RebelRacer

Yea, You heard right, a 3-0-SEVEN

I'm gonna be putting a 350 crank in it and it will be bored out .60 over. Hoping to find some one to calculate my displacement. thanks!

Kyle

Air_Adam

Bore (IN) X Bore (IN) X Stroke (IN) X #Cylinders X .768 = CI displacement

Apeiron

3.935" bore x 3.48" stroke = 338.6 cu in.

Good luck finding pistons.

mw66nova

iTrader: (13)

Ross will make you a set for $750ish. just buy a 350...skip all this small bore nonsense.

ede

nothing like spending your own money on the bullets to shoot yourself in the foot with.

RebelRacer

well, when you get the engine and crank handed to you, its called working with what you have.

another thing, i just read it can be bored .80 over, that would make a 4 inch bore, right?

if thats true, i can just get a set of 327 pistons, and it'll all work out.

and to nova, don't worry, I got a bigger-bore build up in the process right now, just looking at my options with this 307 I got gave to me.

RBob

iTrader: (1)

A lot of the 3-7/8" bore blocks can be bored out to 4". If the one you have can be then do it and make the 327 (as you mentioned). Just make sure to have the block checked for bore thickness first. The casting number may also help in this area.

RBob.

RebelRacer

so basically the 307 with a 4 inch bore and 3.48 ince stroke is getting pretty close to 350, right

RB83L69

So help me understand this....

You've got a "free" block; you're going to spend however many hundreds of dollars on machine work and custom pistons and whatever else, in order to use it.

Or, you could go to the junkyard and get a $50 block; and then you'll be spending ALOT less on machine work, because it will all be nice normal stuff; and ALOT less on parts, because they'll all be off-the-shelf noraml stuff; and it'll go at least as fast and most likely faster in the end, because it'll be more cubic inches.

I'm really struggling with the idea that using that combination of "free" stuff is actually going to cost less than buying the right block in the first place.

Sounds to me like you're using a $20 bill to buy a dime.

A 307 block is 3.875" bore. That means it would have to go to .125" over to make it to 4.000". It won't happen. It's highly unlikely that it'll go past .060", like most every other 307 block. That means, if you want to run ANY OTHER STROKE besides 3.25" (307 stroke), you'll be buying custom pistons.

If you just want to be "different", and spend more money to go slower, then go ahead and do what you're doing. If you want to build a motor for the least money, get a 307 crank and forget the 3.48" stroke. If you want the most motor for the least money, forget the 307 block and get a 4" bore one.

The block is THE SINGLE CHEAPEST PART of the whole short block. It's beyond stupid to allow yourself to be handicapped by that, just because it's "free". You'll run up probably 5-10 times the cost of a block, in custom pistons and machine work.

five7kid

iTrader: (14)

You really need to watch your decimal places.

It's "0.0xx over". For the numbers you used, 0.060" or 0.080" over.

It makes a difference. Before you take any factory casting block over .030" over (with the possible exception of 454 blocks), you need to sonic test it to ensure it has adequate wall thickness to go out as much as you're planning. As RB said, to get to a 350 size bore, it would have to be bored out .125", which is extremely rare in factory blocks. Some very early 283 blocks had enough meat to do that, but of course the factory figured out it wasn't necessary and started reducing wall thickness to match the intended bore only - long before they started making 307's.

Now, building a 307 isn't all that bad. It has a better bore/stroke ratio than a 305 does for breathing purposes, but you still want to use 305-type heads on it. However, if you don't have a 307 (or '68/'69 327) crank, then forget the 307 block and go find a 350 builder.

Like somebody already said...

RBob

iTrader: (1)

Not only close, but it is the standard Chevy 350 engine.

RBob.

RB83L69

Except for the minor detail of a 4" bore being impossible with the block in question... it is true that a 4" bore and a 3.48" stroke would be a 350.

theMachinist

Bore (IN) X Bore (IN) X Stroke (IN) X #Cylinders X .768 = CI displacement

sorry but that formula doesnt work at all.

also you dont need to sonic test every block to bore it .040 or .060 unless your gonna use a turbo or blower. any older casting 350 will go .040 no problem, and you can go .060 as long as your not making a heavy duty or race motor.

88Camaro350

Buddy of mine did that actually. Right in the big toe with a .22lr lol. Needless to say they had to remove his toe joint and fuse his toe back together.

I would stay away from the 307. If you have it and need an engine ASAP I would throw it in and drive it. But save up/look for a 350. It will serve you better.

WhiteLightnin83

correct formula for displacement is (bore divided by 2)squared x 3.1416(PI) x stroke x #of cylinders = C.I.D.... for instance.... 4.030 divided by 2 = 2.015, and squared = 4.06, x 3.1416(PI) = 12.76, x 3.75 = 47.83, x 8 cylinders = 382.67 cubic inches....

RebelRacer

ok, ok, i did some more research.

You guys were right, the biggest bore you can get is 3.925.

but you guys were full of crap about custom pistons, heres the summit part number STL-295AP60 15 bucks a piece. not bad.

building a 307 isn't retarded, its just different, and I still have the 307 crank.

RB83L69

That's a 307 piston; 3.25" stroke. Not a custom piston for 307 bore and 350 stroke. They won't work with a 350 crank.

Apeiron

Sure, those will work with a 307 crank.

They'll work with a 350 crank too, if you don't mind the piston coming out of the block to smack into the head at the top of the stroke and then catching the top ring on the return stroke and tearing the lands out. Or you could pour more money into custom 5.47" rods to make them fit.

Apeiron

Oh, and just for fun, compare the price of your 307's 295AP with a 350's 423NP.

F-BIRD'88

Give you head a shake, will ya!!!

The fact that this motor will have to be $balanced$ throws the whole thing out the window. Get a 350 block and a 350crank and 8 350 rods and rebuild it.

Put the money you saved, into a set of good cylinder heads.
Sell the 307 parts to someone else and start from there.

Air_Adam

Sorry... supposed to be 0.786 not 0.768. It does work. Will get you within .5 CI anyway.

Streetiron85

Actually, if you were determined to go through with this project, a set of 5.56" rods from a 400 would put you in the ballpark for the right deck height with some 307 pistons and a 350 crank. You'd have lots of deck clearance to work with, but it could be milled down .030" or so to tighten it up if you wanted to. I'm not sure about the piston to crank clearance though.
That's IF you were to decide to do it.
I can't advocate it though... Politicts, you know...

vampiroc

Just build the 307 up, stroking it is a waste of time. You can make plenty of power on 5.0L

AsphaltAssalter

Yep, nothing wrong with a 307 as long as it has good heads on it, 307's got a bad rap because they ALL came with 2 bbl carbs, low compression, crappy smog heads, retarded cam timing and emissions that choked them badly. I'd take a well built 307 over a similar built 305 any day if they were a good price and I needed an engine.

RebelRacer

well, looks like i'll just save the 350 crank for my 350. it'll all work out.

vampiroc

yep, any engine will be terrible when it's breathing through a straw all the way to the low compression pistons. 400 powered cars were absolute slow junk back in the 70s with 882 heads, tiny cam, and crap for intakes. 307s aren't completely bore restricted like the 305s are, more potential