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#67333 10/19/2006 2:14 AM | Joined: Oct 2006 Posts: 29 Junior Member | | Junior Member Joined: Oct 2006 Posts: 29 | I have a Chevy 4.1L 250cid Inline 6 Block that is at 60 Over on all cylinders. To clean it up
would need to Bore 80 0ver.
Just exactly what is the MAX Bore for this block?
Has anyone Bore to 80 over? How did the engine run? Blow up? | | |
#67334 10/19/2006 3:27 AM | Joined: Dec 2003 Posts: 510 Shop Shark | | Shop Shark Joined: Dec 2003 Posts: 510 | I wouldn't go more than .060 over on just about any motor. It's my limit. 250s are relatively cheap and plentiful. A lotta times you can find guys giving them away. Check with Nova/Chevelle guys. They're commonly swapping them out to drop V8s in. | | |
#67335 10/19/2006 2:14 PM | Joined: Oct 2006 Posts: 3 Junior Member | | Junior Member Joined: Oct 2006 Posts: 3 | Old Boy--
I've got a 250 I-6 that I'm swapping out for a V-8. It has the integral intake manifold, and is about '81 vintage near as I can tell. It has good oil pressure, but has a broken wrist pin. I have a set of .020 over pistons for it. I'd let it go cheap, and you could put your old cylinder head on it if you don't like the integral head.
Utah Smitty | | |
#67336 10/19/2006 2:47 PM | Joined: Jun 2006 Posts: 687 Shop Shark | | Shop Shark Joined: Jun 2006 Posts: 687 | .080 is too far. I don't think you can get pistons (not sure of that)
I didn't do it, no one saw me do it, you can't prove anything! "Bart Simpson"
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#67337 10/20/2006 12:44 AM | Joined: Oct 2006 Posts: 29 Junior Member | | Junior Member Joined: Oct 2006 Posts: 29 | Thank You for all your help.
The person I purchase this Block claims she has Experts that say the Block is rebuildable.
Yes I trusted her.
Yes I got rip-off.
So If you have a Chevy 250 inline 6 to sell send me a E-mail or message. Im in Texas. | | |
#67338 10/21/2006 3:43 PM | Joined: Jul 2005 Posts: 25 Junior Member | | Junior Member Joined: Jul 2005 Posts: 25 | Just for what it's worth a 250 block,if sonic tested will go .125 and use 327 pistons. The biggest advantage is the wide choice of compression ratios for the 327 pistons. The machine shop operator also told me that the blocks that passed the sonic test had the water jacket area behind the water pump machined down a bit for water pump impeller clearance. That may
be just a coincidence.
Arnie | | |
#67339 10/21/2006 5:33 PM | Joined: Oct 2006 Posts: 1 Junior Member | | Junior Member Joined: Oct 2006 Posts: 1 | What is the minimum wall thickness allowed after boring 4.000" for the 327 pistons? Or what it the minimum wall in a standard 250 cylinder bore of 3.875" that will allow boring to 4.000".? I have access to an ultrasonic thickness meter and could perform the test myself for screening blocks. | | |
#67340 10/21/2006 6:49 PM | Joined: Jul 2005 Posts: 25 Junior Member | | Junior Member Joined: Jul 2005 Posts: 25 | It's been awhile but if memory serves me it depends where it is measured. The thrust side should be minimum of .250,pin sides .125
Arnie | | |
#67341 10/21/2006 9:29 PM | Joined: Oct 2006 Posts: 29 Junior Member | | Junior Member Joined: Oct 2006 Posts: 29 | Hi arnie258 WOW! THANK YOU VERY MUCH.
Block casting number 3994257.
It came up as a 3.8L 230 cid 1963-1970 L-6 Chevy Truck engine. I was told from the seller it is a 250 cid Block? Is 3994257 a 250cid Block?
I do have a Flat spot on cyl wall; just behind water pump opening MIC'S OUT AT .1724
It is the thinest location out of all cylinder walls. My max Bore is 3.945 But all need clean up to say 3.955 The Cylinders Taper down.
Yes I can get 80 over pistons for a 250cid.
327 Pistons? This engine is going in to a boat. So cooling engine water is not a problem. No Salt water;just fresh water lakes in Texas. | | |
#67342 10/22/2006 12:03 AM | Joined: Jul 2005 Posts: 25 Junior Member | | Junior Member Joined: Jul 2005 Posts: 25 | The 230 and 250 blocks are the same,the crankshafts are different. The 230 being 3.25 and
the 250 3.53.
The crankshaft casting #'s are:
230
3788424
3820618
5743013
250
3876802
2779954
360407
I believe the last casting # for the 250 is a lighter crankshaft with less countr weights.
If you can get .080 pistons thats probably the
way to go for your boat.
The .125 bore and use of the 327 pistons is
usually for a maximum effort 250(266 cu. in.) engine.
Arnie | | |
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