Grumbles

So I know the only diff between it 305 and 350 is the bore. Does this mean I could possibly use a 383 stroker kit with different pistons?

I'd just like to keep the factory # matching block if possible.

vetteoz

iTrader: (13)

Could
30 over 305 with 3.75 stroke gives 333ci
Long stroke , small bore ; ain't going to rev
Would need to use 400 rods (5.565 ") with 305 pistons to get correct CH

Grumbles

Sounds like you've seen this done before? Any sort of specifics I should look for? Stock 305 pistons or special castings? standard 383 crank?

Saabster

iTrader: (2)

Keith Black makes pistons for a 305 bore and a 3.75" stroke with a 5.7" or 6" rod.

As for getting a stroker kit and changing the pistons...well you'll have to get the crank rebalanced but that should be all you need.

Standard You'd-be-better-off-with-a-4"-bore rules apply, this is a lot of machine work and everything will need to be clearanced just the same as a 350. But if you want a matching numbers engine I guess this is your only option. Do you want your heads to match as well? If not, you'll want a set of TFS 305 Super 23 heads, the best heads for a 305 bored engine.

Send Casey Butt a PM, he was building a 335 a while, he might have finished now and have some good tips.

EDIT: Personally, if you aren't gonna change the heads, I wouldn't bother stroking the engine.

Grumbles

Thanks for the info Saabster. it's just a consideration for now. I wont be mussing about with the motor again until the 305 dies. That may be tomorrow, or several years from now... if it's tomorrow it's gonna be a 350 :P

Apeiron

As mentioned, a 305 with a 3.75" stroke is a 335. It's a waste of time and money when you can spend the same amount or less to build a 350 or 383, even including the cost of the block. If you want to keep the numbers matching (which in the long run probably isn't going to add value to a TBI car anyway), pull the 305 out and put it in storage, and build another engine to put in for playing with.

Irockz

iTrader: (1)

I built one a few years back,simply because I had the stuff laying around to do it.Mine was a 5.5 rod length unit,made good torque,but was DONE by 3500RPM.It ain't worth the headaches,and will almost always cost more than a 383.I only say almost because I did build mine for the cost of rings and bearings,but I'd say 99 out of 100 people don't have a 1 piece RMS crankshaft,a set of new 305 pistons,and a set of fresh 400 rods all laying around the same place at the same time.Was a fluke deal for me,and one I wouldn't repeat,my question was answered.

afida15

Hey if anyones interested ive got a set of resized 400 rods and a new set of .040 over flattop 4 valve relief 305 pistons. $125.00 for both sets.

305sbc

iTrader: (3)

You can use a factory or aftermarket 3.75" stroke crankshaft, and either stock rods or aftermarket 5.5", 5.7", 6.0" rods with aftermarket pistons.

Since the 305 pistons are lighter, you can get by with less strength in the rods and less counter-balance crankshaft weight. The option of internal balancing then becomes an easier and more affordable option if that's what you choose. If the rear crank flange matches what you've got now, then you can use your factory flexplate and damper if the crank is internally balanced. Some aftermarket 3.75" cranks can be ordered internally balanced. You need to determine your bob-weights (piston & rod) before you order one like that.

A 305 bored 0.030" can easily take a 2.00" intake valve & 1.55" exhaust valve up to lifts around 0.600" intake and 0.700"+ on exhaust, without any offset of the heads or change of valve angle. This is assuming using stock or aftermarket 305 OR 350 heads.

These are the facts. With only about 334 cubes to feed, there is no excuse for a head not to be able to feed the engine to 7000 RPM or more if done correctly. Bore shrouding is a factor that cuts air-flow a few percent, but will not choke an engine. Bore shrouding is easily verified on a flow-bench.
It is nowhere near enough of a factor to be limiting engine RPM.

The fact that not many people actually build the 334 cid engine with the same care or expense as they would have with a larger engine should not be viewed as determining any kind of limitation to such a project.

If economics is the primary factor, then an engine upgrade for performance doesn't make so much sense in comparison to swapping in another stock or used 305 to replace what you have.

Any time you increase performance significantly then you are looking at costly upgrades to supporting systems ( cooling, fueling, induction, exhaust), and upgrades to driveline strength - transmission, torque converter, driveshaft, rear-end, frame stiffening, etc...

If you're in a position to seriously upgrade performance, then you have many choices out there as your method for making the power, to include engine size and configuration.

Saabster

iTrader: (2)

I agree with most of what you've said, but have one question.

What's your source of info on 2.00" valves in a 3.766" bore lifting to .600"? I've never seen that anywhere. The only other info I have that's even close is this thread.

https://www.thirdgen.org/forums/tech...ds-1-94-a.html

He used slightly larger 2.02" valves, but only managed .500". Not saying you're wrong so much as the data I have contradicts your statement.

I do agree with what you say otherwise. There's simply no data to support the "3.766 bore doesn't work" theory. Given the practical 334 cube limit of such an engine (a maximum stroke of 3.75", going for more is just not reasonable) that's no reason you can't feed that with 1.94"/1.5" valves.

InfernalVortex

iTrader: (4)

Why bother? Saving the moneyo n special 383 parts and just building a 350 will be cheaper, make more power, and be more streetable.

Unless this car is seriously rare, a numbers matching block does not matter.

If you're that worried about it, I'd pull the 305 and prep it for storage and keep it somewhere.

305sbc

iTrader: (3)

I've done it in my shop. I was only talking about the valve-to-bore clearance, but with a long duration camshaft piston-to-valve clearance can still become an issue no matter the bore size.

The clearance on any individual engine can vary slightly due to dowel locations in the head & block. That's why I always do an actual mock-up of the parts before trying something that might be close. With something like this you'd want to mock-up several cylinders, at least front & rear on both banks due to possible core-shift and/or dowel variance.
If I ran into a case where the valve was too close or just touching, then I'd just radius the edges of the valves a little more. There is no clearance problem to the point of having to compromise the actual seat on the valve, so it's no problem.

Here are some pics:
http://s702.photobucket.com/albums/w...20on%20305cid/