Big cam idle adjustment, Holly 4150

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HOOCH

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Hi,

I have a 360 that we are just having a heck of a time getting to do a low idle. It will high idle and run just fun but no low idle. We have tried other carbs and nothing works, messed with timing a touch but not a lot of luck there either. Talked to a a few carb shops and don't really seem like they even wanna help me out. Wondering if the gurus on here could help me out.

Specs
71 360 .030 over
Forged internals
Weiand Xcelerator single plane mani
Holly 4150 650cfm
Ported J Heads

Cam specs @ .050
240 duration
Exh .557", Duration 259.6
Int .532", Duration 248.8
Lobe separation 105.7

4 speed standard transmission
3.91 posi
MSD 6AL
 
whats your timing at idle have you toyed 22 at idle,are your secondaries open a tad to let in more air,are you just racing if not you may want a duel plane intake.
 
Snake is right Hooch. You've gotta push the initial timing pretty steep with that cam, even though we don't know your effective compression ratio. As far as the carb, 650 DP's come with 6.5" power valves for the most part. If your idling under that vacuum reading, that will contribute to the lack of low speed idling, meaning it will load up rich.......And depending on your initial timing, I could see that happening with your combo.
 
Initial timing is....14*
My mech has played with it a lil bit

We tried a 4.5 power valve and it made it better, we tweeked the internals in the carb and it's better.

So my pops had a 1000cfm Demon race carb with the 4 corner idle adjustment and we slapped it on to see if we could just get it to idle. And it worked, got the idle down to a smooth 750rpm. So he has a 750cfm Holley race carb with the 4 corner adjustment that he is going to rebuild and slap on there.
 
14* is good for a stock 340-360.

Try 20-24*

If you have it idling, twist the distributor a bit CCW, if it picks up rpm, it wants the timing.
 
Once he gets the new carb rebuilt and put on there I will have him try that, will be a couple of days but I will report back with the findings.


crackedback said:
14* is good for a stock 340-360.

Try 20-24*

If you have it idling, twist the distributor a bit CCW, if it picks up rpm, it wants the timing.
Click to expand...
 
Yes... more initial. My 274xe wanted 20*. And that was in the 230's @ .050. What distributor do you have?

You should tighten that centrifugal curve down to 10-14*.
 
HOOCH said:
It's just a stock mopar distributor.
Click to expand...

Stock electronic?

Will need to be recurved...as shown in the link to Mopar Muscle Article.

Engine will be a turd until you get the timing set right....
 
I had the same problems with mine. Had the mopar 508 cam with 248 dur. Once I put the initial timing at 20 that cured my idle problems. Idles great now.

Fred B
 
No I'm running a MSD 6AL and MSD coil, the only thing stock is the distributor. I've talked to a few sources that say stock mopar distributors are solid and said I won't gain much at all by upgrading. So I've invested the money else where. But once the new carb goes on we will be playing with the timing cause I will not be happy till the car runs perfect.
 
the cam in my 9.5:1 magnum is 242-248 @.050 .550 lift on a 110 lsa, i run my timing locked out at 36 degrees and it idles right at 1000 rpms. as everyone else has said more timing is your friend for idling on large cams. What kind of vac do you see at idle? One thing i did that helped was to eliminate the pv and do all adjusting with jets and bleeds. i only pull 10-11 inches at idle in park, cant remember what it is in gear.
 
HOOCH said:
No I'm running a MSD 6AL and MSD coil, the only thing stock is the distributor. I've talked to a few sources that say stock mopar distributors are solid and said I won't gain much at all by upgrading. So I've invested the money else where. But once the new carb goes on we will be playing with the timing cause I will not be happy till the car runs perfect.
Click to expand...

It does not matter what distributor you have it is the Initial Timing that is not correct....

maybe if you had the timing correct now you would not be buying a new carb....

as said by another...pick your parts and spend your money..
 
We exhausted every option with timing, and modifying the existing carb. But the only thing that has seemed to work was 4 corner idle adjustment. The motor don't pull much for vac, we are getting around 5in around 1000-1200rpm.
 
have you recurved the distributor to get more initial advance?...

if not...you are wasting your time....but then again..it is your time and money..DWT
 
what is your compression ratio. did you recurve distributor
 
What exactly do you mean when you say re curve the distributor? Is there a link explaining how to do this? Im still learning this motor building/tuning thing!

Comp is 10.5:1
 
HOOCH said:
What exactly do you mean when you say re curve the distributor? Is there a link explaining how to do this? Im still learning this motor building/tuning thing!

Comp is 10.5:1
Click to expand...

Did you look in this thread at all?

A review of the post may be in order.

You HAVE NOT exhausted all options with timing because you are still way short on initial settings. It takes some work to get the timing profile set up correctly. When done right, the car runs on an entirely different level.

90-95% of the "carb" problems I've cured have nothing to do with the carb. It was all in the ignition system.
 
I'm guessing the engine is probably less than 10.5cr, was it zero decked? Anyway like others have said turn the initial to 20 maybe as high as 24 if the cr is low. Then see where the idle and vacuum are at. You should be in the area of 10/12 " of vacuum at 1,000rpm with that cam, the cam is not that big. Might have a vacuum leak.
 
Cracked back said it right.... alot of carb problems aint carb at all...

Set that piece of sh*t mopar distributor aside and buy the MSD Pro Billet that matches so you have the trio. Better end play on shaft, better bearings than a stock MP distributor.

Then before you install it, order the advance bushing kit from Don @FBO Systems(4secondsflat.com). It comes with a 10* & 14* bushings. Install the 14* advance limiter bushing. Set initial to 20*, then your total will be 34*..... report back.
 
I couldnt get my Wiand Xcelerator to seal either.
When I ran the 292/509 mopar cam I think at 20* initial it pulled about 12 inches of vacuum @1000, with the RPM Airgap.
I was able to get it to idle at 800 eventually.
 
redfastback said:
Cracked back said it right.... alot of carb problems aint carb at all...

Set that piece of sh*t mopar distributor aside and buy the MSD Pro Billet that matches so you have the trio. Better end play on shaft, better bearings than a stock MP distributor.

Then before you install it, order the advance bushing kit from Don @FBO Systems(4secondsflat.com). It comes with a 10* & 14* bushings. Install the 14* advance limiter bushing. Set initial to 20*, then your total will be 34*..... report back.
Click to expand...

I sell those bushing and for a lot less than FBO.
 
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