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Old 08-09-2017, 08:15 PM
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Having trouble starting my just-rebuilt SBC.

Hey all. So I have a 79 camaro, 350, HEI distributor. I just finished assembling the motor and wiring and when I'm trying to start it, it just keeps cranking and seems to spit puffs of gas out of the carb. To me it sounds like the cam and crank timing is out of whack and unfortunately I didn't check it since I got it back from the engine builder as a long block. My mistake.

So i've triple checked my distributor install as well as my wires tried turning it 180 deg., I'm on the compression stroke for sure, I'm definitely getting gas, and I checked that I'm getting spark, however, the spark appears to be weak even though I'm getting a full 12 volts into the dist. Bad coil?

I'm worried that the engine shop got my internal timing wrong and really don't want to tear apart the whole front of the motor I've come way too far to have to go all the way back. Especially since its pretty unlikely that an engine shop would get timing wrong on a 350. Another bit of info on this, I did the "finger test" to assure that I was on the comp stroke, and I checked again with a scribe in the chamber to see when the piston started going down in reference to TDC mark on harm. balancer And it was at like 22 after on my timing tape when it started moving down. That cant be right.

So long story short, could the weak spark be a bad coil? and cause it not to start? And also, how can I check that my cam and crank are correctly aligned without tearing my motor apart?

Help is definitely appreciated, because I did it by the book and now I dont know what the hell is wrong, haha . Thank you!

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Old 08-09-2017, 09:31 PM
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Update

UPDATE: Got it to run although rough, by turning the dist very hard CCW. So i figured Id move all the wires CCW one post and adjust from there. didn't run at all then. still not sure if the timing is right internally though...

Anyway, do you guys think that I'm off a tooth or two on the distributor gear?? And thats why I had to turn it CCW so much??
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Old 08-09-2017, 10:25 PM
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Very common problem.. Distrib is off. Bring back to true compression TDC and re-stab the distrib.
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Old 08-10-2017, 01:04 AM
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I will definitely give it another go tomorrow, thanks. The harmonic balancer line being way off, is that fairly common? its the right size but its aftermarket.
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Old 08-10-2017, 04:28 AM
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1st, talk to the shop that assembled it to ask them about the balancer timing mark. I would doubt they timed the crank and cam incorrectly, but anything is possible. You MUST know where #1 TDC mark is within a degree or two of accuracy with your balancer mark.

2nd, you need a timing light (dial back would be best).Hook it up to #1 wire and start spinning the distributor until you see it's advanced 10-20 degrees- it will start and idle at that point. This might involve moving the wires on the distributor or re-stabbing it as Bob mentioned.

FWIW, I fresh start every motor with a timing light (even COP) to confirm the timing is close.

Anyway, once it starts move the timing to 25-30 degrees and break in the cam. Not enough timing when idling and the manifolds will turn a bright orange.
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Old 08-10-2017, 06:54 AM
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It appears the cam timing could be "180 out"

Meaning....The camshaft gear dot was installed at 6 o'clock and the crankshaft gear dot was installed at 12 o'clock and the engine builder forgot to rotate the crank one revolution before setting the valves with #1 at TDC.
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Old 08-10-2017, 07:00 AM
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Timing light suggestion about is right on the mark, dont guess if it is right.

Second common issue for new motors is valve lash being too tight, not sure how you set the valves. If you used the spin the push rod technique it is very easy to over tighten the lash and when you get full oil pressure the valves hang open and no compression. I like to leave them loose for initial start up, and then adjust them with the engine running.
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Old 08-10-2017, 08:55 AM
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would it even run if the cam was 180 out though? Ok so I'm going to pull the valve cover to find exactly where TDC is, then put my timing tape on the balancer to know where actual TDC is, try and re install the distributor. And go from there. When I insall the dist, I should install it where I ballpark want my initial timing correct? lets say I'm shooting for 12 BTDC. So I'd set the motor to 12 BTDC then install my dist with the rotor on the no. 1 post right? Because if so, I think i set it way wrong.
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Old 08-10-2017, 09:04 AM
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I test drove a 1966 GTO when the timing chain and valves were installed and set 180 out. It drove terrible for about a mile before I drove it back the the shop.

Pulled the engine and the Pistons had marks on them where the valves were hitting the Pistons!
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Old 08-10-2017, 10:11 AM
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Update

I went out and verified by the compression stroke and the valve placement that I am at TDC. My timing tape was accurate. Then I put the motor at about 12 BTDC. From there set my dist. up and marked where the rotor is and tightened the dist down and installed the cap so that the rotor and post lined up. This should get it to fire correct? id not I have to assume my internal timing is bad?
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Old 08-10-2017, 11:42 AM
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Quote:
Originally Posted by tmillz1293 View Post
would it even run if the cam was 180 out though? Ok so I'm going to pull the valve cover to find exactly where TDC is, then put my timing tape on the balancer to know where actual TDC is, try and re install the distributor. And go from there. When I insall the dist, I should install it where I ballpark want my initial timing correct? lets say I'm shooting for 12 BTDC. So I'd set the motor to 12 BTDC then install my dist with the rotor on the no. 1 post right? Because if so, I think i set it way wrong.

