Timing Problem

[Guest bigfat]

I've got a 305 and the timing mark on the Harmonic Balancer is about where the fuel pump is when you time it by ear. The timing mark on the cover is at 12 o'clock. When I start moving the Distributor to bring it towards the timing mark it won't even run. Won't even get close. Took the timing chain cover off and when the # 1 piston is all the way down the timing dot on the Crank gear is at 6 and the cam gear is at 12 o'clock. When the # 1 piston is all the way up both are at 12 o'clock. Any one have any ideas? Can a chevy run if the timing is 180 out? Need some help.

[Truck99]

A couple of things may be going on here. Your balancer may have spun the outer ring, or your motor may have the wrong balancer for the particular application. Either way, I would bring #1 to TDC and verify that you're on the compression stroke by making sure that both of the #1 valves are closed and the #6 valves are slightly in overlap. If you still have your timing cover off, the timing marks on your cam and crank gears should both be at 12 o clock at this point. If your at this point and the timing mark on your balancer is still way off, I'd say the outer ring has spun on your balancer. You could make your own mark at that point just to set the timing correctly, but I'd go down and get a new balancer quick. If the timing mark is just slightly off from your timing pointer, it may just be the wrong balancer, and you could make your own timing mark to fix the problem.

 

A sbc will run if the timing is 180 out, but it will pop and run very very rough IF you are able to get it to start.

[flyingaces]

TIMING MARKS ON THE TIMING CHAIN SHOULD BE @ 12 AND 6 OCLOCK AT TDC. 6 ON THE CAM AND 12 AT THE CRANK.

[Guest bigfat]

Is every timing gear brand marked the same? Lots of conflict on this one.

[HiTech]

no there are offset gears for cam timing

[Truck99]

TIMING MARKS ON THE TIMING CHAIN SHOULD BE @ 12 AND 6 OCLOCK AT TDC. 6 ON THE CAM AND 12 AT THE CRANK.

Not if you're trying to verify your timing and verify that the rotor is correctly pointing at the #1 plug wire. Remember, the #1 piston will be at TDC twice for each rotation of the camshaft sproket - once on the compression stroke and once on the exhaust stroke. In order for the motor to be set at the #1 TDC COMPRESSION stroke, the dots on both the cam and crank sproket will be at 12 o'clock. When the dots are face to face as you described, the #1 piston will in fact be at TDC, but on its exhaust stroke. At that point, the distributor rotor will be pointing at the #6 plug wire. If we were both standing here at my backup shortblock, I'd show it to you.

 

The only time both of the lifters of the #1 cylinder are on the base circle of the cam is when both sproket dots are set to 12 o'clock.

[J-III]

First, sorry ss99 but you are mistaken, what flying aces said is correct. Bigfat, your cam should be at 6 on the cam and the 12 on the crank. Even though there are different offsets on crank gears for different timing, the appropriate mark will still be at 12 on the crank and 6 on the cam.

[Truck99]

First, sorry ss99 but you are mistaken, what flying aces said is correct. Bigfat, your cam should be at 6 on the cam and the 12 on the crank. Even though there are different offsets on crank gears for different timing, the appropriate mark will still be at 12 on the crank and 6 on the cam.

OK guys. Put the cam in however you want. Just do me a favor - when you have the dots on the crank sproket and cam sprocket both at 12 o'clock, look at the valves on your #1 cylinder and tell me what position they are in. I promise you they will be closed unless you have a bad timing chain set, hence the #1 is on the compression stroke. Now spin your crank around ONE time so that the dots are facing each other at 12 and 6. Look again at your valves on the #1 cylinder - the will be in exhaust overlap - the exhaust will be open. At that point, the rotor should be pointing at the #6 spark plug wire location on your distributor cap.

 

I believe this is exactly opposite on Ford motors, but we're talking about a chevy here.

 

Supertx, where are you when I need you?

