Off Idle Hesitation

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ramcharger

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Since my Ramcharger has become my daily driver for now I decided to work on a nagging problem but first, let me give you the details of my build.

360 LA block decked for 0 clearance and bored .040 over.

KB flat tops. My measured comp ratio is 10.2:1 with a 4.100 bore, .040 thick Cometic head gaskets.
Stock crank turned .010 under.
Eagle I-Beam rods.
HV oil pump.
Stock rear sump truck pan. (holds 6 quarts, gotta love Dodge, lol)
Double Roller timing chain.
MP timing chain tensioner.
Late LA heads machined for 2.02 intakes with bronze guides and some home pocket porting.
Stainless Valves.
Crane valve springs, retainers and locks.
Crane Gold 1.6 ratio roller rockers w/chrome finished shaft, Hughes Engines shaft hold downs and studs, custom hardened pushrods.

Lunati Voodo Cam 60401 with 213 degrees of duration at .050 lift. .484/.507 lift w/1.6 rockers. Very mild and idles in gear @ 650 no problem whatsoever. Starts pulling hard at 2200 rpm and just hauls *** up to 5500 rpm or so. Great cam and I couldn't be more impressed with the Lunati products. This engine is scary fast in a 5600 lb RC and would be one heck of a daily driver in a A-body.

Wieand Action + Dual plane manifold, Exhaust heat blocked. No spacer although a phenolic spacer is in it's future. Carb likes to boil over when hitting hard vertical bumps and the fuel sloshes, even with the vent extensions I pinned in.
Holley 650 double pumper with a QuickFuel throttle body. I can't say enough about how nice the machine work is on these and having a secondary idle throttle plate adjustment is great for big cams. 72 primary jets, 6.5 power valve, no power valve in the secondary metering block and 78 jets. Electric Holley blue pump with a Summit regulator set to 6.5 psi.

MP distributor with a Mallory ignition box and MSD Blaster coil, no coil resistor. 12 degrees initial advance and 36 total not including 14 degrees of vacuum advance.

Tight heavy duty 4x4 torque converter by Hughes with a 1800 stall. I'd say it was more like 1500. 3.55 gears and 33x12.5 tires. 727 with kolene steels and red frictions, bolt in sprag and Trans-Go shift kit installed as "RV" shift.

OK, enough information? lol! Anyway, I was having a severe stutter right off idle. It got better as the truck warmed up, so I was thinking carb. Well, the carb I built this on is old, old man lol! The first thing I thought was the accelerator pump. I looked in the primaries when I lightly opened them up and saw that the pump squirt was inconsistent. I pulled the bowl off and found tons of play allowing the pump arm to twist so I drove the pin out and shimmed the arm. No more play and a consistent squirt :). "Cool" I thought, problem solved. Not. It was better, but not where it should be (I'm really freakin' picky). This is a mild cam and this is an issue that I have never experienced on such a mild build. WTF. :angry7:

I start thinking vacuum leak. I check my vacuum readings and find 20" at idle and 1 3/4 turns out. Perfect really. No leaks here. Timing now comes to mind. I search fuitlessly for 45 min for my kick *** Snap-On digital timing light. Fk, can't find it. It's still in box a somewhere. Crap. The light goes on in my head and remember that every Hot Rod daily driver that I ever built always had the vacuum advance connected to manifold vacuum, not ported vacuum which is how I had the Ramcharger set up. I swapped the vacuum line and now the RC is more responsive from a light throttle opening than I could have ever dreamed. Just touching the throttle just moves this pig to 30 NOW, lol! The tach never hits 1500 rpm and the trans just shifts it's nice tight shifts. It's a torque ORama :). Don't fooled for a minute though, this thing gets over 2 grand and the exaust note changes to a wicked rasp and it freakin goes. Can't bog this down with the double pumper either and I can feel the secondaries open by the change of tension on the accelerator as well as by the seat of my pants.

I swear by my heart of hearts that it's so much harder to build a daily driver that hauls *** at WFOT and is mellow when need be than it is to build a strip only car.

