This is topic 351W vs. 347 in forum Tech Talk at Northern California Ford Owners  .


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Posted by Curt (Member # 6254) on :
 
It seems like the 347 is hella expensive! I know its stronger and all but why not go with a Windsor (yes I know the 302 is a windsor too) then you have 351 cubes to start with, sure its a little wider (or is it taller?) but you can't beat $90 for 49 more cubes!

Obviously the lower intake selection will be limited and smog could be hard, and I doubt its a roller but don't they make 418 kits for the 351?

It seems like for the price of a 347 you could have a bada** 351!

What do y'all think?
 

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Posted by 88DroptopGT (Member # 2535) on :
 
351 Windsors are beefier but you have to buy conversion parts.

Smog is not a big deal since most smog techs don't notice the taller deck of a 351 unless they check engine casting #'s.

Everyone makes 408ci stroker kits for Windsors. Shoot on dart block you can stroke all the way to 454ci!

Building any engine is expensive, but you gotta "pay to play".

Personally I would go with a 351. I'm selling a machined block as well.
 

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Posted by 93PONY (Member # 60) on :
 
Neither is stronger then the other rotating assembly wise. You can get good quality forged components for either motor.

The 351 block is stronger then the 302. However either Dart 302 or 351 will handle far more then we'll ever be able to throw at it.

The 302 has an 8.2" deck height, the 351 has a 9.5" deck height. The rods on an 8.2" deck are shorter & therefore lighter then a 9.5" deck rod. The lighter the rod, the faster the motor will rev. The faster it revs.....the faster it gets through it's powerband. Also, the shorter the rod, the stronger it is....same with pushrods....which are also longer on a 351 vs 302.

Fast reving motors is something that most don't consider when looking at dyno graphs. There's more to it then simply peak power. How fast a motor revs is KEY in how fast the car will be.
 

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Posted by CDT (Member # 5004) on :
 
they both cost about the same to build, if built to the same levels. the 351w block is stronger, but it seems as he 302 blocks only have trouble on boost.
 

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Posted by CobramanPhil (Member # 2170) on :
 

quote:

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Originally posted by CDT:
they both cost about the same to build, if built to the same levels. the 351w block is stronger, but it seems as he 302 blocks only have trouble on boost.

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Probably due to the lack of sealing surfaces between the piston walls...ughhhh another gasket failure
 

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Posted by Joooestang66 (Member # 2828) on :
 
In the long run a 347 will wear out alot faster than a 351.
 

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Posted by CDT (Member # 5004) on :
 

quote:

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Originally posted by CobramanPhil:

quote:

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Originally posted by CDT:
they both cost about the same to build, if built to the same levels. the 351w block is stronger, but it seems as he 302 blocks only have trouble on boost.

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Probably due to the lack of sealing surfaces between the piston walls...ughhhh another gasket failure

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quote:

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Originally posted by Joooestang66:
In the long run a 347 will wear out alot faster than a 351.

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thats really not true
 

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Posted by 2stangs69-91 (Member # 1951) on :
 
hmmm so why do the fastest prostock cars IHRA run bigger motors if smaller faster revving ones would be the ticket
 

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Posted by SPEC -Fabrication (Member # 4980) on :
 

quote:

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Originally posted by Curt:
It seems like the 347 is hella expensive! I know its stronger and all but why not go with a Windsor (yes I know the 302 is a windsor too) then you have 351 cubes to start with, sure its a little wider (or is it taller?) but you can't beat $90 for 49 more cubes!

Obviously the lower intake selection will be limited and smog could be hard, and I doubt its a roller but don't they make 418 kits for the 351?

It seems like for the price of a 347 you could have a bada** 351!

What do y'all think?

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I would take in the note that the 347 is still haveing Rod issues, 331 is much more safer, My friend road races a 331 ony after going threw 2 347's , Rods were snapped in both due to the stroke and High revs for periods of time
 

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Posted by v-town coupe (Member # 2771) on :
 
dman this could go back and forth all day i prefer 347 due to the fact every thing i have is already set u for a 302 and less stuff to buy for a conversion and i also dont have the hood clearence on my car to accomidate a taller deck height cause once u start building a pretty tough motor you will need and intake to back it up! i d like the fact that a 347 will rev quicker but hey any motor will with the right parts and dont let the 347 scare u away they have come a long way with diffrent rod lenghts and what not to kep the wrist pin out of oil control ring but its all prefrence jus my .02
 

