 · Veteran Member

I managed to drive it around the block today.

I noticed my intake manifold was leaking oil at the back of the engine. There was a little hole that ejected oil which I plugged with a bolt, but it pushed the intake manifold gasket into the intake. I removed the intake manifold so I could reseat the gasket, and I found this.

Holy crap. What could have possibly caused this!

-- Edited by blackbird307 on Thursday 22nd of October 2015 12:51:28 AM

4SPEED427 · A Poncho Legend!

Tightened down too much?

Wrong length, does your setup require a special length for any reason?

GLHS60 · Poncho Master!

Looks like an exhaust pushrod.

Thanks
Randy

koolconvertible · Poncho Master!

I reckon that would stop it from starting...i had that problem after an engine rebuild...but first maybe remove timing cover to ensure the timing chain and gears are lined up correctly..

what caused my bent pushrods? the rocker studs were incorrect. Only one was wrong. The hexagonal part of the rocker stud was too high/thick and caused the rockers to bind when adjusting. Removed stud, fitted correct one, started first go...after replacing bent rods...

koolconvertible · Poncho Master!

Also, as carl suggested investigate correct pushrod length. i notice you rocker ratio is 1.6:1 , standard is 1.5:1. This could affect

valve gear train geometry...

blackbird307 · Veteran Member

About my valve train geometry....

I phoned the manufacturer of my heads. Apparently angled pushrods are not uncommon. It's just the way the heads are designed. In order to eliminate the angle, the lifters would require an offset aswell. If the pushrods were actually straight from valve to lifter, they would rub against the cylinder head. The cylinder head intake port holes would be obstructing the pushrod holes, so they cannot move. If you look at the picture, the pushrods are clearly angled away from the intake ports.

So I either have really cheap pushrods, or they're the wrong length.

Beaumont4008 · Uber Guru

I see the bolt you used to plug the oil leak. That is used for your oil gauge sending unit. I think your going to heed some strong pushrods to survive that angle. Did your head manufacture recommend what you should use. What's the manufacture AFR .

ian

koolconvertible · Poncho Master!

I would be utilising that oil pressure outlet for a gauge.....

correct push length

https://m.youtube.com/watch?v=OmzbHgVY3cI

rocker ratio maths

https://m.youtube.com/watch?v=7CKH_cjUD5A

-- Edited by koolconvertible on Thursday 22nd of October 2015 02:59:23 PM

blackbird307 · Veteran Member

Beaumont4008 wrote:
I see the bolt you used to plug the oil leak. That is used for your oil gauge sending unit. I think your going to heed some strong pushrods to survive that angle. Did your head manufacture recommend what you should use. What's the manufacture AFR .

ian

Yes, those are AFR 227 Cylinder heads. The pushrod that broke was also a exhaust pushrod, how did you know that?