Moparts
Need help tuning mild 440
Posted By: Prodart440
Need help tuning mild 440 - 11/07/08 03:14 AM
Ok. I am lost. I have a 71 cuda with a mild 440. 750 holley, mopar dual plane intake, 1 inch spacer, tti 1 7/8 headers with 3" exhaust, 484-282 pulple shaft cam, 3000 stall 727. I cannot get it lean enough at idle. It will pull 9.5in of vacuum in neutral, but drops to between 5-7 in gear. I have a 6.5 power valve. What can I do to get it leaner?? Oh, timing is at about 12 BTD. Thanks!!!
Posted By: 1_WILD_RT
Re: Need help tuning mild 440 - 11/07/08 03:21 AM
Your 6.5 power valve is gonna open when your in gear...I'd drop it down to a 4.5 max...I'd start by adding more intial timing 17-20 degrees as long as the starter will take it...Limit the total to 36 degrees...Does it respond to the mixture screws? If not you may need to drill small (1/16-3/32) holes in the throttle plates to allow the idle adjustment to be closed enought to expose the idle transfer slot....
Posted By: Blown_Hemi
Re: Need help tuning mild 440 - 11/07/08 03:24 AM
Bump the inital timing up to 16º to 18º and have the total timing at 36º to 38º all in by 2500 RPM's. That shoul help your vacuum. Then adjust your carb from there. Always get your timing straightened out first then tune your carb.
Posted By: Prodart440
Re: Need help tuning mild 440 - 11/07/08 03:28 AM
I would bump the timing, but it pings if I do. I need to get a timing light to see when the total timing comes in.
The idle screws are very sensitive. 1/8 turn either way and it doesn't like it.
On another note, what kind of vacuum should the vacuum advance port have??
Thanks!!
Posted By: 1_WILD_RT
Re: Need help tuning mild 440 - 11/07/08 03:50 AM
If it pings right away your right you can't add more intial timing but if it's pinging above say 2000 rpm you need to add more intial timing & limit the total timing... Read this thread...
https://board.moparts.org/ubbthreads/show...rue#Post4774218
Posted By: DartGTX
Re: Need help tuning mild 440 - 11/07/08 03:57 AM
Are the throttle blades closed past the transfer slots on the carb?
My setup is very similar and I replaced the std. hyd lifters with crane "fast bleed" lifters. I went from 11" of vacuum @ idle to 13.5......
Total timing to 34 all in by 2500 rpm.
Good luck
Good luck
Posted By: thedriver
Re: Need help tuning mild 440 - 11/07/08 01:50 PM
sounds like the problem is in the power valve. goin to 4.5 will make a world of difference, and like mentioned, bump the initial timin up some as well.
Posted By: JimG
Re: Need help tuning mild 440 - 11/07/08 02:13 PM
A power valve opening at idle will not cause rich idle.
I'm with 1 Wild R/T in that you need to check t-slot/throttle plate relationship. Drill holes in the throttle plates only as a last resort, after you're sure the timing is where you want it, etc.
Do a search for 68Bullit's post entitled "Holley Rich Idle" or something similar. He had a situation similar to yours and the transfer slot thing is discussed in detail.
What is this carb - a 3310, double pumper...?
Jim
Posted By: Prodart440
Re: Need help tuning mild 440 - 11/07/08 02:38 PM
The carb is a double pumper. The throttle blades are not open too far. I am thinking the powervalve is the issue.
Posted By: JimG
Re: Need help tuning mild 440 - 11/07/08 02:44 PM
Aaron:
Remember, the power valve circuitry is plumbed to the mains, NOT the idle circuit.
You said the idle mixture screws are very sensitive both ways. What's preventing you from very carefully leaning out the idle with them?
Jim
Posted By: mark7171
Re: Need help tuning mild 440 - 11/07/08 02:57 PM
nothing mild about it. imo- a cam like that may need a 1100 rpm idle.
does the engine shake heavily while trying to idle? or is fuel dripping ? if so spring load your needle and seats. it might help.
with 7# at idle, i doubt your vacuum advance is kicking the timming up to give it time to burn that fuel. thats another problem.
Posted By: Prodart440
Re: Need help tuning mild 440 - 11/07/08 03:24 PM
Quote:
Aaron:
Remember, the power valve circuitry is plumbed to the mains, NOT the idle circuit.
