Quote Originally Posted by Hombre259 View Post
A couple of years ago I was building a Pontiac powered 4x4 1953 Ford truck. I had spent a ton and a half of money on that HO 421 and finally the day came to fire her off. She spit and puked a couple of times backfired through the carb but no go. I went back to my Motor Manual for the Pontiac. I had ther cylinder numbering sequence right, I had the firing order right 18436572 same as most Gm's. I pulled and checked the distributer and everything was good to go. Still spit, puke, backfire, I go back to the book and pull the dizzy redo everything 18436572 sequence is correct turn the key-- spit, puke, backfire. Man what could be wrong????? Back to the book FIRING ORDER Pontiac 421 HO 18436572-- Check, Cylinder # Sequence Check. Turn motor over #1 cylinder in correct location, turn the key SPIT, PUKE. BACKFIRE....
Pull the intake, pull the timing cover, reset the valves, check timing marks for timing chain, Everything and I mean everything is as its supposed to be. I redo everything for the 6th time, before I turn the key I go and recheck the BOOK.. Firing Order 18436572, Cylinder # sequence, Man what is this in the third column?? Engine rotation Pontiac all V8's "CCW", Can it be that simple? Or maybe the question should be --Can I be that stupid?

Rewire the dizzy--- 18436572 this time CCW-- Turn the key, Varoooom I had me a gen-u-wine fire breathing monster on my hands. I felt real silly for doing that 6 times before I finally got out of my own way.

Morale to that story is check everything and ASSUME nothing..

Roland

LOL, Yup sometimes we just "over think" it!

I'd bet that every person on here has a story of one of their screw ups. Every time one of my service techs has a problem I tell them go back to the basics, start from the begining and when you find the problem its going to be something simple and/or stupid that was wrong.

My last "dumb one" was on a small block Chevy engine that I had out of my roadster for a year while the car was painted. It's got some nice Moon "no name ribbed" valve covers that I polished up before I put the engine back into the car. Well.......I had the same backfire problems as stated above. Checked TDC, #1 plug wire location, firing order, checked my new MSD distributor, etc. Well I hate to admit it but what it turned out to be was I installed the "valve covers backwards" and they lightly rubbed the valve retainers preventing the valves from completely seating at cranking speed. The covers have a taper "more on one side than the other" and without any lettering it was easy to invert them and it will not work.

A quick compression check would have saved me some time.