Ok I’m finally reaching out for help because I can’t figure this out. I rebuilt the 350 for my blazer project a few years ago and it hasn’t been run much outside of break in and the occasional start up from time to time since the project is still underway. I put in a new cam, original crank. When I installed the timing gears I went dot to dot. I feel like I’ve struggled with the timing ever since I fired it up for the first time, it takes a bit of cranking to start (edelbrock carb) but I’ve always been able to get it running. It seems to run on the rough side, and bogs down when under load (put in gear). Checked vacuum yesterday from the manifold vacuum on the carb, It has about 12-15 lbs of vacuum at idle and I can get it up to mid 20s by adjusting the timing but it doesn’t run as well and when I shut it off at that timing it backfired out of the carb. One issue I’ve had is that my timing mark on my new dampener does not line up with the 0 mark on the tab when the piston is at tdc (cylinder 1) I took the valve cover off last night to make sure both valves were closed (compression stroke) and lined up the timing mark with 0. Checked distributor position and it’s pointing slightly to the passenger side of the engine instead of #1 cylinder. I pulled the spark plug today and just using my phone, videoed the piston travel from as the piston is coming up until it reaches tdc. Basically when my dampener mark is lined up with the 0 on the tab, the piston is just starting to come down, so no longer at tdc. I’ve not adjusted the carb yet, and I have 6psi of fuel pressure at the carb. Long post I know but I want to get all the information out there. Any help is appreciated. Thanks.
CK5
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Balancer timing marks don’t line up with TDC
- Thread starter Jake_C_
- Start date
Paragraphs please to read better .
And years ago before i learned there is more than 1 balancer & pointer tdc combo gm used i had a problem setting my timing as i had them mixed up . I got lucky and set it by ear and good .
And years ago before i learned there is more than 1 balancer & pointer tdc combo gm used i had a problem setting my timing as i had them mixed up . I got lucky and set it by ear and good .
I’ll work on doing paragraphs from now on, you’re right it is easier to read.
I can find tdc using a piston stop, and make a mark on the balancer. I can tell for sure the distributor isn’t pointed correctly which I don’t understand because I’m sure I had it right before.
Your tdc method is fair, not quit accurate. Grab an old spark plug knock the porcelain out thread the metal nut with 3/8 18 tap screw a 2" 3/8 bolt in, grind tip dome shape.
install in #1 cylinder, thread in the bolt, turn crank with short bar by hand, until piston hits bolt and stop. Mark balancer. Turn crank the opposite direction until piston stops at bolt mark crank, tdc will be in the middle of these marks. Do not allow bolt to move between directions.
It does sound like your balancer ring may have spun a bit, late, or retarded. This is assuming these are the same balancer and timing cover from before the rebuild. there are 2 styles for the 350, 12 o clock timing tab and 2 o clock.
install in #1 cylinder, thread in the bolt, turn crank with short bar by hand, until piston hits bolt and stop. Mark balancer. Turn crank the opposite direction until piston stops at bolt mark crank, tdc will be in the middle of these marks. Do not allow bolt to move between directions.
It does sound like your balancer ring may have spun a bit, late, or retarded. This is assuming these are the same balancer and timing cover from before the rebuild. there are 2 styles for the 350, 12 o clock timing tab and 2 o clock.
I have successfully used the method @Wes Harden mentioned above. Also remember to be on TDC of the compression stroke.
You can pull the valve cover and watch what the valves are doing.
You can pull the valve cover and watch what the valves are doing.
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I’m betting the balancer ring moved. Pretty common to have happen. Follow Wes’s procedure to pinpoint tdc and mark the balancer. From there I’ve taken a small center punch to set a little mark on your “new tdc” position so the mark is more permanent than paint or a marker.
However I would validate how much the outer ring moved before even trying to layout new marks. If the has indeed moved at all, it will move again and your efforts would be wasted. At that point get a fresh balancer and go back to making sure 0 degrees on the balancer matches your timing mark.
However I would validate how much the outer ring moved before even trying to layout new marks. If the has indeed moved at all, it will move again and your efforts would be wasted. At that point get a fresh balancer and go back to making sure 0 degrees on the balancer matches your timing mark.
