273 rods in stroker 340

[howard]

I am building a 340-w-1/4"stroked crank and am wondering if 273 rods would be up for the job given there are a lot lighter than stock rods?

[Billydelrio]

I use the early stock rods in my 3.31 stroke 273 and have been taking it to 7000 at the digs for six years now. I used the computer to calculate the maximum "g" acceleration at a few rpms at a 3.58 stroke.

rpm 5000 5500 6000 6500 7000
3.31 g 1502 1817 2163 2538 2944
3.58 g 1624 1965 2339 2745 3185

To determine the maximum force will depend on piston mass.

gotta go

Billy

[6Cuda6]

Mopar Action Tech recommended stoker swap, as long as they are gone over properly

[dave571]

Why not stick with the full float 340 rods?

The 340 was the only SB that had them.

[howard]

6cuda6 - what does your message mean? Mopar Action Tech did recommend 273 rods? If so do you have the issue? I have all the copies (accept for thone I need most likely.

Also if I am not mistaken the 273 rods are full float-w-clips in the wristpin. They seem a whole lot lighter than the 340 rods when I picked them up and "hefted"them?

[dave571]

I'm 90% sure that 273 rods are fixed in the wrist of the rod.

I don't have a book handy to double check, but I remember this topic coming up here about 2 months ago. The conclusion seemed to be that 340 was the only one.

[Dennis Jokela]

Dave:

Early 273 and 318 were full floating wrist pin rods.

Dennis Jokela

[dave571]

How early are we talking about?

The 69 dart I had with a 318 had fixed pins?

[lenweiler]

Why not buy a set of the new sir rods from Eagle. They're excellent pieces for the price, and you'd be hard pressed to resize a set of factory rods, (mag, new bushins, ) for the money.

[howard]

The Eagle H beams I saw were very heavy. Maybe the I beams are lighter and I have no problem spending a few $ for better stuff but I wonder if often times we overlook stock peices for the sake of getting exotic. I am an old school thinker although not cheap. I am also not an engine builder but if I hear of one that has 273 rods that are maybe balanced, magnafluxed etc turning in a 500hp SB-w-a long track record I'm sold.
Howard

[70AARCuda]

The Eagel SIR I beam rods weight in about 600 grams...cost about 225.00.

[lenweiler]

Mr. Cuda is right. The I-beam is Eagle's much less expensive replacement rod. I didn't have scales but I would say they are less weight than the 340-360 rod. The beam is a tad less heavy but there's more metal around the big end, no balance pad at either end, (unnesissary since they're within 1/2gram of each other) and more metal around the bolt boss. The bolts are hp units.
If you want to rev it, I've got some Hamburger rods, fit with 7/16in. rod bolts.

[gotcha]

Mr. Cuda is right......I have switched to Eagle SIR's in all smallblocks. The weight quoted is correct. The price is correct. You cannot bush the pin end, resize, polish, deburr, and add ARP bolts for the price, not to mention new metal.

Back to original question....yes you can run 273-318 rods. You need to fully prep the rod, with the correct bolts.....but anything less than a lightweight Ross, or other lightweight piston will result in eventual rod failure. The most common cause is a heavy piston on the end of a lightweight undersize rod.

They have a limited life cycle of about 200 1/4 mile passes with a TRW type piston. They will fail. Lightweight piston and pin is another story.

The 273 did not have floating pins as an OEM rod. The 318 shared the same 273 rod (1618699) in 64 thru 69 in the 273 and 64 thru 71 in the 318.

[gotcha]

For information only.....the heavy duty rod for race applications that the old Direct Connection sold as a "K" rod with the 7/16 bolts is actually......I hate to say this.......a resized big block Chevy rod sold thru Mopar. I knew that would hurt.

[howard]

Well this is getting complicated. I'm using KB hyperutectic pistons that are actually for a 360 but work-w-a 1/4"stroke crank because of the pin placement in the skirt. Are these too heavy? Can anyone recommend a good street/strip lightweight rod if the 273 rods are no good. Also I must say I removed the pins from the 273 rods and they are floating. I just pulled out the clip and out they fell.
Hey AARCUDA any pics? I have a T/A. Where you at Carlisle this year or the Nats last year?

[dave571]

That's good to know about the full float.

What year was/is the 273?

[howard]

I honestly don't know the year of the 273 that these rods came out of. I now have them rapped up getting ready to send the short block components up to NY for machining. I woul djust love to know if it is worth the rod prep that would be recommended (required). If I get enough feedback about going to a better rod I'll chuck these rods and go-w-what is recommended

[lenweiler]

Howard. The KB's are about light and strong a piston FOR THE MONEY that you're going to find, and probably fine for your application. The sir rods are also the best, strongest and lightest FOR THE MONEY. I've got the same setup put aside( 4in. stroker) when I feel I want to run with the bigger dogs.

[howard]

Hey Lenweiler- I checked out your site - cool stuff.Do you still own these cars? Quite the collection. I have a T/A and would love to go-w-a six pack on this new engine. Have you done anyting to the heads you are running? Do you think the six pack is going to give you good HP. What do you think this combo can give you HP wise? I plan on massaging a pair of stock heads a lot-w-the MP templates. I hope to get about 250cfm flow and would think I could go 450 HP. Why bush the lifter bores? are you running a roller cam?

