Seasons Greetings... I have two questions:
I have rebuilt my L-36 motor and am now trying to get it started to break in the new rings and cam. I have set the timing at 10º BTDC as verified by timing light upon cranking. Newly rebuilt damper and verified mark correct with true TDC. Valves all adjusted half a turn down on the base circles. Spark plug wiring triple checked and getting orange spark (not HEI) from coil cable. Oil pressure at 35 psi upon cranking and coil wire unconnected and fuel (which may be my culprit) is cranking out into jar. Carb pump is squirting so fuel made it into carb. Quadrajet Carb was emptied two years ago when I first began the project and was basically new then (triple gasket per Lars posting). I found this spring under the car and cannot for the life of me figure out what it is from. It was not there all the other times I was underneath when getting motor all connected up. See photos below
Upon cranking to finally try to light it up, It backfired (no flame) through carb and sounded like a gun shot ringing my ears. My daughter filmed this and swears she saw something shoot out the carb. I looked but could find nothing out of order upon visual inspection. (I had already discovered the spring before this.)
The gallon or so of gas in the newer tank is two years old but it looked and smelled fine, so I added 2 and a half gallons of fresh gas to the tank before any cranking occurred. Several attempts to start the engine resulted in backfires through the carb and absolutely no detectible combustion, not even a cough or sputter. Before the rebuild, all plugs fired fine so I know the cap and rotor was working and they just stayed on the distributor in a plastic bag the entire time.
My two questions are...
What the heck is this spring? And, would my next move be to check compression or remove top of carb to inspect, or something else I may be missing? As always, thanks for any input!

roughly 1/4" by 1/8"

 

It looks like some sort of ball detent spring.

 

Sounds like perhaps the timing is 180* out of phase. Make sure #1 is TDC on the compression stroke and that the rotor is pointing (roughly) at the #1 plug wire position.

That spring must be the anti-backfire valve spring.

 

Timing light shows timing is 10º BTDC while cranking, It can't be 180º out if this is showing, right?
Never thought about that infamous anti-backfire spring I've read so much about!

 

Timing mark can still show 10-deg but it'll be on the top of the exhaust stroke (with the intake opening) when the spark happens
M

 

Pull the #1 plug and stick your finger into the hole (LOL like that's even possible on a BBC vette) and bring the motor up to the timing mark, if it's on the proper TDC you'll feel the cylinder pressurize, if not then you're 180 out
(I have a balloon connected to a hose on what's left of a spark plug for just this reason)

If it's easier to get at, the #6 should be the opposite
M

 

A backfire up through the carb means an Intake Valve was open as the plug fired.

I question your Valve-lash adjustment method on a fresh engine. Lifters were more than likely void of oil. Then they pumped up and are holding a Intake Valve open perhaps.
You really don't want to keep cranking on this engine long or you will rub off all the Zinc break-in lube, regardless if roller or flat tappet cam.

I think I would take a quick peak under both valve covers. While a helper jogs the IGN key, monitor each Intake valve with your hand for one that never loosens up while the mates exhaust valve is down. That could be the culprit.

 

Spring looks like the one that goes into the sun visor hinges. Very small.

Car sounds like distributor is 180 degrees out as others have suggested.

Valve lashing is tricky until it isn't. I used to advise the "up and down" pushrod method but the feeler guage method is probably better until you have enough experience with it to not need help anymore. Put a .003" feeler gauge in and tighten the nut until the gauge just barely drags a bit then go a half turn more. That is probably a better way to do it the first time.

 

My rotor points to #1 plug when mark is 10º BTDC. Doesn't that mean it's not 180º out? I did not mention this in first post. I will still verify with plug out and have a helper crank. I am a bit worried about the cam lube situation but I do have a zinc additive in the oil from the cam shop- I hope that helps!
I pumped up the lifters with oil first with a squirt can (before dropping them in) until they were solid and would not compress, before I made adjustments. I did this last time I rebuilt the motor and that seemed to work fine.

