The Stovebolt Site Forums The Shop Area The HiPo Shop Another 261 long stroke engine- - - -

I've been crunching numbers again! How about a 292 cubic inch "261" with a really long stroke? It appears according to the calculator that a 3/8" longer stroke, a set of Buick 350 V8 pistons, (3.800" bore) and some modified 261 connecting rods will combine to build a real torque monster! There's another advantage- - - -Ebay is full of brand new Buick pistons at "baby chicken" prices- - - - -"CHEEP- - - -CHEEP- - - - CHEEP!"- - - - -like $125.00 for a set of 8!

With some different pistons and rods, those "grass cutter" stroker crankshafts can also be fitted to 235, and even 216 blocks, BTW. The 216 goes to 258 cubic inches with pressure-lubricated connecting rods and aluminum pistons, and the 235 becomes a 270! I need an apprentice or two to help run the machine shop!
Jerry

If you were closer to Atlanta I'd sign up for the apprentice job.

No kidding. Wish i knew half of what he has forgotten.

Which stroker crankshaft are you referring to?

I'm using a pressure-oiled 235/261 crankshaft with the rod journals offset-ground to get a 4 5/16" stroke. I'm planning to use a Nissan 2.4L 4 cylinder connecting rod that's almost 6.5" center to center that uses a connecting rod bearing 1.967" in diameter. Either OEM connecting rods or tool steel NASCAR style rods are available with those dimensions. With a little custom machining, that shaft can be fitted to 216, 235, or 261 blocks. A pretty wide variety of pistons can be adapted, to include standard bore 235 pistons in the "216", Ford 223 cubic inch inline six pistons in the "235" and the Buick pistons I mentioned in "261" blocks. There are a few other crankshaft/rod/piston combinations possible, with varying amounts of custom machining involved.
Jerry

Then how would you keep the rods from hitting the camshaft ? There's not a lot of room there.
Plus the head would need some major work to flow that much air !

As far as the rods hitting the camshaft, that wouldn't be a problem with an offset grind. The rod journals can't get any farther away from center at the outside, but the center of the journals gets moved out by making the journals smaller. The rods he's planning on using of course, would need to have smaller journals on the big end to fit the new smaller journals.

I'll let Jerry address your head comment.

The big end of the rod has a smaller cross section, and I'm also retro-fitting them for NASCAR style ARP bolts that thread into the rod rather than using nuts and protruding bolt ends. Building tight-winding stovebolt engines is a fool's mission- - - -low to midrange torque is the obvious way to go. Even the GMC 401 V6 in my American LaFrance fire truck breathes through a tiny Holley 2-barrel about the same size as a Ford 239 cubic inch flathead V8 ran. There's no need for lots of RPM when extra torque is the goal.

The old dirt track adage applies here- - - - -"Horsepower is to brag about- - - - -torque wins races!" I'm building engines for practical power gains- - - -not eye candy for the mouth breathers at a "show and shine". Those guys think dual carbs, Fenton exhausts, and lots of chrome are worth the time, effort, and expense it takes to install them, even though the engine runs crappy afterwards because bolting on accessories without the internal modifications to make proper use of them usually results in less than zero power gains. My stock-appearing "216" with 258 cubic inches onboard will pull hills in high gear that a beaned-up 261 would have problems with.
Jerry

The rods I'm using are a little shorter, stronger than stovebolt rods, with a narrower cross sectional area of the I beam section. That should increase the clearance at both the camshaft and the bottom of the cylinder walls. They're also considerably lighter weight than the stovebolt rods. 216 engines are considered to be boat anchors by most people- - - -free for the taking in some situations. Running a stock-appearing 258 cubic inch 216 block- - - -235 crankshaft, and a Corvette/261 cam with the bearing journals ground down to fit the 216 cam bearings- - - - -sounds like a sleeper to me! Add roller valve lifters and rocker arms, and things could really get interesting! Less drag on the rotating assembly equals more torque at the flywheel. A 270 cubic inch "235" or a 292 cubic inch "261" with the same setup will just add a thicker layer of icing to the stovebolt cake!
Jerry

What vehicle is that engine going to go in?

The first one will be a dyno demo on a trailer to make the rounds of a few swap meets and car shows. After that, I'm guessing there will be a bunch of them to build.
Jerry

So this is your business? You're going to sell the hot rod stovebolts to other rodders?

