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Old 06-22-2018, 05:00 PM
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Adjustable timing tab setup sbc 350

Yes ive searched and read alot on this.

When i built this engine i had setup tdc on the timing tab very accurately when the heads were off with dead stop method. It was perfect. Later added an msd box so no longer could use a rollback timing light so got the msd sticker pack for my damper but my original pointer was covering the sticker too much so i couldnt see any numbers on the tape. I should have at least tried to check timing before removal of my current tab but like an idiot i didnt and just removed it thinking i could used a piston stop but it doesnt hit the piston hard enough to trust it due to the angle and i cant get a reading with a dial indicator that i can trust. Engine in truck and fully assembled, truck runs great and is at 34 or 36 total timing but i dont remember honestly.. really want to confirm before i put the 100 shot on it.. not sure of what to do at this point.. i dont like guessing or pulling heads off.. any thoughts?

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Old 06-22-2018, 09:05 PM
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Quote:
Originally Posted by AutoMech View Post
Yes ive searched and read alot on this.

When i built this engine i had setup tdc on the timing tab very accurately when the heads were off with dead stop method. It was perfect. Later added an msd box so no longer could use a rollback timing light so got the msd sticker pack for my damper but my original pointer was covering the sticker too much so i couldnt see any numbers on the tape. I should have at least tried to check timing before removal of my current tab but like an idiot i didnt and just removed it thinking i could used a piston stop but it doesnt hit the piston hard enough to trust it due to the angle and i cant get a reading with a dial indicator that i can trust. Engine in truck and fully assembled, truck runs great and is at 34 or 36 total timing but i dont remember honestly.. really want to confirm before i put the 100 shot on it.. not sure of what to do at this point.. i dont like guessing or pulling heads off.. any thoughts?
A piston stop should stop the piston so I'd try again. Also, you don't want it to hit the piston hard either anyway. Put stop in there until piston hits it. Then place your mark on the balancer. Reverse direction until piston hits stop again. Put your other mark on the balancer. The middle istance between those marks gives you your TDC.
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Old 06-22-2018, 09:10 PM
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A low budget adjustable timing tab is not too difficult to install IMO (and they are cheap.) Make a home made stop from a spark plug and be on your merry, or Mary, way ( ). Either way I would n't lose any sleep from it. If you don't want to goof with the adjustable tab, then tune it by driving until it pings and back it off a couple of degrees and put the nitrous to it. All you need is a reference point to know how far your retarding it when the nitrous hits. Either way, you don't need to pull a head.
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Old 06-23-2018, 07:45 AM
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I did try the piston stop but itís such a cheap made in China piece of junk loose threads, etc. I do think I did get it last night with a little messing around or should at least be very close (within a half degree) when I first tried it two nights ago i wasnít screwing it in far enough, the threads are so loose I thought it was bottomed out but wasnít.
let me ask you guys this, will the msd box ďchange the timingĒ for example when it was setup before the msd box I had it set to 18 or 20 initial and 34-36 total with a 14 degree bushing, now it shows 28 initial and 42 total.. I know I am not that far off on my marks, starts great runs great etc.. I feel thereís no way Iím really at 28 degrees initial or it wouldnít start hot, what gives here?? I havenít touched the distributor since the msd box was installed, I just donít trust anything about this setup anymore lol I was thinking maybe Iíd back the distributor down to 20 initial later just to see what it does.. Iíve never installed an msd before, I just want it to pull timing when the nitrous is armed or I wouldnít have put it in..
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Old 06-23-2018, 03:14 PM
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It can vary a little based on the voltage rise of the sensor, and at what voltage the old module triggered verses the MSD box. I wouldn't expect it to change more than a couple of degrees. On a square wave distributor sensor, it shouldn't change at all.