The whole reason I posted this huge diatribe was to try to help someone if they have a similiar build and are experiencing the same symptoms. :read2: Merry Christmas everyone! :-D
 
lol... good post Ram. I might suggest the timing curve isnt fast enough, and you can dial in more (closer to 40 total) centrifical if it likes the manifold vaccum setup. The only difference I can see with ported vs manifold vacuum is the part throttle drivability and milage, where (just my opinion) the ported helps more. Of course, with the light boxed up it's impossible to tell...lol.
 
lol... good post Ram. I might suggest the timing curve isnt fast enough, and you can dial in more (closer to 40 total) centrifical if it likes the manifold vaccum setup. The only difference I can see with ported vs manifold vacuum is the part throttle drivability and milage, where (just my opinion) the ported helps more. Of course, with the light boxed up it's impossible to tell...lol.

Yeah Moper, I've got to find that light so I can make some changes. Centrifugal advance as I recall was all in by 2500.

Joe do you have any larger pump shooters than what's in it? Might be worth a try since it's so easy to do.

I do need to pick up a nozzle and pump cam kit. The change has seemed to solve the problem so far. I'll know more on my stop and go 6 mi commute to work and back tomorrow.
 
Yep Fishy, after driving this today I need to double check my pump arm adjustment then try a larger shooter. It has greatly improved but not where I want it yet. It dropped 40 degrees today and the hesitation from a dead stop showed up again.
 
Hey Joe
I changed dist to ported vacuum and it made a world of difference, really comes off idle strong now.
 
Yep Fishy, after driving this today I need to double check my pump arm adjustment then try a larger shooter. It has greatly improved but not where I want it yet. It dropped 40 degrees today and the hesitation from a dead stop showed up again.


I had the exact same problem. Went up a few sizes on the pump squirters and problem solved.
 
Sounds like you had it tuned good for the 40 degree warmer weather and now the cold stuff's making it lean. Had the same thing happen to my Cuda. Back in Sept. I bought a 750 DP and rebuilt it and only had to do minor tuning to get it running great. No hesitation then. Drove it last week when it was in the 40's and man did it hesitate bad.

Joe if you need a 31 or any other squirter let me know. I have a bunch and can stick one in a mailer and send it to you.
 
I agree, try a larger squirter...it should help things...if it dosent work, at least it was not a lot of money to try it.
 
ram, I meant have it all in earlier rather than later... Like centrifical all in by 1800-2K if it doesnt detonate. You can also adjust the power valve level to come in earlier or later by higher of lower rating. That might be the best way, because the load automatically determines if it gets morefuel.
 
Sounds like you had it tuned good for the 40 degree warmer weather and now the cold stuff's making it lean. Had the same thing happen to my Cuda. Back in Sept. I bought a 750 DP and rebuilt it and only had to do minor tuning to get it running great. No hesitation then. Drove it last week when it was in the 40's and man did it hesitate bad.

Joe if you need a 31 or any other squirter let me know. I have a bunch and can stick one in a mailer and send it to you.

You're right and yes I did. I was thinking a megaquirt fuel injection system on the home, lol! I really didn't expect to be driving the RC this winter so I got caught off guard. I'd like to try that 31 if you don't mind. If it doesn't work I'll send back or send you the 28 in return plus a few bucks. I had a whole selection from back in the '80 and sold them off before I moved to colorado. I didn't know it would cost $120 to replace them future, lol.

I agree, try a larger squirter...it should help things...if it dosent work, at least it was not a lot of money to try it.

Agreed! :cheers:

ram, I meant have it all in earlier rather than later... Like centrifical all in by 1800-2K if it doesnt detonate. You can also adjust the power valve level to come in earlier or later by higher of lower rating. That might be the best way, because the load automatically determines if it gets morefuel.

Yes, I knew what you meant. :) And yes, that makes total sense. Now, if I can only find that dam light......lol.

I'm running a 6.5 power valve. I need to run a line from my vacuum gauge in the cab to the manifold to get a good baseline.

The 72 primaries and 78 secondaries (no secondary power valve) seem lean now too at WFO. I may bump up to 74s and 80s after I get the off idle problem resolved. There goes any semblence of fuel mileage.
 
Yep, just replied, :)

Believe it or not, I actually like the tuning process. I'm sick that way, lol.
 
