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OK so about 2 weeks ago i got a 261 engine and a spare 261 block planning to make it a few yer rebuild project on the side. My reasoning for doing the 261 was that all my current 235 performance parts would bolt right up and swap over when changing engines.

Should i just bite the bullet and go big and build a 292 instead? Internal rebuild parts are easier to find its easy to still find performance parts and i would get considerably more power from the engine.

I believe i need to only install new motor mounts for the front of the engine to mount in my 52 1300 but im currently looking into this. I also hear the rad can possibly stay in the stock location providing you use a pusher electric fan (not sure if that 100% true)

IMHO, what people think they need and what they actually need are two desperate strangers, never to meet. We think we need a lot more horsepower when in truth my 30 over '56 235 with Fenton Headers, dual 2x2 Edelbrock intake, '69 overdrive transmission, recently achieved 18.7 mpg on a ~1k trip @ 65-75 mph. This engine has ~95 k miles and burns no oil.

The 261 is plenty of engine, the 292 also a fine engine needs mounting modification and IMHO just doesn't look right in the older vehicle.

There is more involved than just changing the mounts. Nothing from the 235/261 engine will fit on the 292, specifically the flywheel, bellhousing, throttle linkage, & starter. In addition the later bellhousing will not mount to the 52 crossmember.
Fred

Sorry when i meant changing engines in my first line it was from the 235 to the rebuilt 261.

I would agree with Cosmo. Even if the 261 isn't "original" in any sense, it's at least somewhat "period correct." Also, your logic about the parts interchangeability with your current setup makes sense.

As you most likely know:
- adapt the front motor mount
- use your 1952 clutch housing
- use flywheel and clutch assembly that meets your needs (6v or 12v).
- instead of using "pusher fan" consider buying a water-pump adapter plate and use you old/1952 water pump.
http://chev235guy.blogspot.com/search/label/Water%20Pump%20Relocation%20Adapter

Will you have a 6v or 12v electrical system?

Drill the holes in the front timing/mounting plate, water pump adapter for sure, and remember if you have a 6 volt flywheel to use the same starter or always purchase a 6 volt starter (even if its a 12v system). No changes to the trucks sheetmetal at all.

OK so far its leaning towards going with the 261. My 52 has a 55 inline already so the water pump already sits low. To date I have had no cooling issues. (knock on wood)

The 261 build will incorporate the re-drilled timing gear bolts and possibly the relocated higher water pump with the adapter plate if i can find a smaller vibration damper so im not over-driving the pump.

And if i go with he relocated higher pump with a smaller crank pulley i think I might run into issues with my power steering and alternator being under driven. Alternator i know for sure as its currently being under driven and a new smaller alternator gear is on the road to fix the issue.

Yes, the 261 is an improvement. If the choice is between rebuilding the 235 and rebuilding the 261 - go for it.
How much power?
It's 10.8% bigger, but you won't get 10.8% more power since all the breathing functions are now even less sufficient.
With some speed equipment, the 261's advantage is perhaps 15-20 HP.

If you want to see power comparisons for 1955-2nd 235 and 261, here is a chart from the Specifications Manual.

Not alot of benefit in horsepower, but every little bit helps. I wanted full flow oil filtering which is only available on the 58-62 261. I just had my 235 machined to match the 261's full flow system, so its not hard to do that.

My plan is to go with a dual pulley HB for the accessories. I am just going with AC, not PS, but I can't see ANY benefit in using a dual pulley on the Alternator or AC Compressor. The power comes from the crankshaft, not a series of belts. Although, lots of people do it that way without incident.

Smaller Pulley makes it turn faster, not slower? Its why Dave suggests not using the larger HB with his water pump adapter. Overspeeding the fan is not a good thing. I am doing it anyway to see for myself what the difference really is.

On the chart Tim posted...

I'll be the dumb guy that asks...

What is taxable (SAE) horsepower is and how does one convert into something familiar?

A quick google did not return a quick enough answer and I gave up.

A smaller pulley on only the driven component will make it run faster. The drive component being smaller like when changing the the crank pulley to a smaller one will turn an driven component slower.

I posted that for a look at comparisons of the 261 to the 235.

The 261 is 11% bigger ci compared to the 235.

taxable (SAE horsepower 261 vs 235) 33.7 compared to 30.4 - 11% increase

Gross hp (261 vs 235): 135 vs 112 - 20% increase
Net hp (261 vs 235): 123 vs 105 - 17% increase

Thanks Wolf, wasn't sure. I have trouble remembering those little details, thus why I write everything down.

Since torque is what makes it go, what's the torque difference between a 261 and a 235?

That is shown at the link I posted above.

The 261 was designed to provide comparatively-exceptional torque over a wide range of speeds - you can feel it.

Yeah, if this is your first 261 Tim, you will definitely notice a difference. For me, the 261 was the main reason I didn't go with a V8 or some cobbled up system. Its the perfect amount of power for a Pickup. Of course, gearing enhances it even more.