I took the advice I got from "Engine Help" and looked at what would happen if I indexed the distributor a tooth on either side of where I was. Didn't work out. What I did remember was a story about turning the gear at the end of the distributor 180 degrees which resulted in half a tooth change. So I did that. It started and didn't backfire or spit as I increase the RPM. But it did something even stranger.

At 800 RPM it showed 10 degrees. Cool beans. I turned it up to do the 20 minutes of cam work in and at 1500 RPM I took another look at the timing. It was reading 0 degrees. It was going backwards!! I turned down the rpm and it went back to 10 degrees. I also had only 10 inches of vacuum which tells me the valves weren't at one with the universe either. Anyone ever seen this?

Geek

 

not sure, but isnt vacum supposed to be between 15 and 17?

 

Yeah that's where I think it should be. I think the 10 inches is telling me that the valves aren't closing is the right sequence (all of which I think is the distributor)

For lack of any other good ideas, we are going to drop in a known good distrbutor with point and see what that buys us. It's that backwards timing thing that has me stumped!

 

Are you using a dial-back timing light? Is the dial set to zero?

 

Yeah I am John and it was a zero. A friend brought over his distributor from a working Corvette that uses points and not the electronic thing. (pretty dang good friend to take out a perfectly good working distributor huh?) We installed it and took a look at the points to see where the distributor thought everything was supposed to fire with the motor set at 10 degrees before TDC. It was way off. Somehow I am certain I messed up the cam install. Not sure it's the dot thing but it sure could be. The only place the points come even close to a lob to open is if I turn the distributor full retarded. Then the rotor is just barely in front of the #1 post on the cap. I move it one tooth over to try and get some advance and the rotor is way over to #2 post.

This is where you laugh, call yourself a dumb poop and figure that it just builds character I guess. Then you go find an ice cold beverage of your choice, get one for your friend who would pull his distributor, and be glad you didn't pay someone to screw it up for you thereby adding insult to injury.

Geek

 

we need to settle a few myths about timing

"dot to dot" "one tooth off" and "180 degres out"
really mean nothing when you are indexing and setting your timing..

having a tooth off will only change the range that you can swing the distributor before your vac can hits the valve cover or the intake runner.

you need to have 3 things correct.

1) motor is at TDC of the compression stroke
(this would put the cam gear dots both at 12oclock) but you'll never see that becasue your timing cover is back on... and unless you set the valves according to the dots, this wont matter... if you tried setting the valves using the dots as a reference, then you have a problem.

to check, it would be best if you could take your balancer off and put 4 timing marks exactly 90 degrees out. pull the number one plug and stick your thumb over the hole... slowly turn the motor over with a breaker bar until you feel your thumb being pushed away. As you turn, and watch the balancer, you'll see the TDC zero mark approch the timing indicator as the compression pushes your thumb off the hole.

Once you are sure of TDC, you can then go through the firing order to make sure your valves are relatively close and you can be sure that you are setting your distributor correctly.

2) make sure your firing order is correct... you don't want to know how many times i've seen people have the wires out of order as they try to fire up an engine.

3) Dwell or point gap has to on otherwise you'll chase your tail trying to figure out why she won't run at otherwise correct timing. Dwell needs to read 28-32 or you'll have issues.

if you Follow JohnZs post on finding initial timing, and you make sure your points are gapped properly (correct dwell) and that you set your valves correctly, your motor will fire right up.

Good luck

A

 

I saw a bad cam install just a while back. Some friends were trying to change the timming gear/chain on their 70. Apparently, there was another mark on the gear, and they mixed that up with the true timming mark. Very easy mistake to do.
If that thing is one tooth off, it should still start..tho run like crap. good luck.

 

You can't look at the points for reference.

Use Johns advice on stabbing the distributor correctly.

Make sure you are on the compression stroke. put the balancer timing mark (which might not even be accurate-did you check?) at 10-12 btdc. Look to see where the rotor points and if it isn't pointing where the number one plug is, you can either shift your wires on the cap, or re-stab the distributor- whic means you usually have to use a long screwdriver to turn the oilpump shaft so that all lines up.

Once you have those close, you can rotate the dist with the igniton on, and the test light will come on when you get close. I personally use a timing light, and rotate until it trigers, and then back it up a pinch.

IF your dist hold down isn't tight, it is perfectly concievable for your distribtor to turn as you rev the engine, which might be the answer to your reverse timing phenomenon. You want it loose enough to turn by hand, but not too loose that it can move on its own.

Good luck.

 

Thanks for the time in trying to help me here. Understand everything you said and am certainly going to try them before I pull that freaking engine again.

The one thing I don't understand is your statement about the points. In my tiny mind I should be able to install the distributor, set the engine to 10 degrees BTDC and then rotate the distrbutor and see where the points open. In theory that should be the static timing or where you see your timing light flash. Finding that point, I think I should be able to compare rotor position to #1 post location on the cap just to be sure I am somewhere before #1. When I do that, the first thing I find is that if I rotate the distributor to place the rotor somewhere prior to the #1 post, the points aren't anywhere near opening. If I rotate the distributor to where the points open, the rotor is literally closer to #2 than #1 but WELL on the retarded side of the curve. If I install the distributor one tooth either side of that position it still doesn't come close.

However I am going to look at seeing if I can't help the situation by possibly indexing #1 to a different post to see if that buys me something.

