no idea where the timing is.

-
S

steveh

Well-Known Member
Joined
Oct 26, 2008
Messages
239
Reaction score
3
Location
Tampa FL
All,

Now that I have fixed my fuel delivery problem with the help of others under the air fuel forum, I moved this discussion over to ignition cause...

I now have fuel squirting into the carb and it's now firing, wont idle for crap. I can keep it running while playing with the throttle, but it is missing something terrible and backfiring through the carb. Gonna retrace all the plug wires to make sure nothing is crossed. Distributor was a little loose and may have moved some.

Additional circumstance:

1) there is some coolant on the front of the intake, cant keep it running long enough to see where its coming from.

2) Don't have access to a timing light so I don't know if it needs to be advanced or retarded.

thanks
Steve

What
 
Do you have a vacumn gauge? If so you can time it where you get the best manifold vacumn.If not I usually get my wife to hold the brake and rev it up and I advance it till it rattles and then back it off just a little. Tighten it down and drive it and put my foot in it. If it dont rattle its good. Then put a new plug in and run it. Pull the plug and compare it to a plug reading chart,theres several available if you google it.It will tell you if its good, advanced or retarded by the color.
 
You should be able to static time it close enough to run until you can get a light on it.

So why CAN'T you put a light on it?

Bring the engine around and put the marks WHERE YOU WANT the initial timing, IE 10 BTC, etc If in doubt, go more advanced as opposed to retard. That is, 12 for 10, etc.

Remove the dist cap and RETARD the timing (CW for a SB, CCW for a B/ RB) If you have points, advance the dist until the points just open, or if you have electronic, advance until the reluctor tip is just at the corner/ center of the pickup coil.

If you already have water showing, you need to find that out. Gaskets don't "seal up." They either leak or they don't.
 
67Dart273 said:
You should be able to static time it close enough to run until you can get a light on it.

So why CAN'T you put a light on it?

Bring the engine around and put the marks WHERE YOU WANT the initial timing, IE 10 BTC, etc If in doubt, go more advanced as opposed to retard. That is, 12 for 10, etc.

Remove the dist cap and RETARD the timing (CW for a SB, CCW for a B/ RB) If you have points, advance the dist until the points just open, or if you have electronic, advance until the reluctor tip is just at the corner/ center of the pickup coil.

If you already have water showing, you need to find that out. Gaskets don't "seal up." They either leak or they don't.
Click to expand...

He doesnt have a light.This is why I told him the seat of pants method.
 
ok, I'm learning so please be patient and thanks in adv for the help.
Its a 340 with a comp cam 268H cam and holley carb not sure what size.
MP electronic ignition. box is black not orange (not sure what that means)

Talk me through how I manually get it in the ball park so it will idle on its own long enough for me to turn the dist.
 
I thought I just did. Wrench/ bump the engine around so that the timing marks are WHERE YOU WANT the timing to be. That is, if you want the intial timing to be at 10 BTC, then bump/ wrench the engine until the timing marks are at 10 BTC, or a little more maybe 12. On my car it's more like 16-18 BTC

Look at your cap, find no1 wire, remove it for reference, and carfully mark the dist. housing under the center of the no1 wire tower so you know "where it it" with the cap off. I ALWAYS scribe my distributor housing on the top rim under the no1 tower.

Now RETARD the distributor. This is to "get the slack out" of the advance mechanism, etc. On a small block, rotate the dist. CW

Now slowly rotate the dist. back ADVANCED (CCW on a small block) until...................

The points just open if you have points.

-----------------If breakerless, until the tip of the reluctor wheel is right in the center of the core of the pickup coil.

If you do this right, it should fire right up and run just like you parked it last night. It should be close enough that you won't have to "screw" with it until you get a light.
 
