Timing - 40 degrees

[twoseater]

Howdy - I found top dead center and confirmed that the indicator was dead on. The car runs best at 40 degree after TDC. Seems excessive - I don't know why it would want it to run at that degree.

The engine is a 327 (non-original) that apparently has had a CAM upgrade - what is in there I don't know. I'm assuming its due to the Cam - true? If so a can someone explain why? I am timing it by ear now, as opposed to a specific degree. However, I'm not sure doing it by ear really puts me where I need to be or if its masking some other problem (too rich etc)

Also I just put in an MSD dist & MSD 6AL-2 ignition box. Definite improvement for me.....However, the timing with the old dist was the same.

Thanks,
Bill

 

[Chevyman for life]

Are you talking about 40 degrees ATDC at idle? That sounds really strange. Guideline to start with vacuum blocked is usually 12 degrees before TDC, with vacuum advance is more and with centrifical advance at higher is even more BTDC.

Different cylinders fire every 90 degrees so even strobing off a different wire shouldn't end up with that kind of reading.

Gerry

 

[Ron Miller]

Methinks somethin' ain't right with the way you're checkin' your timin'

:eyerole

 

[JohnZ]

There's no way in the world it'd even start at 40* ATDC, and timing has nothing to do with the cam. Make sure your inductive coupler for the timing light is on the #1 wire, and your vacuum advance hose is disconnected and plugged before checking initial timing.

Note: Some timing lights don't like the multiple-discharge spark that MSD systems have below 3000 rpm.

 

[twoseater]

Thanks Guys - The vacuum advance is plugged, motor idling, @ 650 RPM. Light is connected to the #1 plug (drivers side front).

I'm using a timing light where you can set the advance. With it at zero the mark is off the scale. Adjusting the lights advance to down 40* brings the mark to the 0 on the scale.

I know I have top dead center on number one and the scale is spot on.

Maybe the distributor is off? I never checked TDC against #1 on the dist.?

I have a couple timing lights (old sears light without the advance and will check it with that.)

 

[geekinavette]

Maybe the distributor is off? I never checked TDC against #1 on the dist.?

Absolutely verify that!

How much vacuum is it pulling?

 

[twoseater]

10 Inch HG on the vacuum.

Used another sears timing light (has an advance) - same results. I'll check on the dist vs #1 next, as well as verify the firing order.

 

[Viet Nam Vett]

10 Inch HG on the vacuum.

Used another sears timing light (has an advance) - same results. I'll check on the dist vs #1 next, as well as verify the firing order.

You should be pulling more then 10" of Vaccum if your reading off the intake manifold or thru the non timed port tube on the carb.

I'm guessing it should be at least 15 or 20 at idol off the manifold or the full port connection on the carb to the vac gauge.

 

[Chevyman for life]

If you're sure you're hooked to the #1 plug then it doesn't matter where the distributor is. That's the one that's firing the strobe. Now, if you have cross fire from another wire that could mess it up but it would idle really rough. I'd try a non-advance timing light.

Gerry

 

[geekinavette]

Well if the "cam upgrade" was done with one that has some overlap, 10" of vacuum is possible. To loose that much (~5") of vacuum due to cam overlap would result in a very noticeably "lopey" idle. Does it idle very rough?

 

[minifridge1138]

I'm not sure about your timing gun, but my inductive sears timing gun with advance only goes before top dead center.

Also, on a V8 a plug fires every 45 degrees (45 * 8 = 360).
If you were on plug 8, then you would be 45 degrees AFTER #1 fired.
If you were on plug 2, then you would be 45 degrees BEFORE #1 fired.

Does your car have a 2 piece harmonic balancer? If so, the outer piece may have slipped. Common problem when the rubber deteriorates.

The gun is accurate (since you got the same results with another timing gun).

Here's a suggestion:
* Remove the distributor cap
* Turn the engine over by hand until front, driver's cylinder is at top dead center.
* The rotor should be pointed at #1 or #6. If at #1 you're at the top of the compression stroke. If at #6 you're at the top of the exhaust stroke. If you're at something else, then you found a problem.

Good luck and let us know what you find out!!!

 

[twoseater]

You should be pulling more then 10" of Vaccum if your reading off the intake manifold or thru the non timed port tube on the carb.

I'm guessing it should be at least 15 or 20 at idol off the manifold or the full port connection on the carb to the vac gauge.

I'm taking it off the manifold. The needle vibrates +/-, with 10 being the "average". I may try tuning the carb as it has a "rich" smell but I thought it best to start with timing.

 

[twoseater]

I'm not sure about your timing gun, but my inductive sears timing gun with advance only goes before top dead center.

Also, on a V8 a plug fires every 45 degrees (45 * 8 = 360).
If you were on plug 8, then you would be 45 degrees AFTER #1 fired.
If you were on plug 2, then you would be 45 degrees BEFORE #1 fired.