 

Thanks HeadsU.P.-
I was thinking of going through the valve adjustments again but I thought I may have missed something stupid. I will need to do that I think since that's really only the way a backfire up through the carb can happen, right?

 

The crank goes around twice for every one turn of the cam (and one turn of the distributor) so it can point at the #1 cylinder either on the TDC for firing or the TDC for exhaust. You need to check which one you're on and without removing the valve cover and watching the rockers, checking for compression is about the only way. If you are going to reset the rockers then you can verify by looking at the intake rocker at TDC
M

 

That's the exact stupid thing I was forgetting about! I knew about the the cam being half speed, but was thinking if the mark showed up on the timing light on #1 it must be right, and missing the fact that it is at the top but not in the correct part of the cycle. I watched the valves not move as I came up to #1 top but maybe I just missed movement. I will check using the compression out the plug hole to verify. This must be the issue. I will check this during the week and get back with results.

 

Ditto on being 180 out.... Restab it and move on. If you want to be absolutely sure you can pull the valve cover. Both the intake and exhaust are closed on the 1 when the 1 is at TDC.

 

Here is where the issue is.....you do not EVER pump lifters up with oil before installation. What is happening right now is that all 16 valves are open......with the lifters full of oil the check valve inside the lifter will not bleed the oil back out......or other words solid and will not compress....
There is only one 100% sure fire way to rectify this and that is to pull the lifters back out......and drain them.....which is a bitch. I would probably just get another set......and are you using Moly Paste on the lobes?
The lash will not find its way back for quite a few revolutions of the crank........and you are trying not to turn the engine over more than you have to.
You could try to zero lash this to get it to fire but it will be noisy AF......and running it 20-25 minutes like that can give even me anxiety.......
Lifters set themselves immediately from engine oil pressure seconds after start up.....there is zero reason to pump them up in oil and you never submerge them in oil either.
How was this lashed BTW? What procedure did you use?

You may also be 180 out as well.....just blow your thumb off #1 and see where the rotor is pointing.....takes 2 minutes with a helper...blowing the thumb off the spark plug hole is TDC #1......you blow the thumb...and line up #1 on the damper with a bar.....check rotor position. With the valves hanging open it should still push your thumb off.....

Jebby

 

Jebby,
I don't know. Replacing lifters at this point seems to be a "nuclear" option. We still do not know how they were lashed. TDC lashing half of the rocker arms (per the list) then following a 360 degree rotation to do the other half of the list? I know I would. A simple, near zero (feeler guage) static lash would still allow a good break-in. We still need to worry about popping out a retainer clip but, those lifters WILL bleed down.

 

Yup ^^^^^^^^
Absolutely no reason to drain the coolant, remove Rad hose, distributor, accelerator cable and pull the Intake, push-rods and lifters.
There is nothing wrong with the lifters. They will bleed-off, eventually on their own.

What a bunch of unnecessary labor. I would back off the rockers a pinch. But not so much as to cause clatter at start-up.
Check the lash.

 

Spring looks like the little spring that goes between the ***** in the shifter fork cover of a Muncie / BW transmission - did you take the transmission apart too?

 

Maybe nuclear….but the only reason I say it is that I wouldn’t want to f*%k with draining them all after removal….they are new, so with FT’s being relatively cheap….I would go that route as I am impatient like that….
As far as the soft lash break in….I only worry about the clip as you say and a rocker kicking off sideways at 2000-2500 rpm…..but if you were keen on the lash….and paid attention….you could get a touch of preload on them so the engine has enough compression to fire….
And yes….is the lash correct to begin with?

The rub is that I have never had to do this but one time a million years ago for my buddy…..and I forced him to remove, spray them out and reinstall…..
It is his engine but I personally would have to punt if it were in front of me….

Jebby

 

Idle air mix screw spring?

 

good thought