How good do '91 300-I6 heads breath compared to '91 351w heads?
The '91 Shop Manual shows the exhaust valve to be 1/10" bigger on the 300. :)

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I'm wanting to build a -non(!)- racing type engine.
I want a 300-I6 with two more cylinders is all. :)
Peak torque between 2500 and 3000 rpm.

The plan involves using a '91 351w that's got only 73k miles on it.
Putting in a 4 inch stoker crank and short 6 inch rods and hyper pistons.

But what about the heads?
How do they compare to the 300-I6?

The 408w won't look cool like a 300-I6 but it can run like one? LOL :)

It's going into a '91 Bronco with a wide ratio ZF5 with 3.55 gear.

What do you think?

Alvin in AZ

 

a 351W can be made to make low end grunt like a 300 six, but you will still have the 90* crank rotation of power. an inline can deliver 120* of power per stroke, thus creating a more mechanical advantage over the wedge counterpart. the 351 can out perform the six all day long with no sweat, but the inline by design is far superior.

go with a 393 stroker, less money and same torque ($500 scat crank, 351W rods and 302 pistons i believe, not sure on rods)

 

What are you going to learn here that you have not heard here:

https://www.ford-trucks.com/forums/8...ng-engine.html

If you want a low performance gas hog, go ahead and build a long stroke, low compression, small ported/valved 408. Put a 390 cfm 4bbl or a 300 cfm 2 bbl on it. Short shift it to your heart's content.

 

Want a 300 with two more cylinders? Try a Buick or Pontiac straight 8. You will have your six + two but it won't be a 300.

 

I don't understand. :/
I can't "see" what you mean about the 90 and 120 degrees. :/
Care to explain or post a URL for me to read? :)

Alvin in AZ

 

I don't know where you come up with this theory. An engine fires somewhere near TDC and much of the next 180 degrees of crank rotation get power from the power stroke of the 4 cycle motor. Single, twin, triple, four, five, six, 8, 12, 16, however many pistons there are, each cylinder has 180 degrees of power stroke, although you probably get only about 140 degrees of actual power according to some.

A straight or 60 degree V 6 fires every 120 degrees, three per rotation of the crank. Straight or 90 degree 8 fires every 90 degrees, four per rotation.

Torque per pulse is affected by the size of each cylinder. A 300 has larger cubes per cylinder than a 302 or 351, same as a 400. Thus, the 302 has to spin 1000 rpm more to match it, the 351 has to spin only a little higher to beat it, the 400 whacks it all the way through. As smooth as the six is, the eight is smoother with more pulses per revolution.

On the subject, this first one shows the charts of pulses for different engines, and shows torque per pulse higher for the 6 vs. the 8, amongst other things:

http://www.epi-eng.com/piston_engine...on_engines.htm

If you have insomnia:

http://www.apicsllc.com/apics/WP_2/WP_2.htm

http://www.pumaracing.co.uk/POWER2.htm

 

If you want super duty torque out of a V-8, may I suggest this link;
http://www.hotrod.com/techarticles/e...ild/index.html
The Mutt - Over 500hp and 565 lb-ft from Ford's 400m

Starting With An Engine Nobody Wants, The Ford 400M, We Made Over 500 Hp And 565 Lb-Ft With Parts From Ford, Chevy, Mopar, And The Aftermarket.



This is what they got after spending $6,837.62;

 

http://classicinlines.com/history.asp

 

Interesting history, but hardly a technical paper or analysis of power pulses of various engines.

 

Every time a cylinder fires, the crank is
rotated 120* in an I6.
An I6 crank has 3 "throws" 120* apart (3 x 120* = 360*).

A V8 has 4 "throws" 90* apart (4 x 90* = 360*).
Every time a cylinder fires in a V8, the crank rotates 90*.

Imagine standing a crank up on end, and looking down at it.
Without the counter balances and stuff, only seeing the connecting rod journals,
a V8's crank would resemble a +,
while an I6's crank would resemble a Y. See?

No matter how long the stroke in an engine,
an I6 has a head start on low end torque because
of this 120* revolution PER stroke.
As opposed to only 90* in a V style engine.

To blow your mind even more.......
An I6 balances itself out. How?
Every cylinder stroke turns the crank 120*.
That only accounts for 3 cylinders, get it?
What about the other 3? The front half (1,2,3) are a
mirror image of the rear half (4,5,6). firing order of 1,5,3,6,2,4.
See how 1&6, 5&2, and 3&4 all move up
and down together on the same "throws" in mirror image,
and of course two strokes away from each other in the cycle?
Cool, hu? Creates a perfect balance of the motor.

Alvin in AZ needs a good ol' I6.

Murph.

 

That is a great post and right on murph.

Thanks

 

OK, now diagram that out for a V12!

 

One more tidbit...
The Ford 335 series shows a firing order of 1,3,7,2,6,5,4,8.
Ford FE has an order of 1,5,4,2,6,3,7,8.
I don't have the resources, but I suspect that GM and Mopar
could have different firing orders.
They're all V8's, what the heck gives!?

When it comes down to it, the I6 works the way it works.
I doesn't matter who made it; Ford, International, GM, Studebaker...
The firing order remains the same, and an I6 works the way it works, smooth.
And good torque

Murph.

 

Gimme a break, I'm only an I6 nerd!

Murph.

 

I checked that out a long time ago and figured out V8 firing order was
-the same- (for the most part) it's just that Mopar and Gov't Motors
use different cylinder numbering. LOL :)

Murph, did you check this out?
http://www.epi-eng.com/piston_engine...on_engines.htm

Alvin in AZ
ps- my first 'mer'can-made car had a 225 slant six ;)