I have just installed a 650 dp on my 350 which has a Comp Cams extreme energy 286, and a 2600 stall conv. I had a 750 dp which was too big for my application, resulting in less throttle reaponse,little ajdustability,and ran very rich. My engine runs great now, except for my idle. In park I have it set to about 1400 rpms, but when I put it in drive it drops to about 700 and wants to stall. It needs to idle at about 1000 rpms for the engine to stay on at stop signs. I keep it on by gently tapping the throttle when I come to a stop. I can increase my idle to 1000 rpm, but when I put it in park,the idle is bound to go up to 1800 or more. What can I do to fix this situation. All help is greatly appreciated!
Daniel

------------------
1967 El Camino, 350/.40 over,ported & polished camel back heads,750 double pumper, Comp cams 284 with .507/.510 lift,
Edelbrock RPM Air Gap manifold,Hooker headers,posi w/ 3.73 gears,induction hood, TH400 tranny with Quick silver shift kit, and ET Drags for traction, (1/4 mile = 13.112 @ 103.612 mph)

I have the same cam with a holley 650dp on a 350 as well. Its a pretty large cam, and mine won't idle below 1000 rpm either. There isn't much you can do about it, just the nature of things. I have a 4 speed, so i don't have to worry about the idle speed difference in drive though. Maybe a looser convertor would help? Do you have the stock convertor? Comp cams definately reccomends a higher stall than stock.


chris

No, Chris I have an after market 2600 stall converter. It worked well when I had the 750 on it, I don't understand why it won't work with the 650. Could it be the change in vacuum? Is there some kind of device that will increase my idle after I shift to drive and decrease it after I shift back to park?
Daniel

Daniel,

Are you saying that you didn't have idle problems when the 750 was installed? What did it idle at in park and drive with the 750? Have you had a chance to measure idle vacuum with the 650?

That is a fairly large cam but I beleive your should be able to get it to idle in park at no more than 1k and not have it die when shifting into drive - especially with a 2600 converter.

Set the idle at 800-1000 in park then get a vacuum reading on it (ensure you disconnect and cap all other vacuum ports; trans, power brakes, etc). I'm guessing it ought to be around 12-14. Call Comp Cams to verify. Also check your plugs to see if it's running rich/lean.

Let us know what you find out....

Dan

------------------
Awww, fer cyrin out loud, there's that IMPALA guy again.

http://photos.yahoo.com/bc/ss3964spd?d&.flabel=fld1&.src=ph

When I had the 750 I would idle at 1300 in park and 1000 in drive. I have not taken any vacuum readings.
Daniel

Whoops, I missed the fact that you had a non-stock convertor. Now I have no idea why you have troubles with just the 650. I would be interested to know what you find out, because even though I have a 4 speed, my plant will only idle as low as 1000 rpm. And if I let it idle for too long in traffic I need to give it a little goose to keep it from klonking out. I thought it was just the motor loading up from too large a cam, but from the sounds of it, if you had no trouble with the 750, maybe it has something to do with the carb setup. I'd like to know what you figure out, because I maybe I need to setup my carb again. Sorry I couldn't help, good luck!

chris

The idle at 1300 rpm in park is too high even if it idled in drive with the 750 carb. What is your timing like, vacuum disconnected and plugged at idle?

I think you need to start all over with proper timing, adjust the floats, adjust the idle mixture the excel pump etc.

Using manifold vacuum will help with pull against the tq converter also.

------------------
...Dennis
Topless '69 (http://home1.gte.net/ddunio/topless69)

Try to get your initial timing up if it isnt high enough for your cam. With that big a cam you need allot of initial for throttle resp and a good idle. Try to get it up to 16 and see if that helps. CHRIS

Try to get vacuum readings. Also see how far open the throttle blades are at idle. Many times with large cams we turn the idle screw so much that it begins to uncover the transition slots in the venturis. If this happens the car runs very rich at idle and ruins any hope of idle quality. Try getting the car to idle as low as possible in drive without stalling. Then pull the carb off and look at the throttle blades. You can actually see the slots (small vertical slots) in the venturis, or if nothing else the blades will appear to be open. I had a similar problem this summer when I swapped in a 282 cam into my 454. I had idle problems and I could only squeeze out about 9" of vacuum at most. I ended up drilling small holes in the primary throttle blades to allow more air (raising idle speed) so I could back off the screw thereby covering up the transition slots. Car now idles at 750 in drive. It's worth a try...

------------------
1969 Caprice (It's not an Impala darnit!)
427/TH-400 (Soon to be M-20)
12-bolt 4.10 Posi
13.45 @ 105

1966 Caprice
396/325 TH-400
15.38 @ 97.4

Andy and Nick's Highway to Hell (http://www.public.iastate.edu/~amcarthu)

[This message has been edited by LTLCRZY427 (edited 02-02-2001).]

My experience was similar to LTLCRZY427. Rather than drill a hole, though, I pulled my Holley off the car, and there is a screw on the bottom you can use to open the secondary throttle blades a little bit. This allows you to back off the primary idle and cover the transition slots back up. I also believe that vacuum jumps around somewhat with radical cams, and this may affect your distributor advance at idle. Your idle speed then fluctuates all over the place. It's infuriating.

I think you are just going to have to keep playing with it to get it right. Make sure the power valves arent opening at an idle too. My only has inches of v at an idle. Took me quite a while to get it right. With allot of help from you guys here too. Now it idles at 800 in gear and 950 in park. I have a big comp cams 11-605-5 solid in it too. So it can be done. I also drilled the throttle plates, and opened up the secondaries to get it where it is now. Good luck....CHRIS

I have a 350 with comp cams 268, victor intake, 3310 carb, and vortec heads..
I am running a 2004r with stock converter (about 2500 stall) and i have 15 inches of vacuum and can idle at 850 in drive all day long..
I think you have a vacuum leak or need more initial advance..

------------------
Jester
http://www.chevelles.com/showroom/jester1.jpg

65 Chevelle 350, 2004r, 3.73 posi

Drive it like you stole it.

Thanks for your replies this weekend! Your info gives me some good ideas. I will try to get it right this week and hit the track on friday. Hoping to hit the 12's! http://www.chevelles.com/forum/smile.gif
Daniel

Well the idling problem is finally solved. It turned out to be a bad timing chain and harmonic balancer. It is now idling at 700-800 rpm with no problem. It seems to have picked up a bit more power too! Thanks for your imput. I will try to hit the 12's this Friday if the weather holds out.
Daniel