240/250 COMPARISON

[Anonymous]

I WAS JUST WANDERING HOW MUCH HEAVIER A 240 IS THAN A250.
ALSO, ACCORDING TO THE SPEC SHEETS I'VE BEEN LOOKING AT, THE 240 HAS A BIGGER BORE/SHORTER STROKE(4.00X3.180 VS.3.68X3.91)SO AM I CORRECT IN ASSUMING THE 240 IS A "POTENTIALY" HIGHER REVVING ENGINE? SINCE THE 240 HAS A SHORTER STROKE(LOWER DECK) WHERE DOES THE WEIGHT COME FROM? BEAR WITH ME, I'VE NEVER OWNED EITHER ENGINE. THIS IS JUST A QUEST FOR UNDERSTANDING.

 

[rbohm]

8) the 240 is going to weigh about the same as the 300. it is also the same physical size as the 300. i think the weight is around 450lbs with the 250 being about 380lbs.

 

[Anonymous]

Exactly. The 240 does have a shorter stroke, but it has a lot taller deck (real long rod motor). It actually uses the 300's block. The only differences being on the crank and the rods.

 

[Anonymous]

SO CAN YOU REV A 240?

 

[Anonymous]

Yes. I would say you could rev a 240 as far as your breathing limitations will take you. Thats assuming your bottom end is in order. A short stroke and a long rod (6.79) with a rod ratio of 2.13 you won't find many engines with a combination better than that. Just my opinion.

 

[xctasy]

That big ol' 240 has pretty good dynamics for performance potential.

My little 2.3 liter (140 cube) bent six, based on the Capri 2600 motor, has a 2.18 :1 rod ratio with 5.14 inch rods and a 2.36 inch stroke. It's a little like that guy who could pull 8600 rpm in his 144 in-liner...it revs like no tomorrow! This is sort of a case of reverse One-Upmanship, dontcha think?

Best small in-liner I6 for rod ratio is the post 1971 200 Aussie Ford engine. Had 3.126 stroke and 6.275 inch rods, and 9.48 or so deck. Ratio was 2.01:1. Engineering information I have is that the ideal rod ratio is 1.7:1 to 1.8:1 for smooth road performance, optimal block weight and piston speed.

Examples are 3.8/4.2 Jags with 7 inch rods, 4.17 inch strokes and 10.7 inch decks. Engines built soley for torque can go as low as 1.48:1, but these aren't going to be natural revers, and need ultra stout blocks to hack the racket. US 200's, and all 250's all qualify with low 1.5:1 ratios. 400 Chevs break blocks with 1.48:1 ratios.

Higher than 1.8:1 ratios are for racers usally.Engines such as the little Cologne V6'S (below 2.9 liters) are safe to over rev in the lower end, because high rod ratios are good at reducing piston speed. Chevy 302's had really long rods, short strokes. Things like Cosworth DFX'S had super high ratios well over 2.2:1, to save the blocks at high RPM's.

Most drag racers favour low rod ratios to reduce block height. Smoothness is not an issue. Those little 144 I6's, even with there technically flawed four bearing cranks, were revers because of there short stroke, long rod make-up

 

[Anonymous]

I understand the bore and stroke thing ...big bore ,short stroke usually means a high revving engine...but, this whole rod ratio thing is new to me.
I guess I don't quite get it.

 

[xctasy]

I NEVER UNDER STOOD IT EITHER UNTIL 10 YEARS AGO. Bore:stroke ratio has little effect on rev range. Hondas have hit 7000 rpm or more with long stroke engines for years.

Engines that have rods twice a long as the stroke have much less stress imparted on the bores than rods that are 1.5 times the stroke.

Eg 1, a 1971 US 200 has a 7.9 inch deep block, with 1.53" deep pistons, 4.77 inch centre to centre rods and has a 3.126 inch stroke. The rod length to stroke ratio is 4.77 divided by 3.126 inches...1.526:1. Engine weighes about 415 pounds.

