I think the Terminology used in the topic is confusing.
There are 'Long Ram' intakes, and 'Cross Ram' intakes.

The crossram is high performance piece, and installed as one 'unit', while the Long Ram intakes are a pair.
Cross ram intakes where never factory installed on Chrysler models, only the Long ram intakes upto 1964.

What I recall is the 'Short' Long Ram intakes came in use on the 1963 and 1964 Chrysler 300J and K models, and provided power at higher RPMs. Not quite sure anymore if the Short long rams where optionally available on earlier models.

Also the cam used on the 'Long ram' intakes was intalled retarded.
Installing a generic aftermarket cam will most likely skew the efficiency of the sonic waves a bit in the tubes.


As for Steve's question to using longer rods, increased piston dwell won't be 'seen' by the intake system IMO and hardly have any effect on that.

It will however increase the possibility of engine detonation I would think.

Longer piston dwell is welcomed when building an engine for propane.
Propane is a slower burning fuel and having the piston spend a bit more time at TDC helps so it makes better use of the combustion pressure.

There used to be a Dodge Charger which was converted to Propane fuel and also had longer rods installed to help and make more power.
I have the article somewhere.

I have a 74 440 sitting on the Dyno right now and am waiting for a little warmer weather to fire it up. Current temps are -20°F and Wednesday it's supposed to drop to -29°. I have a set of short rams that I am going to try on the motor along with a few different cams. The cams I have are in the 236-246°@.050 along with a bone stocker. Also going to try cast iron exhaust manifolds and some 1-3/4" headers with them. I have the correct carbs and a set of Carter CS 750's to try.
You can probably find a set of short rams on E Bay.

Looking forward to seeing the results. I have read on various sites as well as heard from owners of ram induction cars that a cam being installed straight up negates the manifolds benefit. This car had been hidden out in a hanger for decades and everything I have swapped out has been ancient ie Allstate shocks, Atlas plugs and wires, Gulf sticker in doorjamb. Was happy with myself that I'd never have to reach under a set of valvecovers again to change plugs and here I buy a wedge car and probably one of the most involved ones w/ issues that predate my MoPar knowledge. I built a 392H/518 in a 58 Ply wagon about ten years ago and felt this way, this sickness comes in cycles

I bet those same XR lobes on a 113° - 114° LSA, and loosening up the lash would clean up the idle a lot, and put power in the motor too. Looks like lash adjustment is no easy job.

Tested a 500 motor on Impastato's dyno years ago in the middle of winter. He feeds outside air to the carb, in this case a six-pack. Air temp was single digits on a clear dry day. Peak power correction was like a negative 30 - 40 hp from actual. Crazy high six-pack jetting like I've never seen before.

4 bolts.

Long rams on my '60 Plymouth. It behaves well on the street, runs high 11's in the quarter. Mine are the 'short' rams. Carbs are Carter Competition 500CFM.

Race set-up:


Street set-up:

my rams are the long version, and previous owners chopped out the four hole dividers at the carb bases. also, the heat chambers under the carbs are rotted through.
so since repairs are needed, is it wise to cut the tubes and remove the dividers, effectively making them short rams ? if so, would cutting the dividers a touch shorter make the RPM usable to around 6k ?
has anyone done other mods to these that work out good ?
i'm also planning on trying a pair of thermoquads.
this is for my humpback with projected weight of 2500 or less.

Factory instructions on converting long rams to the 'short' version:

http://www.1960plymouth.com/drag/LongRam-ShortRam.pdf

Agree on the wide LSA

this is an OLD Harley engine I built, this is a 94 inch Harley, very old design with heads I ported on the large side for cid, it is also EFI, the blue run on the dyno is with a 8 inch long individual runner length, very gutless down low, the red line is with 22 inch runners, everything else is the same, this is only for a 2 cyl, X the results by 4 for an 8 cyl

thank you for that link ! i have never seen that before. looks like a relatively easy task to do. would you suggest repairing the 4 holes at the carb pad, or leave the pad open as it is now ?

The “short” and “long” versions are actually about the same overall length, right?

The term is really referring to the length of the divider wall.......yes?

How much difference in length of the divider wall between the two?

I admire you guys who are willing to mess with that stuff...... but it’s way outside of my KISS philosophy.

question #1 and #2, yes.
the third question, i'm not sure.
my one buddy always says : "why keep it simple when you can complicate the sh!t out of it ?"

also, as you probably know by now, i kind of like to try things that are uncommon, or against the grain of proven knowledge.
and i use what i have because of budget and the "what happens if" mentality i have.

having the instructions on the long to short conversion, and being a retired machinist, this looks like i will tackle this job. my intake setup is complete except carbs, and has been hacked on before i got it. it also needs repair on the exhaust heat plenums, so it needs some re-work regardless.
it looks good, and i have zero invested ! sooo......

The "ram effect" depends on the speed of sound so engine size shouldn't affect it. I'd suggest using the factory cam LSA and intake CL and go symmetrically bigger on the lobes.

There is a TON of wall friction and that depends entirely on the length of the divided section and the overall length. This is like pipe friction, which increases as the square of the velocity. Going from 413 to 440 increases the velocity 6.54%, pipe friction increases by 13.5% I think with the bigger engine the power curve to the torque peak increases and then after the torque peak it drops rather dramatically.

For a 500 inch engine it'd be like breathing through a straw.

R.

IIRC the original tuned runner length is 30"?
Deduct 10.5" for the un-cut remainder as per the instructions: 19.5" is now siamese.
I have no idea how any math works out here, but Chrysler almost certainly did multiple back-to-back tests before releasing the mod.
The question: how dependent on the original (mild) cam specs is the new 10.5" length, and would you want to second-guess it?

Personally, if I liked it simple the bowtie brigade would suffice. I m one of those guys that have always been drawn towards the quirky stuff. I've also wondered how and why something works. The worst thing someone can say to me is you can't do that or it will never work. I guess I'm a bit stubborn and bullheaded, more often than not they are correct. But, once in awhile I prove them wrong and that's very satisfying.

I had thought of the wall friction but figured increased swept volume would speed up the charge. Not to beat a dead horse but am I the only one who thinks the longer rod with corresponding longer dwell would increase the ram effect of the moving column of air? Or do you think the head wouldn't "see it" as Herman said. Dogdays I appreciate your cam remark.

are you perhaps, my brother from another mother ?
exactly my way of thinking ! around here, i'm a misfit with my brand loyalty. as always, most are brand x and y, so i get busted on constantly.
plus, all of my wounds are self inflicted.

Pretty much sums it up! My little foray into turbochargers has been a steep learning curve. All the damage I've done has been my own fault. I generally know how hard I can push something without destroying it. Sometimes my NEED for more hp overcomes any common sense I may possess.

Interesting tech article from Hughes Engines that shows flow test of a 'short' long ram compared to more traditional intakes.

Hughes Intake Manifolds Tests