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Re: Cross Ram - inside work - dividers / block offs.....
[Re: LAR_414]
#310003
05/06/09 02:04 PM
05/06/09 02:04 PM
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Joined: Jun 2003
Posts: 9,225
Charleston
sixpackgut
Drag Week Mod Champion
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Drag Week Mod Champion
Joined: Jun 2003
Posts: 9,225
Charleston
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i would think that is a lean condition causing the surging. you probably have just a few cylinders goin lean under cruise conditions.
my jetting on my tunnel ram is all over the place to get fuel where its needed and vice versa.
Gen 3 power 6.22@110, 9.85@135
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performance only racing, CRT, ultimate converter, superior design concepts, ThumperCarbs
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Re: Cross Ram - inside work - dividers / block offs.....
[Re: sixpackgut]
#310004
05/06/09 02:14 PM
05/06/09 02:14 PM
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Joined: Nov 2003
Posts: 6,293
Rock Springs
Bob_Coomer
master
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master
Joined: Nov 2003
Posts: 6,293
Rock Springs
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I assume you read the literature out of the old MP engine books, they show some pop cycle stock damns etc......If not, I wouldn't care a bit to scan them up for you.
Which Cross ram are we talking about exactly?
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Re: Cross Ram - inside work - dividers / block offs.....
[Re: Bob_Coomer]
#310005
05/06/09 02:32 PM
05/06/09 02:32 PM
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Joined: Jan 2003
Posts: 4,573
...gently down the stream
LAR_414
OP
master
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OP
master
Joined: Jan 2003
Posts: 4,573
...gently down the stream
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I have an intake that almost nobody has messed with.....and I like it that way  It's a STR-12 for a smallblock. I've done the only "known" modifications with dams for better fuel distribution. I have an a/f meter (LM-1). I have bungs in both sides of the exhaust. Based on the readings / and the modifications / and the plug readings, everything is good to go for A/F and carbs. I've got this think tuned well. The problem with bucking and kicking is under 1700rpm or so in any gear. This started when I went from a sluch box to a 4 speed. It's not the distrib curve or anything mechanical. Might be the cam, but I'm thinking of trying to reduce the plenum volume to see if it's a low speed air issue inside the intake.
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Re: Cross Ram - inside work - dividers / block offs.....
[Re: LAR_414]
#310006
05/06/09 03:04 PM
05/06/09 03:04 PM
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Anonymous
Unregistered
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Anonymous
Unregistered
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Like Bob said the Mopar racing Guide shows the popsikle stick resin dams...They are for more mid to high range power for Drag racing, mainly stick cars. 
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Re: Cross Ram - inside work - dividers / block offs.....
[Re: LAR_414]
#310010
05/07/09 08:26 AM
05/07/09 08:26 AM
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Joined: Jul 2006
Posts: 4,595
On the south side of Nowhere
S/ST 3040
master
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master
Joined: Jul 2006
Posts: 4,595
On the south side of Nowhere
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Again, I'd say you're trying to make the intake do something it was never designed for. A lot of plenum volume, probably short runners, 2 4-bbl carburetors, direct drive and no RPM = crappy carb signal/low velocity. I'd say, there isn't enough activity going on in there to keep the fuel atomized and is falling out of suspension. If you get this sorted out, you will probably solve it yourself after screwing with it for a long time.  Good Luck.........Just be glad it's not a 340.
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Re: Cross Ram - inside work - dividers / block offs.....
[Re: LAR_414]
#310011
05/07/09 08:40 AM
05/07/09 08:40 AM
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Joined: Jul 2005
Posts: 428
wappinger falls new york
Jimi_Vignogna
mopar
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mopar
Joined: Jul 2005
Posts: 428
wappinger falls new york
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Quote:
I'm looking for some info and possibly pictures of work done inside of crossrams. I may try playing with the insides of mine some more to get out this bucking / kicking / surging that I get in gear below 1700rpm or so. I may try to reduce the overall plenum volume but still have a crossover inside.
Looking for ideas. Maybe even make an adjustible volume via a slide or something, that I can quickly adjust by removing one carb, adjust, re-install carb.
how is your distributor set up? the advance curve has to be right on for large plenum multi carb apps.
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Re: Cross Ram - inside work - dividers / block offs.....
[Re: Jimi_Vignogna]
#310012
05/07/09 08:47 AM
05/07/09 08:47 AM
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Joined: Mar 2003
Posts: 9,099
Rogue River, OR
Jeremiah
master
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master
Joined: Mar 2003
Posts: 9,099
Rogue River, OR
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Quote:
Quote:
I'm looking for some info and possibly pictures of work done inside of crossrams. I may try playing with the insides of mine some more to get out this bucking / kicking / surging that I get in gear below 1700rpm or so. I may try to reduce the overall plenum volume but still have a crossover inside.
Looking for ideas. Maybe even make an adjustible volume via a slide or something, that I can quickly adjust by removing one carb, adjust, re-install carb.
how is your distributor set up? the advance curve has to be right on for large plenum multi carb apps.
I for one would be interested in hearing more of your thoughts on this subject. 
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Re: Cross Ram - inside work - dividers / block offs.....
[Re: LAR_414]
#310014
05/07/09 11:35 AM
05/07/09 11:35 AM
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Joined: Jan 2003
Posts: 1,996
s. e. pa.
calrobb2000
top fuel
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top fuel
Joined: Jan 2003
Posts: 1,996
s. e. pa.
