Firing Order Change

13793 Views 22 Replies 11 Participants Last post by DaveMcLain, Aug 24, 2010

Jon Campbell

Discussion Starter · Jul 25, 2010

Hi all,

I've been doing some reading and I'd like to get some good advice on what to do

. I have a '95 F-150 with the 5.0 Truck firing order (15426378)

(I know this is a BBF forum but you guys mean business and you really know your Ford engines) and I've been told that the 5.0 HO firing order (13726548) is worth some horsepower. I also heard that it is better for engine longevity (but the explanation for this wasn't totally convincing). Any thoughts or theory about this would be really appreciated?

I realize I'd have to change to a cam that is made for the HO firing order. Does the HO firing order have anything to do with exhaust gas pulses (similar to the reason Ford did the crazy "bundle of snakes" headers for their GT40 in the 60's)? Would keeping my stock type single pipe exhaust setup negate any gains to be had from changing the firing order (the only difference in my exhaust setup is a 3" in/out Hushpower Pro muffler and 3" piping? Even if there's only a small improvement I'd be interested in trying out the switch.

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rmcomprandy

· #2 · Jul 25, 2010

Jon Campbell said:
Hi all,

I've been doing some reading and I'd like to get some good advice on what to do. I have a '95 F-150 with the 5.0 Truck firing order (15426378) (I know this is a BBF forum but you guys mean business and you really know your Ford engines) and I've been told that the 5.0 HO firing order (13726548) is worth some horsepower. I also heard that it is better for engine longevity (but the explanation for this wasn't totally convincing). Any thoughts or theory about this would be really appreciated?

I realize I'd have to change to a cam that is made for the HO firing order. Does the HO firing order have anything to do with exhaust gas pulses (similar to the reason Ford did the crazy "bundle of snakes" headers for their GT40 in the 60's)? Would keeping my stock type single pipe exhaust setup negate any gains to be had from changing the firing order (the only difference in my exhaust setup is a 3" in/out Hushpower Pro muffler and 3" piping? Even if there's only a small improvement I'd be interested in trying out the switch.

It may be worth a bit of longevity and slightly increase power with some intake systems yet maybe not; until you test it. However, it for sure will be EXPENSIVE with a Ford Big Block.

crittersf1

· #3 · Jul 25, 2010

Jon, according to Chiltons, Haynes, Shop Key and the ones that I've worked on, the '95 F150's already have the HO firing order. Ive seen a couple BBF's with the 13726548 firing order, didn't seem to make much difference in power.

dixiebandit69

· #4 · Jul 26, 2010

Everything I have read about switching firing orders (look into the Chevy "4/7" firing order swap, because the BBFs and all old-school Chevy/Chrysler/Buick/Olds/Pontiac engines fire their cylinders in the same sequence, they are just numbered differently. Check it out.) for a long time.
What the change in firing order does is it keeps cylinders 7&8 on a Ford (5&7 on a Chevy, etc.) from firing in sequence, and keeps the back of the driver's cylinder head cooler and less likely to detonate because two cylinders arent firing one after the other.
It moves the combustion cycles to the front passenger side of the engine, where there is more cooling capacity. Doing that could allow you to run a more agressive timing curve; you wouldn't have to "crutch" the timing of the engine with retarded timing.
I have also heard that there are benefits in the form of more even loading of the crankshaft (There was a reason why Chevrolet departed from the old firing order when they made the LS series engines.)

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Curt

· #5 · Jul 26, 2010

My new 598 will fire 15486372, same as the old Flathead.

fox501

· #6 · Jul 26, 2010

my 95 150 I had with the 5.0 had the HO firing order i beleave in 94-95 ford started putting the HO in there trucks

Jon Campbell

Discussion Starter · #7 · Jul 26, 2010

Thanks guys,

I guess I lucked out when I found my '95. Good thoughts on the cooling improvements that the 5.0 HO firing order gives (makes sense to me after looking at the way the cylinders fire).

turbo2256b

· #8 · Jul 26, 2010

The firing order was changed from the 302 to the 351W firing order on higher out put 302s for structural reasons. Ford removed a lot of strength from the main web area. About 10 lbs of iron. Wall thickness was reduced in the cylinder walls also but later some was added back to the cylinders because cylinder walls were warping during manufacturing.
The weight reductions of the block were implemented as a cost save and a weight save. Cost save being the real goal.

Back to the firing order change. With the old firing order #1 and #5 cylinders fired consecutivly. Being on the same throw of the crank and the same bulkhead caused a huge load on the #1 main. The #1 main is one of the weaker ones in the block. Using the 351W firing order changed the load to the 4th main which is much stronger (4 and 8 firing consectutively).
This allowed the engine to be increased in power without spending mony on puting iron content back in the block as well as the big expence of changing all the coring of the casting equipment.

