Can you make a 305 stroker with 350 crank and rods?

[PhotonFanatic]

What exactly made the 305 so terrible? Almost anyone you talk to dislikes the 305.

Next question: How would you address it? Say you want to keep the 305 for whatever reason.

 

[SquareRoot]

What exactly made the 305 so terrible? Almost anyone you talk to dislikes the 305.

Next question: How would you address it? Say you want to keep the 305 for whatever reason.

1. The 350
2. Remove and replace with a 350.
3. There is NO reason.

 

[fast 99]

Back in the day everyone wanted to get rid of 305's and install 350's. Rebuilders were drunk with 305 cores. Only credit we were given was on the crank and rods. Everything else wasn't re-usable. 305's heads have smaller combustion chambers. Compression will be high on a street 350 using 305 heads. As stated earlier 305 stroke is the same but crank will need re-balance. A 305 is not a good starting point for larger CI motor.

If it were me, find a 350 and install a 400 crank or get a 400 and install a 350 crank. Yes, I know the journals and balance are different, but parts are available. CI will be in the 375 area. Also, remember 400's use a larger combustion chamber and are only available in the 6-exhaust manifold bolt head. It's one of those how much money do you want to spend decisions?


Reason 305 wasn't desirable is 2-fold. Small CI and emissions restrictions. They were very low HP.

 

[Catbox]

What exactly made the 305 so terrible? Almost anyone you talk to dislikes the 305.

Next question: How would you address it? Say you want to keep the 305 for whatever reason.

The tiny bore of the 305 means that you have tiny valves.
The 305 uses a tiny 3.736-inch bore.
The normal valve size in the “performance” 305 head is 1.84″ x 1.50″.
The tiny bore means that those tiny valves are shrouded in the chamber and have issues filling those tiny bores efficiently.

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The 305 stuff can work well with some work, its just that the 350 is so available that it is easier to start with that engine.
Larger chamber, larger valves, less shrouding of the valves all makes for a simpler combo to get close to right on the first try with expected power and manners.

 

[Bennyt]

If you have a good running 305 in a vehicle, I'd leave it alone. Maybe a manifold swap and headers that can be reused on a 350/400. A few dollars into a rering and bearing kit and freshening it to make it go another 75k miles out of it fine. Once you start putting money into machining and new parts, you are wasting resources.

Other than those minimal mods, put all your money into building a solid 350 or larger. More power, less hassle for comparable dollars.

Only thing worth keeping out of 305 is the rods as they are same as 350. Crank/block/heads just aren't worth keeping unless you just have to have a 305 for some reason.

 

[AyWoSch Motors]

What exactly made the 305 so terrible? Almost anyone you talk to dislikes the 305.

Next question: How would you address it? Say you want to keep the 305 for whatever reason.

I don't have a problem with 305s in general, my van has one and my buddies truck has one, both run great. Good engines, they do what they were meant to do. Mine inparticular was great when it was running, peppy, got me from point A to point B, but one day it randomly decided to spin a bearing.
I ruined the crankshaft and the #1 and #2 connecting rods. So to answer your question, yes its repairable, but it's not worth it to me at the moment. I'd need to find a new 305 crankshaft, new set of connecting rods, and a full rebuild of the engine, and a rebuild of the heads. Block might even need to be machined.
After that happened I actually bought another 305, that I thought I could steal the crank and rods out of, and reuse my old numbers matching block, but it turned out that engine had also started to spin a bearing, and those parts were junk as well.
I ended up finding a killer deal on a nice L98 350 out of a Corvette, rebuilt it and threw it in. Runs great now. That engine only cost $350, and about another $100 or so in gaskets to do a light overhaul on it. Reused the edelbrock performer intake and carb, and a few shiney chrome parts that were on the old one, and I'm back in business. It was a no brainer at the time.
I did keep the old numbers matching 305 block though, for originality sake, incase I ever want to fully restore it. I oiled it down and wrapped it in plastic wrap, and it lives on the counter in the corner of my shed.

 

[AyWoSch Motors]

Back in the day everyone wanted to get rid of 305's and install 350's. Rebuilders were drunk with 305 cores. Only credit we were given was on the crank and rods. Everything else wasn't re-usable. 305's heads have smaller combustion chambers. Compression will be high on a street 350 using 305 heads. As stated earlier 305 stroke is the same but crank will need re-balance. A 305 is not a good starting point for larger CI motor.

If it were me, find a 350 and install a 400 crank or get a 400 and install a 350 crank. Yes, I know the journals and balance are different, but parts are available. CI will be in the 375 area. Also, remember 400's use a larger combustion chamber and are only available in the 6-exhaust manifold bolt head. It's one of those how much money do you want to spend decisions?


Reason 305 wasn't desirable is 2-fold. Small CI and emissions restrictions. They were very low HP.

