Truck drops 1,000 rpm's when put into gear(video)

[Lil Ape]

So I've had this rather annoying problem with my truck ever since I bought it. And I'm not sure what to do to fix it. Whether cold or at operating temp, the truck will idle about 2,000 rpm in P/N more and at 1,000 if it was in gear. I know typically the rpm's will drop a little when put into gear, but this seems like just too much. In the video below, the truck was running around 190 degrees(Tstat opened and dropped it to 175) with the choke open. I had the rpm's set as low as I can go in gear before it would stall out every time. I can't get it lower than 1,000 while in gear. When out of gear, it just sounds like the truck is on a high idle. The carb is a year old holley street avenger 670, barely has any miles on it. And the only thing I've ever adjusted on it was the curb idle screw. And if I remember, I believe I had it set to 12 deg advanced. Don't know if it matters any, but It has a 3k stall converter(supposedly). Anybody know how to fix this? This is really the only current problem I have with this truck And I hate it. Can't even hear the cam lope unless it's in gear. Would appreciate any help.

Cammed c10 - YouTube

[Wrecked1982]

check any vaccum leak small rubber hose etc, does the supossely 3k stall feels like a stall should when launching from a stop at normal speed not hammering it?or does it get going like any normal automatic car?

[Lil Ape]

I have a vacuum gauge that I used once months ago and it read between 10-12 if I remember and the gauge was steady. My cam is supposed to pull between 10-12. As far as the stall, well im not really sure what a high stall is supposed to feel like compared to a stock.

[INSIDIOUS '86]

Doesn't sound like a good style stall to me

What's your cam specs?

And you say 670street avenger? Carb may have to small of a baseplate depending on how Holley achieves the 670cfm

I had the same issue when I first got my motor running
Do you run vac advance and is it on full manifold vacuum?

[mongoose]

stand on the brake and hit the gas see what it wants to spin to without doing a burnout.

[ont_guy_38]

I have a 3500 stall, idling at 800, it prob doesn't drop 100 rpm when put into gear, I would say that's a lot of your problem.

[Lil Ape]

Originally Posted by INSIDIOUS '86

Doesn't sound like a good style stall to me

What's your cam specs?

And you say 670street avenger? Carb may have to small of a baseplate depending on how Holley achieves the 670cfm

I had the same issue when I first got my motor running
Do you run vac advance and is it on full manifold vacuum?

Cam specs are 234/244 duration and .488/.510 lift. And yes it's a 670cfm street avenger. And the vac advance is hooked up to the timed port on the carb.

Originally Posted by mongoose

stand on the brake and hit the gas see what it wants to spin to without doing a burnout.

My tires never start spinning until I hit about 3k and up.

[Lil Ape]

Originally Posted by ont_guy_38

I have a 3500 stall, idling at 800, it prob doesn't drop 100 rpm when put into gear, I would say that's a lot of your problem.

Not sure I follow, what do you mean when you say that's a lot of my problem?

[INSIDIOUS '86]

Alright based on that
1: your carb is too small you need larger throttle blades which help more air get in the engine. Which is crucial for idle with a big cam.
2: for a cam this big. Much more initial is needed. You need to get initial up to 18* static. Then lock out some timing to keep it at *38 total. And have it in by 3000rpm you also need to limit vac adv some as well
3: what intake is it running?

Get your timing set first then we can deal with the carb and get that idle down.
If I can get a cam like that in my truck to run on no stall and idle at 750rpm out of gear and 600rpm in gear then yours shouldn't be to hard.

[Lil Ape]

It's got a rpm air gap manifold on it now. I went with the 670cfm cause everyone was recommending me to stick around the 650 range. Previous owner recommended a 650 double pumper but, I wanted vac secondaries. So went with the street avenger. Static timing..is that base timing at idle?

[cadillac_al]

That truck sounds like most vehicles at the drag strip so I don't see the problem. I always said i buy my cams too small and now i'm sure of it. I want my truck to sound like that. Anyway, most people agree that vacuum advance should be on manifold vacuum. I would try switching to manifold vacuum and readjust the idle and probably idle mixture too.