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Old 06-23-2018, 05:59 PM
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Quote:
Originally Posted by AutoMech View Post
I did try the piston stop but itís such a cheap made in China piece of junk loose threads, etc. I do think I did get it last night with a little messing around or should at least be very close (within a half degree) when I first tried it two nights ago i wasnít screwing it in far enough, the threads are so loose I thought it was bottomed out but wasnít.
let me ask you guys this, will the msd box ďchange the timingĒ for example when it was setup before the msd box I had it set to 18 or 20 initial and 34-36 total with a 14 degree bushing, now it shows 28 initial and 42 total.. I know I am not that far off on my marks, starts great runs great etc.. I feel thereís no way Iím really at 28 degrees initial or it wouldnít start hot, what gives here?? I havenít touched the distributor since the msd box was installed, I just donít trust anything about this setup anymore lol I was thinking maybe Iíd back the distributor down to 20 initial later just to see what it does.. Iíve never installed an msd before, I just want it to pull timing when the nitrous is armed or I wouldnít have put it in..
An MSD box such as a 6AL is not going to alter your timing. There are MSD boxes that have timing adjust to them but if you don't have one of those then the box is not messing with your timing. Just establish your TDC and you'll be golden from there.
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Old 06-24-2018, 01:19 PM
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The box is an msd 6 plus box, it has a step retard function (which isnít working so I guess Iíll be calling msd on that tomorrow) and a two step rev limiter...

Well the best I can tell is my timing marks are really close, I was showing 27 degrees initial and 42 total, I backed it down to 20 initial and 34 total and plugged the vacuum advance back in, idk if the box changed timing a little and/or I wasnít as close as I thought when I set it this spring after the engine got reinstalled, but it runs surprisingly well, idk how it wasnít pinging at 42 degrees of timing the last few weeks lol
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Old 06-24-2018, 06:29 PM
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idk how it wasn’t pinging at 42 degrees of timing the last few weeks lol
'pinging' implies detonation - I'll bet it was, but you couldn't hear it yet. By the time you hear the detonation it's beating itself to death. FWIW, detonation occurs long before you can hear it. Look into how a knock sensor works, it doesn't do anything until it detects knock, but you can't hear it on a stock motor with stock exhaust - throw in a set of headers and loud mufflers and you'll never hear the onset of detonation.

But, perhaps you have a motor that will take 38-39 degrees of all in timing, so the 42 degrees wasn't doing much more than starting to hurt performance. Either way, 34-38 degrees is generally a safe place to be with a normal SBC build that has a decent quench distance. But also consider the other factors that influence detonation - temp range of plug, cylinder air temps and head/plug/cylinder temps that get transferred to the plug strap, fuel quality, etc. All play a role and that's why it's so difficult to give anything other than relatively gross generalizations of where you should set your 'all in' timing at.

Perhaps you're running a cold air intake hose that is mounted in place of a headlight and you've been running this in 50-60 degree weather at highway speeds, I'd guess not, but the same setup with an air intake that is a normal air cleaner in a well sealed engine bay in city traffic on a 90 degree day cannot run the same amount of timing due to inake temps will be 80-100 degrees higher.

Should also mention that the best place to dial in the max amount of all in timing is at a drag strip if you can manage to get some consistent 60ft times.
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Old 06-25-2018, 08:20 PM
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The engine has a tight quench .40 range, running 91 octane, aluminum heads 8.5 dcr 10.3 static, Cooler rainy weather lately.. Iíve never been worth a dam at detecting ping.. in anything really unless itís stupid bad.. I could have avoided this whole issue by knowing my timing before I put in the msdbox, best case scenario itís been ran 500 miles like this, worse case scenario I somehow set it wrong when I replaced the engine block this April and i didnít set it right at that point and it has 2,000 miles, ah well thatís why we check these things... seems to be running fine back at 20/34 degrees haha, mostly embarrassed i didnít catch this sooner.. I put the msd box in In one night and didnít notice any difference so I have to assume I screwed it up in April somehow.. Iím pretty sure itíll handle 36-38 without an issue, no track nearby unfortunately to do proper trials but maybe next time I make it there Iíll bring a light with,
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