Moparts

Cam too big?

Posted By: cornet684me

Cam too big? - 02/13/10 05:47 AM

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.

Posted By: CurYellowBird

Re: Cam too big? - 02/13/10 05:51 AM

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.
Posted By: cornet684me

Re: Cam too big? - 02/13/10 05:53 AM

what about the heads being shaved 50thousands?
wld this not help bump up the compression?
Posted By: DaytonaTurbo

Re: Cam too big? - 02/13/10 05:55 AM

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.
Posted By: cornet684me

Re: Cam too big? - 02/13/10 06:12 AM

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.
Posted By: CurYellowBird

Re: Cam too big? - 02/13/10 06:20 AM

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.
Posted By: cornet684me

Re: Cam too big? - 02/13/10 06:29 AM

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
Posted By: WILD BILL

Re: Cam too big? - 02/13/10 06:35 AM

FWIW, I ran a 555 lift comp cam with 8.6 to 1 CR and had no issues like your describing
Posted By: cornet684me

Re: Cam too big? - 02/13/10 06:42 AM

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"
Posted By: RobX4406

Re: Cam too big? - 02/13/10 07:10 AM

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.
Posted By: Rodney

Re: Cam too big? - 02/13/10 07:22 AM

you may need shorter push rods or adjustable rockers with the heads being machined that much also intake may need checked for proper fit.
Posted By: runinonmt

Re: Cam too big? - 02/13/10 02:19 PM

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
Posted By: DragDart360

Re: Cam too big? - 02/13/10 03:08 PM

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!
Posted By: blownzoom440

Re: Cam too big? - 02/13/10 04:06 PM

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.
Posted By: cornet684me

Re: Cam too big? - 02/13/10 05:07 PM

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,
Posted By: cornet684me

Re: Cam too big? - 02/13/10 05:10 PM

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.
Posted By: cornet684me

Re: Cam too big? - 02/13/10 05:15 PM

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?
Posted By: cornet684me

Re: Cam too big? - 02/13/10 05:16 PM

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
Posted By: cornet684me

Re: Cam too big? - 02/13/10 05:23 PM

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
Posted By: cornet684me

Re: Cam too big? - 02/13/10 05:26 PM

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
Posted By: Dodgem

Re: Cam too big? - 02/13/10 05:44 PM

Did you check the float levels. should have a 6.5 power valve and 70 to 72 front jets.
Posted By: cornet684me

Re: Cam too big? - 02/13/10 05:52 PM

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.
Posted By: runinonmt

Re: Cam too big? - 02/13/10 06:39 PM

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.
While you're atit make sure the floats aren't heavy from a leak,the air filter is clean and that the hood insulation isn't blocking air to the carb. This actually happened to a friend.I won't mention any names.
Ron
Posted By: forphorty

Re: Cam too big? - 02/13/10 07:19 PM

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.
Posted By: jbc426

Re: Cam too big? - 02/13/10 09:20 PM

First things first. What do you have you timing set at, initial and total?
Posted By: MoparDonny

Re: Cam too big? - 02/14/10 12:22 AM

Without a dial-back light, just set the initial timing (at 900ish RPM) to about 14 degrees, then set the mixture screws to about 2.5 or 3 turns(or just set them properly if you know how) finally check the float level once more and once the fuel just comes out of the sight plugs, go back down a 1/4-1/2 a turn. Keep at it, my 383 with 8:1, 800 Double pumper and a MP 274 cam was running mid to high 13's and ran unreal.

Don.
Posted By: dave571

Re: Cam too big? - 02/14/10 02:17 AM

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.
Posted By: RobX4406

Re: Cam too big? - 02/14/10 04:07 AM

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.
Posted By: DaytonaTurbo

Re: Cam too big? - 02/14/10 05:31 AM

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.
Posted By: DaytonaTurbo

Re: Cam too big? - 02/14/10 05:34 AM

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.
Posted By: dave571

Re: Cam too big? - 02/14/10 06:08 AM

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.
Posted By: dragaddict

Re: Cam too big? - 02/14/10 06:26 PM

Run a combo not too far off and found that the MSD box with Blaster coil really helped to clean it up. Everything else has a compromise such as bigger carb is more power less milage, bigger cam is higher rpm to get to usable range. Beter ignition is win/win better per Dr Jacobs. Starting,running,milage and cleaner burn. I also had a problem with an incorrect ballast resistor on a coil-distributor that took some life out of me before we found it. One system at a time works for me.
Posted By: DaytonaTurbo

Re: Cam too big? - 02/14/10 06:32 PM

Quote:



Great minds think alike...LOL




Lol or frozen minds!
Posted By: Dougsmopars

Re: Cam too big? - 02/14/10 06:44 PM

A lot of people are afraid of stall converters. I have a 28 to 3200 stall cars drives like any other car till you mash the pedal. No banging when you drop into gear no 2 footing at a red light to keep it from stalling. Back in the 80's i had a 69 Charger 440 525"lift 290 310 advertised duration 12.5 to 1 tunnel ram motor 4;10 gears and a 5000 stall. That would stall a bit higher just driving around but not that much more then a stock converter. It was very drivable. But it was fun when you mashed that pedal.
Posted By: cornet684me

Re: Cam too big? - 02/16/10 04:34 AM

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!
Posted By: Skeptic

Re: Cam too big? - 02/17/10 05:00 AM

If you didn't index the cam, the cam could be off and you'll chase your tail trying to tune it out. Just lining up the dots isn't good enough for aftermarket parts.
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