backfire problems 302

[sully5]

Not a carb problem from what I see. *Maybe* an ignition problem, I would look for severe timing issues or out of firing order. Most likely a valve train problem.

If it was me, first thing I would look for is a flat cam lobe or a valve hung open by improper lash/preload.

[thcrays]

Just a couple of more things to check without having to throw money at it in parts. Check the mechanical advance in the distributor. It is pretty simple to do. Just pop the distributor cap off and turn the rotor with your fingers, It should rotate or advance and snap back to the starting location without much effort. I have seen these get frozen or stick at times. You can also test the vacuum advance as well and see if it is working properly.

I know that it sounds pretty basic, but sometimes it is the simpliest things that kick our butts.

[R Pope]

Well. at least nobody's telling you that the cam is half a turn out! Haha.

[Anthony]

we were on the right track... sort of.... I guess we kept fighting ourselves.... we were 180 out on the dizzy and the motor does "NOT" have the high output cam so we had plug wires wrong... ... anyway, his car is up and running and sounds great!!!! as soon as he finishes cleaning up the mess from this his Mom will let him bring the uni to the top of the hill..... Also, I don't think the motor he got for the uni is a Cleveland, but a modified... is it worth the $300 or should he wait on something else???

Thanks for all the input and the help guys... I am not a mechanic and I was lost on this....

[62galxe]

If its a C the deck should be right at the timing cover. The M should be elevated about 1 inch. The C will have small block 351W/302 motor mount bosses on the sides. The C use a small block bell housing pattern. The M uses big block bellhousing 429/460 pattern. I think I have this right but im having problems with CRS.

[banjopicker66]

Excellent! Great detective work, too.

I have always understood that the external difference between the 351C and the 351M/400 is the bellhousing. The 351C has the Windsor bellhousing, as fits the 289, 302, 351W - and 300-6. The 351M/400 have the same bellhousing as the 385 engines, the 429 and 460.

Internally, the 351M and 400 are stronger.

http://en.wikipedia.org/wiki/Ford_351_M

"The main difference between 351C/351M/400 engines is connecting rod length and main bearing size. The 351M/400 engines have the largest bearing size and the tallest deck height while sharing the 429/460 bell housing pattern. The 351C engine has a medium main bearing size (2.75") and shorter connecting rods (5.78") than the 351W (5.94") and the 351M/400 (6.58") while retaining the SBF (289-302w) engine mount locations and bell housing pattern. "

[R Pope]

Y'see, there's the problem with diagnosing over the Net! You say it idles well with a slight miss, but the wrong firing order, 180 degrees out or not, will run on four cylinders and pop back on speed-up. Changing the wires 180 degrees while keeping the wrong firing order will still run on 4, just the other four!
I would think there's a big diff between a "slight miss" and running on 4.
Oh, well, it's running now, anyway. Now get to work on that Slick!
Oh, and by the way, the 351M and 400 are Ford's biggest dogs! Find a 351W. The C is a good engine in a light car, but too "peaky" for a truck, and horribly expensive to build.

[Anthony's Son]

kool then, the mustang runs great.. It will sink you in the seat every time you grab a gear... can't wait for the slick to do the same!!.. I'm going to get a C6 to go behind the 351m for and extra 75$.. so i feel I'm doing pretty good.. hopefully have it running by SS.. probably trailered but running
but you know how money goes with a teenager...