Does your car have a 2 piece harmonic balancer? If so, the outer piece may have slipped. Common problem when the rubber deteriorates.

The gun is accurate (since you got the same results with another timing gun).

Here's a suggestion:
* Remove the distributor cap
* Turn the engine over by hand until front, driver's cylinder is at top dead center.
* The rotor should be pointed at #1 or #6. If at #1 you're at the top of the compression stroke. If at #6 you're at the top of the exhaust stroke. If you're at something else, then you found a problem.

Good luck and let us know what you find out!!!

Not top dead center again! Turning the engine was a PIA but at least I get to try some of the other techniques listed from my last posted question

I'll post the results, however, kids and wife are taking me away from the garage so its going to be a few days before I can get back at it. Stay tuned and thank you (everyone) for the replies.

 

[twoseater]

Well if the "cam upgrade" was done with one that has some overlap, 10" of vacuum is possible. To loose that much (~5") of vacuum due to cam overlap would result in a very noticeably "lopey" idle. Does it idle very rough?

Yup, lopey idle. I also have an '80 vette with a 350. The '65 will blow the doors off the 80. I do need to keep the RPMs higher as the car will get "lopey" while driving at the lower end of a gear. Hopefully that makes sense...

 

[KANE]

On my first TPI swap, I placed the distributor back into the engine and it was off. It made the timing appear to be advanced farther than it should have been.

Since then, I've used colored circles to mark the position of the distributor body and then the rotor relative to locations on the car (dots on the case, dots on the fenders). I use three points: a fender, the distributor, and then the fender (or windshield) on the other side. Then, I get out a laser and line up the dots. Makes setting reinstalling the distributor a lot easier.

 

[Vettehead Mikey]

Maybe the distributor is off? I never checked TDC against #1 on the dist.?

The position of the distributor to the motor is irrelevant for timing purposes- the only thing that matters is rotor to distributor position.

What happens if you try to time it to a few degrees BTDC?

 

[Hib Halverson]

40 deg BTDC at idle (hopefully, I read this thread correctly) and the engine would not run, given all else correct) much less start.

My guess is something in the timing procedure, distributor installation or cam installation was done wrong.

For now, let's assume the third alternative doesn't apply. If it does, we have a whole 'nother set of issues to fix and that's a thread for another day.

The first thing to do is find TDC using the "positive stop" method. In this case, do not use any other method if you want to be dead-nuts accurate. To do this with the heads on requires a special tool, which screws into a plug hole and is designed for this this purpose along with either a degree wheel, an indexed balancer or a timing tape. Some speed shops and some cam companies will sell the special tool. It is a tubular spark plug hole insert, threaded internally with a ball-headed piston stop screwed through the center. You install the insert, then vary the depth of the stop to accomplish the checking.

Once you find TDC using that method, then verify that both the mark on the balancer and the index on the timing cover are also correct.

After that, roll the engine by hand to TDC #1 then install the distributor with the rotor pointing generally towards #1 cylinder. If the dist. will not drop into the oil pump drive, pull the coil wire then bump the starter until the dist. drops down.

Static time the engine to about 15 deg ATDC then fire it up. Disconnect and plug the vac. adv. then set the spark about about 10 deg ATDC. Then check total advance.

Note that dial-back timing lights, unless they are really high-quality units are often inaccruate at higher rpms. The best way is a "straight" timing light with either an indexed balancer or one with a timing tape applied.

 

[bwing]

Howdy - I found top dead center and confirmed that the indicator was dead on. The car runs best at 40 degree after TDC. Seems excessive - I don't know why it would want it to run at that degree.

The engine is a 327 (non-original) that apparently has had a CAM upgrade - what is in there I don't know. I'm assuming its due to the Cam - true? If so a can someone explain why? I am timing it by ear now, as opposed to a specific degree. However, I'm not sure doing it by ear really puts me where I need to be or if its masking some other problem (too rich etc)

Also I just put in an MSD dist & MSD 6AL-2 ignition box. Definite improvement for me.....However, the timing with the old dist was the same.

Thanks,
Bill

I read all the comments and I'd like to give my .02 I recall having a similiar problem with my '63 coupe back in 1967 and the distributor was 180* off.

 

[Chevyman for life]

Also, on a V8 a plug fires every 45 degrees (45 * 8 = 360).

Correct me if I'm wrong but doesn't an 8 fire every 90 deg?

The distributor rotor reaches a new cylinder every 45 deg but it rotates at 1/2 the engine rpm. A four stroke cylinder only fires every other rev so wouldn't a new cylinder only fire every 90?

Gerry

 

[bradfordsvettes]

Not sure about the 40 degrees but if you had a large cam With high lift and duration with low compression pistons you would have to bump the timing way up to make up for the low static compression.If it is to far advanced it would grunt like hell trying to start worse when warm.May be a mismatch of parts if it has been fooled with . Steve