Eg 2, a 1971 Aussie 200 has 9.48 inch deep block, with 1.62" deep pistons, 6.275 inch centre to centre rods and has a 3.126 inch stroke. The rod length to stroke ratio is 6.275 divided by 3.126 icnhes...2.007:1. Engine weighes about 530 pounds.

The US version and Aussie one have the same head, but the Aussie one is 115 pounds heavier just to give a higher rod ratio. The US engine is rougher, produces less peak power, and has much more piston side thrust during the movement of the piston. The trade off is clear. To get to the ideal rod ratio, you have to get a longer block or invest in low deck pistons. Adding block height increases engine weight. That's why engineers start with 1.8:1 ratios on the little jiggers and end up with 1.5:1 ratios on the stroked top models...or they just add deck height to the block and find some other way to much up for the mass increase.

Lotsa fun. oops...This should be posted in the hard core section.

 

[Anonymous]

IF memory serves me correctly:

A 200 is about 360 lbs
A 250 is about 420 lbs (because of V8 bell hsg and taller deck)
The 240/300 weighed the same as a 302 V8

 

[Anonymous]

THANKS GUYS I GET IT NOW. I GUESS YOU'RE NEVER TOO OLD TO LEARN SOMETHING NEW.
KNOW ANYTHING ABOUT WOMEN?

 

[xctasy]

1. Regarding women (and cars and bulldozers too!) there's an old profanity:-

If it has t**s, tires or tracks, it'll give you Trouble

2. Engine mass or weight is a little like horsepower, do you want it net, gross or off the wheels? Ford claimed the 3.8V6 in its first incarnation was 400 pounds. The early 4V 302 Windsor V8'S were 470 pounds, the 351C 4V HO was 582 pounds. 351 W 4V was 37 pounds lighter than the shallower block Cleveland. Aussie 2V Cross flow Alloy head 250's were 480 pounds, cast iron cross flows 250's were 51 pounds heavier. The 1977 issue of Autocar quoted the Cologne 2.8 V6 with injection as being 358 pounds, 2.3 Cologne V6 was 348 pounds, the British Essex 3.0 liter V6 was 432 pounds, the 255 Windsor in 1980 Fords was 440 pounds. A Popular Mechanics article in 1973 had the Maverick 250 I6 at 530 pounds.

Problem was, nobody stated the standard of measurement. I'd say a ten inch deck 240 cube six with the same bore spacings as a 350 Chev would weigh over 550 pounds. The Aussie Chrysler 265 Hemi has a thin-wall casting, the same 4.4 inch bore spacing, a deck height 620 thou lower than your 240/300 I6's and was only slightly lighter than a 318/340 Chrysler engine.

You guys figure it out.

 

[Thad]

Never played with the SBF-6s, so a question. Does the 250 have a removable intake?

 

[Anonymous]

hey thanks for the info guys.
i hate to run it in to the ground but the the reason i keep asking all these
stupid questions is (i'm stupid) i'm seriously considering a67 falcon that i can pick up cheap.i really like the body style of these cars. it has a 351w in it which i was thinking i could build and get all kinds of power for such a light body.but i keep getting these mental images of sitting at a stop light
melting my rear tires while a 16yo in a honda civic races past me. so i was
wandering how much weight i could shave off the front end if i dropped a
240 in it. i think that body with a built up high revving 240 and a 5 speed would be very cool and probably quicker off the line if it wasn't pushing all that weight up front. ya think?

 

[Anonymous]

Thanks Ted
You speaka my language

 

[xctasy]

Ted makes sense too. I just have no info on 240/300's. Since it came out in the 1965 Galaxie, you'd bet it would be a trim thin-wall design. Shame I can't find one for my Falc. Would have saved me a motsa on the short stroke crank, 3.3 X-Flow rods and 305 forged Chevy pistons ( rare as rocking horse cr*p now) I put in my spare 250 block. And the 3/8 inch spacer plate I had to make to hook the AOD4 to the Aussie block