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How to find out what Firing order i Have??? 71 302 or 90's HO

calger

Sr. Member
Joined
Mar 5, 2006
Messages
430
Loc.
WESTERN ILLINOIS
New to this so don't beat me up to bad guys.;D
Po Built the motor, i lost the Build sheet.:mad:

I do not know what 302 is in my bronco. Short of pulling the starter, is there any way to find out if it is the 302 from 71 or 302 out of a 90's HO motor.
I just Bought a MSD 6AL, and have a MSD Pro built coming from A member on here. I have never did a Dizzy swap, and don't want to start out on a bad Foot like wrong firing order.
I can take pic's of anything you would like, just let me know. Any help would be great.
Don't want to miss my first bronco run, at the end of the month.;D
 

Socal Tom

Bronco Guru
Joined
Feb 12, 2004
Messages
2,442
Loc.
San Diego, CA
I've never done it, but I suspect that if you pulled both valve covers and watched the pushrods for the intake valves you should be able to figure it out.
Tom
 

00gyrhed

Bronco Guru
Joined
Aug 3, 2006
Messages
2,428
I assume its not running or you would just trace the spark plug wires back to the existing distributor. So everything here assumes the old distributor is out and you are starting from scratch.

Not sure why you want to pull the starter, I guess thats a misprint.

You could pull valve covers and watch the intake valves open and get the order but it will take a while.

You could also pull spark plugs and feel for compression strokes there are only two cylinders swapped, so start with the old order and then if you do not get compression in the righ place go to the HO order and see.

But I am lazy.

I would take a guess and just set it up on way or the other. Set #1 at top dead center. Wire it up and try to start it. If it doesn't run right I would then switch the two plug wires and try again.
 
OP
OP
calger

calger

Sr. Member
Joined
Mar 5, 2006
Messages
430
Loc.
WESTERN ILLINOIS
I assume its not running or you would just trace the spark plug wires back to the existing distributor. So everything here assumes the old distributor is out and you are starting from scratch.

Not sure why you want to pull the starter, I guess thats a misprint.

You could pull valve covers and watch the intake valves open and get the order but it will take a while.

You could also pull spark plugs and feel for compression strokes there are only two cylinders swapped, so start with the old order and then if you do not get compression in the righ place go to the HO order and see.

But I am lazy.

I would take a guess and just set it up on way or the other. Set #1 at top dead center. Wire it up and try to start it. If it doesn't run right I would then switch the two plug wires and try again.

Some one told me that you can get the Vin # that is behind the starter, and find out if it is a a older 302, or one from the 90's.
Yes my Dizzy is still in.
So you are saying that i can just transfer my plugs over to the new cap. It does not mater that i am going from Mallory to MSD?
Like i said i am new to this and just don't want to put my self in a corner.

If i end up doing it wrong, can it hurt the motor, like the cam or valve's?
Thanks For the help oogyhed and Socal Tom.
 

Hazegray

Sr. Member
Joined
Aug 10, 2004
Messages
795
I would personally find out what year the motor is 'cause the later "roller" motors use a different dizzy gear (bronze?). 30 minutes of work and some internet searching is better than $$ down the drain.%)

Do a search on the dizzy gears...
 

00gyrhed

Bronco Guru
Joined
Aug 3, 2006
Messages
2,428
If you have reason to suspect the PO worked on the engine, any cam could have been placed in either block. One things for sure if it the old order it is not a roller cam. Even if the otor falls into the right year range the only way to be sure is to take off the intake manifold.
 
OP
OP
calger

calger

Sr. Member
Joined
Mar 5, 2006
Messages
430
Loc.
WESTERN ILLINOIS
If you have reason to suspect the PO worked on the engine, any cam could have been placed in either block. One things for sure if it the old order it is not a roller cam. Even if the otor falls into the right year range the only way to be sure is to take off the intake manifold.

I was told that once. I guess i should do it to be sure.

When i take out the old Dizzy, would the gear at the end of it tell me any thing?
 

Broncobowsher

Total hack
Joined
Jun 4, 2002
Messages
34,821
Just because the block is new or old doesn't dictate what cam is in it. An early block could have a 351 cam swapped in (unlikely though)
Later model 302 (5.0) were only the 351 firing order if they were the HO version. Even then that doesn't mean it was a roller cam either. '82 to '84 had flat tappet marine cam with the 351 firing order. Then someone could have swapped the cam to either one as well.

So what do you have? If you still have a running engine, follow the spark plug wires back to the distributer and note there position on the cap. Couple of pointers.
1) distributer turns counterclockwise.
2) cylinders on a small block ford start with #1 at the passenger headlight and go to #4 at the passenger feet. #5 starts at the drivers headlight and ends with #8 at the drivers feet.

If you don't have the plug wire still on it, then you are going to have to investigate. Pulling valve covers is one option, but it takes a little patience to keep track of intake and exhaust valves and what is open. You could do it with only removing 1 valve cover.

Another and probably better method is to remove spark plugs #1, #3. take off the coil wire so it won't start. Crank the engine. A good ear will tell if the missing compression (from mission sparkplugs) is contionous (302 firing order) or if there is compression on a few cylinders before the second lack of compression free spin.
Still not sure, use 2 people and put a finger on plug #1 and #1 while someone else cranks over the engine. When #1 blows your finger off the hole with compression, #3 will start just as #1 is ending if it is 302 firing order.
 
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