The other reason I've heard is that 305s dont oil themselves well. They pump it all to the top, and it doesnt return to the pan as well, and they're sensitive to lack of oiling.... or so I've heard. Its seems to have proven itself true in my case.

Doesnt a 400 have the same stroke as a 350, just a larger bore?
If you were going for changing the stroke, I'd either a get a 383 crank and rods to make a stroker, or a 283 crank and rods to make a 327. The 350 bore seems to be the happy medium of all the different engines, but changing the stroke you benefit from either the extra torque and better low end made by a stroker, or a the higher RPM and better top end from less rotating assembly weight.
At least that's what I've reaserched.

 

[fast 99]

In 1968 GM enlarged the crank journals. Early motors like the 283, 265 and pre 68 327 will not interchange with later 350's.


350 bore 4.0 stroke 3.48
400 bore 4.125 stroke 3.75.
In addition, crank journals on the 400 were larger.

If you want a RPM motor and more cubes, go with a 400 block and 350 crank. There are thicker bearings made for the smaller diameter 350 crank.

To my knowledge 305's weren't prone to more oil system issues compared to any other small block. Most oil related failures are caused by low oil or lack of maintenance.

 

[PhotonFanatic]

My buddy used to say they "liked to flatten cams". I guess he meant when they got older. He had a couple of problems out of 305's, and switched to 350's. It seems like the factory 350 was overall more reliable than the factory 305.

 

[fast 99]

My buddy used to say they "liked to flatten cams". I guess he meant when they got older. He had a couple of problems out of 305's, and switched to 350's. It seems like the factory 350 was overall more reliable than the factory 305.

Actually, saw a bunch of 307's with flat cams. Never heard the reason but a guessing was some sort of manufacturing / parts issue or oil formulation changes.

Really, the 305 was a good running motor. It was just a pooch.

 

[RecklessWOT]

The other reason I've heard is that 305s dont oil themselves well. They pump it all to the top, and it doesnt return to the pan as well, and they're sensitive to lack of oiling.... or so I've heard. Its seems to have proven itself true in my case.

Doesnt a 400 have the same stroke as a 350, just a larger bore?
If you were going for changing the stroke, I'd either a get a 383 crank and rods to make a stroker, or a 283 crank and rods to make a 327. The 350 bore seems to be the happy medium of all the different engines, but changing the stroke you benefit from either the extra torque and better low end made by a stroker, or a the higher RPM and better top end from less rotating assembly weight.
At least that's what I've reaserched.

With no actual research done into the issue myself, I was always under the impression that a 400 crank in a 350 made a 383? The 400 did have a larger bore (which was actually its weak point in high power situations) I know that much, but I'm pretty sure it also had a longer stroke.

Anyone more knowledgeable please feel free to tell me if I am wrong about that, I really am going by just what I think I've heard over the years

 

[Bennyt]

My buddy used to say they "liked to flatten cams". I guess he meant when they got older. He had a couple of problems out of 305's, and switched to 350's. It seems like the factory 350 was overall more reliable than the factory 305.

With no actual research done into the issue myself, I was always under the impression that a 400 crank in a 350 made a 383? The 400 did have a larger bore (which was actually its weak point in high power situations) I know that much, but I'm pretty sure it also had a longer stroke.

Anyone more knowledgeable please feel free to tell me if I am wrong about that, I really am going by just what I think I've heard over the years

I believe the cam issue was bad break in or dirt from the factory. Pretty sure GM didn't make their own cams. There is/was only about 5-6 companies making the blanks and about the same making lifters in the US. Crane technologies was the big one if I recall. When I worked at PAW, I used to Rockwell test every failed cam that was blamed on being soft. Never in their history, did they ever find one. The way a cam is poured into casting and cooled is pretty much 100% guarantee of proper hardness. I did disassemble hundreds of lifters and always found residue.

Lifters are the tightest machined part in an engine at 0.0003 clearance. Don't quote me as it's been a long time. One tiny spec of dirt/residue us enough to clog cause a malfunction and the cam to wear erratically on a lobe.

As Fast99 stated..400 crank in 350 makes a 383, good for torque. 350 crank in 400 block makes a 372, good undersquare motor that can rev.

Aftermarket cranks can be had that don't require machining/ spacers to use.

400's were siiamesed bore along with 454 BBC. The casting walls are still thick but run a few degrees warmers as the middle cylinders don't have 360 degree cooling.
The 400's also look different as they have center freeze plug on each side on 4 bolts and a ridge on 2 bolts.

The 2 and 4 bolt block 400 is perfectly acceptable as the center main cap registers are the same width on both. The 2 bolt is usually preferred the last 20 years as you can add splayed caps.

All sb rods are 5.7 except 400 which is 5.565. You can run a 5.7 rod in 400 with proper pistons.

