So, fudge me in the a.....

Im running an 80ish 350 with a holley street avenger carb.

Heres my problem. Motor set to TDC valves both closed by looking under valve cover. LOUD popping coming up through the carb with no really attempt to start (timing around 12* advanced, kinda hard to be sure without it running). Popping is MUCH worse at 0* or retarded. Reset to other TDC so i can rotate the dizzy 180* (again at roughly 12* advanced). Now she tries to start but refuses to stay running, and EVERY time she does start, the carb catches on fire (inside the main body).

Ive rebuilt the carb, and im fairly sure everything is working correctly there. The engine tried to start with no gas peddle pumping or anything (with the dizzy around 180*). Maybe thats still jacked...???

This is a fresh rebuild on the 350, so im 99% sure the timing has not jumped. i set the double roller timing chain at 0 degrees on install and had the notches pointing directly at each other. (both at the center of the motor and not one dot up by the intake and the other by the pan). I have NOT set the roller rockers completely. Im waiting to do that while its running. they are just kind of snugged down.

I know i need gas, timing, compression, and spark to start. I have spark. It has run around 15 seconds before catching on fire, and ive verified with a spark plug and a grounded screw driver. This is a new (run one time in a previous car) distributor and cap. gas is a maybe... It is catching on fire after all. Compression: see running time. Also, i verified all my ring clearances during the install and all were within tolerances. Timing? tf if i know at this point... Spark plugs are set to .35 (or .035, my brain is fried, its the correct gap)


So masters of the corvette universe, ideas?

 

When the timing sprocket marks are aligned. crank dot at 12 oclock and cam dot at 6 oclock, that is tdc #1 exhaust stroke. Engine needs to be turned 360 deg till the crank dot is at 12 and the cam dot is at 12, then you are at #1 tdc compression stroke and the distributor rotor should be ready to fire on #1 wire.

Valve adjustment, I would do a cold adjustment and forgo the running adjustment, millions of gm's were set that way from the factory and since then with no issue, bottom line.

When things are going wrong and getting frustrating, it's best to slow down and go back to the beginning and verify the basics.

 

'75
Im cool with that... I just wanted to be clear as to how i set the gears in place to begin with. As i stated above, I have tried the distributor on both TDC's and both ways im getting weird results.

 

I would doublecheck the valve adjustment, a valve too tight or loose can cause big issues on start up. Stick with the distributor placement that made it try to run and try to advance it from there while cranking .

 

Check your plug wires? Did you set #1 TDC by the valves or the timing mark? Sounds like your timing is screwed up or 180 out.

 

with Stump and 75 for that matter.

If you're concerned about the valve set and you mention they're snugged down - I always used a rule of thumb of 3-4 threads on the rocker stud showing to the fulcrum nut. It's a safe starting point for a stock 350. Adjust from there when running if you don't take 75's advice by setting them before running it. Both ways will get you there and 75's is cleaner for sure !

1-8-4-3-6-5-7-2 going clockwise for your firing order. My gut tells me this is out after reading the thread. Much like Stump is alluding to.
Pull number 1 spark plug, put your finger/thumb over the spark plug hole and bump the engine over with the starter (coil disconnected) in short short intervals - hence "bump".
The TDC you're looking for will put air pressure on your thumb, a fair amount of pressure. The "other TDC" will not.

Cheers.

 

Agree with the thought of rechecking timing. There are varied opinions on cold no run method. This would be a quick way to see if timing is the issue

1. Get #1 piston to compression TDC.

2. Adjust the intake valves on cylinders 1, 2, 5, & 7 by loosening the rocker nut until play is in the pushrod then just take the up and down play in the pushrod and tighten the rocker nut 90 degrees

3. Adjust the exhaust valves on 1, 3, 4, & 8 in the same manner.

4. Rotate crank 360 degrees to get cylinder #6 to compression.

5. Adjust the intake valves on 3, 4, 6, & 8 as above

6. Adjust the exhaust valves on 2, 5, 6, & 7 as above

This method is describe in a few different manuals and should get an engine running

 

Make sure the plug wires haven't been crossed to the wrong cylinders. Read Lars' paper on setting initial timing. Make sure the choke is opening slightly as soon as the engine tries to catch-the vacuum pull-off system. Then, I'd check the carb float height and needle valve. It sounds like you're flooding the engine.

 

I think some of yall are missing that i have tried the timing at both TDC and 180 from TDC (or on both TDC's if you will). One of them CANT be 180 out.. I am having problems with both.
From there though, i am going to reset my valves as stated above and will come back with the results. Im also going to get an extra connector so i can use the spare carburetors i have just for ***** and giggles, and new vacuum caps so i can plug literally everything to make sure that also cant be a cause... (everything is either capped or run correctly, but ive had a bad cap before screw me over, so why not triple check).

 

so, got it set correctly... On TDC it needed a LOT more advance than i thought.. 12* was not enough. Anyway, it runs beautifully!! now on to other issues that have developed like not being able to adjust idle............

 

What carb?

 

holley street avenger.

I found that the electric choke fuse was no longer good (it probably grounded while i was working on the valve covers), not giving the choke 12v. fixed that. So now i can make all the other adjustments i need

 

Is this a brand new balancer on this engine?
Are you checking timing with the vacuum unplugged?
Did you finally lash the valves?

What concerns me is that 12 degrees initial is plenty unless the engine is really radical.....

Jebby

 

no, not brand new balancer. it is the same balancer that was on the (running great aside from a small oil leak) this engine before the rebuild.
All vacuum lines are plugged.
The valves have been lashed.

While checking timing last night, sometimes the timing was dead on at the mark, other times i couldnt see the line on the balancer at all and it was up under the water pump.. I havent had a chance to play this out more and see if i am ******* something up, or if the balancer has come loose and is screwing with me. If the later were true, i assume it would be all over the place all the time, and not just some of the time though.. So PROBABLY user error..

Last night was the first time i was able to run it for more than 15 seconds and get a timing light on it. When it was on and running (and stable), i set the timing at 10* BTDC, which was not far off from what seemed like WAY to advanced (maybe a 1/4 inch of a diameter as far as turning it goes, i dont really know how to better describe that... i didnt turn it much at all). Tonight i will run it more and see if i am still jumping all over the place.

 

Check and verify that TDC "0" on the balancer is truly that.......the outer shell can spin on the inner and throw the mark off.......
Blow your thumb on #1 with a helper then put a breaker bar with a 5/8 socket on the crank.......stick a screw drive through the spark plug hole and "feel" out the top of the piston.......pull the breaker bar back and forth to get the piston to the highest position. Note the mark on the balancer. If it is not at zero......either the tab is in the wrong spot or the balancer is spun.

Finally......are you using a dial back timing light?

Jebby

 

I am not using a dial back light. Maybe the one i have is jacked up too though.... I have several at home, and that was going to be one thing i checked during the process to make sure i wasnt getting an off reading because of the light some how.

I have verified TDC several times over the past few days. Each time i have had the bablancer on the timing tab at zero, #1 has indeed been at TDC. Kinda of makes me question a few things, but weird is not uncommon for me. I have some horrible luck with this stuff.... seriously. For last night (last time the vehicle ran) the timing was set well, and it was running amazingly well. We shall see more tonight!

 

Dale,

Are you saying you can adjust all the valves in two 'positions' of the crank? wow...

 

That's the procedure called out in the factory service manual.

 

Your distributor could be off by a cog and still run with a lot of adjustment. Pull #1 plug and turn to TDC, pull the cap loose and see if the rotor is pointed at the #1 plug wire terminal on the cap.

 

wow - maybe I should look there once in a while!

That's actually really good info.