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hi what cfm carbs are you running ? prob fuel dropping out of suspension due to low speed volicity ? smaller carbs or smaller plenum may be in order for lower speed operation , may have to giv up something to get better operation ? 
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Re: Cross Ram - inside work - dividers / block offs.....
[Re: LAR_414]
#310015
05/07/09 11:37 AM
05/07/09 11:37 AM
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Joined: Oct 2007
Posts: 4,206
New York
polyspheric
master
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master
Joined: Oct 2007
Posts: 4,206
New York
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If that surge is 1 or 2 cylinders lean (which won't show on your sensors) vacuum advance will help.
Boffin Emeritus
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Re: Cross Ram - inside work - dividers / block offs.....
[Re: polyspheric]
#310016
05/07/09 11:59 AM
05/07/09 11:59 AM
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Joined: Jan 2003
Posts: 4,573
...gently down the stream
LAR_414
OP
master
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OP
master
Joined: Jan 2003
Posts: 4,573
...gently down the stream
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I;m running a couple 650 double pumpers. I know that sounds like overkill, but it works quite well.
At this super low RMP that I'm having the issue, the throttle blades are barely halfway into the transfer slot. The air fuel mix is coming totally off the idle circuit at this point. I don't think that the cfm of the carbs is going to change this one bit. These carbs have screw in ifr's and I've played with them as well as the iab's and along with the 4 corner idle screws, it's pretty good.
Even with the A/F LM-1 meeter hooked up, there doesn't appear to be any lean spikes at all. Granted, I can't be 100% for sure, but of the 4 cyl at a time that I can read, the readings are rock steady. And I've seen them fluctuate a bunch of times per second, when there is a lean condition or spark issue. But I can't be 100% correct here.
I'm interested in trying to advance the timing up and try it out again.
I'd like to hear the theory on the reason why the timing would effect a large plenum setup.
I'm sure I'll have to give up something to get some more driveablilty here.
But belive me people, this isn't a huge issue at all. Most people could just live with it no problem, but I'd like to give it a shot and try and tune this out of my combo.
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Re: Cross Ram - inside work - dividers / block offs.....
[Re: polyspheric]
#310017
05/07/09 12:06 PM
05/07/09 12:06 PM
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Joined: Dec 2005
Posts: 1,495
Shelby mi.
JAKE68
pro stock
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pro stock
Joined: Dec 2005
Posts: 1,495
Shelby mi.
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I have worked with this problem on milder motors for a couple of years now. It is because what above had said aboit low flow and alot of volume. I have done alot to calm it down but it cannot be eliminated. Smaller carb or less plenum would work. I have tried to run them ritcher and leaner nothing worked. I can calm it down alot with fixed timing,higher idle,lean idle mixture,cracked open secondaries. This problem is kind of a given when using this intake and not being full race type apllication. I have seen some of my customers try high dollar aftermarket carbs from Bigs,Quick fuel, ect and not have any succsess. Jake
JAKES AUTOMOTIVE
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Re: Cross Ram - inside work - dividers / block offs.....
[Re: Jimi_Vignogna]
#310019
05/07/09 12:18 PM
05/07/09 12:18 PM
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Joined: Dec 2005
Posts: 1,495
Shelby mi.
JAKE68
pro stock
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pro stock
Joined: Dec 2005
Posts: 1,495
Shelby mi.
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Quote:
well you got that covered, do not use vacumm advance,i would keep the timing the way you have it, under the carbs are the carbs just open to the plenum or do you have a 4 hole spacer of some sort, i have one of these intakes here that is going on a 377 with center squrters, this intake is open under neath the carbs, i am planning a pair of hvh super suckers for under the carbs.
Jimi you may be on to something with the four hole spacer as upposed to the open. It may change the signal to the carbs and stable the idle. I have a customer that I can call and have him bring the car back to try that. Put it back on the dyno and see if that looks clean or not. Jake
Last edited by JAKE68; 05/07/09 12:20 PM.
JAKES AUTOMOTIVE
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Re: Cross Ram - inside work - dividers / block offs.....
[Re: JAKE68]
#310020
05/07/09 12:44 PM
05/07/09 12:44 PM
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Joined: Jan 2003
Posts: 4,573
...gently down the stream
LAR_414
OP
master
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OP
master
Joined: Jan 2003
Posts: 4,573
...gently down the stream
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I don't run any spacer at all. I figured that I had enough Plenum volume! Maybe I'll try running a couple 1/2" thick 4 hole ones under each carb. Directly under the carb is just a big valley. I was thinking of making some sort of spacer shaped like a dome to help suspension or puddling. I can also reduce the plenum volume in numerous ways between the two carbs area. Any other ideas?
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Re: Cross Ram - inside work - dividers / block offs.....
[Re: LAR_414]
#310021
05/07/09 01:36 PM
05/07/09 01:36 PM
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Joined: Mar 2005
Posts: 2,172
Ohio
theclutcher
top fuel
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top fuel
Joined: Mar 2005
Posts: 2,172
Ohio
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install a plate between front and rear halves of intake.
Run front 4 cyls on one carb rear on other.
Remove material from divider wall as you see fit for your desires.
Did similar on team g with dominator plenum, basically make it a dual plane.
Last edited by theclutcher; 05/07/09 01:39 PM.
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