I don't know why the revs would drop so much with a 3000 rpm stall converter but I see you can rev it some in gear so it must be somewhat higher than stock stall. I don't think the carb is too small but I had to swear off Hollys years ago because I can't make them work. If I had a hot motor like that, and i couldn't get a Quadrajet to work to my liking, I would probably go with a Holly too. I plan to build a hot engine for my Camaro this summer and I was planning on a bigger cam than that. I think I will try a cam in your size now and that will be hot enough for me.

I have never had an engine that hot but it may not even need vacuum advance. I think your issues are in the tuning and tinkering. It would be nice if you had another known good carb to try but if not, it looks like trial and error........unless a Holly guru chimes in.

[Lil Ape]

Yeah im still kinda new to carbs, timing and everything associated with old vehicles. Still learning. I always heard Holleys were great for power but sucked on staying tuned right. The truck came with a nasty 500cfm edelbrock. But I wanted the power so went with the holley. Its amazing how easy it was to work on these old trucks compared to everything made today. Its nice to see an interior held together with screws instead of clips for once.

[ont_guy_38]

Originally Posted by Lil Ape

Not sure I follow, what do you mean when you say that's a lot of my problem?

I mean the converter seems to be a little tight for that cam, putting too much load on the engine when put in gear.

[gramps77]

Do you have an electronic choke? Is it hooked up?
By "is it hooked up?" I mean, have you verified its getting 12 volts?
I had the exact same setup with carb and had no issues.
You need closer to 18 degrees initial and I had mine set up with the 18 degree button for a total of 36 all in by 3000.
That was what got the best power on the dyno.
Id DEFINITELY start with verifying choke though. I understand you say its open, but how did you verify?

[INSIDIOUS '86]

Originally Posted by Lil Ape

Yeah im still kinda new to carbs, timing and everything associated with old vehicles. Still learning. I always heard Holleys were great for power but sucked on staying tuned right. The truck came with a nasty 500cfm edelbrock. But I wanted the power so went with the holley. Its amazing how easy it was to work on these old trucks compared to everything made today. Its nice to see an interior held together with screws instead of clips for once.

That myth surrounds holleys cause the can tune so fine and so close to perfect that they run diff in summer vs winter.

Do you have a timing light? If not look on eBay for a craftsman dial back timing light. And get it. Pay up to $150 for it if you have too but they are hard to get and worth the money. Hold them like you would a newborn lol.

[INSIDIOUS '86]

Also get a vacuum gauge and tune the idle in gear with the truck against a wall or something until the highest vacuum is reached. Once you do lower the idle screw and then tune again until highest vacuum. Do this till it's as low as you can get it then raise rpm with idle by 75rpm or so. Just not a lot.

Tuning a big cam for street is tricky.

[Lil Ape]

Originally Posted by gramps77

Do you have an6 electronic choke? Is it hooked up?
By "is it hooked up?" I mean, have you verified its getting 12 volts?
I had the exact same setup with carb and had no issues.
You need closer to 18 degrees initial and I had mine set up with the 18 degree button for a total of 36 all in by 3000.
That was what got the best power on the dyno.
Id DEFINITELY start with verifying choke though. I understand you say its open, but how did you verify?

Yes it is electric. And well, I verified it was opening just by watching it with the air cleaner off. The choke flap was fully open when it hit 190 degrees. And slowly closed when truck was off. Dont want to sound stupid..but that is how the choke works right? That flap above the primaries open and closes..

Originally Posted by INSIDIOUS '86

That myth surrounds holleys cause the can tune so fine and so close to perfect that they run diff in summer vs winter.

Do you have a timing light? If not look on eBay for a craftsman dial back timing light. And get it. Pay up to $150 for it if you have too but they are hard to get and worth the money. Hold them like you would a newborn lol.

yes I have one of those cheap actron dial back lights you get at the auto store. I do also have a vacuum gauge thats only been used once. Its been freezing and raining here in tx these past couple days so I havnt been able to work on anything. I should set timing first before I mess with tuning the carb correct?

