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Old 01-01-2008, 07:52 AM
Farmer Buck
 
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Why does a HO Came change the firing order??

In another thread, Scottford 351 talks about HO cams changing the firing order in an engine.-----Can some one help me to understand this a bit more? - Why does going to a HO cam cause a change in firing order? -Is this just in Ford engines (that was the discussion) or all engines? And what would you do then about the timing of the injection? Need to change computers to change the injection sequence also? ---In changing the firing order, would you then just re-order how the wires are plugged into the distributor?

(This is really interesting. It intrigues me.)

Thanks

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Old 01-01-2008, 08:11 AM
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The camshaft is ground differently,IIRC the 5.0HO uses the 351W firing order.From what I have read the computer does not need to be reprogrammed to convert a 5.0 to a 5.0HO The plug wires,and maybe injector wires,have to be changed along with the camshaft.The HO upper intake (If I can find a pic of the one that I bought because my friend (Who decided to get a new DODGE to replace his f-150) who I was helping look for one{never buy parts for people with out cash in hand,you'll get stuck with them }) is also different with a bigger throttle body for increased performance.This may also be helpful to you http://www.boxwrench.net/specs_index.htm

Hope this helps
Shane

Last edited by Chevrolet4x4s; 01-01-2008 at 08:28 AM.
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Old 01-01-2008, 08:44 AM
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Found them.
Shane
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Old 01-01-2008, 10:50 AM
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Quote:
Originally Posted by Lloyd1wv

In another thread, Scottford 351 talks about HO cams changing the firing order in an engine.-----Can some one help me to understand this a bit more? -

Why does going to a HO cam cause a change in firing order? -Is this just in Ford engines (that was the discussion) or all engines?

And what would you do then about the timing of the injection?

Need to change computers to change the injection sequence also? ---In changing the firing order, would you then just re-order how the wires are plugged into the distributor?

(This is really interesting. It intrigues me.)

Thanks
TECH NOTE;

Quote:
351W Firing Order (From A Mustang Monthly Article) Ford changed their small-block firing order beginning with the 351 Windsor in order to ease bearing loads. The late model 5.0 engine also shares this revised firing order. The idea was to eliminate cylinders number one and five from firing in sequence to be easier on the front of the block. The revised order helps a little, however, there are still lots of early 289 and 302s running to 7000 rpm without major bearing or block failures. The camshaft used will determine an engine’s firing order.
Quote:
Camshaft and Firing Order

The firing order is determined by the camshaft in your engine. If you change the camshaft, then this information may not be valid.

ALL 302 5.0L engines from 1982-up have the 50 oz imbalance.

There are three kinds of 302s made from 1982-2001.

• 5.0L HO This engine was used in 1983-1995 Mustangs, Mark VII Lincolns, and some T-birds and Cougars. All Explorer 5.0L engines are 5.0L HO engines as well. They use the 351W firing order, 1-3-7-2-6-5-4-8. Except for the 1983-84 Mustangs, all of these engines are roller cam equipped. They use a reverse rotation water pump and front cover. The 1994-5 Mustang and all Explorers use a unique front cover and water pump.

• 5.0L Full Size Car This engine was used in 1982-1990 Crown Victoria and Grand Marquis. They use the 289-302 firing order, 1-5-4-2-6-3-7-8. Most of these cars are not roller cam equipped, however sometime in the early 1990s they started using roller cams but retained the 302 firing order. They use a standard (clockwise) rotation water pump and front cover.

• 5.0L Truck (except Explorer) These engines are similar to the Full Size Car engines, except they use different intake manifolds and camshaft profiles. They also use the 289-302 firing order, 1-5-4-2-6-3-7-8. They also began using roller cams sometime in the early 1990s. They use a reverse rotation water pump and front cover.

You can retrofit a roller cam in any of these blocks if they are cast with the roller lifter hold-down bosses. These are two threaded bosses in the lifter valley. Most blocks after 1987 have these bosses, and 351W engines after 1995 have them.
As for injector firing order, most were batch fire and would result in a low RPM miss if lead wires were changed. As RPM's increased, injector dwell would allow enough fuel to supply all cylinders. SEFI requires an ECM change.
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Old 01-01-2008, 11:20 AM
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KULTULTZ-- Thanks! You've done a lot of reasearch. That clears up alot of things. I really appreciate your help.

---I've read so many books and articles on Ford engines, rebuilding, performance, specs, etc. It's interesting that there are so many differences in the information between the sources. A person really has to consult a lot of references and compare them before knowing what information is correct.
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Old 01-01-2008, 11:49 AM
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cam and fireing order

the change in firing order on 302s started on marine engines, with high compression and the lighter crank #1 main brg would knock esp at idel, ford at 1 time offered a front main that had less clearance. have a 302with small chamber 65 heads and 289 rods with trimed pistons for 0 deck clearance it sounds terable at 600rpm idel 675 it is ok, will inst a ho fire cam this summer.
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Old 01-01-2008, 02:08 PM
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Quote:
Originally Posted by Lloyd1wv

KULTULTZ-- Thanks! You've done a lot of reasearch. That clears up alot of things. I really appreciate your help.

---I've read so many books and articles on Ford engines, rebuilding, performance, specs, etc. It's interesting that there are so many differences in the information between the sources. A person really has to consult a lot of references and compare them before knowing what information is correct.
Also a lot of OLD WIVES TALES out there too. Take it all with a grain of salt. FORD will do anything to save a penny.
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Old 01-01-2008, 09:34 PM
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The HO firing order began with the 351Ws. Its purpose was to lessen the load on #1 main bearing (rumor)

Trying to think of how to explain it makes my head hurt! so you get a short version.

With sequential injection the harness needs to be repinned to the new firing order so the fuel timing matches the ingition/cam timing so fuel is there at the proper time.

Next problem is the computer is getting feedback from right bank and left bank O2 sensors. since the injector firing sequence is no longer the same, the Os sensor from say, the right bank no longer has exclusive control over the right bank, because it now fires some of the left bank injectors.

Tying both O2 sensors together will give the computer and average of both banks.

I'm fuel injection stupid and I only know what I've run across in my experiences. Im not real familiar with what types of injection is used on which vehicles.
Others will be a better aid than me.


edited because of late night brain fart

Last edited by scottford351; 01-02-2008 at 03:08 PM.
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Old 01-02-2008, 09:32 AM
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Quote:
Originally Posted by scottford351
The HO firing order began with the 351Ws. Its purpose was to lessen the load on #1 main bearing (rumor)

Trying to think of how to explain it makes my head hurt! so you get a short version.

With sequential injection the harness needs to be repinned to the new firing order so the fuel timing matches the ingition/cam timing so fuel is there at the proper time.

Next problem is the computer is getting feedback from right bank and left bank O2 sensors. since the injector firing sequence is no longer the same, the Os sensor from say, the right bank no longer has exclusive control over the right bank, because it now fires some of the left bank injectors.

Tying both injectors together will give the computer and average of both banks.

I'm fuel injection stupid and I only know what I've run across in my experiences. Im not real familiar with what types of injection is used on which vehicles.
Others will be a better aid than me.
H.O. firing order does lessen the load on the #1 main.

Don't understand the "tying both injectors together" thing..do you fire both injectors at the same time? Can't see how that would operate correctly.
Changing the pinout at the computer (at least on a EEC-IV unit) ani't a good idea either. You end up with one bank 25% lean/25% rich each cycle.
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Old 01-02-2008, 03:07 PM
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I meant O2 sensors. so you get a average because you cant conrtol right bank and left bank separately anymore.


I'll edit the op
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