Idle in "drive" problems...

[Rob73-87]

Hi everybody,

I have problems with my freshly rebuild 305 ci in my truck. When the engine`s idling and I shift to "drive" or "reverse" the engine nearly dies (normally it does )

I checked the engine timing - it`s 9° BTDC - so just fine for an engine with a mild cam and so on.

I didn`t discover any vaccum leaks ....?

I really hope some of you have any suggestions

[jd74c-10]

what rpm is your idle set at. you might need to set it a little higher.

[project_77]

also,

what kind of carb are you running? it could be that the idle screws are to far out and you're not using enough of the idle screw itself.

what is your total timing at?

[Rob73-87]

Originally Posted by jd74c-10

what rpm is your idle set at. you might need to set it a little higher.

to be honest I couldn`t find the original GM specs for that `79 305cui motor - I thought "must be between 700 and 800 rpm when setting timing..." - is that right ?
does anybody have that smog sticker underneath the hood for a 305 motor ?? Maybe that would help....

Originally Posted by project_77

also,

what kind of carb are you running? it could be that the idle screws are to far out and you're not using enough of the idle screw itself.

what is your total timing at?

I have a brand new HOLLEY Street Avenger w/o choke (!) - what do you mean with "not using enough of the idle screw itself" - right know I´m confused I think.....

[LONGHAIR]

How much of a "mild cam" are you running?
It sounds to me like the converter is too tight. This puts more "load" on the engine when it is idling in gear, so it drags the idle speed down.
If you simply raise the idle speed, it will be too high in park. This causes banging and jerking when you put it in gear...

[Rob73-87]

well, the cam is the CompCams XE 262 (new) and the converter is a B&m Holeshot 2000. Comp. ratio is 9,8 : 1 with flattop pistons - distributor is bone stock HEI with stock coil - Edelbrock performer manifold - Dynomax headers ....

[LONGHAIR]

Ok......Where is the vacuum advance connected?
When you say "bone stock HEI" do you mean the factory original to that truck?

[Rob73-87]

Originally Posted by LONGHAIR

Ok......Where is the vacuum advance connected?
When you say "bone stock HEI" do you mean the factory original to that truck?

The vacuum advance is connected to the "timed port" of the metering block of the Street avenger carb.
The distributor came off of another car or truck - I have about 8 to 10 Distributors lying around... Are there any big differences ? I didn`t knew ...

[piecesparts]

Are you setting your timing with the tranny in gear? The 600 to 700 RPM recommended is in "DRIVE" not in "NEUTRAL or PARK". The timing could be advanced to 12 degrees, without issue and you may find better fuel economy with that change. If you are running the carb without the idle compensator that many carbs have on them to allow for a faster idle and then drops the RPMs tp a lower setting for shutting off the motor, then you will have to adjust for your tranny's response to the change in the engine's RPM with the idle speed screw.

The cam could be putting you up against your convertor's stall speed and causing some of your issues. Adjusting the idle speed up will take you to a condition of transitioning from the idle circuit to the power circuit in the carb, this is a mess that can be taken care of by changing the converter to a high stall. You have built the engine to a point that the factory settings are out of the norm, so you have to adjust to what you have in your truck.

You did not say what you have for a carburetor.

Let's try something to set your carb up for success. Do you have a vacuum gauge of any kind---or can get one. If you can get a vacuum gauge, this will allow you to set your carburetor more efficiently and make your idle air/fuel mixture work best.

Start by setting the idle air screws at 1 1/2 to 2 turns out.

Connect the vacuum gauge to the intake manifold (So that it is reading a good vacuum signal)--preferrably not to the carb. Take the first idle air screw and turn it inward to the stop (watching the vacuum signal for change) and then back it outward slowly until you see your vacuum signal increase to it's maximum number acheived. Now do the other air screw, the same way. Once you have adjusted the screws to a max vacuum---do the screws ONE MORE time to get the most effective setting you can get. Once completed --- turn the screws inward 1/8 of a turn and your are adjusted to the best air fuel setting you can acheive with your carb.

Check your timing and adjust to a point that the engine is getting the best RPMs but not detonating (pinging on acceleration) or running on (dieseling) when shut off. I set my engines with a tming light that has an "Advance setting feature", and that allows me to adjust timing to a "Total" setting. This is not necessary, but adjusting to a setting higher than the factory will give better acceleration and response to the throttle.

