gameshooter

I have recently rebuilt a 302HO for my truck. I bored it 40 over and put a 270 Comp cam , roller lifters, new crank, reworked the heads and put everything else new on it. Now i can`t seem to get the timing right. Have i done something wrong or what? when I dailed the #1 piston to tdc the timing chain and gears feel right into place with no problems. Now all I can get it to do is back fire. Can anyone tell me what I`m doing wrong?
Thanks Mike

 

jwko

Sounds like you could be 180 degrees off.

__________________

847alexc

Here's a thought, though it would help to know the year other info:

I am presuming you have a 5.0L EFI motor for this...

The original truck motors had a different firing order than the 5.0L HO motors that came in the GT mustangs and such. The reason for this was that the batch fire fuel injection system sprayed fuel in groups (center 4 then outer 4). The firing order on the 5.0L HO and the 5.8 EFI (Windsor firing order). The different firing order is more efficient with the batch spray EFI (1986 1/2 - 1994[?])

When I had ordered a cam for my 5.0L Bronco I noticed the difference and called edelbrock about it and thats what they told me.

Of course that different firing order means different cam lobe positions. Though if you have already installed the cam, all you have to do is change the spark plug wires around. Check the documents with the cam or call the company to see if that is the case.

thefonz

# 1 piston needs to be on compression stroke when you set it or you will be off 180 degrees as suggested. Confirm firing order as suggested.

gameshooter

Thanks for the info. I finally got it to crank but something doesn`t seem right. I`ve got a miss in it somewhere. A friend came over and within 15 mins. he had it running and told me that i had a vaccum leak. Thats why i haven`t been back on the forum. I`ve been looking for that leak. I`d like to replace all the vac line but i don`t know where to buy them or if i can buy them. thanks again for the info, Mike

jwko

Any auto parts store will carry vacuum hose.

__________________

847alexc

Mike,

As per your email, here's the info on the firing order. As I think back to my conversation with the cam company, the change to the 5.0 HO and 5.8 windsor firing order may have started in about '88 or '89. In any case I do believe that If you wired the spark plugs like the 5.0L truck's sticker says that there will be firing problems. Just remember, since it is batch fire the motor can still run... albeit very poorly. I really think this could be the problem. And when its right, you will love the way that truck runs!

Good luck!

Cylinder Numbering...as you are facing in towards the windshield (passenger side will be on your left and driver's side will be on your right)

Windshield

4 8
3 7
2 6
1 5

Grill


FIRING ORDER FOR 5.0L & 7.5L

MOVING COUNTER CLOCKWISE...

1 5 4 2 6 3 7 8


FIRING ORDER FOR 5.0L HO and 5.8L

1 3 7 2 6 5 4 8

MOVING COUNTER CLOCKWISE