jackson 63

I have a 63 SWC 327 340hp engine that I am having problems tuning. If I set the timing at 10 deg BTDC the car runs poorly with low vacuum. If I advance the timing I can get 15 inches of vacuum and the car runs better but my timing mark goes away. The highest vacuum I can get is 15 inches.
I checked for a vacuum leak with propane torch, I did not find a leak.
With the timing advanced the car idles ok. It also seems to have good power on the road.
Wonder if my harmonic balancer rubber has failed. Anyone see that?
The engine is stock with solid lifters

Boyan

What vacuum adv can are you running?

Boyan

You probably have a B28 or B26, but I need to know which one.

LB66383

Yes, your balancer outer ring may have slipped and the timing mark is now way off. The first thing I would do is pull the plugs, get #1 to top-dead-center, and see if the timing marks line up or are way off. My guess is they are way off. I've had success using a dial mic in the spark plug hole to find precise TDC. Sure is a lot easier than removing the head!

I assume you are setting the initial timing with the vacuum disconnected. If so, it doesn't matter what vacuum advance can you are using since it not in play.

tbarb

I agree, the first place to start is find exact TDC. You can use a piston stop but be careful turning the motor because you don't want to damage the piston.

MikeM

Why don't you take a peek at it? Look for herniated rubber pushing out between the inner/outer.

Are you setting the timing with the vac advance unhooked?

Do you have your timing light on the right spark plug wire?

jackson 63

Yes I have the timing light on the correct wire. Vacuum advance is unhooked. When I turn number 1 to top dead center on the compression stroke the timing mark lines up perfectly. I know this is not as accurate as a piston stop, but its close.

jim lockwood

Um, "close" isn't good enough when the likely error is on the order of only a few degrees. Using the piston stop method will give you an exact answer, which is what you need in this situation.

Jim

jerrybramlett

I've never encountered a small block balancer outer ring that has slipped circumferentially. However, I've seen many mis-matched balancers and timing scales.

Chevrolet has moved the location of the balancer TDC mark at least four times since 1963. Of course, each time the factory did that, they also moved the timing scale on the chain cover a corresponding amount.

The most common mis-match seems to be a post-'68 balancer used with a pre-'68 scale on the chain cover. That makes the balancer mark 10 degrees off.

Frankie the Fink

Neither have I but it seems to be the first thing people jump on. If the rubber bond slipped enough to drive the timing notch off the tab scale the car wouldn't be running for crap IMO. It may happen but its prob rare than hen's teeth..

My questions are:

Is the OP setting the initial timing with vac advance plugged at low idle ? Low enough centrifugal weights aren't engaged...

Was the timing ever able to be set correctly ? And has he changed anything since then.

In my mind we may have improperly set valve lash and/or distributor misalignment/spark plug wire indexing...

MikeM

My second thought as well but OP says when the piston is at TDC, the marks are "very close" on the timing tab. If he had the wrong balancer or timing cover, that wouldn't be the case.

The missing link is how he checked TDC.

65tripleblack

When you tuned the engine what did you do?
Set lash?
Changed wires?
Points/plugs/condenser/rotor?

The vacuum line to the advance can is disconnected and PLUGGED when setting timing, right?

Your engine with cam lashed @ .008/.018
should develop about 12 -13 in-hg at about 700 RPM idle if set properly.

How did the engine run before you tuned it?

jackson 63

I have owned this car for 50 years, getting older now and I do not drive it that often. I put on new cap, wires,rotor and points. I did not set the valve lash. I only get 15 inches of vacuum which seems to be low. 65 tripleblack said I should have 12 to 13. So maybe I am ok. I always thought I should have at least 17inches.
Two years ago I had to pull out the crank for an issue, wonder if I got the chain back on correctly.
Vacuum line was unhooked and on my vacuum tester.

MikeM

The chain affects valve timing, not ignition timing.

Several years back, I see you had some confusion over what the timing marks on your balancer meant. Did you get this figured out?

tbarb

Others will for sure help me out with this I am not sure how the distributor would time if the crank/cam relationship was out a tooth. it's possible that is exactly your problem if everything else checks out.

Find exact TDC and see if the damper marks are OK. If so, look at the distributor and see if it's installed correctly and the plug wires are in the cap in the right order. If it's not installed correct and after installing it in the correct position the engine will not run I believe the timing chain gear alignment may be something to consider.

Frankie the Fink

Whenever I've been "off the scale" when setting timing (yes I'm guilty) it was the distributor off a tooth... OR - the distributor clamp wasn't tight!

MikeM

The timing chain holds the cam in a fixed orientation in relation to the crankshaft. The distributor is adjustable after the chain is installed.

The only way the chain can affect ignition timing is if the cam (valve) timing is changed and the ignition timing is not reset to compensate.

65tripleblack

You shouldn't get 15 inches if the engine has a "Duntov" 097 cam installed unless the lash is set too wide. If they are set correctly the numbers I posted above are accurate.

Frankie the Fink

I would get a rock steady 18" on my 270hp 283ci all day long..don't know if that's a valid comparison to a 340hp 327ci though..

MikeM

I checked the vacuum on my '63 327/360 once. It was 15". Valves set at .008/.018. Idle speed 750. Vac advance all in.