This goes back to Mousefink's comment; when setting the SBC up the pip marks when both are pointing in the 12 o'clock position the engine's internals are set to fire number one. The problem this causes is it's difficult to see that the marks are aligned, so builders set the marks facing each other that is crank gear at 12 o'clock and cam gear at 6 o'clock. This then is ready to fire number 6 which is half way through the firing order.


The way to get back from where you are at is to pull the left (drivers) side rocker cover off. Put a 1/2 drive ratchet with a socket big enough to engage the damper bolt's head. Then standing on the left side pull the wrench toward you while observing the rocker motion. When the intake and exhaust are both closed you should see the timing mark coming to zero. Do this a couple three times to get a feel for what you are looking at because the overlap period looks a lot the same but if you keep going once the exhaust is closed the intake will open so till you see this event a couple times it is a little difficult to be sure which stroke you're on when it appears that both valves are closed. Once your confident that number one is on firing then set your distributor up to fire number one.


There is a cheater way out of all of this by assuming the distributor is 180 out, then put the number 1 wire into the number 6 terminal and reposition the firing order from there done right the number 6 wire will be in the number 1 terminal when you get there,,,, like I've never done this. It get's you there without a lot of hassel if the distributor is 180 out.


Bogie
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Old 08-10-2017, 04:14 PM
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Very bad news.

So, I reinstalled the dist properly and also rebuilt the carb. I had to advance the timing a lot to get it to fire. Since im doing cam break in I set the idle really high. Then all of a sudden the whole dr side of my motor literally burst into flames and it looks like It started internally then spread from the carb out. fried my spark plug wires and a few other things. this cannot simply be the distributor not being right. This is an absolute nightmare.
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Old 08-10-2017, 04:24 PM
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The fire described is a gas fire - hopefully you're OK. I'd guess you had a fuel leak of some nature somewhere.

Why did you rebuild the carb???! What is it and what do you mean exactly by rebuilding it?

You set the idle really high - how high is 'really high'?

I'd guess really high was too high, you're rebuilt carb or install had a leak and you experienced a backfire through the carb. Where was the timing thorugh all of this when the idle was 'really high'?
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Old 08-10-2017, 05:26 PM
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Quote:
Originally Posted by tmillz1293 View Post
So, I reinstalled the dist properly and also rebuilt the carb. I had to advance the timing a lot to get it to fire. Since im doing cam break in I set the idle really high. Then all of a sudden the whole dr side of my motor literally burst into flames and it looks like It started internally then spread from the carb out. fried my spark plug wires and a few other things. this cannot simply be the distributor not being right. This is an absolute nightmare.


Too much cranking this puts a lot of fuel past the rings and into the oil pan. I've seen this blow the rocker covers clean off the engine. Yes it can be the distributor not being right, go back to my immediately previous post read and follow the directions. Especially the first about pulling the rocker cover and hand walking it through so you know for sure what you've got. If you can't match the conditions as I describe them then the crank and cam are off time or at least you have enough information to take the next step which would be to open up the timing cover to see what the set up is.


Hopefully neither you the vehicle or the shop have sustained damage. This is freaky but it does happen once and a while.


Bogie
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Old 08-10-2017, 10:42 PM
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Nailhead, thank you I am ok although now am missing quite a few arm hairs. To answer your questions, I rebuilt the carb(edelbrock 1406) because I was starting to think that maybe there was something wrong with it. There were actually a few issues with it. Missing the accelerator pump spring and some other minor stuff. I threw in a rebuild kit and set it according to the guide it came with. The idle was set at roughly 2500 rpm for cam break in. As far as where the timing was, well the distributor was still pretty advanced. I unfortunately didnt have time to retard it before it caught.

Bogie, I didn't read your previous post in time before I ran it, however what you described is basically what i did. And when I found TDC after checking a few times and ensuring both valves were closed on the comp stroke I found TDC was still 22 degrees before(as in BTDC) the timing mark on the balancer. I just figured the balancer was not marked in the right place and adjusted my timing tape.

I really think my cam is off. Because I have spent a lot of time timing this thing and it should've been running perfect. Granted, I've never timed a motor but I'm not a new mechanic even though it probably sounds like it with this disastrous post. the only variable as far as I see is the cam timing. either it jumped a few teeth or was installed wrong. I'm just gonna pull my stupid timing cover soon and see whats up.

So I guess another question is, lets say my cam has been off this whole time, it ran for maybe 3-5 minutes before the fire... Do I need to be in the market for a new cam?

BTW everyone's knowledge and help is very appreciated. Thank you!
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