67Dart273 said:
I thought I just did. Wrench/ bump the engine around so that the timing marks are WHERE YOU WANT the timing to be. That is, if you want the intial timing to be at 10 BTC, then bump/ wrench the engine until the timing marks are at 10 BTC, or a little more maybe 12. On my car it's more like 16-18 BTC

Look at your cap, find no1 wire, remove it for reference, and carfully mark the dist. housing under the center of the no1 wire tower so you know "where it it" with the cap off. I ALWAYS scribe my distributor housing on the top rim under the no1 tower.

Now RETARD the distributor. This is to "get the slack out" of the advance mechanism, etc. On a small block, rotate the dist. CW

Now slowly rotate the dist. back ADVANCED (CCW on a small block) until...................

The points just open if you have points.

-----------------If breakerless, until the tip of the reluctor wheel is right in the center of the core of the pickup coil.

If you do this right, it should fire right up and run just like you parked it last night. It should be close enough that you won't have to "screw" with it until you get a light.
Click to expand...
Yup, that's the way to do it without a light. To get even closer on the timing, pull the coil wire out of the distributor cap, hold it 1/4" from a good ground, turn the ignition switch to the "on" position, and then rotate the distributor in the manner 67Dart273 mentioned until you see a nice spark jump from the coil wire to the ground. At that point, lock down the distributor. Works with either points or electronic ignition. I'd make sure your compression is good before I went much further. Then verify that the firing order is correct.
 
67dart273,

Like I said, I'm a bit of a newbie. Ok quick azimuth check here to make sure I'm goin in the right direction.

1) bump it over to 10-12 BTC
2) mark the dist at #1 so I have a reference point
3) pull the cap
But this is where I get lost.
What do you mean by..."Now RETARD the distributor. This is to "get the slack out" of the advance mechanism, etc."? I know rotating it while running will adv or retard it, but I dont understand what you mean by get the slack out. pls explain
thx
 
OK you want to get the distributor in time. I posted to "retard" because that's the way I do it, easier to retard the dist. and slowly "bring it back" and then stop it where you want

The SPARK happens at the instant the points open, so by swinging the dist towards advanced (from retard) and then STOPPING it at the instant the points open, you have established the timing point.

Now on electronic (breakerless) distributors, you really "don't know" exactly where they fire, because as the reluctor wheel rotates past the center of the pickup coil, it first generates either a positive or negative pulse (depending on type of system) and then immediately the opposite pulse. ONE of these pulses (depending on the system) fires the electronic module and "makes the spark."

So since you don't know EXACTLY where this happens, the closest you need to get is really just put the "tit" of the reluctor wheel in the center of the pickup.

IF YOU WANT TO SEE this better, AFTER you have gotten the engine running and timed, let's say you used your light and timed the engine to 16*. It's running good. OK. Now wrench the engine around carefully and stop it so the marks are right at 16--or where you set the timing.

Now pull the dist cap and look and see where your reluctor wheel/ pickup coil are sitting. That should show you how this relates.

Hope this helps.
 
Yeah its starting to make sense.

moved it to 12BTC.
marked the dist under #1 tower
pulled the cap and the rotor was 180 out from the #1 tower location

So how far am I supposed to turn it. All the way until the mark lines up with the rotor

Sorry for the handholding...just don't want to screw up here
 
Got it....many thanks 67dart273.

I'll spend some more time under the hood, get an appreciation for how it relates and rejoin the discussion at a later date...just damn glad its running again. Greatly appreciate all the help

This place is great.
 
steveh said:
Yeah its starting to make sense.

moved it to 12BTC.
marked the dist under #1 tower
pulled the cap and the rotor was 180 out from the #1 tower location

So how far am I supposed to turn it. All the way until the mark lines up with the rotor

Sorry for the handholding...just don't want to screw up here
Click to expand...

This means that the engine is ready to fire on no6 instead of no1, if the distributor is in correctly and you had it running, so it should be I forgot to mention this What this means is, you have to rotate the engine ONE turn to get the dist. around to no1

To start at the beginning, in order to drop the distributor in, here ya go:

To determine if the dist is on the right stroke (no1 compression) there are two different ways

1. If the valve cover(s) are off, bring the timing marks up to your timing point. Look at no6/ no1 valves. If no1 valves are both closed, no1 is ready to fire. If both no6 valves are closed, no 6 is ready do fire

2 Second method, if valve covers are on, is to remove no1 plug, stick your finger in the hole, and bump the starter until you START to feel compression. You might have to "go round" a couple of times to get the feel.

