Lonh Rods

[bigbrownbird]

Hi guys,
Smokey Yunick once said, "put the longest damn rod that you can in an engine." Obviously, going with long rods and a stroker crank would give a power boost. But what about putting longer rods and shorter pistons with a stock crank? It should build more power, but how much, and where in the RPM range are we talking? Is this a good practice to be doing on a street engine? And the most important question, Is there a set of long rods and short piston for a 474 (460 block) and are they justifiable in price for power? Just a thought running through my head while staring at my block on a stand...

Thanks guys,
Lee

[Gearworks]

you can get a 474 out of just a .060 overbore. with the stock rods. there is a way you can mix and match with the rods from the 370 engine. but i'll be dammed if i can remember how it goes.

and in case you saying "370?" right now, its the 3rd engine in the 385 series family that was only put in BIG trucks. like f700 straight trucks big.

[hotrod78]

You could call a few companies that make rods and pistons and see what they can come up with. I think Chrysler has a 7" rod that might work. You might ask the guys at the 385 series engine forum about this. I'd like to hear some more about your heads cam etc. and what you're planning to do with your Bird. I'm currently working to get my 466 back in my '78 Hope to hear more from you...

[bigbrownbird]

Hey hotrod78,
right now my bird is in two stages- the driving half and the really cool half. I drive my bird with the warmed over 400M and FMX on a daily basis, and then I have another frame that I am putting a lot of suspension mods into, a 460 based engine, and a six speed manual tranny. Hopefully the body will be moved from one frame to the next by March, but right now, the engine is just a block and cranks and the frame is getting blasted. I guess I'm just a dreamer with a big cool car :) Either way, glad to talk to you, I usually plot my progress on the forum. And very cool bird, I dig the slicks.

Lee

[hotrod78]

Except for the oil pan issue. it sounds like you have TWO really cool halves! I miss my FMX, Transgo makes an excellent shift kit for them. I use a C-4 w/ the 460 now. What kind of suspension mods? I'm guessing towards something like a "Pro Touring" car? These cars have beautiful lines, there's really no limit to what can be done with them!

The six speed will be awesome to drive and I'm envious that you're having a frame blasted and starting fresh. Sounds like you have a good plan laid out.

If you haven't already been to the 385 series engine forum, check it out... there's an amazing amount of information there ( on head porting, cams, intakes etc. ). Hopefully I can get everything squared away this winter and be ready to get some street miles on the car before beating on it. The tires are 29 X 11.5 Quick Time Pro DOT's. They fit pretty decent and I'm hoping to get the car hooking well enough to get into the 11.90's and maybe start considering a 10 second trip once I'm sure the motor/chassis is good enough to handle spray. Dreaming from there, it's on to the Lenco, big tires and 4 link stuff. Glad to know you'll be keeping us updated on your progress, anywhere we can see photos of it?

[Gearworks]

nice bird HotRod!! VIVA La' Big Blocks!

hehehehehehehe

[bigbrownbird]

Hey guys,
Gearworks hit it on the nose... gotta love the almighty big block!!! As for you, Hotrod, Sounds like a very mean machine, I might just build another bird after college with that mean drag look. But my bird is a high milage driver, I just can't ride to Virginia and back on a four link. And, thanks for asking about the pics, but sorry, I don't have any digital cameras and I really don't have any acess to a scanner. But when i do, you guys will se my bird, don't worry.

Lee

[hotrod78]

Until you make the switch, all the stuff big block guys say sounds like BS, and then you try one and wonder why you ever messed with anything else! I have a soft place in my heart for the 351C's and 400's, with the right heads and cam they can rock, but they're expensive to get reliable power out of.

I think the key with a regularly driven 4 link or ladder bar suspension will be comfortable seats! ;) I'm not sure how much street driving can be done until heim joints start wearing out.

Compression is about the only thing that can make a car undrivable in my opinion and even that's open to debate if a big enough camshaft is used. I don't have a scanner or digital camera either I usually get photos put on a floppy disk at wally-world. Thanks again for the compliments!

[marine165]

Originally Posted by bigbrownbird

Hi guys,
Smokey Yunick once said, "put the longest damn rod that you can in an engine." Obviously, going with long rods and a stroker crank would give a power boost. But what about putting longer rods and shorter pistons with a stock crank? It should build more power, but how much, and where in the RPM range are we talking? Is this a good practice to be doing on a street engine? And the most important question, Is there a set of long rods and short piston for a 474 (460 block) and are they justifiable in price for power? Just a thought running through my head while staring at my block on a stand...

Thanks guys,
Lee

:: puts on his Mechanical Engineer hat:: Okay, longer rods...
Yes, longer rods are better. The longer the rod is, the closer the piston gets to perfect sinusoidal motion, which decreases the maximum instantaneous speed and acceleration, as well as increases piston dwell time, so that combustion gets closer to perfect constant-volume combustion.
All that engineering crap to say that the longer the rod, the higher the compression ratio you can run on the same octane without knock. Your engine will also be more efficient. Now, it won't be that much more efficient (and remember, efficient equals power) for the same compression ratio, but like I said before, the magic of longer rods is that you can run higher compression without knock. And increasing compression is where you really get the increases in power and efficiency.
The longer rods will also decrease stress on your crank, due to lower accelerations, if that is something you are concerned about.
This whole stroke/con rod length ratio issue is actually why I really like Mopar engines, and why I would really like to build up a Dodge 383 into a solid-lifter high RPM screamer. It has the bore of a 426 but the stroke of a small block. And rods a mile long to boot. Excellent... ::tents his fingers::
Anyway, hope this wasn't too boring, and I hope this helps!

Mike

[marine165]

Actually, I have a great resource for this kind of question.

http://www.nhra.com/tech_specs/engine/

It will give you the vitals on just about any engine you can think of. Bore, Stroke, displacement, number of cylinders, and more often than not con rod length.

Hope this helps.

Mike

P.S.
Dodge 383
bore 4.250
stroke 3.375
con rod 6.360

Sweeeeet... :)

[Gearworks]

dang Mike!

You were just waiting for a question like that weren't you?
Hehehehehehe...

paul :cone