I’m currently looking at a car that has a “bored 305” and I’m just trying to figure out what that would equate to in CID. It’s a 305 .20 over. I’ve heard a 305 .30 over is around 310 CID so I’d assume it’s something close to that.

 

.020 over with stock stroke makes it 308 and change.

 

(Bore ÷ 2)² x 3.14159 x stroke x (number of cylinders) = swept volume

 

what would these be good to rev to?

 

5,000...

 

It's still a 305. A tiny overbore makes no material difference to ANYTHING about how it runs. It's just had some maintenance done on it.

"Good to rev to" depends more on the induction system (heads, cam, intake, exhaust) than anything to do with "overbore". Plus of course, the quality of the bottom-end build, in terms of survival. But the induction system determines its ability to produce useful power at any given RPM.

 

Bingo, heavy cranks, crumby balancing, makes for a very frustrating SBC to work with. Especially with the .020 pistons, God only knows what kind of claimer pistons he's got in there. Not a fun engine to build. Below 5000-RPM just about bulletproof in my opinion. Anywhere above that, it's a freaking ticking time bomb, especially with those pistons....

- Rob

 

Slap a TPI on it and never worry about exceeding a safe RPM.

 

All other things being equal, the same as a stock-bore 305.

 

Here is an example of a 400 hp 7000 rpm+ 305.
I would have used a solid lifter cam like the Comp magnum 294S-10 cam, but.....

When hot rodding a 305 just keep in mind the small bore limits you to intake valve size. 1.94".
It won't slow you down.
Lots of good ways to skin this cat.

http://www.hioutput.com/tech/400hp/400hp.html

 

If 400 hp is not enough for you lower the compression ratio and supercharge it.
About 35-40% more HP than the N/A high cr combo version. (larger chamber 1.94 heads dished pistons) 7.5:1 cr for boost on pump gas.

 

Isn't that the one that blew up before it finished its 3rd dyno pull?

 

Without evidence. .......?

 

Sorry, "evidence" is on YOU, not me. You'd have to go dig up the old Hotrod article that mouth diarrhea thing you posted was based on.

If memory serves (after all, it's been well over a third of a century now) they built a couple or 3 305s at various levels of aggression and dyno'ed em. Would have been in maybe 85 or so. Typical Hotrod article as far as that goes, and certainly entertaining and somewhat thought-provoking, in a random way. Seems like they took a stock 305 short block, could have been a L69 one with the X rods, and progressively stepped up the H/C/I they bolted onto it. The final and most aggressive build, the 400 HP one, made its 400, butt blew up before it completed its full sequence of pulls. I could be Rong of course, maybe I've been hypnotized and had false memories installed by the black helicopters? Iunno. A look at the original article would be fun though if anyone could locate it. I don't think I have a copy of that issue anymore. A leisurely doddering back down Memory Lane in our walkers just to see where a little piece of pop culture that refuses to die, actually got started, might be enjoyed by all.

That said, I have NO DOUBT WHATSOEVER that 400 HP could, and has been, made, by a 305. At least once. The issues are more along the lines of, is it A Good Idea to use a 305 if your goal is 400 HP in the first place and you weren't rules-constrained or the like, which would certainly entail either very high RPMs, or some form of The Force, either of which would demand a well-built short block; whether the OP's motor in question has been prepared with an appropriate level of detail for such a task; whether someone who would ask "what would these be good to rev to" would be ready to deal with it; and stuff like that.

 

Found it.

https://www.ebay.com/itm/362954301151

Older than I thought. Probably was a LG4 short block since the L69 had only existed for less than 2 months at the terminus ante quem for when that article would have had to have been written.

 

From the 1983 article -

 

What exactly is the big issue. This engine ,after who knows how many dyno runs over the whole course and being installed and rung out in the car . Who knows if it was over reved and or saw detonation how many time. lost a rod bearing.. It was repaired and likely went on to live a long life.

I bet it was detonation. This is like striking the piston and rod with a hammer. Distorts the rod big end and this causes the rod bearing to spin.
This will happen to a 350 or a 383 just the same.
**** happens.
Its still a fun buid on a 305 sbc that you can do.
At 10.6:1 it will need good gas. 92+ octane.
This builder learned that the hard way.

In a 3500# hot street car with the right gears and converter is mid 12's capable. In a full prep race like a stock eliminator car it is mid/high 11's capable.
Ya its racey.. Just like the 60's era 302 z/28.
But it is a easily sourced and built 305.