Why did ford change the firing order for H.O. and 351 W motors?

[Max Power]

Wasn't my theory, just a theory.

If the 351 firing order was kinder to bearing loading, why does the 351 have larger mains and why did it take them 25 years into windsor production to figure it out?

Not discounting the theory, but that seems inconsistent.

 

[Route666]

Perhaps they were worried about bearing speed, and didn't want to make them bigger until a suitable material came along?

 

[sportsroof69]

I found an article on the web that talked about changing the f/o on a V8 and how many different f/o's there were. I think they found 8 different orders without changing the crank. Some made the engine smoother and some resulted in more power. I'll google it up and see if I can find it.

From Crane cams:
Chevrolet has traditionally designed engines with a cylinder firing order of 1-8-4-3-6-5-7-2. While this firing order is determined by the crankshaft layout, it is hardly set in stone. Each cylinder has a "companion" in the firing order. This "companion" cylinder will hit TDC at the same time as its counterpart, one on the power stroke and the other on the exhaust stroke. These cylinders (1 & 6, 2 & 3, 4 & 7, and 5 & 8) can be interchanged in the firing order without altering the crankshaft. Some racers believe that there are gains to be had by switching cylinders #4 and #7 (firing order 1-8-7-3-6-5-4-2). This can enhance fuel distribution, especially in open plenum type intake manifolds and add 5 - 10 horsepower.

 

[bifs66]

Unless I've made a mistake, the SBC actual firing order is exactly the same as the early 289/302 small block Ford. Since Chevy's NO. 1 cylinder is the front driver's side and they are numbered alternately across the engine; while Ford's NO. 1 is on the passenger's side and the cylinders are numbered in a row, the Chevy's 18436572 comes out EXACTLY equal to Ford's 15426378. So if Ford engineers decided that it was technically better to change to 13726548 in the later-developed 351W and 5.0s, then I would have to assume that it had some merit. However, I doubt that most of us could detect or evaluate the differences between the two versions.

 

[ratio411]

One of the Ford orders, Windsor/HO, I think, is identical to the SBC order.
Dave

Edit: Well, someone stole my thunder... Apparently it was the SBF that matches the Chevy order.
Also, a previous post says that Chevy guys change their FO for a power increase... I don't have the brain power tonight, would someone like to translate that changed FO into Ford and see if it matches the W/HO order? If so, that would be extremely interesting.

 

[D.Hearne]

Wasn't my theory, just a theory.

If the 351 firing order was kinder to bearing loading, why does the 351 have larger mains and why did it take them 25 years into windsor production to figure it out?

Not discounting the theory, but that seems inconsistent.

It didn't take them 25 years to figure it out, the 351W has had the different firing order all along. Clevelands did also. I once went into the Motor Repair manual on a slow day, and looking at all the different firing orders for American V8's, I sat down and compared them all. Bottom line if I remember correctly was that there is only two different firing orders used for V8's in the years covered by that book ( 64-70) Cylinders are numbered differently, but the basic firing orders were either one of two

 

[Max Power]

Took em 25 years to figure it out on the 302.

 

[bifs66]

Since Ford determined that the firing order should be modified in 1969 with the introduction of the 351W, I doubt it took them 25 years to think about doing it to the 302. It just so happened that with the introduction of the updated, roller-cammed 5.0 block, it became a convenient opportunity to change the firing order at that time as so many other components were changed also (block casting, crankshaft (50 oz imbalance), valve train, pulley/water pump arrangement, etc. They even changed the "name" of the engine...5.0/HOs.

 

[D.Hearne]

Since Ford determined that the firing order should be modified in 1969 with the introduction of the 351W, I doubt it took them 25 years to think about doing it to the 302. It just so happened that with the introduction of the updated, roller-cammed 5.0 block, it became a convenient opportunity to change the firing order at that time as so many other components were changed also (block casting, crankshaft (50 oz imbalance), valve train, pulley/water pump arrangement, etc. They even changed the "name" of the engine...5.0/HOs.

The firing order was changed before the roller cam came out. This happened in 1982 and the only reason for it was Ford's decision to use an already existing 351W marine cam in the "new" 5.0 H.O. The 5.0 designation happened in 1979, well before the H.O. motor came about. Crankshaft changes happened about 1981 or 82. The Pedestal rocker arrangement also happened well before the H.O. in 1978. Water pump and front end acessory drive setup also came about in 1979.

 

[ashford]

i thought that the change in firing order was to help a little in smoothness in the intake tract. so i wrote down on 2 pieces of paper the cylinders and numbered them as they fired. assuming a dual plane intake where 2,3,5&8 share one side of the carb and 1,4,6&7 get the other, i thought the different firing order would even out the pulls on the venturis, but both firing orders give evenly spaced pulls. the only thing different is the order in which cylinder pulls from the carb eg. 1-6-7-4 to 4-7-6-1.

the only thing i saw there that would help from a performance standpiont is that with manifolds the cylinders exhaust chase one behind the to the outlet instead of one in front of the other when 2 neighboring cylinders fire one after the other with the 351 f/o.

 

[STSFCTN67]

I had no idea that I could be running the wrong firing order this whole time.

So with my setup of a late model 351W {serpentine stlye balancer} with a E303roller cam, should I be using the 1,3,7....firing order that on my Stealth intake??

 

[D.Hearne]

Ford Racing's roller cams all use the 351W firing order. 1-3-7-2-6-5-4-8

 

[Max Power]

""So with my setup of a late model 351W {serpentine stlye balancer} with a E303roller cam, should I be using the 1,3,7....firing order that on my Stealth intake??""

You have to run whatever firing order your cam dictates.