I run a 383 stroker motor and have a 2400 stall convertor in my tranny, since my Comp Cam is a little agressive. I have set my idle at approximately 900 RPM in neutral and the idle in gear is around 700 RPM. The truck is very driveable and works quite well with these settings.

[Rob73-87]

Originally Posted by piecesparts

Are you setting your timing with the tranny in gear? The 600 to 700 RPM recommended is in "DRIVE" not in "NEUTRAL or PARK". The timing could be advanced to 12 degrees, without issue and you may find better fuel economy with that change. If you are running the carb without the idle compensator that many carbs have on them to allow for a faster idle and then drops the RPMs tp a lower setting for shutting off the motor, then you will have to adjust for your tranny's response to the change in the engine's RPM with the idle speed screw.

The cam could be putting you up against your convertor's stall speed and causing some of your issues. Adjusting the idle speed up will take you to a condition of transitioning from the idle circuit to the power circuit in the carb, this is a mess that can be taken care of by changing the converter to a high stall. You have built the engine to a point that the factory settings are out of the norm, so you have to adjust to what you have in your truck.

You did not say what you have for a carburetor.

Let's try something to set your carb up for success. Do you have a vacuum gauge of any kind---or can get one. If you can get a vacuum gauge, this will allow you to set your carburetor more efficiently and make your idle air/fuel mixture work best.

Start by setting the idle air screws at 1 1/2 to 2 turns out.

Connect the vacuum gauge to the intake manifold (So that it is reading a good vacuum signal)--preferrably not to the carb. Take the first idle air screw and turn it inward to the stop (watching the vacuum signal for change) and then back it outward slowly until you see your vacuum signal increase to it's maximum number acheived. Now do the other air screw, the same way. Once you have adjusted the screws to a max vacuum---do the screws ONE MORE time to get the most effective setting you can get. Once completed --- turn the screws inward 1/8 of a turn and your are adjusted to the best air fuel setting you can acheive with your carb.

Check your timing and adjust to a point that the engine is getting the best RPMs but not detonating (pinging on acceleration) or running on (dieseling) when shut off. I set my engines with a tming light that has an "Advance setting feature", and that allows me to adjust timing to a "Total" setting. This is not necessary, but adjusting to a setting higher than the factory will give better acceleration and response to the throttle.

I run a 383 stroker motor and have a 2400 stall convertor in my tranny, since my Comp Cam is a little agressive. I have set my idle at approximately 900 RPM in neutral and the idle in gear is around 700 RPM. The truck is very driveable and works quite well with these settings.

wow - that was lots of information !!

Frank, thank you for your time - I appreciate that very much !!

Well, - you wrote that I should set the timing in "drive" !? I think I heard that before - I`m not sure - okay I will try this (with a buddy stepping on the brakes )!

ANd I will buy a Holley Vaccum gauge - it`s already ordered! Ah, you asked what kind of carb I`m running....it`s a 670cfm Holley Street Avenger (80670 Holley part No).

I`m planning on building a motor similar like yours (383) for my shortbed truck , - but I need to fix my londbed first...

[piecesparts]

I did not mean to say: to set the timing in DRIVE and I apologize for that---my fingers got ahead of my mind. Just set the idle RPMs in drive so that you get the right setting of around 600 to 700 RPM. Set your timing in PARK, in the shop with the idea of getting the most out of the engine.

[LONGHAIR]

Originally Posted by Rob73-87

The vacuum advance is connected to the "timed port" of the metering block of the Street avenger carb.
The distributor came off of another car or truck - I have about 8 to 10 Distributors lying around... Are there any big differences ? I didn`t knew ...

Yes, there are differences in the timing curves, it depends upon what year and vehicle it came from. They all "look" the same....and the deceiving thing is that in all reality you can "just drop any one in" and it will run....but not "right". But since many people think that they are all the same, they don't associate the problems with the distributor itself. They may get around to thinking that it is the "timing"...but that just makes then get out the timing light and set the "Initial" timing, which is not the whole story.

The next issue is "ported vacuum".
I would assume that you have it there because the carburetor's directions said to do that.....
I am really not sure why the carburetor people (not just Holley) think that they can tell you were to put the vacuum line? It should be connected in the place where the distributor is set-up for it to be....and it does matter.

You really need to deal with the advance curve of the distributor first. IMHO, it should be set-up so that you can run with the vacuum advance connected to the "full vacuum" fitting....but as piecesparts said, actual vacuum plays a part in this too.

I would think that your "Holeshot" converter would be loose enough to eliminate idling issues.