Stroking a 305

[Turbolq4]

305s small bore causes an issue called valve shrouding. Means that the cylinder wall is close to the edge of the valve which effectively reduces the air movement in that area. This is compounded by the already small valve in an inefficient head designed for emissions compliance.

Small blocks are exactly the same on the outside. All of the accessories bolt up, manifolds, trans, etc. You would be the only person that knows what's actually in there.

The only thing to do to the stock engine is rering it, replace the bearings, rebuild the heads, and put it back in the car absolutely stock. They run exactly as intended. No reasonable amount of time or money will make it produce good power or get good mileage. In real world use they get the same mileage as a mild 350, just have far less power.

 

[olds307 and 403]

Power can be made with a 305 and there are many 1.94 intake valve heads out there, don't build the stock heads. Stay smaller on the intake runners, otherwise low end torque will be sacrificed.
See what oversize pistons come in the kit but your block will need the cylinders measured to see how much of an overbores is needed.

 

[olds307 and 403]

Either this head but need a Vortec intake which only come in squarebore.
https://www.summitracing.com/int/parts/nal-12558060/overview/make/chevrolet
or this head, normal intake.
https://www.summitracing.com/int/parts/drt-10024365a/overview/make/chevrolet

 

[Rktpwrd]

My car originally came with a 305 as well. I yanked it out, freshened up the engine bay, rebuilt the engine, and dropped it back in.

Or did I?
Surprise, this is actually a Vortec headed 350 making roughly double what the old 305 used to when new.
The point is, you can reap all the benefits of a larger displacement and more powerful engine without sacrificing anything more than maybe mileage and still make it look exactly the same. And for cheaper than what you wanna do. That’s the only real reason the 305 was in there in the first place, just enough power to move it down the road but not be a total fuel pig.

There’s a reason that the results of your searches have all yielded the same “just drop a 350 in it”, it’s because it’s the voice of experience of everyone that’s already been down that road.

But to each their own. Good luck.

 

[olds307 and 403]

I am seriously considering a 87 442, a 307 is another small bore motor an a weak block. I would do the same as above, Olds 350 painted semi gloss black with the Performer intake with the script ground and a the factory carb, air cleaner and maybe Thornton manifolds.

 

[lilbowtie]

The 305 was designed as a stroker. As you have heard, and if you investigate you will find it's not a good HP candidate. I don't know what kind of HP numbers you would like to see but there are enhancements you can bolt on for improvements. Seeing it's your daily driver your not looking for much. I will side with the others on the swap. It will be easier, quicker, and probably cheaper and enhance it's value as RKTPWRD did; to lift that numbers correct 305 out (come on it's a chevy in a Pontiac) and drop a crate engine in. You can always keep the 305 to be correct. Check this article http://www.superchevy.com/how-to/en...-how-to-mod-a-305-with-bolt-ons-add-168-rwhp/

 

[DRIVEN]

I won't try to talk you out of it.
-Overbore just enough to clean it up.
-Vortec 305 heads and matching intake.
-Select pistons for a 9.0-9.5 compression ratio.
-Contact cam company for selection.

305s have dinky bores and that limits high RPM breathing. Build for torque and don't worry about revving past 4500.

 

[fleming442]

Tiny bore=zing it to the moon!
(As long as it'll flow)

 

[bob64]

It seems to me that you wish to keep it matching numbers, well if that's the case then you won't be changing the heads. Keeping your car matching numbers won't add value when talking engine.

I rebuilt a 305, why cause it was for a Elcamino that was going to one of my daughters. I had the heads all re-corded and well what a lame 305, but it won't be the cause of her getting hurt! It ran good and still is a gas mixer.

If you have it in your head to rebuild it, then plain and simple rebuild it, don't stroke it as it's a waste. Reduce drag(fan) on the engine and change up the exhaust.

 

[UNGN]

A "matching numbers" motor in a plastic bag in the corner of a garage will add as much value to your car as it does installed and running and pumping out 180 Hp.

Matching numbers motor only means something if the motor meant something and 305 didn't and still doesn't and won't ever.

Now if GM put a factory 350 in there, then "matching numbers" might have meant something.

Find a Vortec headed 350, put the 305 in a bag and get on with your life.