Camshaft 180 degrees out???
June 8th, 2013, 02:05 PM
#1
Registered User
Thread Starter
Join Date: Mar 2012
Location: Livingston, LA
Posts: 86
Camshaft 180 degrees out???
I picked up a mildly built 350 SBO last year and I think the cam may have been installed 180 degrees out. (If possible) #1 cylinder is at TDC on compression stroke. The rotor (points ign) is pointing at #2 cylinder, the #1 plug wire on the distributor is at the 3 o'clock position. the car hasn't been on the road yet but runs fine other than a vac advance issue and a few vac leaks I'm working on. My question is, if it was installed 180 out, would that mean when installing my new HEI distributor it would have to be installed 180 out?
June 8th, 2013, 02:24 PM
#2
Registered User
Join Date: Aug 2007
Posts: 2,250
As long as the dots are lined up, not possible. The cam should be degreed and may be a tad off. However, the distributor can be installed incorrectly. Since the firing order is 18436572, it sounds like it is a tooth or two off.
Last edited by captjim; June 8th, 2013 at 03:46 PM. Reason: sp
June 8th, 2013, 03:09 PM
#4
Registered User
Join Date: Aug 2007
Posts: 2,250
June 8th, 2013, 03:30 PM
#6
Registered User
Thread Starter
Join Date: Mar 2012
Location: Livingston, LA
Posts: 86
It hasn't been on the road but it runs fine at idle both in park and drive, putting around my house. OK so I must have some other issues with my timing and or distributor other than the vacuum advance. I'll start from scratch and do it by the book when I install my new distributor, thanks for the help
June 8th, 2013, 04:13 PM
#7
Registered User
Join Date: Dec 2011
Posts: 7,286
I don't think it would run if the crank to cam timing were off more than oh 1 tooth.
As for the plug wire positioning... it seems like you don't realize that when you put the distributor in, it matters little where the rotor ends up pointing. Really, what difference does it make?
By convention, the Olds V8's I am most familiar with point the rotor's contact more or less towards the #1 cylinder. I have had occasions where if the distributor to cam engagement is one tooth off, then the housing can't be turned far enough to time it properly. Easy fix, just re-insert the distributor 1 tooth either way.
No matter where your rotor ends up pointing when the crank is at TDC compression #1, that is by definition.... the #1 plug wire post.
As for the plug wire positioning... it seems like you don't realize that when you put the distributor in, it matters little where the rotor ends up pointing. Really, what difference does it make?
By convention, the Olds V8's I am most familiar with point the rotor's contact more or less towards the #1 cylinder. I have had occasions where if the distributor to cam engagement is one tooth off, then the housing can't be turned far enough to time it properly. Easy fix, just re-insert the distributor 1 tooth either way.
No matter where your rotor ends up pointing when the crank is at TDC compression #1, that is by definition.... the #1 plug wire post.
June 8th, 2013, 04:45 PM
#8
Registered User
Thread Starter
Join Date: Mar 2012
Location: Livingston, LA
Posts: 86
OK I'm learning, that makes since. I must not be at TDC, cause the rotor is not at #1 plug wire. I said #1 wire was at 3 o'clock but it's actually closer to 1 o'clock. I'll recheck TDC tomorrow. Any tricks to checking without a helper?
June 8th, 2013, 06:23 PM
#9
Connoisseur d'Junque
Join Date: Sep 2010
Location: The Hudson Valley
Posts: 21,183
The three ways I know of are:
To find the compression stroke, either look at the rockers, or stick something in the hole and see where it pops out.
- Eric
- Use a dial indicator, with the probe going through the spark plug hole and resting against the piston.
Find the point of maximum deflection. - Use an old spark plug base with a bolt screwed through it.
Roll the crank back and forth so that the piston taps the end of the bolt.
Tighten the bolt a bit at a time, so that there is very little distance between where the piston taps it going in each direction, then split the difference. - Use a whistle attachment that screws into the spark plug hole.
It whistles as you approach TDC on compression, then nearly stops at TDC, then starts again as you move away from TDC.