You said the idle mixture screws are very sensitive both ways. What's preventing you from very carefully leaning out the idle with them?
Jim
If I move the idle mixture screws in at all, the engine wants to die. I think they are set perfect. After reading your link, I am thinking I need more initial timiing. I can put more timing in, but then it pings. I think I need to re-curve the distributor and work on that angle first. I read the article on the distributor slots and am leaning that way.
Posted By: Prodart440
Re: Need help tuning mild 440 - 11/07/08 03:30 PM
Quote:
nothing mild about it. imo- a cam like that may need a 1100 rpm idle.
does the engine shake heavily while trying to idle? or is fuel dripping ? if so spring load your needle and seats. it might help.
with 7# at idle, i doubt your vacuum advance is kicking the timming up to give it time to burn that fuel. thats another problem.
I have the idle set at 900 in neutral, and 700 in gear. The engine does not shake too bad at idle. There is no fuel dripping either. What should the ported vacuum switch pull for vacuum??
Posted By: mark7171
Re: Need help tuning mild 440 - 11/07/08 04:25 PM
you want more timming at idle, so i'd connect it to full vacuum instead of ported.
i dont know what your build "should make" , vacuum wise. with the correct timing more than 9.
the vacuum advance goes away when you give it gas. it wont be the cause of pinging on normal throttling situations. the clowns that hammer it may have some problems...with their "brain".
your mechanical curve will be the culprit of causal throttle pinging.
700 rpms ? thats a big cam in there.
Posted By: JimG
Re: Need help tuning mild 440 - 11/07/08 04:26 PM
Quote:
If I move the idle mixture screws in at all, the engine wants to die. I think they are set perfect. After reading your link, I am thinking I need more initial timiing. I can put more timing in, but then it pings. I think I need to re-curve the distributor and work on that angle first. I read the article on the distributor slots and am leaning that way.
Hi Aaron:
I'm a little perplexed by the idle mixture screw situation. If you turn the screws in (lean) to the point the engine stumbles, are you still getting the rich condition? That's what's confusing. Sitting here trying to visualize where additional fuel is coming from still makes me suspect the throttle plates are open too far at idle, causing the mains to operate. But you said that's OK, so I'm still confused.
How far open are the secondary blades? Did you look at those when you looked at the primarys? The same thing can happen back there too, and people sometimes overlook it.
You can try dropping your float level some and see how it responds, although that usually affects part throttle more than anything.
Other than that, I dunno...
I agree with checking the timing, certainly, and getting that dialed in, but (again) retarded initial timing usually results in the throttle plates being open too far at idle and...well, we know the rest!
I ran an almost identical engine in my car before I built the current one. 446", piston tops flush with the deck, same cam as you, home-ported 452's, DP4B intake, and a Holley 3310. I was running 16-18* initial timing, 38* total, and it worked well with no pinging. I had to drill 1/8" holes in my primary throttle plates, for what it's worth.
Jim
Posted By: mark7171
Re: Need help tuning mild 440 - 11/07/08 04:30 PM
jim there should be no reason to drill any holes at the level he is playing.
Posted By: Prodart440
Re: Need help tuning mild 440 - 11/07/08 04:43 PM
I guess I should get the timing figured out before I even decide to play with the carb. I will see what it like on the initial, and figure total from there. So 36* all in by 2500??
Posted By: JimG
Re: Need help tuning mild 440 - 11/07/08 04:45 PM
Hi Mark:
I've had to do the "hole in the throttle plate" thing on almost every 440 with a Holley 750 I've ever had my hands on. And always as a last resort, after making sure everything else is OK, mainly timing.
Having said that, I will say that in many of those cases, the problem could have been fixed by opening the secondary plates a little more. I realize I'm in the minority here, but I prefer drilling the holes in the plates over opening the secondary throttle stop because the latter, especially on larger-inch engines, causes a rich condition at high vacuum because the high vacuum pulls additional fuel through the secondary transfer slot. I know that most people prefer NOT taking a drill to their carb when there's an alternative, and I can certainly understand and respect that.
I guess there's lots of ways to skin a cat!
Jim
Posted By: JimG
Re: Need help tuning mild 440 - 11/07/08 04:47 PM
Quote:
I guess I should get the timing figured out before I even decide to play with the carb.
That should always be the plan as long as the carb isn't so far off as to prevent you from messing with the timing!
Quote:
I will see what it like on the initial, and figure total from there. So 36* all in by 2500??
