freshly rebuilt sbc will not start

[JP_67_GMC]

I have tried everything that I can possibly think of, along with several other people. Just rebuilt a 350 for a 72 Gmc, HEI distributor and an edelbrock carb that were used with great success. I have my timing on, I have firing order memorized. The Distributor is NOT 180 off. The rocker arms are not to tight, it is grounded to the frame. It has all 3 essentials but they refuse to work together. I do get a slight pop like one cylinder is firing when I play with the distributor but I can never hone it in to get it working. Also the cam in in correctly and I have brand new spark plugs and wires. I have moved the distributor around several times with no success, basically start fresh by taking everything off and starting over. Thanks

[Lanman1972]

Any chance the rotation of the distributor is different than the way you have the firing order going. Clockwise versus Counter Clockwise.

[Coley]

Have you done and confirmed the 2 basic checks:
-Fuel: looked down the carb to see it squirt, smell its presence? Maybe put/squirt a little fuel down the carb manually with a when turning it over.
-Spark: Are you dead certain that the distributor is putting out? have you seen or tested for a spark at one or all plug lead points? Do you have a spark tester?
Start there, keep us posted.
Coley

[67 cst swb]

By saying it "has all 3 essentials".
I assume you are saying it has Air, Fuel and Spark?

I would say that if you are getting a pop when you move the distributor.
My guess is that you are 1 tooth off on the distributor.
Only other thought is a bad rotor. A coil is "typically" either good or bad, so it wouldn't cause an erratic or occasional pop.

[JP_67_GMC]

Yes it has gas coming out the accell pump holes, I know which direction the distributor spins. Has backfired once, and I pulled a plug to visually check for spark.

[Davidf]

If the engine has "all three essentials" then it has to run if there is compression. I surmise the distributor/ignition is where problem lies. Spray a shot of starting fluid down the throat of the carb while someone else tries to start. If it fires, then you have a fuel problem. If not an ignition/timing problem.

[67 cst swb]

Originally Posted by 67 cst swb

I would say that if you are getting a pop when you move the distributor.
My guess is that you are 1 tooth off on the distributor.

In case you missed this thought.

[geezer#99]

Originally Posted by JP_67_GMC

Yes it has gas coming out the accell pump holes, I know which direction the distributor spins. Has backfired once, and I pulled a plug to visually check for spark.

So what way does the rotor spin?
Clockwise or counterclockwise?

[hugger6933]

Clockwise 18436572

[tranz am]

Originally Posted by geezer#99

So what way does the rotor spin?
Clockwise or counterclockwise?

Clockwise.

[Lanman1972]

Is it possible to misaligned the timing gear marks during assembly? Just throwing stuff at the wall to see what sticks!

[muley]

Perhaps the power wire to the distributor? "On when the key is on, and "off" while cranking?

[cleszkie]

HEI module going out and producing erratic/weak spark? I know some people will say that coils and ignition modules are either good or not and no inbetween. But that is not the case. I've experienced in and out coils and modules.

Also, do you have the correct plugs for the engine? I once rebuilt a SBC and switched from stock iron heads to aluminum heads and installed the same plugs (new ones) that I was running in the iron heads into the aluminum heads. Long story short, the aluminum heads had a thicker wall at the plug ports and the electrodes on the plugs were not even making into the combustion chamber. Engine barely ran. Switched to plugs with longer reach (longer threaded zone) to get the electrodes into the combustion chambers and everthing worked perfectly. Just two simple things to check out. Good luck.

[Longhorn 70]

It could be so many things. Since you said it has fuel, and I imagine it has air to burn, I'd check ignition timing first.

Does it have a tach? Does it move while cranking? Have you had someone crank and checked timing with a light to see if you're close? If it is close but still no start, then the suggestion Lanman asked would be my next check.

best of luck

[MARKDTN]

Originally Posted by Lanman1972

Is it possible to misaligned the timing gear marks during assembly? Just throwing stuff at the wall to see what sticks!

This is always a possibility. That is what I was thinking.

[trac209]

One thing is for sure if you have a flat tapped cam don't crank the heck out of it until you figure out what's going on or you'll wipe the cam lube off and it could wear the cam on startup

[john]

Did you set cam timing like pic for #1? If not it is timed for #6.

[rripp]

Does it have compression on every cylinder? I ask because you could have put too long of bolts in the intake around the 2 and 6 cylinder and it bent a push rod and isn't moving the valves. It will backfire when it does this...ask me how I know...

[enaberif]

Lets start with some basic things.

1) Do you have 12v at the terminal for the distributor with the key on?
2) You ensured 100% you were on TDC #1 compression stroke when you set the timing?
3) Have you verified TDC properly with balancer to timing tab?

[Davidf]

Originally Posted by john

Did you set cam timing like pic for #1? If not it is timed for #6.

Oh man, no wonder on EVERY sbc that I have rebuilt, I always seemed to have the dizzy in 180 degrees out on first start attempt. I immediately knew what was wrong, but not WHAT was wrong. After reading up a bit, it makes since. I learned something day, thanks for that.

PS. Even the service manual says to align the dots (and, its always assumed #1 is on compression stroke).

[Mr Handy]

Originally Posted by Davidf

Oh man, no wonder on EVERY sbc that I have rebuilt, I always seemed to have the dizzy in 180 degrees out on first start attempt. I immediately knew what was wrong, but not WHAT was wrong. After reading up a bit, it makes since. I learned something day, thanks for that.

PS. Even the service manual says to align the dots (and, its always assumed #1 is on compression stroke).

I just did cam and head swap on my 283 and I read somewhere to align the dots then turn the engine over one revolution to be TDC on the compression stroke. Worked out perfect other than I was 1 tooth off.

Was very hard starting and only started with the canister all the way against the intake and was still 8* retarded. Surprised it even started.

[Rustoholic55]

I had a shorted dizzy rotor once, drove me nuts! Pulled the rotor off, and found a burn (short) right to ground. It was over 20 years ago, and I'll never forget it.

[CastIron]

If the distributor is new and replacing a points distributor, make sure the power wire going to the coil is not the original resistor wire.
If the distributor is a tooth off, try rotating it a little in each direction and see if it fires. It can run like that, but the timing mark on the balancer won't be right.

[piecesparts]

Have you checked the pickup coil inside the distributor? If it is weak or bad, it will not start. To change it out, you have to pull the dizzy and take the shaft out of the dizzy housing. While you are in there, go ahead and change out the module. Just my $.02 worth.

[chevytruckluver]

Just so everyone is clear about this...A Chevy small block is a 4 stroke engine, the strokes are intake, compression, power and exhaust. There are 4 essentials. It wont run on just 3.
they also have to happen at the correct time. Valve timing and distributor timing are 2 different things.

JP 67 GMC hasn't replied since before noon. maybe he got it going?


If I were in his shoes I would start here.
1. pull #1 spark plug and confirm TDC by having a helper bump the starter while I held my finger over the spark plug hole and feeling the air being pushed out the hole. Then looking at timing marks.
2. pull dist cap and verify that the distributor is aligned with the #1 spark plug wire.
3. Confirm firing order, 18436572 and rotation. Spark plug wires are not crossed.
4. Re install the dist cap. before re installing the plug in the cylinder head, plug the wire on the spark plug and ground the spark plug to the frame or motor somewhere and crank the engine over to check for spark.
3. If these are all good and the engine is getting fuel, and has not fouled the spark plugs it should start. Assuming the timing is correct on the cam and crank gears.