Cam too big?
#612117
02/13/10 01:47 AM
02/13/10 01:47 AM
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Joined: Dec 2007
Posts: 1,639 Brandon, Ms
cornet684me
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Brandon, Ms
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i have a 1973 motor home 440, i bought from a buddy, basically stock motor, except the heads have been shaved about 50thousands, i have 750 holley model 3310, electronic ign. with stock ecu, headers, eddy performer air-gap, the heads have been reworked, the bottom end all stock, my problem is, the cam is xtreme engery comp. cam 274 .488/.491 110, i do not have the car on the road yet, i have driven around the block, however sitting in my garage at idle, it is fouling plugs out and the gas smell while running will burn your eyes, i have about 14pds of vac. at idle and about 8 to 10pds in gear, i have changed out the power valve to 3.5, and i have been told to try going down with the jetting? do you think that i can run this cam with the low compression 73motor or do i need to go down with the duration to about a 268 or lower? or do you think i can jet the carb down and run this set up? it is 727 auto, withy 3.55 sure grip , i have the timing set to the best the car can run with this set up, i have put a light on it, however , i cannot figure out where the timing is, however, i know the timing is not the issue here, i have the car running great other wise.
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Re: Cam too big?
[Re: cornet684me]
#612118
02/13/10 01:51 AM
02/13/10 01:51 AM
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Joined: Feb 2009
Posts: 583 San Antonio, TX
CurYellowBird
mopar
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mopar
Joined: Feb 2009
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San Antonio, TX
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Your compressions is probably too low with a motor home engine. I think the stock CR on those engines were like 8:1 or 8.5:1. I know that comp recommends that the xe268 be run at 9:1 CR. So I can imagine with the 274 you would want somewhere near 9.5:1. Fouled plugs meaning your not getting adequate burn, so compression is probably the main factor.
Project War Bird:
1971 Plymouth Roadrunner
383 4 speed with air conditioning
GY3 Curious yellow
All original
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Re: Cam too big?
[Re: cornet684me]
#612120
02/13/10 01:55 AM
02/13/10 01:55 AM
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Joined: Feb 2003
Posts: 21,318 Manitoba, Canada
DaytonaTurbo
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That is a bit of cam for an 8:1 compression 440, but you do not have a cam problem, you have a tuning problem. I've got a low CR 440 as well with a cam in it that's only a bit smaller than yours and it runs great.
First, get ready to dive into setting up your distributor properly. Timing affect fueling, fueling does not affect timing. Your 440 is going to like lots of initial timing, it'll tolerate 18* initial and 40 or more total, although with adding extra total timing above that I don't think will gain you anything. Your carb sounds like it's jet too rich. Buy a holley jet kit and start jetting down the primaries. Also your 440 will like a 3000rpm stall converter and a 3.73 or numerically higher rear end.
Also, even with that .050 of head milling, you're likely only around 8.3 or so CR where stock was more like 7.8.
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Re: Cam too big?
[Re: DaytonaTurbo]
#612121
02/13/10 02:12 AM
02/13/10 02:12 AM
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Joined: Dec 2007
Posts: 1,639 Brandon, Ms
cornet684me
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so what you are saying is, with some tuning , i should be able to make this set up work, i have the motor in a 1968 dodge coronet, 727 with stock covertor and i have 3.55 gears, so you think i can jet the carb. down to get the running rich down a bit, i really do not want to run a stall or higher gear, it is really just going to be a weekend cruiser, not a drag strip car , i really like the feel of the big cam, however , i am getting tired of changing out plugs about every other mth, just sitting in the garage at idle, i did go around the block, the car runs out strong, however, the raw gas fumes are terrible, it will light the back tires up, however, the gas fumes come into the car , and just sitting at idle, you can see the flood smoke coming out the tail pipes, car running way to rich.
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Re: Cam too big?
[Re: cornet684me]
#612122
02/13/10 02:20 AM
02/13/10 02:20 AM
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Joined: Feb 2009
Posts: 583 San Antonio, TX
CurYellowBird
mopar
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mopar
Joined: Feb 2009
Posts: 583
San Antonio, TX
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Yes with proper timing and rejetting the engine should run fine.