At age 76, with some pretty serious health issues, I'm mostly just playing games. Getting a running prototype and some dyno measurements out there to show what's possible when thinking outside the box is my main goal. Most so-called engine builders are too lazy, or incompetent, to explore what's actually possible by combining parts that weren't intended to work together. If I manage to get a few of these Rube Goldberg projects running, I'll leave it to someone more ambitious (or greedy) to put them into production.
Jerry

Now that's the spirit of hot-rodding.

I like your thinking Jerry.

Frank

I had quite an example to follow- - - -in the late 1940's and early 50's, my father was assembling flathead Ford V8's for his 34 Ford 3-window dirt track coupe with bore and stroke combinations that other engine builders said were impossible. 300+ cubic inches and over 11:1 compression from a 239 cubic inch original engine, running on methanol and Hydrogen Peroxide!
Jerry

And folks called me crazy, experimenting with vintage water injections.
Compared to running on methanol and hydrogen peroxide, water injection looks almost conventional and lame :-)

It's all about having fun with it anyway.

If I would be after HP, I would in bolt an LS and call it a day (like so many).
Or if I wanted to stay inline, a Ford 300 or Jeep sixbanger, with all that available speed parts for those engines would be an easy choice.

But actually - an LS, or even a small block V8 swap is pretty boring in my book (like most of those uniform hot rod builds these days).
At least form me, it's much more fun to get additional 20 more horse power - with some quirky idea/method - out of my (already hopped up) 261, than having 200 HP more by just dropping an V8 in there.


Frank

Technical grade peroxide (20% concentration by volume) produces more free oxygen in a combustion chamber than an equivalent volume of nitromethane. Hair bleaching peroxide, by comparison, is 4% concentration. Here's Dad's fuel mix from the 1950's- - - - -

Methanol- - - -75% by volume
Peroxide- - - - -20% by volume
Amyl Acetate- - - -5% by volume

The Amyl Acetate is a wetting agent to help the peroxide and the alky mix well. The mix is super corrosive- - - -they ran a stainless steel 8 gallon beer keg for a fuel tank, stainless steel tubing all the way to the carburetor, and ran the carb dry between races to keep the fuel from eating the bottom out of the float chamber! The carb got rebuilt once a week, right before the Saturday night racing program.
Jerry

I guess your dad can be proud of you.

In the 60s and 70s , my grandpa and my dad where running a so called EES-Garage.
It was part of AAFES (Army & Air Force Exchange Service) and located in one of the 4 US casernes here.
That's where the GIs had their private vehicles serviced.
That was my playground as a kid., and that's how I got into American cars.
My grandpa was a race mechanic before the war, and he taught me all he knew about modifying engines.
He was also a "thinking out of the box" man, I guess that's why I like that so much.

darn - I really miss him.

Frank

One of these days, I'm going to build a hotrod powered by a Jaguar DOHC inline six, or maybe the Toyota Supra copy of the same basic design. I've got a partially completed Excalibur kit car stashed away that will weigh somewhere around 1500 pounds when it's road-ready. It's the one that resembles a late 1930's Mercedes. It's going to have a Mustang II front suspension and a Supra independent rear suspension with the frame-mounted final drive. Engine options will include several GM choices, from a Mercruiser Marine 4 cylinder through various inline and V type sixes, and possibly a V8 or three. All those engines share the same bellhousing bolt pattern. With the hood closed, nobody will know what engine I'm running on a particular day!
Jerry

I'd volunteer as an apprentice...if I weren't so far away.

I keep coming back to this thread and reading it. I've always liked the ol straight 6's, but I've developed a whole new type of respect for them while I tinker on my 261. This thread is the essence of old school hotrodding, and that's coming from a dude who's about to turn 31.

These old engines are way over-engineered, especially where the block and crankshaft are concerned. The cylinder head is the choke point, so building for increased RPM is a bust from the get-go. More torque, from increasing both bore and stroke, is definitely in play, however. That also makes it possible to hide the modifications deep inside, an advantage for people who want to keep the engine compartment looking original. An extra 30 cubic inches or so, and the corresponding increase in compression, regardless of the original displacement, yields some pretty impressive results on the dyno. For the guys who don't want to telegraph their punches by adding external accessories such as dual carbs and exhausts, having that extra torque on tap is a real advantage.
Jerry

If "successful" means "It wins races"- - - - -those engines were very successful. Dad's driver, who also ran our body shop, took plenty of victory laps at the American Legion Bowl in Nashville, and several other tracks in middle Tennessee, southern Kentucky, and north Alabama in the early 1950's.
Jerry

292 cubic inches, higher compression, lighter rods and pistons, using commonly avaiable parts, that would be a game changer. There have not been any real good alternatives in terms of compression, lighter rods for years and years now. Would be a nice change of pace to be able to maximize where these motors like to live in terms of torque and lower rpm.