Again I really appreciate all the inputs.

geek

 

its not just the points opening that fires the plug but a combination of the points opening, and the timing of when the rotor makes contact with the terminal that the plug wire is attached to.....

If you notice, the width of the terminal on the rotor is more than a few degrees.

It has to be this way because
As your motor revs, the centrifugal advance weight and springs cause the rotor to advance (touch the plug terminal earlier) ,and your vaccuum advance also pulls the plate (where the points are screwed to) which breaks the circuit earlier.

REMEMBER THE POINTS ONLY ACT AS A BREAKER...

Like a circuit turning on and off... in any electrical system, like your house.. you have circuits, and appliances are pluged into those circuits... so you could have the power on in a given circuit, (points open) but if you don't also have the lamp switch turned on, (rotor facing the correct position) or plugged in for that matter, you won't get power to the bulb (or spark plug)

Did you double check your point gap or dwell?

so, eyeballing only based on when the points open is only part of the equation, and quite likely enough margin of error that it throws your timing off far enough to make it seem like everything else is wrong.

You could have the points opening, but the rotor facing the wrong terminal. With 8 cams on the shaft for the points, and 8 terminals on the distributor cap, that gives you 63 opportunities to get it wrong, and 1 opportunity to get it right LOL.

Good luck

Aaron

 

Geeks, I agree with everything that John Z and aaronZ28 have said, but I have a couple of tips that may help you.

Instead of holding your thumb over the spark plug hole of No.1 cylinder (passenger's side frontmost hole), take out all of the other plugs and leave No. 1 in. Now rotate the damper with a breaker bar using the nut that holds it on. When you feel resistance, you're on the compression stroke and your timing mark on the damper should be approaching the timing tab marks for 0 degrees.

Buy a clear distributor cap from Jegs and install it if the distributor is in the engine. This lets you see exactly where the rotor is in relation to the No. 1 plug tower. Easy!!!!! Also great for stabbing distributor in the block. Once in, remove it and re-install your black cap.

Also, get a piece of clear plastic film about 1/2-inch wide and long enough to wrap around the damper. Before mounting around the damper, measure the exact circumference of the damper with a cloth tape. (My wife has a couple for sewing, etc.) Next cut the plastic film the same length as your circumference measurement and divide it equally into 8 measured segments. I use a Sharpie to make a black line that is visible against my orange damper. Make one mark with a dot to reference No. 1 cylinder. You can also label the lines with the firing order sequence which may help as you rotate the damper clockwise. Attach the plastic film around the damper using scotch tape and you now have a reference for TDC of all your cylinders for adjusting the valves. Remove after setting the valves and keep for next time you need. These are simplistic tips, but they can help if the frustration of getting everything adjusted seems overwhelming.

 

I think you mean No. 1 cylinder is on the driver's side.
Roy

 

Oops!!! U R right. I guess my Blue Oval memory is creeping back!! Thanks.

 

Coves4me - Your plastic film and sharpie idea are good, but you need to make only 4 marks.....every 90* around the damper. It takes two engine revolutions for all of the cylinders to reach TDC and fire, not one.

 

Ooops..I did it again. U R Right. I have to find something to blame, now. The wife is out, the dog is out, I know!!!......it's the Rain!! Yeah, that's the ticket. 4 marks will do 'er.

 

To find #1 easily, take an old spark plug, knock out the guts, add a balloon and hand tighten in #1 hole.
Turn engine with a wrench, when balloon starts to fill you're coming up on #1 compression, then watch the balancer marks to complete.



To aim the dist, hook up an oem meter with a buzzer, or a powered 12v test lite and connect to the point leads. Use the lite to aim the rotor to #1 terminal on cap. You can drill out the #1 position in an old cap to make it easier.

This should get you running close enough for the timing lite.

 

Today I started the engine and ran it for half an hour to break in the cam. It ran perfect and only got to 180 degrees running at 2000-2200 rpm. Here's what we found.

The timing going backwards was me - I was screwed up and only thought I saw it or what I saw was the light picking up an adjacent wire and firing from that. (Yeah that's my story!)

The spitting and backfiring was a function of being WAYYYY retarded and not the dots on the timing gears both being at 12 o'clock.

How did we fix it? We took the coil mount bracket off so that we had a huge area to swing the distributor to set timing rather than the normally confined area that we live with on Corvettes. Put the distributor in so that it was looking at #1 about where we thought it should and then did the 10 degrees BTDC static setting It lit with a little adjustment albeit rough and we ran it up to 2K where we timed it at about 34 degrees for the cam break in run. The small tube of the vacuum advance wound up pointing literally straight out the right side of the car. Never could have gotten there with the coil bracket in place.

Now that I know where it times at, I can adjust the install over so that it will fit into the smaller area and still give me the room to do the fine adjustments to the timing.

Thanks to all who were giving me ideas on how to proceed.

Geek

 

Geek

With the Vac Can pointed all the way to the right tells me you were not at TDC when the Dist was installed. Just my thought on that.

I had a 427 that was giving me fits on timing and once I used a TDC tool to locate true TDC I discovered the harmonic balancer and timing cover Zero timing marks were off by 4 deg. I took a sharpie and made a new TDC line on the balancer to match the zero mark on the timing cover, re-stabbed the Dist and setting the timing after that was a breeze.

I know the cam was installed correctly so my guess was a mismatched timing cover and harmonic balancer.

 

glad it worked out for you. I know you were probably laying in bed,thinking about it jsut before sleep. lol