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-   -   pontiac 350 idles at 1000 rpm in park 600rpm in drive (http://www.hotrodders.com/forum/pontiac-350-idles-1000-rpm-park-600rpm-drive-221875.html)

starin 07-18-2012 09:57 PM

pontiac 350 idles at 1000 rpm in park 600rpm in drive
 
Hey guys so thanks everyone helping me with my firing order issue / timing gear issue.

now my next problem is that when i have the car in park it idles at 1000 rpm but when i put it in drive it idles at 600 rpm. i sprayed some carb cleaner around the intake and carb base and no change in rpm. I'm pretty sure i have no leaks. the motor is a pontiac 350 out of a 1972 lemans. it has the original points distributor but i put a petronix in it. however im new to the whole world of wrenching and did not change the springs or the plate or the vaccuum canister and these were all original.

when i timed the car i disconnected the vac advance and plugged it as well as plugged the manifold source. i timed it at 12 degrees. when i hooked the vacumm advance line back to the manifold vac i was under the understanding the timing was supposed to go up a little. when i put the timing light to it. at idle it was still at 12 degrees.

do you guys think the distributor is the problem? i bought an A1 CARDONE reman distributor today and am going to swap my pertronix into that. but if its not the problem id rather save the money.

what do you guys think?

Thanks in advance.

dub 07-18-2012 10:46 PM

I think I got it---
When the vacuum advance is hooked up, it shouldn't change at idle. Once the throttle is engaged, and your vacuum rises, that when it is supposed to advance timing.
As for the idle issue, the engine is supposed to run at a slightly higher RPM while in park. When it is in gear, it is supposed to drop a little but. Now Im not sure what you pontiac motor is supposed to idle at, but I have a stroker 350 that idles at 750 while in park, then drops to about 5-550. It dosent sound like anything is wrong.

Mike

cobalt327 07-19-2012 12:00 AM

Quote:

Originally Posted by starin (Post 1575054)
Hey guys so thanks everyone helping me with my firing order issue / timing gear issue.

now my next problem is that when i have the car in park it idles at 1000 rpm but when i put it in drive it idles at 600 rpm. i sprayed some carb cleaner around the intake and carb base and no change in rpm. I'm pretty sure i have no leaks. the motor is a pontiac 350 out of a 1972 lemans. it has the original points distributor but i put a petronix in it. however im new to the whole world of wrenching and did not change the springs or the plate or the vaccuum canister and these were all original.

when i timed the car i disconnected the vac advance and plugged it as well as plugged the manifold source. i timed it at 12 degrees. when i hooked the vacumm advance line back to the manifold vac i was under the understanding the timing was supposed to go up a little. when i put the timing light to it. at idle it was still at 12 degrees.

do you guys think the distributor is the problem? i bought an A1 CARDONE reman distributor today and am going to swap my pertronix into that. but if its not the problem id rather save the money.

what do you guys think?

Thanks in advance.

If the timing isn't changing at all when you hook the vacuum advance back up, either you are using "ported" vacuum, the vacuum advance is sticking, or the diaphragm is leaking and the vacuum advance can is no good.

You can use a different vacuum port that has vacuum at idle (called "manifold" vacuum) to see if the timing and idle speed picks up. If it doesn't the can is bad or is binding.

Setting up a performance advance curve is very important- as I told you already and if you go to the link I gave you in the last thread you can bone up on it. The article is on the HEI distributor but the timing info still applies. Just remember the Pontiac distributor turns CCW, so the weights and advance cam will be "upside down" from a picture of a Chevy distributor.

You want to be sure the mechanical advance is not coming in when the engine is idling in Park. If it is, the idle speed will drop when the engine slows when you put it in gear- and that slows the idle speed even more.

If there's room for it I would be installing a HEI distributor yesterday! The resistor wire used w/the GM points ignition needs top be replaced, otherwise it's a plug and play deal.

starin 07-19-2012 12:19 AM

i plugged the vacuum advance straight to a manifold nipple and it stayed at 12 degrees just like when i disconnected and plugged the vac advance hose. i dont think and hei will fit, the points is already almost at the firewall. i'll try the distributor tomorrow after work and let you guys know how it goes.

Mr. P-Body 07-19-2012 07:09 AM

Many Pontiacs come from the factory using "ported" vacuum. Not unusual.

A new vacuum advance unit is cheap and easy to install. Standard Ignition part no. VC-24A.