[Lil Ape]

Originally Posted by ont_guy_38

I mean the converter seems to be a little tight for that cam, putting too much load on the engine when put in gear.

Oh I see. Well my particular cam recommended a 3k stall. Which, according to the previous owner it has. But I have my doubts if if really is cause he also told me it was a 3.73 rear end, which I later discovered was only 2.56's..so im not all sure what is true and what isnt. Though he did ask me if I "wanted the old torque converter"..so it could have been truly switched..

[INSIDIOUS '86]

Yah set timing then tune the carb.

You do it that way because that effects the fuel burn with timing. You can vary fuel ratio just with timing.

As for your stall issue it seems tight to me as well. But the issue stems if it's to "grabby" in gear and loads the engine down. But once we have everything dialed in then we will be able to tell

As for you balancer moving we can fix that.
You will need a friend and a yellow grease pen and a 5/8ths socket and ratchet and a piston stop tool and a flywheel turning tool.
You need to turn the motor over to tdc and mark tdc on the balancer by rotating the engine clockwise till it stops on the piston stop mark it on the balancer. Then have your buddy rotate the engine the other direction from the flywheel side till the piston hits the piston stop. Mark this spot. Halfway between those two marks is true TDC. Erase the other two marks and you can now set your timing pretty accurate.

[piecesparts]

You have an issue that many experience when they step up on the cam specs and have to get the vehicle to idle while sitting in gear. First of all, you are not idling in the idle circuit of the carburetor. At 2000 RPM, you are definitely in the transition or cruise area of your throttle plate to venturi reference points. Second, you are coming on against your tranny and that is why the RPMs drop from the 2000 to 1000 RPMs. The stall numbers that you have on the torque converter are definitely lower than what you were told. If the stall were at 3000, then the truck should sit, in gear, at an idle of 700 to 900 RPMs and work right.

You can solve many issues with just the right torque converter and that would get you on the right path, if you update that item first. That way you know for sure what you have.

As for the carb being a 670 CFM. It should work well on this set up if all you do is drive the truck on the street. Especially on an engine that is in a heavy truck. Carb manufacturers look at what they are putting carburetion on and consider the velocity of the air flow to what the weight of the vehicle is. So a 3200 pound Camaro can effectively use a 700 CFM carb better than a 4000 pound truck could. It is what is needed to get the vehicle moving and how that air flow affects the venturis in the carb. Where the size of carb comes into effect is #1 if it is small, then it will run out of air flow at higher RPMs and limit your performance if you run the enigne at full throttle. #2 If the carb is too big, it will flood out the cylinders with more fuel at a lower air flow and since the velocity is down, cause plating out the fuel additives on your valves. This is not good either.

[LONGHAIR]

I am with piecesparts on this. You definitely have too much "load" against the engine when you put it in gear. If your converter really is a 3000 stall model.....something is very wrong with it.
Your other issues are just symptoms, they will go away when the underlying problem is fixed.
It's not a cheap or easy fix, but it needs to be done.

[gramps77]

Yes thats how the choke works but it sounds like the same issues Ive had with it NOT working.
As mentioned, I had to set timing to 18 initial with 36 total all in by 3000 with this cam.
Is the idle screw not allowing the idle to come down all the way? is it acutally hitting the stop when it should be in idle?

Have you checked it to verify that your throttle blades are not hanging up on maybe the carb gasket? Thats another easily overlooked place for this type of issue

[LONGHAIR]

That would keep the idle high and even "not adjustable", but would not account for the difference from being in gear to neutral.

[CMCustoms]

I was having similar problems with my 750 vs holley on my 350. The problem was the secondary throtle blades closed to far resulting in the primary side to be opened too far opening up too much of the idle transfer slot. You set the primary side and the adjust your idle speed with a small set screw on the secondary side. There is alot of info if you Google idle transfer slot that can describe it in more detail. After setting mine it now idles at 900 in neutral and about 800 in gear.

[LONGHAIR]

That can also be achieved by drilling a 3/32" hole in the primary throttle blades. This allows more air at idle without opening the throttle with the idle speed screw.