I just recently installed a 350 sbc with new performance heads and cam. I did all the basics in preparation for break in process. High zinc oil, water instead of coolant, and set distributor rotor pointing toward cyl 1 at tdc compression etc. When I first tried to start it, it actually fired up without struggle and sounded pretty smooth for a ballpark timing. I turned it off before the 30 min high rev period to clean up the work area. It started again maybe 1 more time but after that I got a dead crank. So far I have tried everything I know as a non expert to find the problem. Added 5 gallons of gas as tank level was low. Verified all distributor wires were plugged in, correlating to the firing order. Made sure carb was getting fuel. Double checked sensor connections at distributor ( although I haven’t checked to see if they’re getting voltage)
I verified that the distributor was sending spark to the spark plugs. And tried with choke off / on /partially closed. You can hear that the engine has compression when you turn it by hand. I am really out of ideas and am stuck because it fired up on the first try and then just fell to dead crank. The last option would be to reinstall the distributor a third time to tdc compression. I had it set at 0 degrees on the balancer the first time, the second was maybe 4 degrees advanced as it was dark and lamp batteries died. even it if was a few degrees off, it should still start just run really rough right? I took valve cover off to be certain it was tdc on compression. The last try would be to very carefully set the balance at 0 mark on tdc again with distributor facing cyl 1. If anyone has any ideas I would really appreciate it as I’m pretty stuck.

 

Have you pulled th dist. cap and cranked the motor over to verify that the rotor is turning?

 

If it started and ran I would not focus on the timing so much unless the distributer was loose at the time it ran. Normally if distributer timing is off you should get at least a back fire. Even a full 180 degs off I have seen fire ***** shooting out the carb.

If I had to guess the motor was running rich and when you shut it off the plugs got fuel fouled. I would pull a couple of plugs and see what is going on.

After saying that I have seen all kinds of issues in rebuilt motors. I would love to say "its always this" but that is simply not true. Here are a few Ideas for things to check.

Defective carb, There could be something floating around in the carb blocking fuel flow ( will the car start on a fuel dump into the carb, use two cycle gas/oil until the Cam is broken in). Don't fill the bowl shoot directly into the carb. If you want you could try a quick spray with carb clean just to see if it wants to try to start.

Distributer issue, Is the distributer turning? I have seen gears installed wrong or defective right from the factory. This can cause a timing jump on acceleration. Make sure the distributor is tight. The gear wants to push itself away from the cam. also verify the pin is there and installed correctly. You said you have spark but are you sure it is strong enough? Coils are the king of work once when new. Followed closely by condensers. Both can cause weak spark that may jump the plug without compression but will not jump a plug under compression. I always test spark with a spark tool, they have built in resistance, if it fires the tester it will fire a plug.

Exhaust restriction, Bad cat or gasket installed wrong. A vacuum gage would read near zero at cranking.

Large Vacuum leak: Hose tears or get knocked off, It would need to be a large line like the brake booster or a PVC line that uses manifold vacuum. This would also cause a low vacuum reading on a gage.

I only ever saw one engine what jumped valve timing right after a rebuild. That involves a defective chain missing guide and an installer that did not check anything.

There are a few others that are common with cars that have their emission system intact.

 

Yes when the engine first started I had the distributor snug but not tightened down. Loose enough to move by hand but not so that it could move by itself. However it’s possible I left it too lose and maybe it did jump out. Either way I already took it out and reinstalled it a second time at cyl 1 tdc compression.

Another thing I noticed was when I pulled cyl 2 spark plug to check for spark, the motor sounded much more alive during crank. As in it was no longer A dead crank but kind of misfiring or backfiring. And when I put the spark plug back in, the engine returned to a dead crank no coughs or rough combustion at all. I’m a diesel mechanic so I just know the basics of these gas engines. I can pull distrb. Out again and check gears for damage.

 

i have not verified that, but I was getting spark so I assume the rotor has to be turning for the spark plugs to light up right? I’m a diesel mechanic so if I’m wrong I’d appreciate any correction.

 

Gear damage was one thought I had,another is many times I've seen a dizzy set in at TDC but not fully engaged in the cam gear so when it drops all the way in it's off a tooth or two.

 

Is this HEI or points?

I am having a little trouble thinking about how a single plug out would cause the motor to do anything but gallop. The only things that come to mind is the motor is speeding up and the spark may be stronger in the next cylinder inline to fire.

Heads up, pulling a plug on a motor that still has fuel and spark is dangerous. Partially atomized fuel being forced out of the cylinder faster and farther than you think and is just looking for any spark. I have seen pros not thinking and rushing to check things only to catch the whole engine bay on fire.

 

it is a Hei distributor from what I can tell. And thanks for the heads up

 

Took off distributor cap, and this little contact point fell out. It fell out when I took off the old motor as well but I thought it was normal and just saved it. I looked at it a little closer and it seems like it was broken off, there seems to be a piece of it on the cap itself still. And the piece I have in my hand doesn’t look like a clean cut. Again I’m not too advanced in distributors and gas in general I’m an all diesel guy lol. I’m hoping this is my problem.
Edit* Well I installed a new distributor cap and rotor and still no start. . There are spark marks inside the cap so I’m guessing it’s not a defective piece. I checked the gears for damage and it looks solid. I’m officially out of ideas. There are two small vacuum lines on the carb that are loose and free right now since the intake manifold doesn’t have the right ports as my old 350. However one of the lines is just for the choke on the carb, and the other goes to the top of the carb on the rear side. Would it not start if that line was not getting vacuum? Either way I hooked up a random hose I found lying around, it’s rubber and not the right size so I forced it into the vacuum ports just to test to see if that was the problem but the engine STILL did not start. Really not sure what else it could be

 

Ok good news and bad news. The good news is I think I found the problem with the no crank. Bad news is that the gas has started mixing with the oil. Pulled the plugs they looked dirty and smelled like gas. Pulled distributor same thing. Drained the pan and lots of gas/oil came out. I stupidly didn’t change the fuel pump or even filter from my old 350 ( I foolishly figured since it was working fine on previous engine it would be enough to get me going on new one.) This makes the most sense to me because sometimes when I try to crank it after a day or 2 of no cranking, it struggles badly. Until eventually it breaks free and then cranks no problem. Battery is fine and starter is semi new. Which means it could have been trying to hydrolock but I broke it free in time? I could be wrong but these are just my theories. I’m planning to get new fuel pump and pour new oil in Tommorow to let the pan dry out. Any tips on what I should do to clear gas from the oil passages? Or will it just evaporate? same goes for oil pan.