JDBob62

I have a 62 327/300 that I have been trying to determine cause of suddenly loosing timing. (See other threads I have posted since Aug 08)

I pulled the timing chain cover as someone suggested. Timing marks on cam and crank sprockets line up perfectly (cam at 6 o'clock and crank at 12 o'clock) but there is approximately 1/4 1/2 inch slack in the right (passenger) side of the chain. I will be replacing the chain and sprockets as previously suggested on CF.

When the timing chain marks are aligned and no. 1 cylinder is at TDC and both valves appear to be closed, the distributor rotor points to approximately 1 o'clock. If I hand turn the engine until the distributor rotor points to 7 o'clock for no. 1 cyl, both timing marks on the sprockets are now at 12 o'clock.

I understand the importance of the correct timing between the cam and crank.

I also understand the importace for correct timing between the distributor rotor and piston (on compression cycle) to fire the spark plug.

Question: Should the timing sprocket marks be in alignment (6 o'clock for the cam and 12 o'clock for the crank) when the distributor rotor is also in the 7 o'clock position to fire no. 1 plug?

I have not pulled the distributor yet, but that is the next step. (Car had run very well for almost 1 year and in particular the day before it started back firing, sputtering, hard starting. I retimed and it held for 1 day then started acting up again.)

I know that this is very basic Automotive 101 knowledge and that I may not even know what questions I should be asking. However, I am trying to learn and at the same time not do something stupid. I am right at the edge of my understanding and do not want to screw up this no's matcing car.

Thanks in adavance:

Bob

BADBIRDCAGE

Mark on both sprockets at 12:00 puts cylinder number one at TDC in the firing position.

Rich

AZDoug

Personally I found it easiest to install with the marks in closest proximity (6 top, 12 bottom), so there was no doubt they were lined up, then rotate engine crank one full revolution to #1 TDC and install distrib with rotor pointing at the 7-8 o'clock position.

Doug

MikeM

That's the way I do it also.

Before you pull that distributor check the shaft end play in it as outlined in your other thread. A new timing chain will not stop your distributor timing from slipping.

If you have no end play in the distributor, you can fix that while you have it out.

mikem350

In other words dot to dot is #6 firing.

Funny this is never mentioned in manuals

JDBob62

Thanks to all for info and to MikeM350 for zeroing right in on omission in manuals. My questions may seem a neusance to some but I firmly believe that the devel is in the details.

MikeM: Please explain how to check distributor staft for end play.

My purposes in pulling the distributor are:
1. To check gear for possible missing tooth as suggested in another thread.
2. To reposition tach cable into center of fire wall hole.

Please clearfy for me about re-installing the distributor. So long as I have not moved the crankshaft & cam and not rotated the distributor shaft I can rotate the distributor assembly clock-wise equal to one or two gear teeth to center the tach drive cable?

LB66383

You can do one of two things -- you can lift up the distributor, disengage it's gear from the cam gear, rotate it clockwise, then re-engage the gears and drop the distributor back in.
OR

With the distributor installed, rotate the body clockwise, then move all of the plug wires counterclockwise one hole in the cap.

Then, in either case, reset the timing.

midyearvette

now there's a smart dude.......

MikeM

See post #6 and #15.

About post #6, you can also run a feeler gauge under the distributor base and see if there's a gap to the manifold. That's with the gasket removed.

http://forums.corvetteforum.com/c1-a...-firewall.html



You need to re-read this whole thread. Everything you need to know is in there including advice TO NOT index the spark plug wires in the wrong place.

Also, I don't think you're clear on the gear at the bottom of the distributor shaft. It has an odd number of teeth. The gear is held to the shaft with a roll pin. One side intersects the gear between two teeth, the other side intersects a tooth. There is a small dimple on the gear. To be OEM correct, the dimple and the distributor rotor should be pointing in the same direction. If not, knock the pin out and turn the gear 180*. Some after market cams will not be properley indexed so this isn't a hard and fast rule but a guide.

Re-read that thread.

Ironcross

Doug, you can leave the engine alone without rotating and set up on #6 as if it was #1

AZDoug

That is true, and I have done that on new engine installs, but I always used a Sharpie or some other marker to mark the exact postion of the rotor in relation to the housing at #1 TDC and the housing in relation to the manifold, on cam removal from a running engine so when i dropped the distib back in, the timing was exactly where it should be on start up.

That also ensured the distrib gear wasn't a tooth off, as it would be obvious.

Doug

Steve59

Don't mean to hijack the thread but since rotation of the distributor came up I'd like to get a little more info. (59 vette 283, single 4 barrel)

I'm installing the passenger side top ignition shielding bracket that holds the coil. The vacuum advance can is in the way and I need to rotate the distributor COUNTER clockwise to get the can out of the way. I don't want to pull the distributor unless I have too.

Am I correct in stating that if I rotate the distributor counter clockwise (say from 8 to 7 o'clock using the vacuum advance can as a pointer) and move all of the wires clockwise one post, that will put me in the ballpark to go ahead and do a normal timing adjustment?

I'd like clarification as to how far you can rotate the distributor counter clockwise while moving the wires clockwise one post.

Thanks for the info.

JohnZ

Yes, as long as you move the distributor housing 45*; however, you'll end up with the wires mis-indexed in the cap, and the vacuum advance may wind up against the #8 intake runner instead of against the plug wire support.

Why not just pull the distributor up a couple of inches and install it correctly so the wires are indexed where they belong?

Steve59

two reasons (hope they make sense)

1. didn't want to worry about:

a) breaking something when I didn't have to move it;
b) screwing up the movement of the distributor and going to far missing the proper cam gear;
c)having the rotor move inside the distributor and losing the location;
d) having to play with/ rotate the oil pump shaft.

2. Wanted both options in case one got screwed up.

I appreciate the info. Thanks.
Steve