With stock iron heads, 38* is the mostly agreed upon number.
Jim
Posted By: Prodart440
Re: Need help tuning mild 440 - 11/07/08 05:27 PM
They are mildly ported iron heads. Just the bowl area. Still 38*???
Posted By: Moparmedic440
Re: Need help tuning mild 440 - 11/07/08 06:45 PM
I run the same cam in my 440 Roadrunner and feel your pain. First thing take your idle vaccum in gear and divide it by 2 and that's the power valve you need to run, this is off the Holley web site. Get used to a rich idle you can't lean it out enough. This cam needs a 1000 rpm idle, the timimg spec's for this purple shaft is around 32 to 35 degree's at 2200 rpms. You will have to put lighter advance springs and let the distrubator advance manually. Hang in there you will get it.
Posted By: RapidRobert
Re: Need help tuning mild 440 - 11/07/08 11:23 PM
If the throttle blades are opened far enough to where you are into the transition slots could the PV being open be making you too rich since you are partly into the main circuit at that point
Posted By: Mr.Yuck
Re: Need help tuning mild 440 - 11/08/08 01:27 AM
put the cam shaft in the trash can, it's never going to run lean enough. It's bracket racing cam, if you have 9.5 your about on. What is your compression??? 10:1 or more would be best. They are made to run form 3k up. if you keep the 484 get used to stinky low rpm cruises.
Posted By: 383man
Re: Need help tuning mild 440 - 11/08/08 03:54 AM
Remeber if the P/V diaphram is blown it will pull fuel right into the intake. Ron
Posted By: 1_WILD_RT
Re: Need help tuning mild 440 - 11/08/08 03:58 AM
Quote:
Remeber if the P/V diaphram is blown it will pull fuel right into the intake. Ron
Yes it will... 
Posted By: macmic87
Re: Need help tuning mild 440 - 11/08/08 07:11 AM
Quote:
Bump the inital timing up to 16º to 18º and have the total timing at 36º to 38º all in by 2500 RPM's. That shoul help your vacuum. Then adjust your carb from there. Always get your timing straightened out first then tune your carb.
Posted By: DartGTX
Re: Need help tuning mild 440 - 11/08/08 09:23 PM
I completely AGREE with drilling the holes. The 750 DP I put on my car in 2001 has a 3/16th hole in ALL 4 throttle blades. I haven't had to touch it since installation and it idles at 1050 in P/N and 800 in gear.
BTW, I used a power valve PLUG to aleviate the chance of EVER having one blow again.
Good luck
Posted By: 383man
Re: Need help tuning mild 440 - 11/09/08 02:30 PM
Quote:
Quote:
Remeber if the P/V diaphram is blown it will pull fuel right into the intake. Ron
Yes it will...
Sounded like you needed to know that. Ron
Posted By: Prodart440
Re: Need help tuning mild 440 - 11/10/08 04:00 AM
So I was playing with the timing the other night, and I forgot to hook up the vacuum advance. The car seemed to run the same, but without the problems of it pinging when I get on it. I set the initial timing at about 12*. I still don't know what and when the total timing is and when it is in.
Posted By: ThermoQuad
Re: Need help tuning mild 440 - 11/10/08 05:59 AM
whoa nellie.....no matter what you do to the carb ie drill holes etc, the distributor needs a custom curve or this car will not run properly or in simpler language it will be a pig.
18 initial, 32 total, slow advance rate till all in by 2400 rpm.
Put the recurved dist back in the car, set the initial at 18 and set the idle at 1000 rpm and adj the mixture screws to the highest vacuum reading. Readjust the idle to 950 rpm and put it in gear and see what happens.
When you get to that point please come back and we will help you finish.
Posted By: Mr.Yuck
Re: Need help tuning mild 440 - 11/10/08 01:34 PM
Quote:
So I was playing with the timing the other night, and I forgot to hook up the vacuum advance. The car seemed to run the same, but without the problems of it pinging when I get on it. I set the initial timing at about 12*. I still don't know what and when the total timing is and when it is in.
With that cam you don't even need a vacuum advance. I wouldn't worry about initial and have 38* full at 2600rpm. As mentioned before no matter what you do, if you don't have good compression, 3000 stall and 3.91's or better the car is going to be slow out of the hole.
Change the PV, drill the throttle plates and re-curve the distrib, set your timing and let us know how it goes.