idling problems, Running problems, PROBLEMS

J

jim reese

Active member
I have finally gotten the engine together and been through several folks now and still the car will not idle normally. It is a 250 with the aluminum head, intake, a CSC-264-10-DHS cam, roller rockers, dual outlet headers, bored 30 over, 390 Holley, Electronic dist.

When I start up it idles in park(automatic trans), if I let it warm to 190 degrees it will go into drive and then I need to instantly hit the throttle, then it will kind of idle. Then next time I come to a stop it usually dies and will nearly always die at an intersection. I have taken to driving like it is manual shifting into N

The idle is set around 800-900(guessing no tach) in drive. Does anyone have any ideas on how it should run other than not? It has been checked extensively for vac leaks, none. Valves have been adjusted several times, fuel, floats have been adjusted several times. Any ideas?

Also does anyone know where I can get the cam card as I did not seem to get one when the parts came, or how to get it to run "normally?"

I have about had it and am having thoughts of selling the thing. Any help would be very much appreciated.

Jim Reese
 
What kind of vacuum readings are you getting in park and in drive?

What is your initial timing and total timing with the vacuum can connected in drive and park? You may want to hook up to manifold vacuum if you are not already connected to a manifold port in order to get more advance and a better idle. Make sure the the vacuum advance is working. If it is not contributing, you may be running at higher idle with the plates open more than they need to be and the result is an inconsistent idle. Vacuum at advance at idle will increase the engine vacuum, allowing you to get a more stable idle with less throttle plate openning.

You may need to check what kind of vac advance you are getting from your distributor set up. By that I mean get a vacuum pump, gauge and timing light. Plug the vac port on the carb or manifold. Hook up the distributor to the vacuum hand pump. At different levels of vacuum measure how much advance you are getting. With a modified engine that has lower engine vac, your vacuum advance cannister may have too high of a setting. If it is adjustable, you would want to lower the point when it starts comming in. You can buy different vac cans that start and finish the advance at lower vac levels.

If all else checks out and part of your problem is low vaccum, it may be possible to advance the cam to help with the automatic transmission. Another option would be Rhoads lifters that help the low end torque. But I don't think your cam is wild enough to merit them.
Doug
 
Most importantly, dont give up! :) Been there, its frustrating as all get out when you throw a bunch of money at it and it wont run right. You'll find it and fix it.

Ron
 
Did you try adjusting your idle mixture screws? What jets and squirtor are you running? Whats your base timing set at?

Spend the $40.00 and get a tach :wink: Base idle should be around 800-1000 rpms. Dont guess at it.

What is your power valve size and what does your vacuum look like at idle and in park?

Later,

Doug
 
You could work your way up the food chain slowly. First make sure the choke is working properly and all the slides and adjusters are running free and cleanly. Then get a vacuum gauge. It is the least expensive and most basic of the gauges. Remove the vacuum line to the distributor and connect the VG to the manifold vacuum source.

1) Check your vacuum at idle (in Park). Turn/adjust the distributor until you get max vacuum. Stop there. (Stock vacuum is higher than 18 lbs. Aftermarket cam will give a different number. That is why I said 'max' vacuum.)

2) Now adjust the idle fuel mix for maximum vacuum. That means: turn the idle fuel mix screw in until it begins to stumble, then back it out slowly until you achieve the max vacuum. Then back it off just a little more.

These will give you approximate 'good timing'.

3) Block the wheels and put it in Drive. Adjust the idle and fuel mix to max vacuum. This will get you very close to proper timing. Next you can get/borrow a dwell tach and adjust the timing by numbers to dial it in right. Stock idle is 750 to 800 RPM in drive.

If it still dies when you put it into gear, I think there is a problem in the transition from idle to operational circuits. That or there is another problem that the others have mentioned, including the cam.
 
Questions
What is your vacuum at idle in gear and in park?
What distributor are you running?
What is your timing set at?
 
gtm1086

vac at idle is 14-14.5
vac in drive 5.5-6
timing is 10 adv
Distrib is the DUI

At the moment I am not sure what the rpm is at idle.

This week I plan to take the simple step of locating and replacing all the vac hoses, guessing that if one is leaking or improperly fitting that is a cheap easy fix.

Thanks for the help and suggestions.

Jim
 
Hello Jim

Vacuum in park looks very good. In drive does not. Don't quote me on this as I run a five speed but doesn't your automatic have a vacuum line running to it? Could this be the source of the loss of vacuum.

I would also try bringing the timing up to around 12 to 14 degrees for just general run quality. I pretty much keep advancing until the motor starts to ping under load then back it off to where it does not.

Idle rpm in park should be around 800 to 900 rpm which should give you around 700 in gear
 
Ditto.

Plus, the ring on the harmonic balancer may have slipped; a not uncommon problem with these engines. You would to well to find the true TDC, mark the balancer with a white pen and set timing from there.
 
gtm1086":z0x5od6q said:
Hello Jim

Vacuum in park looks very good. In drive does not. Don't quote me on this as I run a five speed but doesn't your automatic have a vacuum line running to it? Could this be the source of the loss of vacuum.

I would also try bringing the timing up to around 12 to 14 degrees for just general run quality. I pretty much keep advancing until the motor starts to ping under load then back it off to where it does not.

Idle rpm in park should be around 800 to 900 rpm which should give you around 700 in gear
Click to expand...

This is exactly what I'd suggest as well, however I idle at about 450 just as the book says, 700-800 is too high.
 
update on what the mechanic told me this afternoon.

I relayed the information for you all.

He said the rpm in park is 1100rpm
He said the rpm in drive is 550
They ran some check on the cam indexing and said it falls within spec when I asked him about the 4 degree adv?
He said they checked for vacuum leaks and found none.

The jets in carb are whatever it shipped with and when I asked about setting the timing at 12 to 14 he said they tried that and it did not run any better.

He is on a mission to speak with Clay Smith cams to find information on the cam.

Seems like a large drop for park to drive considering what you all have said.

Ideas, reasons..?

Thanks Jim
 
They might want to check to see if the vacuum advance is working properly and also check the balancer as Ludwig mentioned to see if the TDC mark corresponds to actual TDC.
Doug
 
Jets on the Holley 8007/390 are 51 Primary. Secondary a 134-34 Plate. Power valve 65. Squirter .025. Plain Vac Sec spring and just guessing, a White pump cam.

With your vac readings in drive (5.5-6) it would appear that the power valve (6.5) may be opening but I'm not sure if that would cause the condition you are describing.
 
Holley power valves are easy enough to get. There's also a "
block-Off" plug that can replace toe PV, and you'd know if that's part of the problem (besides low vacuum). Where's your PCV Valve connected? Have you tried plugging it to see what happens? Guess I should reread the whole thread, but I gotta go, and I'll forget later. :oops:
 
Jim, with a 110 L/C cam, your idle in park should be at least 1000-1100.
When placed into drive 750 rpm's will help your condition.
To fix part of the problem, replace your stock torque converter to a converter at least 2300-2600 stall speed.
This will allow the engine to idle at 750 rpm in drive & thats where it should be with a 110 L/C camshaft.
You might want to run the heater hose to the intake manifold below the carb & that will also help your curb idle. Bill
 
Not to throw out too many targets, but if you're relatively sure the cam is dialed in correctly, and there is no vacuum leak, have you considered the possibility of a bad DUI module

-Robert
 
I still think something is wrong with the vacuum. idle in park looks good in gear is way low. Also it seems that a 600 rpm drop when put into gear is high.

If everyone is absolutely sure there is no vacuum leak. Can you try another carb???
 
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