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Posted by JoeT (Member # 298) on :
 
don't forget to budget for:

drop motor mounts, swap headers, 351w pan, different timing cover, different accessory brackets, different flywheel, the already mentioned different lower intake, the motor is both wider and taller (not all 351s are 9.5", some are 9.2", watch out when ordering a rotating assembly if you have an early windsor block) and there's probably a few odds and ends which may come into play like possibly needing a different hood depending on your intake/carb/motor mount choice.

all told the swap parts for a 351 negate any real $ savings over going with 'just' a 347

Then again, IMHO we shouldn't be comparing a 351 vs a 347.... I would say compare a 408/427 vs a 347.

Don't forget the ~ 60# weight penalty the 351w block carries (comparing production blocks).

Also, if you're considering a 351w, for many of the same reasons you should also consider a 460 (or a 454 )
 

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Posted by 93PONY (Member # 60) on :
 

quote:

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Originally posted by 2stangs69-91:
hmmm so why do the fastest prostock cars IHRA run bigger motors if smaller faster revving ones would be the ticket

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As we all know, there is no replacement for displacement.....
I don't see you racing a Honda.
Why do they use aluminum rods?
Apples to Oranges.....but you know that. You just like bust'n my balls from time to time.

There are no real issues with the current line of 347's.
The oiling/longevity issues were due to the oil ring & pin locations. This was 'fixed' with a support rail under the oil rings. Even better is the 5.315 rod with a 331 piston. No more issues.... There is no reason why a properly built 347 will not last YEARS racing & 100000+ miles if taken care of.

[ December 20, 2005, 10:57 PM: Message edited by: 93PONY ]
 

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Posted by stoauto (Member # 2803) on :
 

quote:

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Originally posted by SPEC -Fabrication:

quote:

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Originally posted by Curt:
It seems like the 347 is hella expensive! I know its stronger and all but why not go with a Windsor (yes I know the 302 is a windsor too) then you have 351 cubes to start with, sure its a little wider (or is it taller?) but you can't beat $90 for 49 more cubes!

Obviously the lower intake selection will be limited and smog could be hard, and I doubt its a roller but don't they make 418 kits for the 351?

It seems like for the price of a 347 you could have a bada** 351!

What do y'all think?

---

I would take in the note that the 347 is still haveing Rod issues, 331 is much more safer, My friend road races a 331 ony after going threw 2 347's , Rods were snapped in both due to the stroke and High revs for periods of time

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quote:

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Originally posted by JoeT:
don't forget to budget for:

drop motor mounts, swap headers, 351w pan, different timing cover, different accessory brackets, different flywheel, the already mentioned different lower intake, the motor is both wider and taller (not all 351s are 9.5", some are 9.2", watch out when ordering a rotating assembly if you have an early windsor block) and there's probably a few odds and ends which may come into play like possibly needing a different hood depending on your intake/carb/motor mount choice.

all told the swap parts for a 351 negate any real $ savings over going with 'just' a 347

Then again, IMHO we shouldn't be comparing a 351 vs a 347.... I would say compare a 408/427 vs a 347.

Don't forget the ~ 60# weight penalty the 351w block carries (comparing production blocks).

Also, if you're considering a 351w, for many of the same reasons you should also consider a 460 (or a 454 )

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quote:

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Originally posted by CDT:

quote:

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Originally posted by CobramanPhil:

quote:

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Originally posted by CDT:
they both cost about the same to build, if built to the same levels. the 351w block is stronger, but it seems as he 302 blocks only have trouble on boost.

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Probably due to the lack of sealing surfaces between the piston walls...ughhhh another gasket failure

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I was talking about block failures

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After a gasket goes south during a run..guess what goes next if you don't immediately shut off the car...KABOOM! A gasket going is sort of a prelude to a eventual block failure...sort of like playing with fire if you think about it
 

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Posted by Curt (Member # 6254) on :
 
how much cheaper are the 331's?
 

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Posted by Apexmotorsports (Member # 5307) on :
 
331's are sometimes more expensive... I imagine because there is less demand for them than 347s.

For a 351 you have to remember also that the engine will sit higher and you will need to get a new hood and intake. 351's are great for massive TQ but they are heavier and taller than a 347 or 302 based stroker engine. Installing a 351 will also add to the problem if the Mustang being too heavy in the front... you don't want any more weight in the front if you can help it.
 

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