weird timing issue SBC 350 ?
08-28-2012, 09:09 AM
#1
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weird timing issue SBC 350 ? I can't figure this out so I'm hoping the pro's can give me a hand.
I am working on my wakeboarding boat, it's a classic.. 1989 Malibu euro F3 with the mercruiser 5.7 V8 basically a 350 sbc with marine manifolds
I was having problems with the old points style distributor so I went ahead and bought a coil-in cap style HEI accell billet distributor. Everything is new ignition wise(distributor, coil, rotor, cap, wires) besides the plugs which I had recently changed but I regapped them at .035. Also need to mention I am not running the vacuum advance, I have the vacuum port at the base of the distributor blocked off.
I started out by getting the engine to TDC and verified that TDC was 0 on the Timing tab, set the distributor in the hole with the rotor facing cylinder #1 and fired her up. The boat cranked right up and I tweaked the distributor by ear first and now it cranks smooth, idles smooth, also revs smooth. But the timing mark has me baffled. I do not have a dial back distributor which would be nice to help explain to you guys the issue but I will try to explain the best I can. I am looking at the front of the engine and balancer and will explain the readings I get like the readings on a clock. 0 on the timing tab is at the 2 oclock position.
crank engine and it idles with the timing mark at 12 oclock (way advanced probably 40 degrees) but is not entirely steady it has a little movement in it but not much maybe 5 degrees. If I retard the timing any it will shut off and/or not recrank. but when cranking at this timing it cranks smoothly as sounds correct.
slowly rev engine the timing increases proportional to RPM to around the 10 oclock position (best guess would be about 60 degrees)
as I get past a certain rpm 3000-3500 or so the timing mark jumps back to the 1 oclock position and holds steady no movement at all (at this point the distributor is fully advanced, and the mark is no longer advancing). This spot is where I believe the timing should be at. (in relation to the timing tab it is at about 30-35 degrees)
It has me baffled as to why the mark is so far advanced and then bounces back to normal after you rev the engine past that certain rpm. By the way I did this several times and The timing mark does this consistantly. The only thing I could think of that would be causing this would be the weights or springs inside the distributor (all brand new) but i dont see how those items would effect the mark like it is. Has anyone had expirience with this or have any idea's? I am planning to take the boat out this weekend. If I was just trying to time the engine by ear I would say its done because it really sounds like its running great but the mark scares me and I dont want to tear anything else up by taking it on the water.
I am working on my wakeboarding boat, it's a classic.. 1989 Malibu euro F3 with the mercruiser 5.7 V8 basically a 350 sbc with marine manifolds
I was having problems with the old points style distributor so I went ahead and bought a coil-in cap style HEI accell billet distributor. Everything is new ignition wise(distributor, coil, rotor, cap, wires) besides the plugs which I had recently changed but I regapped them at .035. Also need to mention I am not running the vacuum advance, I have the vacuum port at the base of the distributor blocked off.
I started out by getting the engine to TDC and verified that TDC was 0 on the Timing tab, set the distributor in the hole with the rotor facing cylinder #1 and fired her up. The boat cranked right up and I tweaked the distributor by ear first and now it cranks smooth, idles smooth, also revs smooth. But the timing mark has me baffled. I do not have a dial back distributor which would be nice to help explain to you guys the issue but I will try to explain the best I can. I am looking at the front of the engine and balancer and will explain the readings I get like the readings on a clock. 0 on the timing tab is at the 2 oclock position.
crank engine and it idles with the timing mark at 12 oclock (way advanced probably 40 degrees) but is not entirely steady it has a little movement in it but not much maybe 5 degrees. If I retard the timing any it will shut off and/or not recrank. but when cranking at this timing it cranks smoothly as sounds correct.
slowly rev engine the timing increases proportional to RPM to around the 10 oclock position (best guess would be about 60 degrees)
as I get past a certain rpm 3000-3500 or so the timing mark jumps back to the 1 oclock position and holds steady no movement at all (at this point the distributor is fully advanced, and the mark is no longer advancing). This spot is where I believe the timing should be at. (in relation to the timing tab it is at about 30-35 degrees)
It has me baffled as to why the mark is so far advanced and then bounces back to normal after you rev the engine past that certain rpm. By the way I did this several times and The timing mark does this consistantly. The only thing I could think of that would be causing this would be the weights or springs inside the distributor (all brand new) but i dont see how those items would effect the mark like it is. Has anyone had expirience with this or have any idea's? I am planning to take the boat out this weekend. If I was just trying to time the engine by ear I would say its done because it really sounds like its running great but the mark scares me and I dont want to tear anything else up by taking it on the water.
08-29-2012, 11:22 PM
#3
I can't figure this out so I'm hoping the pro's can give me a hand.
