302/351w weakness
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Elder User
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From: Campton
302/351w weakness
I can't remember where but i think i read that the 302/351w have a common weakness and i believe it said it was the connecting rods. Can anyone verify if this is true and if so if you bought a set of arp connection rods would that eliminate the weakness.
Cargo Master
Joined: Dec 2004
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From: NE Texas
It sounds like you're speaking of the rod bolts. They are pretty small, but don't pose a problem in normal service. For racing purposes, you can upgrade them, but never approach the changing of rod bolts as a simple matter. They should be changed as part of a rod rssizing operation by a competent auto machinist.
The other weakness indirectly related to the rods is the fact that the shorter stroke engines such as the 289 and 302 have a very short rod ratio that very commonly results in cracked piston skirts. Again, under normal use, this poses no problems. For racing applications, there are pistons available that alleviate this problem.
Hope this helps.
The other weakness indirectly related to the rods is the fact that the shorter stroke engines such as the 289 and 302 have a very short rod ratio that very commonly results in cracked piston skirts. Again, under normal use, this poses no problems. For racing applications, there are pistons available that alleviate this problem.
Hope this helps.
FTE Legend
Joined: Jun 2006
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From: Ottawa, Ontario
Yes the rods are the weak link in these motors.. and more so on the 351 because the block will handle a lot more power than the 302. Common wisdom says the stock rotating assembly is good up to about 400hp, and ARP rod bolts are good insurance but having ARP bolts installed in the stock rods will cost about the same as buying better rods with ARP hardware already installed so there's really no point reworking the stock rods.
Posting Guru
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Actually the Bottom ends of both engines are pretty strong, but the 302 's short comings are the Block.
I was part of a test, in a drag raceing enviroment. We built the top end of a 302 in an 88 Mustang. It included a home made plenum. Shortened rear end 35 inch slicks power glide tranny. Stock bottom end, not rebuilt, it had 86000 miles on it. we thought it would be fun to put as much HP threw it that we could, until it blows.
This engine had close to 650 HP and ran low 10's consistantly. What broke on the enigne, was the block. It cracked between the lifters.
That is 1 example. I also have pictures of more 302 block failures, even with ARP studs, holding the rotating assembly together.
I was part of a test, in a drag raceing enviroment. We built the top end of a 302 in an 88 Mustang. It included a home made plenum. Shortened rear end 35 inch slicks power glide tranny. Stock bottom end, not rebuilt, it had 86000 miles on it. we thought it would be fun to put as much HP threw it that we could, until it blows.
This engine had close to 650 HP and ran low 10's consistantly. What broke on the enigne, was the block. It cracked between the lifters.
That is 1 example. I also have pictures of more 302 block failures, even with ARP studs, holding the rotating assembly together.
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Elder User
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From: Campton
Actually the Bottom ends of both engines are pretty strong, but the 302 's short comings are the Block.
I was part of a test, in a drag raceing enviroment. We built the top end of a 302 in an 88 Mustang. It included a home made plenum. Shortened rear end 35 inch slicks power glide tranny. Stock bottom end, not rebuilt, it had 86000 miles on it. we thought it would be fun to put as much HP threw it that we could, until it blows.
This engine had close to 650 HP and ran low 10's consistantly. What broke on the enigne, was the block. It cracked between the lifters.
That is 1 example. I also have pictures of more 302 block failures, even with ARP studs, holding the rotating assembly together.
I was part of a test, in a drag raceing enviroment. We built the top end of a 302 in an 88 Mustang. It included a home made plenum. Shortened rear end 35 inch slicks power glide tranny. Stock bottom end, not rebuilt, it had 86000 miles on it. we thought it would be fun to put as much HP threw it that we could, until it blows.
This engine had close to 650 HP and ran low 10's consistantly. What broke on the enigne, was the block. It cracked between the lifters.
That is 1 example. I also have pictures of more 302 block failures, even with ARP studs, holding the rotating assembly together.
Posting Guru
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I have been out building another garage in my backyard,
to many hotrods.
The only thing I would reccomend, if you are doing a complete rebuild on a 351W is... This is what I do... Turn the crank down 10 thousanths, open up the oil passages, of course champferr them. and add a high vol oil pump, like a melling.
The reason I turn the crank down, is not only to get a fresh surface, but the engine will tend to wind up quicker, have the shop that turns the crank, get the bearings. Ask for Clevite 77's.. balance the rotating assembly.
I turn my 351w around 72 to 7500 rpms. I tested it at 8500 to, but there was no real gain. My buddy shifts his at 9200 or 9500 rpms depending on track altitude. These engines will hold together, but he breaks alot of oil pump drive shafts, and uses an accumulator to prevent engine failure.
The Mustang in my signature, and vid has a stock 351 windsor crank, that came out of a 90 F250. It is turned down .010. I built the engine in 02, and it gets punished.
Like I said sorry I didnt get back to you sooner, winter is coming, I procrastinated, on this garage.
to many hotrods.
The only thing I would reccomend, if you are doing a complete rebuild on a 351W is... This is what I do... Turn the crank down 10 thousanths, open up the oil passages, of course champferr them. and add a high vol oil pump, like a melling.
The reason I turn the crank down, is not only to get a fresh surface, but the engine will tend to wind up quicker, have the shop that turns the crank, get the bearings. Ask for Clevite 77's.. balance the rotating assembly.
I turn my 351w around 72 to 7500 rpms. I tested it at 8500 to, but there was no real gain. My buddy shifts his at 9200 or 9500 rpms depending on track altitude. These engines will hold together, but he breaks alot of oil pump drive shafts, and uses an accumulator to prevent engine failure.