To find the compression stroke, either look at the rockers, or stick something in the hole and see where it pops out.
- Eric
June 9th, 2013, 06:44 AM
#12
Old(s) Fart
Join Date: Mar 2007
Location: Northern VA
Posts: 47,300
I picked up a mildly built 350 SBO last year and I think the cam may have been installed 180 degrees out. (If possible) #1 cylinder is at TDC on compression stroke. The rotor (points ign) is pointing at #2 cylinder, the #1 plug wire on the distributor is at the 3 o'clock position. the car hasn't been on the road yet but runs fine other than a vac advance issue and a few vac leaks I'm working on. My question is, if it was installed 180 out, would that mean when installing my new HEI distributor it would have to be installed 180 out?
June 9th, 2013, 07:34 AM
#13
It is also possible that the distributor was put in out of time and then someone moved the position of the plug wires to retime it. Is the number one plug wire in the correct position on the cap?
June 9th, 2013, 08:07 AM
#14
Registered User
Join Date: Dec 2011
Posts: 7,286
The cam rotates at one-half crank speed. By definition, the cam is 180 deg off on every other rotation of the crank.
==================
Exactly.
Crank at TDC, cam must have its timing mark at 12:00 or 6:00. Turn the crank 1 revolution to TDC again, and the cam mark will then be at the other allowable position. Repeat.
No other configurations result in a running engine.
Use your timing tab and balancer mark to determine TDC. To ensure these marks are accurate, piston motion can be detected with a wire in the spark plug hole to follow the piston. Move crank back and forth until the rod is moved up and out as much as possible. This will get you pretty close. If the timing marks are not within oh 1/4" of dead-on then you cannot rely on them and need to address that issue first. Without a helper you would need to fabricate a holder to babysit the wire while you fiddle the crank and watch the wire motion. Coat hangers come to mind.
Which TDC is the one when spark should be made? The one between compression and power strokes. A couple handy ways to determine that:
__1) Put something over the spark plug hole and bump the starter little by little until the compression blows that something out of or off the spark plug hole. The "something" can be your finger, a cork, a wad of paper or tissue, etc. This method is fast, CERTAIN, and requires no more dismantling.
__2) Another method, handy if the rocker cover is already off, is to watch the valves. At the WRONG TDC, the E valve will be just closing and the I valve just opening, so both will be moving. At the CORRECT TDC, both valves will be stationary and will not have moved for many degrees of crank rotation- close to a half turn.
"Now, the DISTRIBUTOR rotates at the same speed as the cam. It IS possible for the distributor to be 180 out, but then the engine wouldn't run at all."
=================
I disagree there... on a fine nitpicking detail. It is possible for the PLUG WIRES' CONFIGURATION to be off by 1 to 7 locations, and/or jumbled in order, and/or in the reverse Brand-C order. But, "the distributor" [as a unit], has no particular position that it MUST be installed at. Just remember that, [with the crank at TDC in firing position]
wherever your rotor points when you install the distributor
IS, BY DEFINITION, THE POST ON WHICH YOU MUST PUT THE #1 PLUG WIRE.
If you do that, then proceed in the correct direction, placing them in the correct order, the plug wires cannot be wrong, and the distributor cannot be wrong (*1).
For reasons of following convention, and following the CSM [Chassis Service Manual] suggestions, I recommend pointing the rotor at cylinder #1- the front left cylinder- for points distributors, and pointing the rotor at the brake booster for HEI systems. There's some silly reason like how the plug wires cross at the rear of the cap that makes the HEI happier with the rotor pointed at the brake booster when firing #1 cylinder.
*1 NOTE- until the day when you find that you can't turn the distributor housing far enough one way or the other because the vacuum canister hits on the intake one way and the firewall the other way. In that case, you need only pull distributor off the cam gear, move it one tooth either way, and re-insert. Now one or another of the plug wire posts can be aligned to make spark at the proper crank position w/o the distributor body bumping up against something.
==================
Exactly.
Crank at TDC, cam must have its timing mark at 12:00 or 6:00. Turn the crank 1 revolution to TDC again, and the cam mark will then be at the other allowable position. Repeat.