Problem is it's not about making it a strip car. The stall converter and gearing that DaytonaTurbo is mentioning is what the car should have to run with that cam properly. Comp cam even says to run a 2200+ stall with that cam. As far as gearing, 3.73's would be best but I think you may be able to get away with 3.55's.
Last edited by CurYellowBird; 02/13/10 02:20 AM.
Project War Bird:
1971 Plymouth Roadrunner
383 4 speed with air conditioning
GY3 Curious yellow
All original
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Re: Cam too big?
[Re: cornet684me]
#612124
02/13/10 02:35 AM
02/13/10 02:35 AM
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Joined: Dec 2007
Posts: 10,542 BROOK PARK, OH
WILD BILL
Senior Member of the Junior Dragster Club
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Posts: 10,542
BROOK PARK, OH
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FWIW, I ran a 555 lift comp cam with 8.6 to 1 CR and had no issues like your describing
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Re: Cam too big?
[Re: cornet684me]
#612126
02/13/10 03:10 AM
02/13/10 03:10 AM
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Joined: Apr 2005
Posts: 12,271 Overpriced Housing Central
RobX4406
I Live Here
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I Live Here
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Quote:
i will start with the jetting, i will get back with you with update , once i change out the jets thanks for the info and help
Get the initial timing figured out FIRST!
Anything else at this point is chasing your tail.
If the idle drops more than about 200 or so RPM when put in gear, you have the throttle blades too far open. Give it more initial and get the blades closed up. It may want in excess of 20* initial.
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Re: Cam too big?
[Re: Rodney]
#612128
02/13/10 10:19 AM
02/13/10 10:19 AM
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Joined: May 2005
Posts: 416 Franklin Co. Illinois
runinonmt
mopar
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mopar
Joined: May 2005
Posts: 416
Franklin Co. Illinois
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That cam is nowhere too big for your setup.You need to start at the beginning with the carb.The power valve has no effect at idle.Check the fuel pump pressure, float levels,power valve for a leak (this WILL affect idle),power valve gasket-not only for tears but position on the power valve.Before fine tuning be sure to set the timimg.I know I'll get flamed for this but a power valve in the 8.5 to 10.5 range will give excellent results with a properly tuned carb. Ron
Last edited by runinonmt; 02/13/10 02:36 PM.
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Re: Cam too big?
[Re: DragDart360]
#612131
02/13/10 01:07 PM
02/13/10 01:07 PM
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Joined: Dec 2007
Posts: 1,639 Brandon, Ms
cornet684me
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you know, when i hook up the vacum advance and give the car gas, the car start to mis, then i unplug the vac. advance and the car runs fine, i am wondering if the dist. may be the problem, i really do not know how to use a timing light, when i followed everybody's advice and set the timing at 35, the car runs like crap, so i adjust the timing with touch and sound and vac. guage, and the car runs fine, except for the running way to rich,
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Re: Cam too big?
[Re: Rodney]
#612133
02/13/10 01:15 PM
02/13/10 01:15 PM
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Joined: Dec 2007
Posts: 1,639 Brandon, Ms
cornet684me
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OP
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when i bought the engine from my buddy, he did have adjustable rocker arms, he put back the stock rocker arms when i bought the engine, however he did run the engine, he sd he had no problems, he had a eddy torker intake, headers, 750 double pump holley, the adjustable rocker arms, msd6 ign., i have 750 holley single pump, performer air gap intake, headers, and stock elect. ign, with stock ecu unit,and stock rocker arms, do you think i need to change to his set up?
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Re: Cam too big?
[Re: Rodney]
#612136
02/13/10 01:26 PM
02/13/10 01:26 PM
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Joined: Dec 2007
Posts: 1,639 Brandon, Ms
cornet684me
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OP
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power valve gasket-not only for tears but position on the power valve
what do you mean the position of the power valve? i did replace the power from 6.5 to 3.5 with a new one
Last edited by cornet684me; 02/13/10 01:27 PM.
