Working on my 75 F250, newly purchased, and encountering problems. When I got the truck it hadn't been factory maintained for at least
40 years. When I say factory maintained I refer to using only OE parts and approved service methods. The truck was loaded down with
electrical fire hazards and detuned to burn regular fuel.
The truck originally had a 360 2bl in it but now has a 390 4bl. I believe one of my mechanic buddies, a real good mechanic, Sold him an upgrade
The truck only has 76,000 miles but the owner hauled a piggyback camper to Cape Hatteras twice a year and wanted more HP to keep
up on I95. Here on the East coast when folks wanted to get more performance out of an engine they usually threw away the OE air cleaner
and all the hot air induction parts. This resulted in an engine that performed very badly in cold weather.
OK, I'll get to the point. I started my quest to return this engine to it's original performance standards, by finding a Holley 4160 to replace the
Carter AFB. As with all parts bought of the net, I had breakage in shipping and missing parts so I set out to rebuild it before installation.
In my foolishness I purchased the worst carb kit ever. Not important!

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Not sure what you're doing with the "1 of 2" thing, but the firing order of the FE engine never changed. It is usually cast into the intake manifold on OEM manifolds.

As you face the engine, 1-2-3-4 are on the left side, front to back, 5-6-7-8 are on the right side front to back.

 

So, is there a question in there? Or are you missing the second half? Help us help you

 

Sorry, I got distracted before I got to the real point of the message.
In 1969 I had a friend with a Mustang that had a 351W in it. He recamed it and had some dead cylinders. I checked and his wires were
all connected in the right places. I couldn't help him, but saw him a few nights later and he'd found out that changing to that particular cam
changed the firing order to the Cleveland spec. Afterward it ran fine.

My comment and question are, Does anyone have any knowledge if that phenomena sometimes occurred on FE performance cams?

This truck was originally a 360 2Bl but was bored out to 390 4Bl so I'm pretty sure a different cam was installed at that time. The man
that owned the truck has dementia and the tech is dead so there's no one to ask. The cap and rotor look fine although not OE. I know
the dwell and the engine timing are right. Given that the only things that I know that cause backfiring through the in take are crossed
wires or wires crossfiring into each other. I have a set of decent 8mm wires on an old 460 here. Today I'm going to try them on and
see what happens.
Thanks for your reply and your patience-------Phil
.

 

Seems to me that the point of firing on the ignition cycle is determined by the position of the pistons, rather than the cam. A cam which would change the firing order of the cylinders would merely leave you with an inoperative engine. My $.02.

 

Your 2 cents are wrong. The cam does determine the firing order of the engine.

You can't just randomly space the lobes on the cam, but there are two different firing orders for small block Ford engines. One is typically called the 302 order, and there was also a 351 order. Two cylinders were swapped in the firing order. The pistons in both cylinders were at top dead center at the same time. One was at the top on the power stroke, and one at the intake stroke. Changing the cam switched the one on the power stroke to the one on the intake stroke, and vice versa.

The FE never had cams that did this.

 

Sort of, the crank of a 302 and 351w pump the pistons in the same order but there are 2 cam sequences available(firing orders). The 5.0 HO uses the 351w firing order.

regardless. OP, I would start with fresh cap, rotor and wires and double check the basic timing. Pull plugs and take a look. Fouling will cause problems.

 

Learn something new every day!

 

[QUOTE=Mark Kovalsky;19050212]Your 2 cents are wrong. The cam does determine the firing order of the engine.

Right on Mark! It is actually called the overlap stroke. Looking at the rocker arms during that period both the valves are open. The
low pressure drag across the tail pipes causes a superior scavenging process. The exhaust valve opens and the combustion
gasses blast out into the header or manifold. The low pressure effect on the tail pipes continues the cylinder's purge cycle and in
the meantime the intake valve is opening. The velocity of the gasses in the cycle draw fresh mixture into the cylinder. In a
naturally aspirated engine it'd the best you can get. Problem is, all that purging wastes fuel so economically and environmentally,
this is bad tech (these days) but sure runs good.!

You can't just randomly space the lobes on the cam, but there are two different firing orders for small block Ford engines. One is typically called the 302 order, and there was also a 351 order. Two cylinders were swapped in the firing order. The pistons in both cylinders were at top dead center at the same time. One was at the top on the power stroke, and one at the intake stroke. Changing the cam switched the one on the power stroke to the one on the intake stroke, and vice versa.

 

Remember, It's a four stroke cycle!

 

Okay, but did you try the standard FE firing order?

 

Also, FWIW with this engine: A 360 is not "bored out" to make a 390. The 360 is 4.05 x 3.50 bore and stroke, and the 390 is 4.05 x 3.78. To change to a 390, the crank and rods have to be replaced. There are mulitple piston options for the 390 as OEM, depending on year and application.

"All 360s become 390s on sale day..."

That said, when running right, either one will move the truck down the road.

Firing order as shown on OEM manifold:

https://secure.cougarpartscatalog.com/c8ae-9425-a.html

 

FWIW= From what I’ve witnessed? Sorry just trying to get it down

 

For what it's worth.

 

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What I was getting to, when cook called, was that the only two conditions I know about that could scramble the firing order and
cause backfires through the intake are cross-firing due to bad wires and incorrect wire placement. I knew from the work
I did on Friday that I had a fuel leak between the throttle plate and the venturi block so on Friday eve I pulled it off again
and retightened with a #3 Phillips.

I reinstalled it yesterday morn and retraced the plug wires again. My dist primary wire had hardened and the plug that
seals the hole where the wire goes through had shrunk tilll it no longer fit tightly. I had a neoprene stopper here and
drilled a hole through it. I then clamped a Dremel tool in my workmate with a 1/2" grinder bit and shaped a new plug. I
installed a new wire in the plug and put the terminals on and it worked out great. So I put the dist back in and reset
the dwell and the static timing and buttoned down the rotor and cap.

It started instantly and was idling on the cold idle cam. I adjusted the timing to 6 degrees before and just let it warm up.
The mixture screws have no effect on the idle so I guess I'll have to try a new power valve today. So I'm thinking the
dead cylinders were a result of the internal fuel leak, but that doesn't explain the backfiring. The truck runs pretty
strong despite the poor idle.

Thanks for the reminder about the "stroker kit". I had a friend that installed a 410 Mercury crank and rods in a 390 and it was
pretty awesome.