No other configurations result in a running engine.
Use your timing tab and balancer mark to determine TDC. To ensure these marks are accurate, piston motion can be detected with a wire in the spark plug hole to follow the piston. Move crank back and forth until the rod is moved up and out as much as possible. This will get you pretty close. If the timing marks are not within oh 1/4" of dead-on then you cannot rely on them and need to address that issue first. Without a helper you would need to fabricate a holder to babysit the wire while you fiddle the crank and watch the wire motion. Coat hangers come to mind.
Which TDC is the one when spark should be made? The one between compression and power strokes. A couple handy ways to determine that:
__1) Put something over the spark plug hole and bump the starter little by little until the compression blows that something out of or off the spark plug hole. The "something" can be your finger, a cork, a wad of paper or tissue, etc. This method is fast, CERTAIN, and requires no more dismantling.
__2) Another method, handy if the rocker cover is already off, is to watch the valves. At the WRONG TDC, the E valve will be just closing and the I valve just opening, so both will be moving. At the CORRECT TDC, both valves will be stationary and will not have moved for many degrees of crank rotation- close to a half turn.
"Now, the DISTRIBUTOR rotates at the same speed as the cam. It IS possible for the distributor to be 180 out, but then the engine wouldn't run at all."
=================
I disagree there... on a fine nitpicking detail. It is possible for the PLUG WIRES' CONFIGURATION to be off by 1 to 7 locations, and/or jumbled in order, and/or in the reverse Brand-C order. But, "the distributor" [as a unit], has no particular position that it MUST be installed at. Just remember that, [with the crank at TDC in firing position]
wherever your rotor points when you install the distributor
IS, BY DEFINITION, THE POST ON WHICH YOU MUST PUT THE #1 PLUG WIRE.
If you do that, then proceed in the correct direction, placing them in the correct order, the plug wires cannot be wrong, and the distributor cannot be wrong (*1).
For reasons of following convention, and following the CSM [Chassis Service Manual] suggestions, I recommend pointing the rotor at cylinder #1- the front left cylinder- for points distributors, and pointing the rotor at the brake booster for HEI systems. There's some silly reason like how the plug wires cross at the rear of the cap that makes the HEI happier with the rotor pointed at the brake booster when firing #1 cylinder.
*1 NOTE- until the day when you find that you can't turn the distributor housing far enough one way or the other because the vacuum canister hits on the intake one way and the firewall the other way. In that case, you need only pull distributor off the cam gear, move it one tooth either way, and re-insert. Now one or another of the plug wire posts can be aligned to make spark at the proper crank position w/o the distributor body bumping up against something.
June 9th, 2013, 09:46 AM
#15
Registered User
Thread Starter
Join Date: Mar 2012
Location: Livingston, LA
Posts: 86
right now the #1 plug wire is at the 1 o'clock position on the cap and the rotor is pointing at the # 2 cylinder (180 degrees apart) @ what I think is TDC. That's why I thought maybe it was installed 180 out. I still haven't confirmed TDC, having trouble finding a large enough socket at home, might have to wait till I can get one from my shop during the week.
June 9th, 2013, 10:57 AM
#16
Registered User
Thread Starter
Join Date: Mar 2012
Location: Livingston, LA
Posts: 86
Done deal!!! I used Octania's paper wad and Eric's rocker trick and bingo, rotor is at #1 plug wire on cap, (1 o'clock position) and timing mark is dead on. After reading what Joe wrote( 1/2 rotation to 1 rotation) I figured I must have been on non compression stroke. When installing my new HEI should I point the rotor at the MC and start with #1 there or drop it in as is? I might have clearance problems dropping as is. I need to learn to ask for help more, I've been trying to figure this out for a week. Thank you guys very much, I now understand the distributor a little more.
Thread
Thread Starter
Forum
Replies
Last Post
StickW31
Parts For Sale
1
September 9th, 2012 06:57 AM
getitmann
General Questions
20
July 12th, 2012 06:58 PM
