Is ok to bore out a 307 to 350. that would save me a lot of head ache if so

Biggest pistons available for a 307 is .060 over.

Stock bore and stroke is 3.800" and 3.385" respectively.

[(1.9")^2*PI*3.385]*8 = 307.118 that's the current cubic inches...volume.

[(1.93")^2*PI*3.385]*8 = 316.893 that's the volume in cubic inches with the .060" oversize pistons.

How do you plan on boring it out to 350?

Even with the oversize pistons, the stroke would need to be 3.73865--.353645 over stock....and as far as I know there isn't even a stroker kit for the 307. 350 and 307 are totally different engines.

TOC Admin
Brando

i was just wondering if it would be possible. i have a shop i go to for various things i need done when working on cars.

You'd have much less headaches dropping in an Olds 350 if that is what you're after.

TOC Admin
Brando

will the olds 350 will bolt in a 84 delta 88 with no mods? if there are mods that need to be done, what are they?

Hi Jeht Black, hello everyone,

Welcome to TOC.


He did hot say "bore it out to 350". The statement is misleading, at best. Any overbore, by itself, is less cost effective than the bolt ons he rejected

FWIW: All Olds V8s from '49 to '90, are Rockets.


Yes. Externally, all SBO (small block Olds) are the same and are interchangeable. Use your existing bracketry and you'll be fine.


Yes, if you only shop on the internet.


Actually he would bore it to 4,057". Any top quality shop could do it for him. Not cheap, and they would also advise him to use a 350 block. But if he wanted to pay ........


Right. Or for any other Olds. Kits are for those who want to follow the crowds. Individuals make their own kits.

Anyone want to guess how my 425 grew to 437?


There are lttle, if any external differences between the SBOs (307, 330, 350, and 403). Internally, the block castings were changed to accomodate the different cylinder bore diameters. Crankshafts are all dimensionally the same.

307 heads were cast with smaller ports to match smaller CID, but also in order to meet the stricter emissions standards of the late '80s. Externally, except for going from 10 to 5 bolts per valve cover, and the smaller ports, they are the same.

Norm

So it is possible to bore the 307 out, and put 350 pistons in it? I was thinking of it as I was posting that reply, thanks for the heads up. Perhaps I should have read this before posting...

Not sure by what you mean: "Yes, if you only shop on the internet." .060 is what Clevite states is the biggest oversize piston available for that year 307, as well as any local auto parts store would say...unless the parts person happened to be experienced with Oldsmobile V8 engines, specifically the 307.

As to how you got the 437, taking a guess...
.060 over pistons would make it a 437, I see no listing for a 425 at federal-mogul's website. So I'm guessing you used the .060 over pistons for a 455 since it has the same stock bore size as the 425.

If he was to have the 307 bored out to a 350...would they add sleeves for added strength and reliability? I've never had an engine bored, how much does it usually run? I'll find out soon enough, but just wondering.


TOC Admin
Brando

Yes, possible, just not practical.


Anything good in it?


I don't think I'd be looking on the internet for a 3¾" piston for a 307 Olds. Odds would be better at my local machine shop.


For only that year? How about another manufacturer?


Or just good at reading parts catalogues?


Close. Did you think I'd bring it up if it was that easy?

437.97921237728985 = 438
437.14609569598510 = 437


I did not use Federal mogul pistons.


Good, you are beginning to think outside of the box.

425 and 455 have different strokes and rod lengths. The pistons have the same 4⅛" diameter, but the 425 compression height is 1.612" and the 455 is 1.735".

Using the same 7" rod, the 455 CH would have to be about ⅛" shorter. Removing that much from a piston top, would probably render it useless. I used the 7" rods.


No. They would add the sleeves to keep the coolant in the water jackets.


Depends on many factors. The geographical area, the shops hourly rate, and how much material is to be removed, are a few.

You have not talked a shop yet?

Norm

Give up?


4.185 x 3.980 = 437.97921237728985 = 438
4.155 x 4.030 = 437.14609569598510 = 437


Thirty over Badgers were in it (.039" in the hole) already. Due to a spun bearing, the crank needed repair, so it got offset ground.

.050" extra stroke got the pistons up to .014", and the CR from 8.8 to 9.6.

Norm