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
OP
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Joined: Dec 2007
Posts: 1,639
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
Posts: 583
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
Too Many Posts
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Too Many Posts
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Posts: 21,318
Manitoba, Canada
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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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Brandon, Ms
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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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Senior Member of the Junior Dragster Club
Joined: Dec 2007
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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Posts: 12,271
Overpriced Housing Central
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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
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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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OP
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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
OP
top fuel
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OP
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Joined: Dec 2007
Posts: 1,639
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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
OP
top fuel
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OP
top fuel
Joined: Dec 2007
Posts: 1,639
Brandon, Ms
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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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