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Cam too big? #612117
02/13/10 01:47 AM
02/13/10 01:47 AM
Joined: Dec 2007
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Brandon, Ms
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cornet684me Offline OP
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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.


Re: Cam too big? [Re: cornet684me] #612118
02/13/10 01:51 AM
02/13/10 01:51 AM
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San Antonio, TX
CurYellowBird Offline
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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
Re: Cam too big? [Re: CurYellowBird] #612119
02/13/10 01:53 AM
02/13/10 01:53 AM
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Brandon, Ms
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cornet684me Offline OP
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what about the heads being shaved 50thousands?
wld this not help bump up the compression?

Re: Cam too big? [Re: cornet684me] #612120
02/13/10 01:55 AM
02/13/10 01:55 AM
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Manitoba, Canada
DaytonaTurbo Offline
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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.

Re: Cam too big? [Re: DaytonaTurbo] #612121
02/13/10 02:12 AM
02/13/10 02:12 AM
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Brandon, Ms
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cornet684me Offline OP
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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.

Re: Cam too big? [Re: cornet684me] #612122
02/13/10 02:20 AM
02/13/10 02:20 AM
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San Antonio, TX
CurYellowBird Offline
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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
Re: Cam too big? [Re: CurYellowBird] #612123
02/13/10 02:29 AM
02/13/10 02:29 AM
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Brandon, Ms
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cornet684me Offline OP
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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

Re: Cam too big? [Re: cornet684me] #612124
02/13/10 02:35 AM
02/13/10 02:35 AM
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BROOK PARK, OH
WILD BILL Offline
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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

Re: Cam too big? [Re: WILD BILL] #612125
02/13/10 02:42 AM
02/13/10 02:42 AM
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cornet684me Offline OP
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thanks for the input Bill, i maybe getting back with you if i do not figure out the right mix to get this motor to running like a 440 should, i have heard " mopars are hell to tune however once they are tuned they run like hell"

Re: Cam too big? [Re: cornet684me] #612126
02/13/10 03:10 AM
02/13/10 03:10 AM
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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.

Re: Cam too big? [Re: cornet684me] #612127
02/13/10 03:22 AM
02/13/10 03:22 AM
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Central Oregon
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Rodney Offline
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you may need shorter push rods or adjustable rockers with the heads being machined that much also intake may need checked for proper fit.

Re: Cam too big? [Re: Rodney] #612128
02/13/10 10:19 AM
02/13/10 10:19 AM
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Franklin Co. Illinois
runinonmt Offline
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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.
Re: Cam too big? [Re: runinonmt] #612129
02/13/10 11:08 AM
02/13/10 11:08 AM
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South Jersey, NJ
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DragDart360 Offline
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Quote:

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 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




I had problems with mine that we thought were carb related but could not find the timing mark with a light as you mentioned. Made all kinds of changes to the carb and no help. I was advised if there was no timing mark there was an ignition problem. Replaced distributor and wa la timing mark
appears and the engine runs great. As said fix the ignition first!


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SB 408, Bullet roller 264/268 @50 .636 SSDS stage 2 Edelbrock heads, 1 7/8 Headmans, 1050 dominator by Dom, 9.867 @ 133
Re: Cam too big? [Re: cornet684me] #612130
02/13/10 12:06 PM
02/13/10 12:06 PM
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ELYRIA,OH
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blownzoom440 Offline
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start with the idle mix screws turning them in untel it almost stalls.you may need to spray some carb cleaner in the idle air bleed hole there may be dirt in there for starters.

Re: Cam too big? [Re: DragDart360] #612131
02/13/10 01:07 PM
02/13/10 01:07 PM
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Brandon, Ms
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cornet684me Offline 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,

Re: Cam too big? [Re: blownzoom440] #612132
02/13/10 01:10 PM
02/13/10 01:10 PM
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cornet684me Offline OP
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i have set the idle screws several times with my vac. guage, the most vac. i can get is about 14pds at idle, when i put in gear i lose 2to 4pds of vac.

Re: Cam too big? [Re: Rodney] #612133
02/13/10 01:15 PM
02/13/10 01:15 PM
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cornet684me Offline 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?

Re: Cam too big? [Re: RobX4406] #612134
02/13/10 01:16 PM
02/13/10 01:16 PM
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Brandon, Ms
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cornet684me Offline OP
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i have to keep the idle at 1000 to get the engine running good at idle in gear, when i put in gear at 1000 if only drops to about 900 to 950 at idle, so i think i am okay there

Re: Cam too big? [Re: Rodney] #612135
02/13/10 01:23 PM
02/13/10 01:23 PM
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cornet684me Offline OP
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the intake fits , my buddy sd he also shaved the intake ports .050 to match the heads, i do not know about the push rods, my buddy sd he put shims on the rocker arms , so this should be fine

Re: Cam too big? [Re: Rodney] #612136
02/13/10 01:26 PM
02/13/10 01:26 PM
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cornet684me Offline 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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