That’s where they should be. Things are ok doing this for an idea as long as we don’t suspect the timing chain slips
Should be ok here
I have an actual piston stop that came with my cam degree wheel kit. Just an outer threaded part that screws into my spark plug hole and and inner threaded part that can screw in or out.
I have done that stop method in the past and I had a mark on the balancer. I actually just redid it before your reply and got it as accurate as possible. With my phone camera I confirmed that the piston is at its highest at this new mark (the new mark is about half an inch off my previous mark). The distributor is still not pointing at the number one cylinder so it obviously needs rotated. Maybe this is my problem.
The actual grove on the balancer looks like it is right at 12 o’clock which would explain why it’s never lined up correctly. Btw this is a new balancer that I bought when I built the engine.
So I thread the stop in, rotate the motor, clockwise and mark it
Then rotate the motor counterclockwise, and make another mark
Split the difference between the two and at your top dead center
Since you replace the damper, when you get the motor, likely got one that is keyed offset of where your top dead center Mark was at on the whole damn
Then rotate the motor counterclockwise, and make another mark
Split the difference between the two and at your top dead center
Since you replace the damper, when you get the motor, likely got one that is keyed offset of where your top dead center Mark was at on the whole damn
If the dampener is known good and your marks just don't match, you can try to source a different timing tab, or just put timing tape on it. The timing tape I put on mine 15 years ago still looks new.
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viewing the piston at its highest point is only ball park. Remember the piston stays at it's highest point in the cylinder for several degrees, depending on stroke, rod length, ,yada yada. This is only on tdc crank for 1 of those degrees. It can get you close.
@Bent77 I think you’re right about getting the incorrect balancer for my timing tab location. Using some painters tape and a ballpoint pen I marked stop to stop and then split the difference and marked the balancer. @Wes Harden i was only checking piston height to confirm it wasn’t still on its way up or down.
I just reinstalled the distributor, it was a tooth or two off.
Should be clocked correctly now. I’ll button everything up and try to fire it up and set the timing with my new mark. Initial timing should be about 12° advanced?
@Blue85 i didn’t even know timing tape was a thing, I’ll have to pick some up that would be perfect for my application.
I just reinstalled the distributor, it was a tooth or two off.
Should be clocked correctly now. I’ll button everything up and try to fire it up and set the timing with my new mark. Initial timing should be about 12° advanced?
@Blue85 i didn’t even know timing tape was a thing, I’ll have to pick some up that would be perfect for my application.
Got the timing set at 12° advanced, fires up quick with one gas pump. It runs pretty well although it seems a little shaky, maybe it’s just the cam? This is my first 350 with an aftermarket cam. Here are the specs: 
The shaking isn’t bad but If I found out it was missing I wouldn’t be surprised. I’m going to run it and pull one plug wire at a time and see if that tells me anything, if not im just going to leave it alone. Worst case scenario it blows up and costs me thousands…
Vacuum is better now though, sitting firmly in the green around 18-19.
The shaking isn’t bad but If I found out it was missing I wouldn’t be surprised. I’m going to run it and pull one plug wire at a time and see if that tells me anything, if not im just going to leave it alone. Worst case scenario it blows up and costs me thousands…
Vacuum is better now though, sitting firmly in the green around 18-19.
I have that same came in my 350. It doesn't idle rough. Check your firing order, especially 5 and 7
That cam is pretty mild. Vacuum numbers look good
Agreed that cam should be relatively smooth. Not much more than a stocker for a production truck 350.
Just some food for thought….
make sure entire ignition system is in prime shape before messing w the carb tuning.
Just some food for thought….
make sure entire ignition system is in prime shape before messing w the carb tuning.
@Wes Harden I’ve double and triple checked the firing order, I’ll feel really stupid if I have it wrong but I’ll check it again.
@76zimmer the ignition system is brand new. Hei distributer, new plugs and wires.
@76zimmer the ignition system is brand new. Hei distributer, new plugs and wires.
While searching and diagnosing a problem don’t discount the possibility of new parts being bad/damaged - a plug could be cracked, or issues with cap & rotor or even a bad plug wire or two.
While searching for issues verify that everything is properly functioning - many mechanics have let simple issues eat their lunch because they assumed that new parts were in good working order.
Your problem might be deeper than these parts but validation is important in narrowing it down.
Also, agreed with what’s said up above; that cam grind is very mild and should let the motor idle very smoothly.