The Mustang in my signature, and vid has a stock 351 windsor crank, that came out of a 90 F250. It is turned down .010. I built the engine in 02, and it gets punished.
Like I said sorry I didnt get back to you sooner, winter is coming, I procrastinated, on this garage.
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Elder User
Joined: Apr 2009
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From: Upstate New York
2x on the oil pump shaft weakness. The best oil pump driveshaft I ever used was an older Ford SVO unit, which still runs in my motor today.
As for the stock rods, I've run 302 stockers with stock bolts up to 7500 rpm in street motors for years and they lived. Some arp bolts along with the older 289 ribbed end caps is nice insurance, however.
The 302 blocks that are pre-1981 are, if I recall, about 40 lbs heavier than the 1981+ 302(5.0) blocks. If you pick them up you can really feel a huge difference in the weight. Most of that weight difference comes from the main webbing area, where Ford reduced a lot of the material I assume to save money and to make the fox body cars handle better.
If you run the newer blocks, 450 hp is about the limit, and the older blocks should stand up to 700 hp before they split and the crank bails on you. If you run forced induction or increase the stroke, those estimates drop by quite a bit. I run a billet steel main stud girdle on my 1972 302 block, because it's stroked to 3.25", and so far it's held up nicely with a little over 500 hp naturally aspirated, even at 8500 rpm.
As for the stock rods, I've run 302 stockers with stock bolts up to 7500 rpm in street motors for years and they lived. Some arp bolts along with the older 289 ribbed end caps is nice insurance, however.
The 302 blocks that are pre-1981 are, if I recall, about 40 lbs heavier than the 1981+ 302(5.0) blocks. If you pick them up you can really feel a huge difference in the weight. Most of that weight difference comes from the main webbing area, where Ford reduced a lot of the material I assume to save money and to make the fox body cars handle better.
If you run the newer blocks, 450 hp is about the limit, and the older blocks should stand up to 700 hp before they split and the crank bails on you. If you run forced induction or increase the stroke, those estimates drop by quite a bit. I run a billet steel main stud girdle on my 1972 302 block, because it's stroked to 3.25", and so far it's held up nicely with a little over 500 hp naturally aspirated, even at 8500 rpm.
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Posting Guru
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To improve on the factory set-up for longevity you should get the next size up piston that your engine will bore to. Have the crank turned .010 under, the rods resized, and have the whole assembly balanced. To go one step further, have the engine blueprinted. This will cost a fair chunk of change, but a stock motor like that would run forever.
ARP doesn't make rods, they only make the bolts that go in them. You can find aftermarket rods (Eagle and Scat,et.al) on Ebay or at Summit or Jegs.
What kind of motor are you going to build?
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From: Campton
It really all depends on what you are going to build. If you are just looking for longetivity in a stock engine, there really isn't any weaknessess in a 351W other than loose manufacturing specs. All the factory parts can stand up to more than the stock motor will deliver.
To improve on the factory set-up for longevity you should get the next size up piston that your engine will bore to. Have the crank turned .010 under, the rods resized, and have the whole assembly balanced. To go one step further, have the engine blueprinted. This will cost a fair chunk of change, but a stock motor like that would run forever.
ARP doesn't make rods, they only make the bolts that go in them. You can find aftermarket rods (Eagle and Scat,et.al) on Ebay or at Summit or Jegs.
What kind of motor are you going to build?
To improve on the factory set-up for longevity you should get the next size up piston that your engine will bore to. Have the crank turned .010 under, the rods resized, and have the whole assembly balanced. To go one step further, have the engine blueprinted. This will cost a fair chunk of change, but a stock motor like that would run forever.
ARP doesn't make rods, they only make the bolts that go in them. You can find aftermarket rods (Eagle and Scat,et.al) on Ebay or at Summit or Jegs.
What kind of motor are you going to build?
FTE Legend
Joined: Jun 2006
Posts: 31,930
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From: Ottawa, Ontario
just a little bit above stock. basically i want to get in my truck and go. i dont want to have to worry about weither my truck will make it to my job which is 45 miles away or make it home at 5am when i get off. i just want it to purrrrrrrrrr like a kitten and take me to my mom's house which is up a steep gravel road with a huge hill. i dont tow anything just drive.
Junior User
Joined: Jun 2009
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From: Athens, GA
So you can't buy 351W rod bolts that just drop in with stock rods? I am approaching the point of building my spare engine and am trying to figure out everything I'll need. I'm much more knowledgeable about small british motors, so pardon my ignorance.
Thanks for the help guys,
Josh
Thanks for the help guys,
Josh
Post Fiend
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From: Charles Town, W bygod Va
Yes the rods are the weak link in these motors.. and more so on the 351 because the block will handle a lot more power than the 302. Common wisdom says the stock rotating assembly is good up to about 400hp, and ARP rod bolts are good insurance but having ARP bolts installed in the stock rods will cost about the same as buying better rods with ARP hardware already installed so there's really no point reworking the stock rods.
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Paul O
Quote from a few posts up
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Paul O
Quote from a few posts up
FTE Legend
Joined: Jun 2006
Posts: 31,930
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From: Ottawa, Ontario
Oh you can get ARP bolts for the stock rods.. have a set in my 351. But they don't just drop in they are pressed in and the process of removing and installing the bolts can distort the bearing opening so they often need to be machined round again, and that's where the extra cost come in.
Junior User
Joined: Jun 2009
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From: Athens, GA
And I'm guessing that the cost of machining (as mentioned above) is close to the 250 to 300 range I've seen for I-Beam rods from Eagle or Scat (depending on the shop of course)? Are the stock bolts fine for a stock rebuild with upgrades geared to reliability and a small increase in low rpm power?
Josh
Josh