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'67 327 idle engine stall

 
Old 10-21-2012, 02:54 PM
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KSL '67 101234
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Default '67 327 idle engine stall

I recently purchased an off-the-frame restored 1967 convertible. The engine is the base 327 with a modified cam and Holley 4bbl. The 2-speed power glide was replaced with a 350 Turbo Hydramatic that is fitted with a shift kit. I don't know the cam specs, but the engine sounds so wonderful at idle around 650 rpm. Problem is the engine stalls when placed in gear, and sitting at a stop light with as many uninsured, cell-phone drivers in California makes for a nervous time when the light turns and the engine stalls. I can compensate for the stall by feathering the idle with the brake on, but again I'm compensating when these engines should be able to handle the various cams, carbs, and tranny setups.

The car was not driven for months while it was being sold, and I have no idea how often it was driven since restored. My guess is not much, maybe 100 to 150 miles a month since 2006 when the restoration was completed.

I've been given two different pieces of advice to follow to correct the engine-stall situation. Change the cam back to stock, or install a torque converter with a high torque stall. Before I do either, I am going to have my mechanic (me) go through the engine settings and ensure timing, dwell, fuel-mixture, plugs etc are not creating the problem. I have partially plugged jets (they whistle) from deposits probably associated with infrequent use. Berryman's should treat that issue after burning through a few tanks of gas.

I have read some of the other posts that deal with idle issues, so before making an unneeded cam or torque converter change I thought I'd check with the experts - small block, auto tranny Corvette owners.

Lastly, I thought since I have the original power glide that I'd have it rebuilt and see if a higher torque-stall converter can be installed with it, and replace the 350 tranny with the power glide. Any comments on that idea? Also, are the power glide and 350 trannys the same length, or was the drive shaft modified for the 350?

Last edited by KSL '67 101234; 09-29-2013 at 09:13 PM.
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Old 10-21-2012, 03:46 PM
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Before you start a wholesale changeout of items that may not need changing, start with the basics like you seem to be after: timing, dwell, plugs, condition of distributor cap, rotor, vacuum advance canister (does it hold vacuum and is it the correct profile for your cam), richness setting of your carb at idle in neutral vacuum plugged, fuel filters plus other items I'm sure some of the other guys will chime in on.

Once you have those set up at an idle speed you're happy with (stock 300hp is about 550-650), richness mixture leaned per spec, reconnect the vacuum can and adjust to the rpm you like at that config. Now put it in Drive (with a helper stepping on the brake) and adjust to the idle speed you like there (most likely will have to raise it again). My 300hp Powerglide shows about 850 rpm in neutral no A/C on. When I put it in gear, it drops to about 650 rpm and then adding the A/C it drops further to about 575-625 depending on whether I'm in stop or go traffic. It's a trial and error step by step process. You'll eventually arrive at the setting that works best for you. Wait till you get to the hot starting fun with what I presume is a Holley. A real hoot of a good time.
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Old 10-21-2012, 04:10 PM
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tha whistle is bad. put new blue gaskets in the carb.
i guess u will have it rebuilt by a pro. bad carb gaskets don't come back EVER.
Nothing is wrong with the trans.
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Old 10-21-2012, 05:41 PM
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performance cams work better with a higher stall converter and helps foot swapping from brake to the gas pedal...to.keep the idle up at red lites.....the 350 or powerglide will perform the same....you need a converter to alleviate the problem...I suspect the engine is fine and does not need more parts.......change the converter!
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Old 10-21-2012, 05:49 PM
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If you're idling at 650 rpm in neutral, that's probably too low to start with. Set it up to 750 rpm in neutral.

Next, check your vacuum advance timing and see if it is dropping off when you pull it in gear. If the timing falls off, that alone will drop your idle speed and can cause a stall.

