4playta

Alright I can already see the just buy a 350 answers comming but I would like to be alittle different plus money is real tight. Wifes camaro has a 307 in it and a 307 has a 3.875" bore and a 3.25" stroke and I am toying around with the idea of putting in a 305 crank that I have. A 305 crank has a 3.48" stroke and then punch it out 30 over. So basically a 307 is a 283 with a 327 crank what I would be doing is creating a super stroked 283...would this combo work? If so what would my displacement be bored 30 over? Also I know 305 heads work real well on 307's because it ups the compression to around 10.1 but if I bore and stroke it would I be better off running 350 heads? I have all the parts to actually make this work if it is feasible.

five7kid

iTrader: (14)

The factory never made a 3.875" bore x 3.48" stroke engine, and the aftermarket didn't pick up on it, either. Read: "custom pistons". Translation: "Much more expensive than just buying a 350 and building it".

3.875" + .030" = 3.905". 3.905 squared, divided by 4, times 3.14159, times 3.48", times 8 would give you the displacement.

Do the math and let us know your answer.

Compression would depend upon final combustion chamber volume (because you would naturally install 1.94" intake valves in 305 heads, deshroud the valves as necessary, and polish the chambers after cleaning up the ports), piston dish/relief volume, deck height, and compressed head gasket opening volume.

KrisW

iTrader: (5)

Around 330 cubic inches?

Anyway, I toyed with the idea as well with a 307 from an old truck I had. I say this: if you have the stuff lying around and you're going to replace a worn out 305, then why not? It is like overboring your 305 more than you ever could.

350 heads work fine and so do 305 heads. Just make sure that you have 1.94 intake valves and flat top pistons. Your compression on the street will be good. I'm talking 80's heads, NOT 70's crap. Some LG4 carb 305 heads should be almost free to come up with. 1.94s and some port work will go a long way.

Good luck!

4playta

Or realy strokin a 283...lol! Anyway yeah I never thought about the fact that the factory never made a 3.875 bore X 3.48 stroke so I guess I stick with stock pistons...just wanted to know if the crank would work for this little winter project to put alittle more umph in the womans ride.

five7kid

iTrader: (14)

You put stock 307 pistons in with a 3.48" stroke crank and you'll push the tops of the pistons 0.115" out of the cylinders. Last I checked, that isn't a good thing.

KrisW

iTrader: (5)

I have heard some of the old timer chevy guys (they remind me of sofakingdom) talk about when they would bore out their 283's to 4 inch and run those pistons when racing.

I don't know what the thickness is of your cylinder walls, or a 283 for that matter, but you may want to check it out.

I have some old (from the 50s and early 60s) Buick engine blocks that will go .125 safely. 307s are the last of the 283 castings (some have the same casting number and crappy canister oil filter, like mine did) but with the larger journal castings.

Maybe it would be worth the money at the machine shop to sonic check the cylinder walls?

4playta

What pistons would I need to make this combo work? Or could I just machine the top of each piston and or maybe run a thicker head gasket? I have a lathe and mill at work so i could machine them myself but I dont know if it would be safe to take that much off thats why I was thinking a thicker head gasket and just machine alittle off the top of pistons? Then again 0.115 out the top would give me a killer compression ratio...lol!

Sonix

iTrader: (1)

No, you can't machine those pistons that much (off the top). Pin height would be WAY too high i'd think.
That's.... dicey. I'd highly recommend you throw the 307 in the trash and start without the mindset of "use what I have". What YOU have will take more money away from you than the amount of HP you'd get out of it

KrisW

iTrader: (5)

Probably right, but that's what these forums are for. Get your brain cylinders warmed up and up to the right rpms so that when you actually DO something, at least there is a little perspective...

The pistons you need for a custom 307 would probably run 500 or 600 bucks from Ross or JE...

I did see the world's fastest 3rd gen (a red Camaro) featured at Bonneville in a magazine. He was setting speed records with his SBC, and he began by using a 307 block. I don't know if he has switched it out now or not...

4playta

Thanks for the info everyone I learned something today. I guess I will just keep it a 307 then, not going to throw it in the trash it only has 12,000 miles on it. Maybe I will just give her alittle 100hp shot of spray.

KrisW

iTrader: (5)

If money, really IS tight, some LG4 heads, 1.94 valves, and some porting will go a long way while stretching your dollars. Combine that with a cam, and you're still better off than the 305 guys!!

4playta

Well when I bought the car for her the guy just put the motor in it, it came from a 69 truck or something. He had the motor rebuilt 10,000 miles ago and crashed it so he put the motor in the camaro. It had a 2brl on it and I put the next size bigger cam from stock and an edelbrock performer manifold with holley 600 vs and she is pretty quick also has a 373 posi that came from my ta because I got a rear with disk brakes...problem is she drove my TA and now she feels the need for speed...LOL! Nothing funnier then watching a chick smoke ricers!

KrisW

iTrader: (5)

Most likely you got a fresh short block. My 307 truck heads had NO BOLT HOLES FOR ACCESSORIES IN THEM! That's not good in a third gen...

five7kid

iTrader: (14)

FWIW, in what I think was the first PHR magazine Engine Masters Challenge, one of the top performers was a 307 stroked to 3.75" with out-of-the-box Fast Burn heads. The displacement was limited to 360, or something like that, had to be generally available parts for heads and such, and they used the "average" horse power between 2500-6000 RPMs (not sure of the exact numbers). They guy had to have special pistons made for him, but that was within the rules of that round. His build approach was to have as long a stroke as possible with the displacement allowed to enhance the lower RPM power. It worked.

Cost him something like $20k to build that engine.

I'd agree with the 416 heads on the 307 approach. Pretty sound plan. But, I wouldn't go to the expense of stroking it.

BTW, 307 blocks are only good for about .060" overbore. Only the really early 283's could go out to 4".