Hey all I have an issue that has been driving me insane.
First off, I re-adjusted my valves and resat my distributor about half a dozen times. It's a stock rebuilt bottom end (polished crank, new bearings, new rings, hone, etc) with a 224/230 CC cam and vortec heads.

When I go to start the motor, it cranks and cranks and eventually backfires out the carb. I am seriously doubting this is a timing issue after checking the distributor and firing order over and over again.

I am not very comfortable with how the intake manifold is seated, I spoke to Edelbrock (7516) and they suggested laying a 1/4" thick bead of RTV in place of the front and rear manifold gaskets. I am questioning if their is a vacuum leak; and would this cause the motor to backfire out the carb?
Next, my carb is not brand new. I had it on another motor for a few days and when I took it off it sat in it's box on my shelf for a few years (its a 4160 but its part # 0-80457S).
Only other thing I am reusing is a HEI distributor I had laying around that worked when it was last used a few years ago...


Open to any suggestions/tips/help!

 

I was going to say timing before I read the post. If the carb sat for a few years, is it a Q-Jet, then it may need a rebuild. Gaskets do dry out. Is the HEI dizzy correct to the car?

 

It's a Holley 4160 style carb but apparently it's a newer design. All I can tell without taking it apart is that it isn't leaking fuel anywhere.

I believe it's a stock HEI distributor with a new cap and rotor. The module was removed because I have a MSD box (that has been sitting for a few years too).


I have seriously checked my timing so many times. I've never goofed on this in the past and I doubt after half a dozen attempts that it's wrong still.
Any chance of a vacuum leak doing this? I really want to reset the manifold but don't want to waste my time if it's not a potential solution.

 

Distributor 180 out?

 

Defiantly not unless I've only gotten lucky in the past. When my timing mark is at 0 degrees both valves on the #1 cylinder are uncompressed and the moment I turn the motor over anymore the valve starts to open. I have physically checked to see that the piston is at TDC as well.

My only experience with the distributor being 180 degrees out is hearing a sound that resembles a plunger being pulled off a tile floor.

 

Cam installed wrong?

 

Had a similar issue checked it all a million time and sure enough wires 2 and 4 were reversed. Try a good known carb that will eliminate you wasting $ there.
Sounds like ignition

have a full 12 volts to teh hei?

 

This doesn't really mean you are TDC on #1. As if you look at #6 both valves should be uncompressed as well (and is probably at TDC). I would spin the motor over by hand and watch for the #1 intake valve to open and close. Once it closes and you bring the mark to 0 it should be TDC on #1. The fact you say the valves start to open as soon as you spin past zero tells me it isn't right (you are in the transition between exhaust and intake stroke, AKA 180 out). It should take almost half a turn for the exhaust valve to start to open after TDC #1.

 

That is exactly what I was thinking. Also even with the distributor in right the base timing could be far enough out to cause it to backfire up through the carb.

 

+1. Intake should close and then the compression stroke should start. When you rock the motor back and forth when #1 is TDC neither valve should move.
It may not be 180 out but it is definitely off.

 

You guys were right. Fired right up on the engine stand after I cleaned the carb, cleaned the distributor and resat it starting at TDC. Did something right cause it fired up...
Thanks everyone for the input.

 

Good to hear a success story.