250ci+

MPGmustang

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okay, just for the fun of it... Xtacy will love this thread...

okay, how big can a 250ci get??? using a US 250ci block, and an Classic Inlines Alum head, what can be done to make it 'bigger' in cubes...

I know one 'could' bore the block .060 for a nice 256ci engine, but what else? con-rods, crank, pistons,???

then what would the 'hypothetical' durability be? would it hold up to the 'i6 bullet proof' name?

there was a thread about the 200ci becoming a 221ci with different rods and pistons.

anyways' just thinking out there and day-dreamming...
 
fer instance:

The 250 in my '61 Comet has pistons that raise the displacement to @ 260 cid. The AMC/International application TRW piston's require an .070 overbore. 'been running five years and still some power left to find ...

HAve Fun



 
You could sleeve the cylinders to four inches and offset grind the crank probably like a quarter inch or more. I have been toying with the idea since I heard the phrase "aluminium block" tossed around.
 
8) i think mike(azcoupe) built one that displaced something like 275ci(?).
 
I have a 250 crankshaft that has been offset ground to fit a Mitsubishi rod.
If I recall the stroke is 4.27 inch. That's up from the stock 3.91.

But we'll probably never use it. To weak I think. The rod bearing journals are so small, the stroke so large, that the rod journals are "outside" of the main bearing journals. So the only thing holding the crank together are the crank counterweights.
And the rod ratio is so bad it would probably push the piston into the side of the cyl. wall.
Sure we could get longer rods, and very short pistons, all of which are totally doable (not cheap....but doable!). But we figured it wouldn't be dependable with what we do with Kelly's Falcon.

Later,
Will
 
If you really want to stretch it with stock rods and crank, you can overbore .080" to 3.76" and offset grind the crank to get a 4.040" stoke. You end up with 269 cubes.

You also end up with very thin cylinder walls. Sleeving might even be needed, depending on how much core shift there is. You'll need custom bearings or bearing spacers.

THEN....after spending all the $$$ to do all that, you have an engine still saddled with a cylinder head that can't breath. The key to more power is not always cubic inches. The real trick is to move more air thru the engine - Turbo (see Does10's car), supercharger, CI aluminum head, crossflow adaptation.....It really wouldn't matter if you got 300 cubes out of that block, the head limits you to only so much power.

So, if you really want a 250 that runs hard, start with the top end first. Port the heck out of the log, get a 2V head, or just break down and buy a CI head. That's the most cost effective way to get power from a naturally aspirated 250.
 
Looks like
turbo + alu head = a cross flow (500hp, 400tq)
no?
 
Exactly....

I figured with the cost of the aluminum head and the custom parts needed to convert it to FI I could just grab a 250 Xflow.....did it.

Tossing a turbo on it for more power. I am not looking to make more than Does10s ...just looking to do it cheaper and easier (hopefully).

The part killing me is the US dollar has tanked since I bought this motor in 2007.....bringing up some speed parts is going to cost alot more now (as are shipping costs)

Back on topic though....

To run a stroker crank I think you would need a taller deck (ALOT taller....like 1"+) to help with the rod ratio.Boring out to a 4.00" bore just isn't very doable with putting in some wet sleeves. (they would be paper thin too)

I think the best bet is just a solid bottom end and rotating assembly and boosting it to make power.
 
'boosting it to make power'
OH, TOTALLY DIFFERENT: X-flow AND turbo...why both?

I don't go to those 2 forums here (well I did 2 the x-flow, but they juss beat me up. 8^0 )...how much tq can U put on the head bolts & what kind do U get - to take the extra 'boost'? What's the difference between a pop off valve and whatever-the-other-one is?
Doesn't it need "inter-cooling"?
Thanx
 
To run a stroker crank I think you would need a taller deck (ALOT taller....like 1"+) to help with the rod ratio.

:unsure: With stock 250 pistons down the hole 0.123 to .150, I think there is plenty of deck height for longer rods and a stroker crank. I don't know what the practical limit of stroke is but there is room for much more than stock.
 
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