erieaddict

First of all, i have been lurking here for about 3 weeks learning about my 1978 corvette that i am just getting back out on the road after painting the body and redoing the interior for the last year.
This is a great resource and i thank the admin folks for a terrific site.
In reading this site i decided to move ahead with a timing advance curve kit. I purchased, cap, rotor, wires, coil, plugs and advanced kit. I figured i would check the timing, vacuum and idle before tearing into it.
My car is a l48 350 auto, pretty much all stock except for headers and a true dual exhaust. i did have my carb rejetted do to the new exhaust. the car starts, runs smoothly at all rpms and also starts fine warm, no pinging.
Back to the issue, when i took a reading of the timing with the vacuum disconnected and plugged at the advance can, i could not see the timing mark. i shut her down, rotated the crank and cleaned off the timing mark and put a dab of yellow paint on the groove. Started the engine back up and still couldn't see the timing mark. if i move the timing gun over to the right side of the motor, i can see the timing mark. It is like it is out by 180 degrees. i am sure i have the inducter on spark plug #1, the first plug on the left side, what could i be missing to get my tinming mark back to the timing tag? Thanks in advance!

TimAT

Pull the #1 plug, (left front as you stated) remove the distributor cap and have a helper bump the engine over. Confirm that the timing mark(s) line up when you a sure you're at #1 firing position.

Mooser

Well if it was somehow out 180 deg, you would have to go under the car over on the pass-side to see it.

If it runs smooth, it can't be out that much unless the harmonic balancer has separated and spun.

Couple of questions, don't take it the wrong way.

1.. your down on the #1 plug (front driver side) and not up in the wires somewhere that might have gotten mixed up by accident

2.. Are you checking it at idle speed (under a 1000 lets say)

3.. your not using a dial-back timing light that is set to something other than zero

Mooser

Jeff_Keryk

Perhaps your timing mark is ok, your plug wires are 180* out.

erieaddict

mooser, not taken the wrong way at all. any guidance is appreciated
1.. your down on the #1 plug (front driver side) and not up in the wires somewhere that might have gotten mixed up by accident?
I have my timing light pick up down by the plug boot on number 1

2.. Are you checking it at idle speed (under a 1000 lets say)
Idle speed is at 850 and drops about 100 rpms when i disconnect the vacuum

3.. your not using a dial-back timing light that is set to something other than zero
No, i have a craftsman regular old timing light with no dial on it.

Jeff, interesting, how would my wires get 180 out of time? Would the engine still run?

oldalaskaman

whoever installed your dizzy, started #1 wherever the rotor pointed to, reset the dizzy, rewire per small block spec's
the other option, your harmonic ballancer ring has splipped

mds3013

Do you have the inducter right at the #1 plug with the arrow pointed towards the plug? Assuming it has an arrow. If you have it at the front drivers side plug you are on #1. Incorrectly installed dist. with wires adjusted for that condition would not change where the timing mark shows up. I am thinking slipped outer ring on balancer. I may not be thinking correctly however. It has been a long day. Mooser's idea about set back timing light not set to zero could cause it also. Good luck with it. mike...

Mooser

I don't want to think about this but that line has to line up with tdc #1 regardless of where the dizzy is and the spark has to hit at #1, even if the dizzy is out any number of stations, it still needs to fire #1 at TDC (well you know, around tdc) so that shouldn't matter.
I'm going to have to say unless someone did something bizarre with the cam-gear, it pretty much has to be the balancer has spun
Mooser

Mike hit save before my brain started.

Do like TimAT said and bring #1 up to tdc (put your finger on the hole make sure it's pushing air out so you know it's not the exhaust stroke) and see where the mark is. To be dead sure, you'll need to pull the valve cover and watch the rockers.
Mooser

my 76 ray

I respectfully disagree. If someone did that, it would still be firing when number 1 is approaching TDC. I do agree with the slipped balancer theory. I would find true TDC and see where the mark is then.

scottyp99

You can always make a new mark, once you find top dead center on the compression stroke for cyl. # 1, but if the dampener has slipped, who's to say it's not going to keep moving around? If it's a slipping dampener, the only fix is a new dampener. Or JB Weld.


Keep the shiny side up!
Scott

oldalaskaman

ya know yer right, I brain farted

Jeff_Keryk

I was thinking your timing light lead might not be on #1 cylinder. But if it is, I would have to guess your dampner is shot.

aussiejohn

Just a thought, as the timing is out by 180 degrees, could this be caused by having the camshaft installed 180 degrees out? In other words, the timing mark on the cam was exactly opposite from where it should be, relative to the mark on the crankshaft.

I'm probably wrong, but could this account for the timing mark to be so far out?

Regards from Down Under.

aussiejohn

7T1vette

Exactly correct. It's about the only way you can get a SBC engine to run well with the timing mark 180 degrees off-position. Someone has mis-indexed the alignment marks on the timing gears.

markdonc

There is no such thing as putting the cam in 180 degrees off. Since the crank turns 2x for every turn of the cam, if you turn the crank 1 full revolution & allign the timing marks everything except maybe the distributor should be where you eant them.

larrywalk

Slipped balancer ring?... Check to see that the TDC mark aligns with the keyway slot of the hub (pre ~69, or 10 deg CCW after). As a rough check, the pulley bolt on one of the 3 arms of the hub also should be aligned with the keyway slot.

wombvette

Yep, Most common with these engines.

74Ken

The other thing I would suggest is try another timing light, just in case that one is defective. You could be panicing over something that really isn't there.
Borrow a friends light and check to see if his light reads the same way.

Ken

Mike Ward

Care to think about that one for a while?

7T1vette

Whatever you think, Mr. Wizard...