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Re: Cam too big?
[Re: Dodgem]
#612138
02/13/10 01:52 PM
02/13/10 01:52 PM
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Joined: Dec 2007
Posts: 1,639 Brandon, Ms
cornet684me
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yes, the floats are fine, the carb. did have a 6.5 power valve, i have replaced with 3.5, i was going to take apart and go down with the jets, i am going to try this next week, a buddy just called he will bring me a good dist. that he has to let me try to see if is my dist.
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Re: Cam too big?
[Re: runinonmt]
#612140
02/13/10 03:19 PM
02/13/10 03:19 PM
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Joined: Nov 2006
Posts: 1,454 oklahoma
forphorty
pro stock
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oklahoma
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Quote:
Quote:
power valve gasket-not only for tears but position on the power valve
what do you mean the position of the power valve? i did replace the power from 6.5 to 3.5 with a new one
I have seen power valves with the gasket off center sitting on the step allowing a leak. Ron
Yep, the old gaskets had tabs to locate it, i believe. Don't think any of the new ones do. I like to hold the metering block flat when installing the PV.
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Re: Cam too big?
[Re: cornet684me]
#612141
02/13/10 05:20 PM
02/13/10 05:20 PM
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Joined: Mar 2007
Posts: 3,275 West Coast, USA
jbc426
master
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master
Joined: Mar 2007
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West Coast, USA
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First things first. What do you have you timing set at, initial and total?
1970 Plymouth 'Cuda #'s 440-6(block in storage)currently 493" 6 pack, Shaker, 5 speed Passon, 4.10's 1968 Plymouth Barracuda Convertible 408 Magnum EFI with 4 speed automatic overdrive, 3800 stall lock-up converter and 4.30's (closest thing to an automatic 5 speed going)
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Re: Cam too big?
[Re: MoparDonny]
#612143
02/13/10 10:17 PM
02/13/10 10:17 PM
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Joined: Dec 2003
Posts: 5,314 Carstairs, Alberta, Canada
dave571
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A couple of things.
What you are describing is typical of a low comp engine with a larger cam and not enough intiial timing. You can jet it all day, if you like. But it won't run any better till the timing is sorted out.
.050 off the heads of a motor with the pistons .170 in the hole, doesn't do much. It'll be 8:1 on a good day.
Ideally, I think you want to advance that cam 4 degree's or so to make it better down low..
The rock stock converter isn't doing you any favors. The misconception is that you can't drive a converter with more stall on the street. A well built performance converter will drive like a stocker under light throttle, and flash to a higher rpm on hard launch. A 3K converter would be a nice match for that.
If I was curving a distributor for you, I'd recommend 18 intial, and 35 total all in by 2800.
The 3.55's are fine. I run way more cam with 3.73's, and didn't lose any ET when I switched from the 4.10's I had before the 3.73's.
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Re: Cam too big?
[Re: cornet684me]
#612144
02/14/10 12:07 AM
02/14/10 12:07 AM
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Joined: Apr 2005
Posts: 12,271 Overpriced Housing Central
RobX4406
I Live Here
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I Live Here
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Quote:
i cannot figure out where the timing is, however, i know the timing is not the issue here
ummmm, yeah ok... yet it's fuming you out...
If you give the engine more initial advance does it pick up RPM?
That cam should idle below 1000rpm.
I wonder if you turn the idle down you get a drop in timing. Mechanical being bled in at a low RPM. Happens all the time.
The carb is running on the transfer slots, that's part of the reason it's fuming you out.
If you don't have a timing tape, do a hillbilly timing tape. With the timing mark on the pass side, turn the balancer line to the bottommost indicator mark, mark a line 15* towards the top of balancer, turn the new marked line down to the lowest tab mark and make another mark 15* up. Now you can get the timing set in a range to about 45* BTDC.
DO NOT set the car using the total timing method. Set it by most vacuum/constant rpm, starter kickback or advancing until it no longer pick up RPM/resetting to constant. Somewhere in the 16-22* range should work. Shoot for an idle rpm of 900 in park.