Remember the 215 cubic inch Buick/Olds V8? It had a 3 1/2" bore size, the compression height is very close to right to use with a pressure-lubed stroker crankshaft in a 216 block, and a 60 over piston duplicates a 235 bore size with a MUCH lighter weight piston and can be used with an H-beam Nissan tool steel rod capable of handling 500+ HP. All in a package that looks like a 216 from the outside. Close to 260 cubic inches.

www.ebay.com/itm/264700871203?

Jerry

Here's a diagram of the modification to the 235 crankshaft:

The small diameter rod journal is for a Nissan 2.4 L engine which has a connecting rod 6.498" long. This slightly shorter rod than a stovebolt engine, and a Ford 223 cubic inch piston works with a 235 engine, and pistons for 215 or 350 Buick engines work for 216's and 261's. Displacement ends up from 258 to 270, to 292, depending on which block is being used.
Jerry

Super cool. I wonder how many machine shops know how to offset grind a crank nowadays, and what they charge when they do?

Do you have to do anything with the wrist pin to adapt the Nissan rod to the Ford 223 piston?

My teenage son drives a frontier with the 2.4L. Still runs too good for me to start parting it out, though!

Depending on the specific piston/rod combination that's being used, either the piston, or the rod needs to have a bushing installed to adapt the wrist pin diameter. The stock Nissan rod has enough small end diameter to be reamed for a bigger bushing, while the H-beam tool steel rod uses a 22 MM wrist pin and the piston needs a reducer bushing in the wrist pin holes to match the smaller pin. Nothing anyone with the unmitigated gall to call himself a "machinist" can't handle with a piloted chucking reamer and a Sunnen hone!

Since the big end of the rod is narrower than a stovebolt item, bronze thrust washers need to be installed at the top to keep the top of the rod centered in the piston and make the rod bearing ride the middle of the crankshaft journal over the oil hole.

I've only found one machinist in middle Tennessee willing to offset grind crankshafts and he stays booked solid around a year in advance. That's why I bought my own crank grinder. Now it's just a matter of getting the shop wiring upgraded to 3 phase power so I can use it, plus a couple of other pieces of 3 phase powered equipment. Coilover practically gave me a rotary 3 phase setup- - - -now it's just a matter of getting off my lazy behind and getting it wired up!
Jerry

Jerry, just asking because I have no business identifying myself as a machinest, lol, if the big end of the Nissan Rod is narrower then a stovebolt rod, can you off set grind the crank to essentially fit the rod? In other words the offset grinding creates the cheeks on the crank journal to keep the big end centered?

It's possible, like the slight stroke increase the "Cadillac 261" article that was published here some time ago using 292 6 cylinder rods, but most machinists are unwilling to modify a grinding wheel to the width required to do that job. Can't say I blame them, since those wheels cost several hundred dollars and it takes a major teardown of their grinding machine to change wheels. Most of those guys are in business to make a profit, not accommodate some hotrodder's off the wall ideas! Very few stovebolt builders are willing to go out and buy a crankshaft grinder (like I did) just to tinker with changing strokes. I'm so goofy I actually bought TWO of those machines!
LOL!
Jerry

The usual offset grind for the 292 rod increases engine size by 4.76% (235 becomes 246.7"). Depending on what you can do yourself and where you live, it may cost $75 per inch gained (and $150 per HP). You certainly won't get 12 hp (1 HP per inch) back.

The remainder of the reported size change is due to:
1. using a 261
2. boring it to .090" (Cadillac + .040" used in the stroker)
Those choices alone (with stock stroke) are far more valuable: 273.6".

The "Cadillac" stroker engine uses a too-short connecting rod with a big end that's not able to accomplish enough offset to make a noticeable change in torque, and pistons that are as scarce as a chicken with lips. Other than that, I guess it's OK. Has anyone actually built one of those engines and dyno tested it? The first stroker I'm planning to build using the Nissan rods and Buick pistons will be a dyno test mule. Yes, I've got a dyno. Then all the theoretical number crunching and pontification will become moot points. One of my competitors on a little quarter mile dirt track in California had a sign on the back of his car- - - - -"When the green flag drops, the BS stops!"
Jerry