 

[Heavy Duty]

I've been turnig wrenches on small block Chevys for 35 years, and the STANDARD chain alignment on #1 cyl is dot to dot: 12 oclock crank, 6 oclock cam. IF you have a cam gear that requires the mark at 12, it must be an oddball or a special performance manufacturer.

 

Some of the old Olds engines used to do a 12 oclock alignment, as well as some fords. In reality, either mark will work on a carburator engine (with the exception of an odd-fire 3.8L, but we won't even get into that). As long as you stab the distributor correctly, there is no problem.

[Guest bigfat]

When the timing marks on the crank gear and cam gear were either both at 12 or one at 12 and one at 6 the timing mark on the harmonic balancer was at 9 o'clock. Why is that?

Both valves are closed when both of the marks are at 12 now. Not even sure how we got that accomplished, which sux but I think it's fixed.

[Truck99]

When the timing marks on the crank gear and cam gear were either both at 12 or one at 12 and one at 6 the timing mark on the harmonic balancer was at 9 o'clock. Why is that?

Both valves are closed when both of the marks are at 12 now. Not even sure how we got that accomplished, which sux but I think it's fixed.

That's because the crank sprocket turns twice for every one revolution of the cam sprocket. I think that's where the disagreement is. I think we're making this more complicated than it should be. When you intall a cam for the first time, you line the dots up at 12 and 6 as these guys are suggesting. However, if you leave it that way and stab the distributor with the rotor pointing at the #1 plug wire, you'll be 180 degrees off timing. If you want to leave it that way, fine, but understand that you should stab the distributor with the rotor pointing at the #6 plug wire, not #1. If you want to stab the distributor and have the rotor pointing at #1, you've got to rotate the crank 360 degrees back to TDC again. This will place the #1 back at TDC, but this time it will be on the compression stroke. This will allow you to stab the distributor and have the rotor pointing at the #1 wire. I think we're all on the same page with this, it's just a matter of how you choose to stab the distributor.

 

One thing is for sure, you're not at TDC of the #1 compression stroke with the sprocket dots at 12 and 6. That's just a fact. You're on the exhaust stroke. Now this topic is exhausted!

[Guest bigfat]

take it you mean how the timing gear marks line up? The marks are small stamped round indented circles on the outer faces of the gears positioned in line with a gear tooth. If you disassembled the intake and distributor already, you first probably held your finger over number 1 cylinder spark plug hole until it shot out compressed air & the distributor cap rotor was facing number one pick-up, but when you got the timing gear cover off, you saw the mark on the crankshaft gear at the top of the gear as well as on the camshaft gear. That's because on the typical Chevy small block the timing gear marks are lined up right next to each other when number 1 cylinder is at the top of the EXHAUST stroke, not at the top of the compression stroke, as you would think. No big deal. The crankshaft turns twice for every one camshaft rotation. Just roll the motor clockwise either with a remote starter switch, or temporarily place the harmonic balancer back on the crank, & with all the spark plugs out, roll the engine by hand until the timing gear marks come around right next to each other (camshaft gear mark at bottom, crankshaft gear mark at the top). Change your gears & chain, & do all the engine work you need to do. Make the distributor the LAST thing you install. You can roll number one piston to the top of the compression stroke again, then drop the distributor in until it seats on top of the intake with the distributor rotor pointing straight forward for number 1 cylinder. Or, if you haven't disturbed the timing position yet, just point the rotor to number 6 cap pickup position as you drop in the distributor. Hope this helps.

 

Chase,

 

I found this on the internet. Does it make sense to you. Just wondering.

 

Jody Wayne Stuart.

[Truck99]

 

Sounds like whoever posted that knows exactly what they are talking about!

 

...and probably does a better job of explaining it than I did, but he said the same thing.

 

Let us know how she runs after you hit the track again. Hopefully the problem is fixed.

[ford12]

6 on cam and 12 on crank way iv always done it.