240 +30=?

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Apr 2, 2008 | 09:28 PM

66slick

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From: Hochfeld, Manitoba

240 +30=?

I have a 66 Merc with a 240 It runs great and does not burn any oil.

A while back I found a plate on the motor indicating a re-manufactured engine.

My vision is not 20/20 but as far as I could tell it read mains-010, rods-010,
cylinder bore-030.

Could anyone explain these numbers to me and tell me if this engine would be able to be rebuilt if needed in the future?

Also, what would the displacement be now?

Apr 2, 2008 | 09:35 PM

bigblockford_390

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From: East Helena MT

The .010 for the Rods and Mains mean they had to cut .010 inches off of the jurnals on the crank shaft to clean them up, there for to take up the extra clearance your bearings need to be a total of .010 larger (.005) on each half.

.030 on the cylinders means they bored the engine .030 to clean them up. Same as above you have to take up the extra clearance with larger pistons and matching rings. I do not have the spec in front of me for a 240 six cylinder but with a little basic math you can figure out the exact new cubic inch displacement, but my guess going 30 over you are only going to add a couple of inches, 3 maybe 5 above the 240 but that is just a guess, get the numbers and it is simple math.

Jeff

Apr 2, 2008 | 09:44 PM

66slick

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From: Hochfeld, Manitoba

Thanks, would the 240 still have enough cylinder wall left for any future rebuild?

Apr 2, 2008 | 09:54 PM

bigblockford_390

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From: East Helena MT

Quote:

Originally Posted by 66slick

Thanks, would the 240 still have enough cylinder wall left for any future rebuild?

Some one with more knowledge will surly chime in sometime. In the mean time here is my two cents. Most engines are good for 30 over, some that is the max, and some can go a lot more. With that being said the best thing to do is take the bare block to a machine shop to have it sonic checked. They will be able to tell you how much you can go over.

The other option is to have the block sleeved, where they will hog out the block and press in a new cylinder. That is very expensive and on a 240/300 six cylinder block that are a dime a dozen in my opinion not worth it. I would only consider it on a rare block, but it is an option.

Jeff

Apr 3, 2008 | 03:58 AM

camperspecial65

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From: seattle

My guess is the block itself is a pretty easy find as my gut..rumbling and all...tells me its prolly the same beast well into the 70's car and trucks...
Whats your take on this Bill ??

- cs65

Apr 3, 2008 | 07:12 AM

312

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the block can go to .060 and the crank to .030.so its rebuildable.on some old hard to get cranks they will go to .060.

Apr 3, 2008 | 10:49 AM

Flame Out

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From: Northern New Mexico

To go .060 over on the cylinders does that mean oversized pistons rather than just rings? I have a rebuilt I6 235 ci on a 1942 C, eh, another manufacturer of quality trucks. The engine was professionally rebuilt and their plate states .060 over on the cylinders and .030 elsewhere. I always wondered if that meant new pistons. The old man who bought this truck in the early 1950s and sold it to me is long gone. I will have to wait a few more years to ask him.

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Apr 3, 2008 | 03:00 PM

bigblockford_390

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From: East Helena MT

Quote:

Originally Posted by Flame Out

Weather your engine was bored .020, .030, .040, .060 and so on you have to have larger pistons with matching larger piston rings to take up the clearance caused by boring the engine out. If you don't the engine would have a serious compression loss and the pistons would be slapping the cylinder walls which would destroy them in no time.

Same goes for the crank, if you have the journals turned you have to install larger bearings to take up the clearance.

Jeff

Apr 3, 2008 | 05:28 PM

#10

66slick

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From: Hochfeld, Manitoba

Thanks for all the good info folks. I assumed that because the 240 and the 300 shared the same block, that the 240 would have lots of cylinder wall to spare. I suppose that most of the extra cubic inches comes from a longer stroke?

Has anyone ever heard of a 240 head on a 300 as a simple performance upgrade?

Apr 4, 2008 | 12:35 AM

#11

garbz2

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From: Glendale Arizona

Yes.. the 240 head perks up a 300... it will raise the compression about 1 point.

The 240 and 300 are identical castings. the same bore diameter is used for each.

A 30 over bore on a 240 is a 30 over bore on a 300. the extra cubic inches are in the stroke of the crank.

One of my project engines is to assemble a stroked 300 with a custom crank....Just have not found the cash to fund it yet...

Garbz