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The two different firing orders questions
1) Is there any differance in performance, all else kept the same?
2) Any differance in the sound of the engine? 3) Why did Ford change the firing order? Did they ever say why they did this? |
Fi
Hi,
1-no 2-yes 3-It was done for emissions,maybe less nox,who knows? Perry.:MECOOL: |
If I remember correctly the firing order of the 351W was set differently than the other members of that engine family (260,289,302, and it seems there was one smaller 221?) to reduce fatigue on the crankshaft in the 351 application. The 351 firing order was standardized for both Windsor engines with the advent of the 5.0 HO. Regardless of what might be said I would imagine the bottom line of the standardization of the pattern was the bottom line, i.e. only one cam blank for both engines. Funny thing is the 5.0 has a propensity of breaking cranks and splitting the block down the middle even at stock or near stock hp levels.
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Thanks guys.
At first I thought there could be know differance in performance. Then I thought it could change the exhaust scavenging (SP?) and even smooth out flow in the intake. So then I thought it was possible that it could impact performance, so I had to ask. I sure would like to hear both engines side by side, just out of curiosity. I'll have to pay attention at some car shows. Is that factory cast iron cranks that tend to break? I wouldn't think anyone would stroke and build more Hp with the smaller mains of the 5.0 block if the larger mains 351 block already soves the problem. If the cranks are a known problem, I will rule a 5.0 completely out right now. However if steel cranks are OK then I may keep it on my maybe list. |
There are no problems with the stock 5.0 crank or block up to 400 fwhp. the only time you run into problems is with power adders and poor tune. the standard 5.0 rotating assembly from 86 thru 92 is very durable. I have a stock 86 motor in my mustang that has 300000 mile on it. I seen motors sprayed at 150hp level on a conservative tune last for several years. You can break the block with boost or spray but I would think that you would be hard pressed to destroy one naturally aspirated.
later dennis |
In the late 70's, Ford engineering basically went down the tubes.
We ended up with the modular engines, bigger dimensionally, severely limited internally. The engineering plan was apparently to design and build a motor bigger than the biggest big-block Ford made, to install in vehicles (someone, I hope) they forecast were going to get smaller due to the gas shortages. The 'plan' was to take up a larger percentage of the available volume in these smaller vehicles? These same engineers, when faced with developing the H.O. 302, which didn't roll over and die for the modulars, were looking for more HP. So, they pulled a existing cam out of a 351W performance catalog and used it in the 302. More power from that cam; cheap 'development' costs. That's all the reason for the change in the 302's firing order. As for the 351's firing order? Petty change for pettiness sake? Just to make it different from GM's firing order? Maybe to take some load off of the front main bearings which in the old firing order were hit bang bang in sequence while the new order gives them a little rest between hits? Anything Ford has done since 1970 has not impressed me. |
As has already been posted, it was indeed main bearing loading that Ford was re-distributing. I would have to look at the early order, but think it had to do with not having 2 firing pulses (one after another) on the same main. The other comment about the early H.O. cam is also correct, the original cam used in tests was a 351 marine cam. That neccesitated the 302 change, although the initial change made in the new (at the time) 351W was main loading.
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Funny thing is, I had been told a long time ago that the reason for the change in firing order was because the old firing order had a tendency to crossfire between the two cylinders that were adjacent. The main bearing load explanation seems to make more sense.
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And you think people argue about BB vs SB! This is the main point of contention 5.0 vs 5.7. Unless you have tot use an 8.2 deck height Windsor due to smog or class restrictions you are always better off to start off with a 9.2 or 9.5 deck block. The 5.0 has several limitations that can creep up even at stock levels http://forums.corner-carvers.com/showthread.php?t=27451 they break blocks, break cranks, and the deck moves because it is too thin so they blow head gaskets. I have a 93 Cobra with 105k, I put all but 10k on it, that has never had a wrench on it and still has the traction limited feature. It still has the original clutch and transmission untouched it is also no it's 6th set of tires. I also have an 88 LX that I bought 11 years ago for $1300 because the kid broke the stock crank in the stock motor into 3 pieces.