As far as power limits, my gm based block makes well over 550 HP and I have a nitrous system that gets me a few hundred more. My block was pretty heavily modified before NRE built the motor. I do believe I am at the limit with a factory block though and pushing to a 1000hp would probably end it.

I also have a bigger SB that uses all custom parts and displaces over 450ci and can be built up to 483ci if wanted. I never finished it and it sits in storage due to a failed 32v conversion. With the NRE TT setup we estimated 1650-1850 hp.

And that is why the 305 isn't preferred.

 

[greyghost]

Wow, that was a while back now. Yeah I've learned way more about all that since.
In my case, the 350 in question broke a connecting rod and it swung around and smashed everything, but suprising the crank looked okay. After closer inspection the crank was a little damaged as well. But the original thought was just put that crank in my old 305 block. After doing research I realized that would be been difficult and a waste of time. I got a nice 350 to put in my truck instead, the other 2 blocks are just good for core charge.

To answer your question, yes putting the 305 heads and intake on a different block would be fine. It's been done. In fact, my 283 has 305 heads and it's a great little engine. But on my old engine the old 305 heads were junk, had 1 cylinder that would fowl plugs because of a bad valve seat I'd guess, and one of the valve stems on the other side was mushrooming over. They wouldve needed to be rebuilt.

No you can NOT make 305 stroker, wud require longer connecting rods as 305 uses same crank as 350, bore is 3.75 where 350 has 4." bore. totally diff block, not enough metal to open bore up that far, possibly get .030 over ,but blocks are boat anchors, way more torque use a inline six. 305 is strickly a cure for emissions, that mean no power,no fuel economy, no torque, just junk n not really worth putting money into with large supply of 350's w/ 4bolt mains cheap to add bearings scuff up cylinders n add new or scuff up used pistons w/ new rings, small chamber heads , 450 lift cam is max with piston valve relief. in todays technology...LS engine better yet cheap, plenty around still run, massive HP. buying a wreck cheap gets you all factory parts and aftermarket mounts $20 , modified ECU $50, tranny w/OD heres website with engine specs https://www.corvetteactioncenter.co...g-block-engine-bore-and-stroke-chart-283.html

 

[greyghost]

With no actual research done into the issue myself, I was always under the impression that a 400 crank in a 350 made a 383? The 400 did have a larger bore (which was actually its weak point in high power situations) I know that much, but I'm pretty sure it also had a longer stroke.

Anyone more knowledgeable please feel free to tell me if I am wrong about that, I really am going by just what I think I've heard over the years

yes partially right 400 crank into 350 block 4" bore plus 400 rods with 3.75" stroke special made piston to accommodate for long stroke is also internally balanced so also is needed harmonic balancer off 400 n flexplate or flywheel off 400. why the 383, the 400 was susceptible to overheating due to using same block , but larger sleeves and punched out to 4.125 in. leaving very thin cylinder walls, adding a steam vent hole between cyliders in top of block what they called siamese block as cylinders touched each other side by side, theres a hole in gasket but not head to match location, small block is totally same on outside, giving any sb head will bolt up, intake, exhaust, acc is where most problems occur , there is early model and late model head mounting hole placement. this i experienced first hand as early models had alt. on drivers side, after '69 moved to pass. side, and all crank journals enlarged .15 " https://www.corvetteactioncenter.co...g-block-engine-bore-and-stroke-chart-283.html

 

[AyWoSch Motors]

No you can NOT make 305 stroker, wud require longer connecting rods as 305 uses same crank as 350, bore is 3.75 where 350 has 4." bore. totally diff block, not enough metal to open bore up that far, possibly get .030 over ,but blocks are boat anchors, way more torque use a inline six. 305 is strickly a cure for emissions, that mean no power,no fuel economy, no torque, just junk n not really worth putting money into with large supply of 350's w/ 4bolt mains cheap to add bearings scuff up cylinders n add new or scuff up used pistons w/ new rings, small chamber heads , 450 lift cam is max with piston valve relief. in todays technology...LS engine better yet cheap, plenty around still run, massive HP. buying a wreck cheap gets you all factory parts and aftermarket mounts $20 , modified ECU $50, tranny w/OD heres website with engine specs https://www.corvetteactioncenter.co...g-block-engine-bore-and-stroke-chart-283.html

Wel technically you could make one. If ya bought a 383 stroker kit for a 350, and just put the longer connecting rods on the smaller pistons. And then have the crank balanced for the lighter assembly.
Its doable, but as you stated, would be a waste of time. I agree 350 is a way better starting point for "hopping up".

I disagree on the LS note. Cant stand the stupid things in anything other than what they came in from the factory.
They are great engines. They make good power, reliable, good mileage, easy to hop up, and nowadays with all the swap kits probabaly be pretty easy to swap, no disagreement there, but they're not for me. I want nothing to do with them personally. I'm old school, dont like computerized crap.