HOT 261 L6 Chevy? 250 hp possible?

Ok Ive tossed around a lot of ideas on power plants over the past 8 months and i cant say im still 100% on this one but i would like some insite on this subject.
Is it possible to get 250hp to the flywheel out of a 261 L6 with out a supercharger.I have read the May 1955 Hot Rod and they only come up with 197 hp.I was wondering if there was anymore new hp tricks for this engine since that article was written 53 years ago or is 200 hp about all she wrote on the ole 261 6 slammer?
Matt

 

A friend built one with Caddy V8 pistons and a Sig Erson cam, ported head and all like that. Never saw a dyno, but it blew past many a V8 on the oval track. If the rules had let him run more than one carb, I would guess 250 HP would have been easy.

 

Squeezing .95 hp/cubic inch out of a 235/261 cylinder head is asking a lot of it. You can't do it with high rpm, because the head won't breathe in the upper range. Any 261 that ever managed 250hp that I heard of (without tricks like nitrous or supercharging) had a 12 port head on it. Think of what it would take to wring that much horsepower out of a Ford flathead, and you've got a good idea.

 

Those 261's run so smooth. Don't know about upper horsepower but great engine to play with. I have 2 of them.

 

Nitrous should do the trick, just try not to hurt the block with it, they don't make them anymore.

Also the caddy pistons, 292 chevy rods, and offset ground crank will give you about 20 more cubes, which can't hurt your chances of making more hp.

 

put a nice 350 in that old chevy and laugh and point as you pass the six cylinder guys on the freeway.

 

and they'll laugh as they blow past you at the gas pump!

 

I've never heard of it without a blower, etc...

Even if you could do it normally aspirated, it would be totally un-streetable...

 

not if you put in a bigger tank.

 

Ok so i take that 250hp is not possible Nat Asp.....So 250 hp is possible with a supercharger?

 

Probably....but you'll be wanting to pay out for a set of good forged pistons and, if it were my engine, a conversion to GMC rods.

 

That was my next question what about a 302 GMC motor can i use one of those in my 49 coupe?

 

Yes. You'll have to move the radiator forward and modify the front of the oil pan sump for clearance.

 

Have to think you could build a later 292 Chevy six to make that kind of power and most people wouldn't know the difference between that and the 216 the Chevy came with in the first place.

 

+1 vote on the 292

It may not be a huge issue, but you should be able to at least touch 250 with high compression pistons, a cam, lump-port head, and a 4bbl on a budget a lot less than putting a huffer and forged pistons etc. into a 261.

Just my $.02, but your $1.00

 

Ok so the 292 would be better swap for my 49? I kinda like the nastalgia of a six but i want a little umpf when i romp on it.
Will the 292 bolt right up? What did the 292 come in?

 

I know a guy with a 292 in his 50. He got some goodies from CLifford including a 2x4 intake and headers. He said it will go sideways when he stomps on it.

292s are a little taller and a little longer than a 235/261, but should fit with a little work. You might have to move the radiator a little. We did that on my wife's 51 so we could keep the long 235 water pump. Pretty easy.

Get Leo Santucci's book on the bigger 6... I think it's called the Chevy Inline 6 Power Manual or something like that. It focuses on the 250-292 family. YOu can get a LOT of power outta those things.

 

I think...think...Langdon's sells mounts you can use to put the later series motors into your car. Tom's a good guy to talk to anyway. 292's came in 3/4ton and up Chevy trucks from 62 to the late 80's. There is a version that has the intake manifold cast as part of the head, which are generally regarded as garbage for speed purposes. If you found one in good condition though, the non-integral head bolts right on...

FWIW, my '63 (originally a 230 car) has a 292 in it (stock lower end, lump-port head, HEI, Offy 4bbl manifold and Edelbrock 600CFM carb). With the stock trans and rear end, I can spin the tires at will in first, and it'll pull pretty hard through about 85MPH. Haven't had it faster just I chicken out.

In terms of makign lots of power with the 292, check out the page detailing Leo's new car: http://www.cdpautomachine.com/leo/leo.html. OK, it's pretty exotic, and far from streetable or "budget", but 1300HP? Now, i just have to figure out the "80% of the function for 20% of the price" ratio....

 

If you want to be very nostalgic, build a Chev 261 or a GMC 270 or 302 as they just look older, (as they are) and were a very popular swap back in the day. They are all great torque monsters and that is what you need anyway to get you scooting. If you want the most power you can get from a straight 6 at a cheaper price but with much less nostalgic value, go with the 292. The old .02¢ worth. I like the newer family of 194, 230, 250 and 292 as well but they are just not as cool to me as the older dudes. You could run a 292 and convert it to the older valve cover design like the Faux Olds covers if you wanted.
BlackCherry

 

The 292 has the same bellhousing pattern as the V8's, so it won't bolt up to anything 216/235 related. You will need to change the bellhousing, tranny, and convert to an open driveline, if you haven't allready.
If you do go this route, and want to keep the under the floor pedal setup, you will need a special clutch linkage part, as the fork angle will be different than the stock 49-54 car has. PM me if you go this route, as I have what you will need for this. I also will have motor mounts available soon, or you can get some from Tom Langdon or maybe Chassis Engineering...

In the end, putting in the newer style six is about the same amount of work as doing a V8. You will be better of with the newer six than a 235/261, but it comes down to what do you want...

 

i got a 1968 gmc 292 in my 51 chevy hardtop its all stock on the inside i just regasketed it it makes about 180hp stock i didnt have to hack out the firewall but i cant run a fan so i got an aluminum radiator works good with an electric fan there good strong reliable motors its's my favorite motor

 

so did u figure out what motor ur goin with

 

No not yet im just more confused?????? Did the 292 come in 1/2 ton pickups too?

 

Yes. They can be identified by the right motor mount being farther forward than the left one. Other versions of this motor have the mounts straight accross from each other.

 

I dont know about that, I past a newer corvett at around 103 comming back from the drags !!!! ALL we had to do is yell over to him, and ask how fast are we going ? Speedo does't work ! Then put it to the floor and he was laughing as we passed him !...oh ya by the way still getting 23 MPG !

 

Thats funny! LOL! What motor are you running 292,261?
Later Matt

 

Yeah, go for another belly button small block...zzzzzzzzz...........

Lots of us would rather have an inline. They are all inherently torquey motors, and torque is what moves the car. A decent 292 will make buckets of low end grunt, you won't have to wind it to 5 grand to make power. We're talking 4.120" stroke here. Lighter than a bent eight, seven main bearings, lots of speed parts available, bolts to a bunch of good trannies, and the sound... What's not to like?

 

Im running a 250 with 307 flat top pistons a reworked head W/ bbc roller rockers, a offy 4v intake and 390 holly carb... a 5 speed with .73 OD and 3:73 rear end gears..Did I metion it runs high 15's low 16's in the 1/4 and I drive it ever were...Im a registered six offender LOL

 

Can anyone tell me the factory trq and hp specs on a 292 i cant find it anywhere???
Will the 292 hook to a T5 without the adapter?

 

Yes it will with no prob, my newest project is a model A with a 292 and a T5 I used the 292 flywheel and the clutch and pressure plate out of the camaro.