When the Cobra engine wears out it will be removed and wrapped up and a 351 will take its place. The Lotus 7 that I'm building will have a 96 roller 351 in it. Lots more could be written but those that are convinced will not have their minds changed. One of the primary concerns brought up is that the Windsor weighs 50 lbs more, so that is because there is more metal where it needs to be, in many cases by people who have bolted a blower on a 302 so it will make about the same power a NA 392 will. |
I agree with you hsss that a 5.7 is stronger than a 5.0. I do not agree that a that a 5.0 is going to break the crank at stock to moderate hp 400 fwhp. Most of the crank failures are on very high mileage vehicles that where going to break anyway. I've seen several late model 5.7 split a block also. Best bet if your making power adder hp is to buy an aftermaket block or if you cant afford that find a 69 thru 72 351 windsor. Just my opinion. Sorry I hijacked this dudes thead I'll shut up.
later dennis |
No, I think that is the kind of info he is looking for. The LX in my garage that broke the crank has less than 80k on it with no power adder but the kid had southsides on it. I think the breakage has more to do with useage than hp. To me the bottom line is if you have no investment in a block start with a 351, no replacement for displacement, if you are going to run it hard get a 3.85 forged crank. If you are going to expect NASCAR performance find a Cup engine.
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I have a book "how to build max performance ford v-8s on a budget" written by George Reid. In about 3 different places he states the duration is a measurement of camshaft rotation, which is dead wrong, it is crankshaft rotation. There are other examples that I will not go into, but I am quite certain that this book is far from being a great book. He said that 1975 to 1984 castings were poor quality for both 5.0 and 351. Cracking is one issue. He also states that the Mexican blocks have wider mains and much more nickle in the iron. He claims they are a better block.
Any of you hear any of this before? |
Some of what he says is true, although possibly written incorrectly. I think the metal content of Mexican blocks is probably debatable. The mains however are thicker( not wider) in the caps themselves.They aren't any thicker than 289HiPo mains, which they are obviously modeled after. For the amount of extra insurance that little bit gives I wouldn't spend any $$$ premioum for one. For real power an aftermarket 4 bolt block is the only way to go. If you don't plan on more than a 450Hp small block (that's what Ford rated their last Trans Am 289) a mexican block would be a good builder, if you want more then put the change you'd have to pay for the mexican block on something that is designed to take it. When the word began circulating years ago about Mexican blocks they could be purchsed for about the same as a regular one, now everyone that has one seems to think they are highly prized and the prices reflect it.
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You know the drifted subject of 5.0 blocks splitting has really been bugging me.
I read through the link that hssss put in his post. A lot of information and good pictures of cracked blocks. This is the first I have heard of this, but I haven't been hanging around people who are running engines hard at higher rpm ranges. The thought that crossed my mind was pre-detonation. If the tuning is off or the compression too high for the octane ran, ect. ect., this can kill an engine is seconds. Shelby and Ford were getting 450 hp out of the 289 back in the early days of the AC Cobra, by some accounts anyways. So this leads me back to: were the blocks of the 60's superier to the 70's and 80's? What about the 90's? On one hand, the block is definately thin, but on the other hand, people have been supercharging the 5.0 up to 500 even 600 hp. Least ways that's what the magazines print. I would think that 300 hp failures would mean that 500 hp wouldn't last a week. Yet you can buy 400+ hp crate engines. %/ I am confused (talking myself in circles). ::confused: Can anyone clear some of this up for me? |
Olddog
You have a point a poor tune can kill any engine. HSSS makes some good points but I've never had any problem with any 302 that I've had but they all have been performance rebuilds except for one stock one. The guy that built two of my motors has built several strokers based on late model blocks and most of them are nitrous adder motors with no problems. Everything will break eventually at the drag strip or race track for that matter. Thats the price of speed. later dennis |
Firing order
Hi I have the firing order for 351 windsor. The only problem is there is they show where one is on the distributor. And a different pictures one is a different spot on the distributor.any help would be good thanks.
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We were told it was done to avoid crossover from having 7 and 8 fire consecutively....and replace it with 6 and 5 firing consecutively.
I've never found a difference in performance. I seem to have the 1, 5, 4, 2, 6, 3, 7, 8 burned into my brain alongside my service number (old vets will get that, younger vets never had one)... but I've never managed to memorize the 351 version. |
Brodie, the distributer isn't in the exact perfect position. Doesn't affect performance. Just makes it a PITA to make spark plug wires look pretty.
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