I'd like to try that 31 if you don't mind. If it doesn't work I'll send back or send you the 28 in return plus a few bucks. I had a whole selection from back in the '80 and sold them off before I moved to colorado.

Pm me your last name (old farts memory strikes again) and address again and I'll get it heading your way. Don't need anything for it. You helped me out awhile back with your old cam I needed for a test.
 
Pm me your last name (old farts memory strikes again) and address again and I'll get it heading your way. Don't need anything for it. You helped me out awhile back with your old cam I needed for a test.

Oh man, I forgot about that. :) PM is coming shortly.
 
Fishy,

Got the .031 nozzle a little ways back and just now have installed it and went for a test cruise. Problem is solved! :) Heavy truck plus 3.55 gears plus tight convertor plus tall tires (33x12.5) = larger nozzle. I'ts virtually neck snapping right off idle. :-D

Thanks man! You need the small nozzle back? It's .025.
 
I like the way you describe that cam, as it's what I plan to put in my 318 for my '70 Duster. Hopefully it reacts the same way!
 
Mope, It's the first Lunati I ever used and I'm very impressed. The powerband should move up 200 to 300 rpm in a smaller engine as you plan on using it in and the idle may not be quite as smooth. If an experienced ear listens to my build, they could tell I've got a larger than stock cam. It's got just a bit of what I call "motorboat idle". Similiar to what a factory high-perf v-8 power boat would sound like at idle. Sounds pretty darn good really. I'll see if can post a vid tomorrow.

I've always used either Comp or Crane. A Lunati will go into my next stroker build, hands down. I had to richen it up quite a bit over the larger Crane that was in it (three main jet sizes). That tells me it's pulling more air and it doesn't try to pull me through stoplights with the tight convertor either. It's a neck snapper right from 1500-1600 rpm where the convertor stalls then the power starts to build until about 2100-2200 rpm, the exhaust just snarls and it moves this heavy pig. Enough to throw me in another lane too quick if I snap it in second to pass. It's kinda scary with the old RC suspension. :) This is at mile high altitude too. Tack on 18% to 22% more power at sea-level.
 
Mope, It's the first Lunati I ever used and I'm very impressed. The powerband should move up 200 to 300 rpm in a smaller engine as you plan on using it in and the idle may not be quite as smooth. If an experienced ear listens to my build, they could tell I've got a larger than stock cam. It's got just a bit of what I call "motorboat idle". Similiar to what a factory high-perf v-8 power boat would sound like at idle. Sounds pretty darn good really. I'll see if can post a vid tomorrow.

I've always used either Comp or Crane. A Lunati will go into my next stroker build, hands down. I had to richen it up quite a bit over the larger Crane that was in it (three main jet sizes). That tells me it's pulling more air and it doesn't try to pull me through stoplights with the tight convertor either. It's a neck snapper right from 1500-1600 rpm where the convertor stalls then the power starts to build until about 2100-2200 rpm, the exhaust just snarls and it moves this heavy pig. Enough to throw me in another lane too quick if I snap it in second to pass. It's kinda scary with the old RC suspension. :) This is at mile high altitude too. Tack on 18% to 22% more power at sea-level.

Well, I'm in Monument, so I'm even higher up than you are.
 
Well, I'm in Monument, so I'm even higher up than you are.

True enough, but now I'm having a big fat rum and now I'm higher than you!! LOL! Just kidding man. I bought my Duster from a guy in Monument. Seems to be a lot good people there. Relax..... We both know that a 45 min drive from either of us will bring us up to 10000 ft plus.

Fuel injection can solve a lot of our altitude probelms and I'm working on that via a Megasquirt system. Google it. :)
 
Really? How long ago did you buy it? It seems like around here there's the rare '70-something redneck Camaro driver, and that's it. What worries me is having to adjust the carb if I go on a long trip, as the altitude usually changes by at least 1000 ft.

BTW the other night I rolled a nice fat blunt, I'd have to argue with you on our "altitude" levels! (LOL!! j/k).
 
Let's see, the day after Thanksgiving of 2007. Guy had a restored '70 Duster and an older 40 something dodge truck. His buddy had a real nice older ford truck too.

I've got a switch on the dash of my RC that allows me to pull out a pre-programmed amount of timing.
 
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