If this is your first visit, be sure to
check out the FAQ by clicking the
link above. You must be an NCRS member
before you can post: click the Join NCRS link above to join. To start viewing messages,
select the forum that you want to visit from the selection below.
I have been having difficulty trying to get the car timied correctly, I removed the #1 spark plug and checked for TDC , the timing mark was lined up however the distributor cap rotor is pointing to the #6 cylinder not #1, shouldnt it be pointing towards #1? Is the distributor installed incorrectly?
I show an initial timing of 30 degrees at idle and the car runs fine so I assuming that something is installed incorrectly.
With everything lined up( timing mark & TDC ) and you can't get the rotor pointing to #1 with the distributor housing in its correct orientation it is very likely you need to remove the distributor and change the gear orientation 180.
Wayne thanks for the quick response, If I were to leave it as is how would it effect my initial timing, I am a little nervous about pulling the distributor as I have not done it before.
Your dist. is installed correctly, though the timing may be slightly advanced. When you pulled your dist. cap and the rotor was pointing at #6, it was indicating you were at TDC of the exhaust stroke. Had you rotated the crank one more revolution the rotor would have pointed at #1.
Depending on the motor in your car, initial advance with no vacuum advance should be around 6*-12*, with vacuum advance hooked up you can add 12-16 more degrees, depending on the advance can in use. Check the arcvives for Duke's posts on detailed explanations of timing. If you don't have any spark knock under existing conditions you are okay. If you have some knock, retard timing 2-4 degrees.
Thank you for the response, Yes the dist. is correctly installed and everything lines up where it should that is why I could not understand why my timing was so advanced, I believe I am getting an additional 14 degrees based on the archives for having the gear off by 180 degrees?
I have switched to Dukes advice on vacuum cans and using a full manifold vacuum source.
I did rotate the crank but never felt TDC again until the rotor pointed to #6 cylinder again?
My initial is now set at 28 degrees with no engine knock. Dist window is lined up with approx centerline of car.
1966 L72 (425 hp), newly rebuilt. New carb, rebuilt Ti dist. Everything else basically new. I have checked the archives but could not find exactly the answer I was looking for. Yes I have the vacuum can disconnected and plugged.
From the archives the answer I came up with is that the gear is probably installed wrong unless I am missing something else? Do I need to pull the dist or can I just add 14 degrees to every timing number I map.
have someone crank the motor a little at a time with your finger plugging # 1 plug hole and feel for air blowing out--you will know you are on the compression stroke---do not insert finger down into the cylinder---good luck
L-72 has ported vacuum advance, so if you don't disconect it, it should make no difference in the timing reading unless you installed a non-OE cam with more overlap that required more idle throttle opening.
Notwithstanding the above, the VAC signal line should always be disconnected and plugged when checking initial timing.
Also you should test to see when the timing increases due to centrifugal advance. On some Corvette engines the centrifugal starts at a speed below where the engine will idle acceptably, like SBs with 30-30 cams. And unless you test your centrifugal curve, you have no idea how it behaves.
If the dist. gear is installed "backwards" you often cannot achieve the desired initial timing spec before the VAC interferes with something.
In a nearby thread someone asked how the dist. cap on a mag pulse distributor should be oriented, so review that thread.
If everthing else fails, set the engine at 10 degrees TDC on the #1 compression stroke and remove the distributor. Check gear indexing, correct if required, and reinstall it with the rotor about 45 deg. to the right of centerline. If it won't drop all the way look at the oil pump drive slot and reorient it with a paint stirring stick as required to mesh with the drive gear. The rotor will rotate CCW as the gear meshes. Watch this when you remove the distributor so you get a feel for how much it rotates, which is about 20-25 degrees.
Once the distributor drops all the way down rotate the housing until the stationary and rotating pole pieces align. The window should be near normal to centerline. Snug the bolt and start the engine, and you should read a little less than 10 degrees timing. Adjust it to spec and tighten the hold down bolt.
If you see the #1 piston at TDC, the timing marks line up, and the rotor is pointing at the #6 wire terminal on the cap, you're NOT at #1 TDC on the compression stroke - you're at #6 TDC on its compression stroke. To verify that you're on #1 TDC on the compression stroke, pull the driver's side valve cover and look at the valves on #1 cylinder - they'll both be closed.
We use cookies to deliver our services, and to analyze site activity. We do not share or sell any personal information about our users. For additional details, refer to our Privacy Policy.
By clicking "I AGREE" below, you agree to our Privacy Policy and our personal data processing and cookie practices as described therein. You also acknowledge that this forum may be hosted outside your country and you consent to the collection, storage, and processing of your data in the country where this forum is hosted.
Tweet
Comment