Need some help with timing issue 90 Jimmy

[phrogs]

Ok quick backstory this is a 90 Jimmy 5.7

I blew the motor, so I pulled it had not ignition issues before I yanked it.

I have rebuilt the motor New guts all through out, 30 over pistons and that's the biggest difference, The camshaft I put in is a stock one nothing special.

This is not my first rodeo with a 350 but I am stumped. I have never had a issue like this..

I know I am at TDC on the #1 I have triple checked it.
Wires are on the cap correctly checked it over.
plugs are set at .35
Dizzy is set up on #1 and the timing mark is on zero at the balancer.

Brown and white wire by the brake booster is unplugged.

Tried to get it going and the only thing I can get is a backfire through the exhaust no matter how much I try to adjust the dizzy same thing or nothing it just cranks and cranks.

I have fuel and spark. I am going to double check my compression just to be sure, but I set up the piston rings as per the GM engine book.


Parts I had when it was running.
Accel dizzy cap, rotor, wires and plugs.

I had a spare distributor so I went to napa and bought a new Reman one that came with a new ignition module.
Changed the dizzy cap and rotor to the Napa ones.

Still doing the same thing.

So I have a friend on the way to help me figure this out but is there something I am missing with these trucks when you do the timing?

any help is appreciated.


Next it check compression, change out the wires to the AC delco ones I have and maybe get new plugs.

Need some suggestions on what plugs to get this thing going

thanks

 

[375 H&H]

there are two top dead centers of the four stroke cycle. the compression stroke and the end of the exhaust/beginning of the intake stroke.

are you sure you have it set on the compression TDC? if not, set to TDC, pull the distributer, turn the crankshaft one revolution, and re-install the distributer and give it a whirl.

 

[phrogs]

Yep I know and I even tried flipping the dizzy just for grins and no working

 

[y5mgisi]

Backfiring out the carb is a sign that the timing is off, valves are too tight, or the timing chain was installed wrong.

 

[phrogs]

It's Not backfiring through the intake.

 

[y5mgisi]

Ah yes. I clearly miss read that. And your certain you got the dots on the timing gears lined up correctly?

 

[phrogs]

Yeah I figured it out, I had done the valve lash on the engine stand and had no compression. I backed off the valves and it fired right up. Ugh I fell dumb after that but it's always something simple.