gmgearhead

hello I have a sbc 350 I bought and ran for about two years in my truck I am now going to school in august for high performance engine machining , I started tearing the engine apart to get it ready see what I need and discovered the bore size is 4.250 and am highly confused as it is a early 80s block and not an aftermarket block (14010207) I am building a 350 with 3.75 stroker crank 177 weiand blower and 100 shot of nitrous and was wondering with it being bored out this much if it would even work ?

tealman92

Why nos and a blower?

novaderrik

at .25" over- 1/4" overall, or 1/8" per side- there should be almost no gap between the cylinders and there would probably be holes into the water jackets on a 350 block..

are you sure it isn't actually 4.025", which would be .005" under a standard .030 overbore size and within the realm of an improperly calibrated cheap caliper?

Night rider327

iTrader: (13)

It's not 4.250" for sure. Throw what ever tool you measured that with away and buy another brand.

That would be big block 427 and 454 bore sizes.

The most you can overbore a common sbc is 0.060" This would give a 350 a bore of 4.060"

truckerz

iTrader: (2)

Not to mention .060 is suspect. Depending on the casting, even .060 might be to thin to depend on with a blower and N2O. Some have had luck running that over bore, others haven't. If it is .060 make absolutely sure you have enough material between bores, and that material is in perfect shape.

gmgearhead

Because that is what I want ? Why not nos and a blower ?

thtanner

iTrader: (1)

Why was ford even mentioned? I'm not one for brand bravado, but it just came off as weird.

redneckjoe

aliceempire

iTrader: (14)

Three hundred and fifty thousandths over...awesome.

ASE doc

NOS and a Blower? I see where this is going. My advice, for what it's worth and if you'll listen is dump the OE block and buy a Dart. The reliable limit for a factory block is 450hp for 2 bolt main, 550 for 4 bolt main. If you're really serious about a blown, NOS injected build, you will be looking at over 1000hp. The Dart SHP is good to about 700 with billet main caps. The Little M is good for over 1,000hp. A build that will handle that power level with any kind of reliability will require the Dart Little M and a list of parts that totals about 10 grand just for the long block. That's using the cheapest parts available at that level.

I also hope you've got lots of money for drivetrain parts.

zraffz

Absolutely nowhere because it wont ever happer just like all these other "imagination builds"?

Damon

Can we get a picture of the deck surface between the bores, please, before this post degenerates any further? With a bore spacing of 4.4" on a SBC it's not possible to have 4.250" bores.... not even on the big-mamma 400 block. There wouldn't be enough webbing left between the bores to leave the thickness of a matchbook. Not to mention you'd be into the water jacket in several places.

ASE doc

I think we can all agree that the 4.25 is a measurement accuracy issue. The only SBC block I can think of that might allow a 4.25 bore would be a 4.5 bore spacing aftermarket block. We know that this isn't what the OP has. He just needs to repeat his measurement.

If as stated, he is enrolled in a training program for engine machining, he will soon learn what it takes to build a reliable boosted/NOS injected engine.

Regal105

I don't visit this page all that often any more.... But when I do, I see a post like this every time.

zraffz

Yeah seriously. You mean you can't grow a ******, throw on a flannel (or a stained white t-shirt with a pack of Marlboro Reds rolled up in the sleeve), bolt on an 8-71 and spray it with a 1,000 shot of nitrous?!

redneckjoe

It will most likely need the turbo encapulator to hold up?

zraffz

Now I understand how my girlfriend feels when I tell her why I spent 5 grand in a week on motor parts lmao