Re: cross ram physics
[Re: Twostick]
#2612998
01/27/19 12:17 PM
01/27/19 12:17 PM
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Joined: Nov 2010
Posts: 3,696 jersey
Spaceman Spiff
master
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master
Joined: Nov 2010
Posts: 3,696
jersey
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How many bolts do 1961 413 valve covers have? Stock 440 has 6, the early 413's had 4 but I'm not sure when they changed.
Kevin 4 bolts.
526 cubes of angry wedge, pushbutton shifted, 9 passenger killer!
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Re: cross ram physics
[Re: Handygun]
#2613046
01/27/19 02:16 PM
01/27/19 02:16 PM
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Joined: Jan 2003
Posts: 693 Dunnellon, FL
longram60
mopar
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mopar
Joined: Jan 2003
Posts: 693
Dunnellon, FL
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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:
Last edited by longram60; 01/27/19 02:22 PM. Reason: added image
1979 AMC Spirit, NHRA Q/SA
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Re: cross ram physics
[Re: longram60]
#2613053
01/27/19 02:40 PM
01/27/19 02:40 PM
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Joined: Sep 2003
Posts: 19,687 north of coder
moparx
"Butt Crack Bob"
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"Butt Crack Bob"
Joined: Sep 2003
Posts: 19,687
north of coder
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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.
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Re: cross ram physics
[Re: BSB67]
#2613076
01/27/19 03:50 PM
01/27/19 03:50 PM
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Joined: Aug 2011
Posts: 2,885 Pattison Texas
CSK
master
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master
Joined: Aug 2011
Posts: 2,885
Pattison Texas
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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. 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
1968 Charger COLD A/C Hilborn EFI 512ci 9.7 compression, Stealth heads, 4.10 gear A518 ODtrans 4100lb,10.93 full street car trim 2020 T/A 392 Stock 11.79 @ 114.5
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Re: cross ram physics
[Re: Handygun]
#2614045
01/29/19 02:45 PM
01/29/19 02:45 PM
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Joined: Jan 2003
Posts: 14,515 So. Burlington, Vt.
fast68plymouth
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 14,515
So. Burlington, Vt.
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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.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
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Re: cross ram physics
[Re: fast68plymouth]
#2614056
01/29/19 03:03 PM
01/29/19 03:03 PM
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Joined: Sep 2003
Posts: 19,687 north of coder
moparx
"Butt Crack Bob"
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"Butt Crack Bob"
Joined: Sep 2003
Posts: 19,687
north of coder
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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......
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Re: cross ram physics
[Re: moparx]
#2614153
01/29/19 05:22 PM
01/29/19 05:22 PM
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Joined: Jan 2003
Posts: 16,376
dogdays
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 16,376
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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.
Last edited by dogdays; 01/29/19 05:24 PM.
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Re: cross ram physics
[Re: Handygun]
#2614237
01/29/19 08:09 PM
01/29/19 08:09 PM
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Joined: Oct 2007
Posts: 4,213 New York
polyspheric
master
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master
Joined: Oct 2007
Posts: 4,213
New York
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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?
Boffin Emeritus
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Re: cross ram physics
[Re: quickd100]
#2614560
01/30/19 01:42 PM
01/30/19 01:42 PM
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Joined: Sep 2003
Posts: 19,687 north of coder
moparx
"Butt Crack Bob"
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"Butt Crack Bob"
Joined: Sep 2003
Posts: 19,687
north of coder
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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 ? 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. 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.
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