I just purchased a 70 F100. The previous owner said it has a 351 W in it. The Engine was dressed as a 351 W, but it has a 302 firing order. I attempted to put HEI ignition in it and got a 302 distributor. It did not fit, the oil pump drive on the new distributor was 1/4". The old distributor oil pump drive is 5/16. I am getting the distributor for a 351W. Just for fun, I set this up with the 351W firing order, and it would not run, put it back, and it fires right up. What besides having the wrong cam in this will cause the firing order to be wrong for this engine?

 

The first thing is to identify what engine do you have?

This is one of the primary visual clues to look at to determine which one it is. Notice the distributor hole in location to the intake rail at the top of the block.



289/early 302s and non-H.O 5.0L engines have a firing order of 1-5-4-2-6-3-7-8. All 351Ws and H.O. 5.0L engines have a firing order of 1-3-7-2-6-5-4-8.

 

Is the intake gasket edge about even with the distributor bolt pad, or is it about 1" taller? That will tell you if it's actually a 302 or 351w.
It is possible to put a 302 cam in, though.

On edit- Fact checking takes too long.

 

Well as you can see must only be oil pump drive not turning the rotor.
Orich

 

Another visual clue is to count the number of valve cover bolts. If there are (6 ) in each valve cover, it's a 302 or 351W.

If there are (8) valve cover bolts, it's could be a 351C/351M/400.

The water thermostat housing is on the right, forward end of the intake on a 302/351W. On a 351C/351M/400, it sticks straight up out of the forward end of the engine block.

 

351W oil pump drive is 5/16". 302 is 1/4". Distributors are not interchangeable. The cam sets the firing order. They are interchangeable, for the most part.

 

351W and 302 share the same basic valve covers, heads, timing cover, water pumps, and exhaust manifolds. Intakes and oil pans are different. The "dress" is the same, unless you mean there's a sticker.

 

It seems everything but the firing order says this is a 351W. I really don't want to change the cam anytime soon. Thanks for the clarification!

 

Did you check the block height in relation to the Dizzy hole as noted above? You either have a standard 302 cam in a 351W or a 351W oil pump and driveshaft in a 302.

 

I rebuilt a 302 for a fellow employee one time, He bought all the parts. Got it together and it would not start, only backfire every once in a while. I messed with for several hours. I was almost ready to pull front end apart and check timing chain, Had never put one on wrong before, but there is always a first time. Then I remembered him saying something about putting a 351 cam in it. Changed the timing and bingo. fired right up.
Someone might have put a 302 cam in it they had already purchased or something.