I am working on my wakeboarding boat, it's a classic.. 1989 Malibu euro F3 with the mercruiser 5.7 V8 basically a 350 sbc with marine manifolds
I was having problems with the old points style distributor so I went ahead and bought a coil-in cap style HEI accell billet distributor. Everything is new ignition wise(distributor, coil, rotor, cap, wires) besides the plugs which I had recently changed but I regapped them at .035. Also need to mention I am not running the vacuum advance, I have the vacuum port at the base of the distributor blocked off.
I started out by getting the engine to TDC and verified that TDC was 0 on the Timing tab, set the distributor in the hole with the rotor facing cylinder #1 and fired her up. The boat cranked right up and I tweaked the distributor by ear first and now it cranks smooth, idles smooth, also revs smooth. But the timing mark has me baffled. I do not have a dial back distributor which would be nice to help explain to you guys the issue but I will try to explain the best I can. I am looking at the front of the engine and balancer and will explain the readings I get like the readings on a clock. 0 on the timing tab is at the 2 oclock position.
crank engine and it idles with the timing mark at 12 oclock (way advanced probably 40 degrees) but is not entirely steady it has a little movement in it but not much maybe 5 degrees. If I retard the timing any it will shut off and/or not recrank. but when cranking at this timing it cranks smoothly as sounds correct.
slowly rev engine the timing increases proportional to RPM to around the 10 oclock position (best guess would be about 60 degrees)
as I get past a certain rpm 3000-3500 or so the timing mark jumps back to the 1 oclock position and holds steady no movement at all (at this point the distributor is fully advanced, and the mark is no longer advancing). This spot is where I believe the timing should be at. (in relation to the timing tab it is at about 30-35 degrees)
It has me baffled as to why the mark is so far advanced and then bounces back to normal after you rev the engine past that certain rpm. By the way I did this several times and The timing mark does this consistantly. The only thing I could think of that would be causing this would be the weights or springs inside the distributor (all brand new) but i dont see how those items would effect the mark like it is. Has anyone had expirience with this or have any idea's? I am planning to take the boat out this weekend. If I was just trying to time the engine by ear I would say its done because it really sounds like its running great but the mark scares me and I dont want to tear anything else up by taking it on the water.
I am working on my wakeboarding boat, it's a classic.. 1989 Malibu euro F3 with the mercruiser 5.7 V8 basically a 350 sbc with marine manifolds
I was having problems with the old points style distributor so I went ahead and bought a coil-in cap style HEI accell billet distributor. Everything is new ignition wise(distributor, coil, rotor, cap, wires) besides the plugs which I had recently changed but I regapped them at .035. Also need to mention I am not running the vacuum advance, I have the vacuum port at the base of the distributor blocked off.
I started out by getting the engine to TDC and verified that TDC was 0 on the Timing tab, set the distributor in the hole with the rotor facing cylinder #1 and fired her up. The boat cranked right up and I tweaked the distributor by ear first and now it cranks smooth, idles smooth, also revs smooth. But the timing mark has me baffled. I do not have a dial back distributor which would be nice to help explain to you guys the issue but I will try to explain the best I can. I am looking at the front of the engine and balancer and will explain the readings I get like the readings on a clock. 0 on the timing tab is at the 2 oclock position.
crank engine and it idles with the timing mark at 12 oclock (way advanced probably 40 degrees) but is not entirely steady it has a little movement in it but not much maybe 5 degrees. If I retard the timing any it will shut off and/or not recrank. but when cranking at this timing it cranks smoothly as sounds correct.
slowly rev engine the timing increases proportional to RPM to around the 10 oclock position (best guess would be about 60 degrees)
as I get past a certain rpm 3000-3500 or so the timing mark jumps back to the 1 oclock position and holds steady no movement at all (at this point the distributor is fully advanced, and the mark is no longer advancing). This spot is where I believe the timing should be at. (in relation to the timing tab it is at about 30-35 degrees)
It has me baffled as to why the mark is so far advanced and then bounces back to normal after you rev the engine past that certain rpm. By the way I did this several times and The timing mark does this consistantly. The only thing I could think of that would be causing this would be the weights or springs inside the distributor (all brand new) but i dont see how those items would effect the mark like it is. Has anyone had expirience with this or have any idea's? I am planning to take the boat out this weekend. If I was just trying to time the engine by ear I would say its done because it really sounds like its running great but the mark scares me and I dont want to tear anything else up by taking it on the water.
You can pull the heads and use a dial indicator to verify TDC as well - whatever tools you have at your disposal. This is what i have always done. Until you are sure that mechanically the dampener is correct itself then we are shooting in the dark.
Next is to get a secondary timing gun. You cannot question the hardware used to test.
Set the initial to around 12 degrees, inital + center should be all in at where you are now - 30-35 degrees @ 3kRPM.
I would also verify the HEi is not defective. Just because it is new does not mean it works. Take the HEI appart and verify the counter weights can in no manner stick advanced intermittently.
Would be nice to know your alititude - sea level timing is different than 5000+ft altitude timing. Poor analytics of chamber design for 4 stroke motors is to blame here - this could also be an issue to be mentally accounted for.