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rmcomprandy

· #9 · Jul 26, 2010

WoW, production 460's with the H.O. firing order ... I'd have to see that engine to believe it 'cause FORD never manufactured one.

Jon Campbell

Discussion Starter · #10 · Aug 22, 2010

5.0 H.O. in my Truck

Just to clear something up. I've got a 5.0 L in my '95 F-150. Any advice on making a set of headers for it (I'd really like to try a "bundle of snakes" setup or else do a properly balanced long tube single exhaust or do a tri-y single exhaust. What would your thoughts be on the feasability of each. My main goal is power first, sound second, cost third.

DaveMcLain

· #11 · Aug 22, 2010

The Flathead firing order is interesting too but did you know that on the Flathead Ford while the cylinders are numbered the same as any Ford with number one in the front on the right side of the engine. BUT, number one is NOT the front cylinder of the engine! It's actually number 5 that's the one in the front isn't that weird?

Pontiac engines do something similar whereby number one is the front cylinder on the left yet the right bank is in front of the left bank.

crittersf1

· #12 · Aug 22, 2010

DaveMcLain said:
The Flathead firing order is interesting too but did you know that on the Flathead Ford while the cylinders are numbered the same as any Ford with number one in the front on the right side of the engine. BUT, number one is NOT the front cylinder of the engine! It's actually number 5 that's the one in the front isn't that weird?

Pontiac engines do something similar whereby number one is the front cylinder on the left yet the right bank is in front of the left bank.

Well, International V-8's were timed off of the number 8 cylinder.

crittersf1

· #13 · Aug 22, 2010

rmcomprandy said:
WoW, production 460's with the H.O. firing order ... I'd have to see that engine to believe it 'cause FORD never manufactured one.

Never said that FORD made it, have seen some with cams ground that way in a couple of different mud trucks. None of them would tell me who the cam grinder was.

ITSA 91

· #14 · Aug 22, 2010

As I recall the bundle of snakes was designed primarily to keep the exhaust system inside the body lined of the Indy cars.Buy some flanges and some u-bends and build what you think will work.

fireballferkey

· #15 · Aug 22, 2010

crittersf1 said:
Never said that FORD made it, have seen some with cams ground that way in a couple of different mud trucks. None of them would tell me who the cam grinder was.

wouldnt the crank have to be cut diff to? I asked a ford Tech about this once (frpp hot line) cause Im using a 5.0 efi harness on my build and Im allmost 100 percent possitive he said the crank would have to be cut diff to doesnt make sence to me though. I may end up having a new cam cut with the 5.0 H.O. firing order as comp cams can do this with no problems just call them and tell them what ya want...

DaveMcLain

· #16 · Aug 22, 2010

The crank configuration does not change. In a V8 there are always two pistons at TDC at the same time so either of those cylinders could be the one being fired with the other, it's running mate, on overlap. V8 cams have been ground that fire two cylinders at once, flat cranks have been used, all sorts of stuff that doesn't make much of a difference in the positive direction.

International V8's were timed differently but the cylinders were numbered and arranged conventionally.

G-Code

· #17 · Aug 23, 2010

Firing order diagram. I believe Kaase is on record as saying there no power difference but his mountain motor cranks with the old flat head firing order last much longer at high rpm with the firing change.

G-

Jon

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G-Code

· #18 · Aug 23, 2010

DaveMcLain said:
The crank configuration does not change. In a V8 there are always two pistons at TDC at the same time so either of those cylinders could be the one being fired with the other, it's running mate, on overlap. V8 cams have been ground that fire two cylinders at once, flat cranks have been used, all sorts of stuff that doesn't make much of a difference in the positive direction.

International V8's were timed differently but the cylinders were numbered and arranged conventionally.

I was told by some smart guy some time ago that there are 8 possible running orders on a 90* V-8 there are only 3 that won't beat the engine to death.

I wonder what firing order Keith Black Nitro engines run.

G-

fireballferkey

· #19 · Aug 23, 2010

DaveMcLain said:
The crank configuration does not change. In a V8 there are always two pistons at TDC at the same time so either of those cylinders could be the one being fired with the other, it's running mate, on overlap. V8 cams have been ground that fire two cylinders at once, flat cranks have been used, all sorts of stuff that doesn't make much of a difference in the positive direction.

So your saying I can run a stock 460 crank and have a custom cam cut with a late model (1989-1993) 5.0 H.O. cam firing order 1-3-7-2-6-5-4-8 and have no problems with it runing? If so Im very happy to hear this as with running sequential firing injectors on a efi set up this will help with my idle issues and make tuning ALOT easier. IF any one out there knows for sure please chime in...

DaveMcLain

· #20 · Aug 23, 2010

I can't see that it would cause ANY problem at all. But the cam core and grinding will be costly. I think it would be a lot easier and less expensive to just rewire the harness and change the firing order of the injectors.

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