Baseline the carb at 1.5 turns out on the idle mix screws. Start over.
DO NOT be concerned with total timing now. That's the second piece of the puzzle.
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Re: Cam too big?
[Re: RobX4406]
#612145
02/14/10 01:31 AM
02/14/10 01:31 AM
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Joined: Feb 2003
Posts: 21,318 Manitoba, Canada
DaytonaTurbo
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Like I said before timing affects fueling, fueling does not affect timing get that timing setup correctly initial AND total before you even dink around with the carb. Until you do that you are wasting your time. I run a 76 440 with stock pistons and the lunati 60303 cam which is 226/234 @ 050 to your 230/236 not much difference. Mine runs/drives just as cleanly as it did with the stock lo-po cam which is said to be more like 210. This combo loves a well tuned distributor, you can NOT just bolt one in right out of the box and go. Mine likes 18* initial, maybe more yet, but I had been running it (needlessly) on pump 94. You will want a lot of initial timing like that, with the total near 40 all in somewhere around 2500. You need either a dial back timing light or timing tape for your balancer. Once that distributor is dialed in, then and only then start to tinker with the carb. Without the correct timing, you will not be able to tune out that bad bog when you snap to WOT nor will you get any kind of a clean burn.
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Re: Cam too big?
[Re: cornet684me]
#612146
02/14/10 01:34 AM
02/14/10 01:34 AM
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Joined: Feb 2003
Posts: 21,318 Manitoba, Canada
DaytonaTurbo
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Quote:
so what you are saying is, with some tuning , i should be able to make this set up work, i have the motor in a 1968 dodge coronet, 727 with stock covertor and i have 3.55 gears,
Stock converter is doing you no favors, and the 3.55 gears are marginal but doable. The problem with the stock converter is you're only going to get a 2000rpm flash out of it and your motor is going to be soggy and not respond the best when you snap to full throttle and the motor is not able to flash stall to above the rpm where your total timing is in at. The smogger CR motors are more sensitive to the correct balance of timing and stall than this same cam in a 10:1 440 would be.
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Re: Cam too big?
[Re: DaytonaTurbo]
#612147
02/14/10 02:08 AM
02/14/10 02:08 AM
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Joined: Dec 2003
Posts: 5,314 Carstairs, Alberta, Canada
dave571
master
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master
Joined: Dec 2003
Posts: 5,314
Carstairs, Alberta, Canada
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Quote:
Stock converter is doing you no favors,
quoting me
Quote:
The rock stock converter isn't doing you any favors.
Great minds think alike...LOL
Quote:
The smogger CR motors are more sensitive to the correct balance of timing and stall than this same cam in a 10:1 440 would be.
For sure. The lower comp makes for a lazy burn. Needs more timing sooner, to compensate.
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Re: Cam too big?
[Re: cornet684me]
#612151
02/16/10 12:34 AM
02/16/10 12:34 AM
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Joined: Dec 2007
Posts: 1,639 Brandon, Ms
cornet684me
OP
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wow, thanks for all the input, from what i am reading, sounds like i need to get someone over to my house to teach me about timing, i have tried all the tricks everyone is saying, i have marked top dead center, put timing tape 2 1/4" and 1", the problem is i cannot get the car to run correctly trying to do this by the book timing, when i try to do by the book, the car runs like crap, then i hook up the vac. gauge and do it by ear and feel, i get the car running great, except for the flumes out the exhaust, i am going to break down and load it up on trailer and take it to expert in timing next week, i will give Moparts update, everyone has told me the problem is in the Timing, and the only reason i avoided it , is because i really do not know anything about getting this done, i was hoping to put some jets in carb and fix it, i should have known , this wld be too easy, Thanks for everyone's thoughts and input, i really think it is the timing too, i think i am running 18 to 20degress at idle, i cannot figure out the total timing yet, i have been just trying to do the timing by ear, vac. gauge and feel, starter drag etc., i guess this old shade tree trick is not going to work with a high performance cam, i will get back with Moparts once i try to get the timing thing sorted out!
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