[gotcha]

Howard....if you get a chance post the casting number on that rod. There really is no 273 in OEM configuration listed in any of my reference material, and no replacement bushing listed for any 273 of any year, and I have never taken apart a 273 with floating pins that I can recall.

Possibly someone bushed them or they are something else?

Just curious.

With a reasonably light piston and pin combo your rod lifespan is greatly increased with that rod.

[howard]

Well this is a problem - I have a pallet wrapped up-w-that sticky stratch wrap. The only thing I can do (other than wait on feedback from others) is talk-w-the engine guy I am using when he receives the pallet and ask him. I knew I should have written the part number down when I saw it on the rod. Does anyone know what is a practical $ amt for "reconditioning" these stock rods. They have a mojor amat of steel on the bottom and I'm sure they can be hacked off and balanced-w-being a whole lot lighter than they are now. Maybe I'll drop thihs thing in my 92 2wd Dakota! That would be fun except for grenading rear axle and tranny I guess.

[lenweiler]

Unfortunately, no Howard. I don't own most of the cars any more. Like most guys, to experience all the mopar muscle I must sell a car to buy another. My son, who developed the website thought it might be a blast to show the past cars. I'm down to the bee and the dart.
We bush the pushrod holes on the intake side only. It' s an old trick my machinist developed years ago when he did porting for roundy-rounders up here. I's so the porter can max out the intake runner and not worry about the breakthrough factor.
Hughes Racing Engines is doing it on their maxed out port jobbies.
I nixed the sixpack for the stealth. I'm looking for better response off the line.
You shouldn't have a problem squeezing the flow out of those castings. Chrysler was way ahead in domestic head design back then. Factory stuff is too often overlooked.

Howard. Checkout Nut 'n Bolts on my website and under heads you'll see exactly what I've done. Although it's a little condensed. Len

[badcaruda]

All stock 273 and the early 318 could be found with full floating pins. I believe everything went to pressed pins in the seventies sometime.

[howard]

I suppose it is all moot at this point. After considering the cost to recondition and thouroughly check out these rods I figure some Eagle H beams are better and they are supposed to be good for well over 500HP???

[lenweiler]

I got the cheaper 'I' beam rod from Eagle, and with the Hughes cam, and W2 heads I can expect an easy 500 horse and feel comfortable with those rods.

[howard]

500 hp sounds good - tell me what is the stroke on the crank? Mine is only 1/4". Any good deals on heads? They have rally come down as far as aluminum in the past several years. It seems as affordable as the W2s???

[lenweiler]

It's a MP piece. It's got a 4'' stroke. The 500 hp est. is from Dave H
Hughes, not Lenny.
The W2 castings are a real deal up here since Chrysler seems to honour the Canadian buck. These castings are probably cheaper since it's not exactly bolt on. When I move up to stage 2 and jerk the 340 for the stroker I may not even use them. I still like the idea of putting my own work on the engine.
Bolt on seems too easy. Guess I love pain.
P.S. The W2's outflow the Ed's by a long shot. If you're considering a hiwinder, I'd study these!

[howard]

when you say stage 2 is this the stage 2 that hughes sells> I am sorry to sound so unfamiliar but Iv'e not heard of satge2 except for deaelrs that offer diffferent "stages" of head porting. I don't know exactly what it is worth but although flow is very important isn't there soemthing to be said for the Ed ehads being aluminum and being able to get a higher compression-w-a cooler combustion chamber? If you were in my shoes what would be the choices you would consider for heads? I know a guy in our club-w-a set of ported/polisher T/A (X??) heads. He asked me to make him an offer but didn't have a clue and think they may be exotic more than valuable

[mr_340]

The 273 rods that were in my 1967 Dart (273/2bbl) were floating with bronze bushings. I've pulled the same basic rods out of the early (pre-1970 or so) 318s. I think you could put good rod bolts in them and have them resized. The 273/early 318 rods look like a SB Shivy rod. With a lightweight piston and pin, they would probably work.

The late 318 (cast crank)/340/360 rods look more like a BB Shivy rod. I'm kind of surprised the Shivy boys haven't figured out to run a 360 rod in their BBs (smaller rod journal, stroke the crank, etc.)

[lenweiler]

Howard. The stage 2 I was referring to was my move up to going faster.
Now that being said, I don't know if I'm qualified to suggest a head for your application. I know, usually what I want and what I need to get there.
If you' re looking for torque then usually one stays away from max. port cross-section and goes for a really good 3 angle valve job, no runout, no guide clearance (.001) and good flathead valves. Close attention to seat and angle widths.
For the next step, a really high-detail bowl port is next. This will usually mean more RPM.
Be prepared. The higher the port level, the higher the rev's and more cam. Rule of thumb.
I'd steer clear of the ta's. They're old, probably dear, no hardened seats, and not enough flow gain, especially when compared to the commando or magnum head. Or even the mid to late 360 castings opened up to the bigger valves.