When you START to feel compression, turn your attention to the timing marks, which should be "coming up." Continue to bump/ wrench the engine until the marks are at your timing point.

NOW you have no1 "up and ready to fire," and the dist. rotor should be pointing to no1
 
I agree with above. Adjust the timing for max rpm or max vacuum, preferably with the tranny in drive (insure parking brake works, chock wheels, etc). My engines usually idle OK from ~20 deg BTDC to 5 ATDC. If it runs faster at far advance ~30 deg BTDC, I think a sign that your idle mixture is lean. Advancing more is usually good, except if it causes pinging at WOT. That is why new cars have knock detectors and the controller responds to that. If it runs OK in neutral, even wanting to rev up with a little advance, but dies when you put in it drive, I think that is also a sign of too lean. Your cam is more aggressive than the factory one, meaning better for high rpm racing, so the engine will never idle as well as original. Some people prefer that blub-blub sound. Rhoads variable lifters are one cure.

A timing light will only help if the timing mark on your damper is correct. The outer shell sometimes slips when the rubber gets old. However, whenever I suspected mine wasn't right (because engine wanted a lot of advance) and I checked the marks against a dial indicator on the piston (w/ heads off), the mark was perfect. I think the carb was too lean, which was a constant problem with my 225's Holley 1920. There are many surplus timing lights and dwell meters, since not useable on most cars since ~1990. Check ebay or craigslist. I found both in a rolling tool box my wife got at the thrift store.
 
Thanks for all the help, it is runnging again. Put a timing light on it and set it at 16 BTDC (w/vacuum adv disconnected and line plugged. Idle at ~750. All of that was done with it in Park though...No bog when I get on it. haven't stayed in WOT too long, tie rods are shot so its a bit scary right now.

While working on it, I noticed that the previous owner had the vacuum advance hooked up to the small vacuum port above the air fuel mixture rather than on the bigger port located at the base of the carb (front corner on the passenger side). Which one is correct? didn't seem like there was much vacuum comming out of the smaller one...so I switched it. Assuming I should plug the smaller one above the air/mixture screw.

Seems like I can get more out of it, Can I trouble you guys to talk me through fine tuning it a little more? All the back and forth working on it today raises a few additional questions in my mind.

1) what order should be followed when tuning? Timing, idle, air/fuel, idle again
2) adjusting the idle speed should be done with the vac adv reconnected right?
3) what kinda vacuum would be normal for this engine (described below) I messed with the mixture screws a little but vacuum stayed right around 10.
4) I thought with this cam, the idle should be a little lopey, but its not (so maybe it still aint exactly right)

Engine was done several years ago by the previous owner. 69 340 40over; X heads,headers, holley 4bl vac secondaries (CFM 650 I'm guessing) comp cam high energy Cam 268H. I don't know squat but the specs don't look to much more aggressive than factory.

as always, thx in advance and appreciate the assist
 
The vacuum advance should be connected to ported vacuum, not manifold vacuum, so you'll want to reattach the hose to the small nipple that only has vacuum when you open the throttle. 16 BTDC is a bit much but if it doesn't ping, it may work for you. I'd back it off to 10 and see if you can get that manifold vacuum reading up. It should be over 16 inches at idle. You may have a vacuum leak somewhere or a lumpier cam than you think. When I do a tune-up, I do it in this order.....Valve adjustment (if applicable) compression test, new plugs, new points/condenser (if applicable) cap, rotor, wires if needed, set timing and idle speed/mixture (you may have to back and forth on this until both are correct). Timing is with the vacuum advance hose disconnected and at proper idle speed. I also test the PCV valve for function at this time too. Replace air cleaner element if necessary. Do a road test.
 
You must log in or register to reply here.
-

Back
Top