HEI should fit fine concerning the body. If you have an older afrermarket intake, THAT may interfere. A factory Q-Jet intake will be fine with HEI.

Jim

T-bucket23 07-19-2012 08:15 AM

To be honest I would say it is normal for the rpm to drop at least 200 rpm in drive and I have seen more. I would not be concerned. Also dont put in that Cardone. Bring it back, they have the worst parts that you can buy.
Your idle does not change with the vacuum either because it is connected to a ported source or the diaphragm is NG. Pull the hose off the distributor end and check for vacuum, you should be able to feel it with you finger. If you cant it is probably connected to a ported vacuum source. This is not always right or wrong, it depends on the application.

starin 07-19-2012 01:16 PM

It idles like it has a vac leak but no leaks so well see what happens

cobalt327 07-19-2012 04:58 PM

Quote:

Originally Posted by starin (Post 1575218)
It idles like it has a vac leak but no leaks so well see what happens

One at a time, remove all the vacuum hoses and block the port off. If the idle quality improves when a particular vacuum hose is removed and the port is plugged, you will know you just found the faulty accessory or hose. This included the power brake booster and any emissions equipment that may still be on it.

I don't remember you saying what you're using for a carb or intake, so this is a shot in the dark: If you have an EGR valve (mostly '73-up but who knows what year the engine you have is or what changes might have been made, etc.), it could be sticking open or leaking. Just disconnecting the vacuum line to the EGR doesn't mean it can't leak or be stuck open, either.

If the intake manifold was recently installed, it is not at all unusual for the intake gaskets leak vacuum. If this happens on the underside, it can be hard to tell by using propane or spraying WD-40, etc. because of how the ports are near the valley cover.

The carb can be internally losing vacuum because of wrong or damaged gaskets or the power circuit (power valve on a Holley, power piston on a Q-jet or step up springs on a Carter/Edelbrock) can be stuck in the open position which can cause a rich idle condition that imitates low vacuum.

What is the vacuum reading at idle? Have you pulled the plugs to see if they're sooty from a too-rich air/fuel ratio?

starin 07-19-2012 10:42 PM

well i put the cardone distribitor in there, i pretty much gutted it since i have the pertronix kit. im amazed how much better the car runs, the timing actaully advances now. so i timed the car at 10 degrees with the vac plugged. once i hooked the vac back up it advance to about 18 degrees with all lines installed. does that sound right? the car still idles at 1000 rpm in park and drops to approx 600 in drive.

the car has a edelbrock intake, edelbrock 600 cfm carb, no egr. ill the vac line thing but i really only have 2 vac lines, one for my transmission modualtor and one for the distributor

starin 07-19-2012 11:42 PM

so i found that my pcv valve grommet that leads to my carb is rock hard and probably leaking vacuum, it was getting late so tomorrow im going to buy a grommet and valve, hopefully this fixes my low idle problem.

cobalt327 07-20-2012 05:36 AM

Quote:

Originally Posted by starin (Post 1575364)
so i found that my pcv valve grommet that leads to my carb is rock hard and probably leaking vacuum, it was getting late so tomorrow im going to buy a grommet and valve, hopefully this fixes my low idle problem.

Might as well get a new PCV valve if its old. Be sure the PCV hose is supple and not hard, too.

Most stock vacuum advance cans give more than 8 degrees advance at idle if hooked to a manifold vacuum source. Are you using ported of manifold vacuum for the vacuum advance? If you are unsure, try a different vacuum port for the vacuum advance and see if you get more advance.

If it's hooked to a ported vacuum source you might see some advance even though there's not supposed to be vacuum at idle from a ported vacuum source. You may see vacuum at a ported vacuum source if the throttle blades are opened more than usual for some reason. This is most often seen w/a performance cam that has low vacuum at idle, but can be seen w/a stock cam if there's a vacuum leak.

What type of cam do you have? Have you checked the vacuum at idle?

cobalt327 07-20-2012 06:16 AM

Did you check on:
Quote:

You want to be sure the mechanical advance is not coming in when the engine is idling in Park. If it is, the idle speed will drop when the engine slows when you put it in gear- and that slows the idle speed even more.
Check by disconnecting and plugging the vacuum advance, then see if the timing drops when you put it in gear. Use a helper, or set the parking brake and chock all the wheels securely if you try to do this by yourself.

You might need to increase the curb idle speed if the idle drops when you disconnect the vacuum advance. The idea is to simulate the same rpm the engine is at when in Park, then recheck when in Drive, without the vacuum advance being in the picture.


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