What years was the 240 cu in engine produced. My block casting number has D5 on it. The engine is in a 65 ford f-100, the original engine was a 240. So someone has changed the engine with a 1975 engine, but what is it and how do I determine what size it is.

 

The 240 was built from 65 until 73(IIRC.) There are 2 possibilities, a) the 240 could have been re-built with a later 300 block(the 240 and 300 cranks are interchangable) or, b) they may have bolted in a 300, the easiest way to tell is to check the stroke, pull a spark plug, and stick a piece of wire in, and bring the engine to BDC, a 300's stroke is 3.98" and, a 240's is 3.18"
1982 F100 SWB 4x4
300 HD, 9.5:1 compression
Clifford 270H, Hedman Hedder
2½" unmuffled duals
NP 435/205
160,000 miles, 152,000 as a 2wd
Hear the 300: [url:http://www.bigblocksix.com/f100swb/cammed.mp3|Idle] [url:http://www.bigblocksix.com/f100swb/cammedrev.mp3|Rev]
1985 F150 HD, 300 HD
70,000 miles
1980 F100 Custom, 300/Np 435
60,000 miles

 

 

The 240 and 300 have the same block but different cranks.

 

More than likely a 300. How many belt grooves on the crank pulley? 240's have 2, 300's have 3. Or, if you want to be scientific about it you could pull a plug and measure the stroke.

 

The 240 was built from 65 until 73(IIRC.) >>>>>

I think that probably 65 thru 74, but not sure after 74...But...I think 74 was probably the last year. Actually, I hadn't realized that until reading this thread. In my Chiltons book, I show a cutoff of the "A" engines after 74...My 74 F-100 has a 240. I guess it must be one of the last ones...Anyway, if 74 is really the cutoff for the 240, that means that D5 engine should be a 300 if the engine is complete as built. But I guess it's possible they slapped the old 240 heads on a 300 block. Some do that for the higher compression...But if I had to bet money, I bet they just took the easy route and slapped a complete 300 into it. I agree...The sure way to tell is by measuring the stroke. But that wouldn't verify which heads I don't think...The heads probably have a stamp, but I'm not sure where it is...Probably on one of the ends...I didn't know about the pully count thing...But to test it, I went and looked on both of my trucks. "I have a 300 in one, and a 240 in the other. " Sure nuff, my 300 has a 3 groove pully, and my 240 has a 2 groove pully. Dang...I would have thought they were the same...Never had noticed that... MK

 

LOL yeah, it's not a very impressive way of telling them apart I agree. But so far I've never seen it fail.

 

I'm guessing the weight needed to damp the 300 is more, and they use the larger damper pully to hold more rubber, or whatever.....
The crank is different between the two...If that is the case, the pully count test should be very accurate as far as ID'ing a lower end. If they slapped a 240 damper on a 300, it would probably shake fillings out...MK

 

Just an FYI -- I have a 300 damper on my 240, which I put on after considerable discussion with a couple of engine builders as well as the "Damper Doctor" -- he professionally rebuilds dampers for antique/high performance vehicles.

There is NO PROBLEM putting a 3 ring damper on a 240. You will get a better dampening effect, which the heaver, longer stroke of the 300 needs and the 240 likes as well. You will theoretically sacrifice a miniscule bit of accelleration preformance, as there is more weight in the 300 damper. But it is negligable.

I wager, though I cannot prove, that the 240 in a car had a 3 ring damper on it. 3 rings are seen more often on 300 engines because you couldn't get a pickup with power steering or AC in 65-74 unless it had a 300. So they needed more rings on the pulley. I surmise that the 240 just didn't need three ring pulleys, so it didn't get them.

Remember -- in the 240 and 300 the damper just absorbs harmonic vibrations that occur due to the rythmic flexing of the crank as the various cylinders fire. It does NOT balance the crank. The crank is inherently balanced in an I6. (Which is not to say that a stock crank is PERFECTLY balanced -- further perfection can be achieved with blueprinting, from what I understand, but I am not too knowledgeable about how that is done in an I6).

 

This isn't always true. My stock '67 F100 with the original 240 has dealer installed A/C(only way you could get A/C at the time) running off of the 2 rib pulley. The alternator and water pump run off of the back one and the A/C runs off of the front one. I think 300's had 3 rib pulleys because they were used for heavier duty purposes(forklifts, F350's, etc.) that might had to run a hydraulic pump or generator. They installed 240's in Galaxy 500's, but I've never seen one in person so couldn't tell ya about the pulley =)

 

My 240 has a 3 rib original pulley. It originally came in a 1966 Custom 500 full size car with dealer added AC and no power steering. The engine is now in my 1971 F250.