I'd do this before thinking about changing converters or transmissions.
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Old 10-22-2012, 09:42 AM
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Matt Gruber
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easy test:
idle in N, warmed up.
turn in 1 idle mix screw. it should stall.
reset screw to smooth idle.
turn in #2 screw, it should stall.
if either screw has no effect, carb needs rebuild.
normal is 1-2 turns out.
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Old 10-24-2012, 12:18 AM
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Matt, as you noted the engine stalled when either idle mixture screw was turned in fully clockwise. I turned each mixture screw back out 1 and half turns from seated setting, while maintaining idle speed at 750-800. Engine still stalls when gear engaged.

Last edited by KSL '67 101234; 04-26-2013 at 01:51 AM.
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Old 10-24-2012, 12:25 AM
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Originally Posted by MikeM View Post
If you're idling at 650 rpm in neutral, that's probably too low to start with. Set it up to 750 rpm in neutral.

Next, check your vacuum advance timing and see if it is dropping off when you pull it in gear. If the timing falls off, that alone will drop your idle speed and can cause a stall.

I'd do this before thinking about changing converters or transmissions.
Thanks for your reply Mike. I raised idle speed to 750. How do I check the vacuum advance timing? What equipment/guage is needed?

Last edited by KSL '67 101234; 10-24-2012 at 12:28 AM.
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Old 10-24-2012, 09:55 AM
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so it still stalls?
TEST #2.
try 900 rpm N.
still stalls?
TEST 3
while idling at 900
C clamp vacuum advance hose shut. this locks timing.
put in drive. runs OK? or stalls?
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Old 10-24-2012, 11:05 AM
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Originally Posted by KSL '67 101234 View Post
Thanks for your reply Mike. I raised idle speed to 750. How do I check the vacuum advance timing? What equipment/guage is needed?
Check the timing with a light before you put the car in gear. Try to check it again in gear and before the engine stalls. If the timing drops off, that will tend to kill your engine idle speed just like putting the car in gear.

If the engine stalls and you can't get a reading, see what amount of advance you have with the engine idling in neutral. Disconnect the vacuum advance and plug and then move the initial advance up enough to what was previously noted. Then try it again. Check your timihg again to see if what you previously set is still present.
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Old 10-24-2012, 09:31 PM
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Originally Posted by MikeM View Post
Check the timing with a light before you put the car in gear. Try to check it again in gear and before the engine stalls. If the timing drops off, that will tend to kill your engine idle speed just like putting the car in gear.

If the engine stalls and you can't get a reading, see what amount of advance you have with the engine idling in neutral. Disconnect the vacuum advance and plug and then move the initial advance up enough to what was previously noted. Then try it again. Check your timihg again to see if what you previously set is still present.
X2. It's normal for the rpm to drop when put in gear. If you're already getting some centrifugal or vacuum advance at idle in neutral you could be losing some of that advance when the idle rpm drops. Less advance results in less torque and you no longer have enough to overcome the resistance of the converter.
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Old 10-26-2012, 12:52 AM
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Originally Posted by Vetterodder View Post
X2. It's normal for the rpm to drop when put in gear. If you're already getting some centrifugal or vacuum advance at idle in neutral you could be losing some of that advance when the idle rpm drops. Less advance results in less torque and you no longer have enough to overcome the resistance of the converter.
So X2, your comment leads me to believe that you are advocating a higher torque stall converter.
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Old 10-26-2012, 01:02 AM
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Originally Posted by Matt Gruber View Post
so it still stalls?
TEST #2.
try 900 rpm N.
still stalls?
TEST 3
while idling at 900
C clamp vacuum advance hose shut. this locks timing.
put in drive. runs OK? or stalls?
My workload prevents me from working on my car until this weekend. Also, I need to find my old tuning equipment from the mid-70's used on my '31 Ford with a 327 Vette engine and '66 SS396 Chevelle. Lot's of great advice to follow.

Last edited by KSL '67 101234; 11-04-2012 at 11:06 AM.
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Old 10-26-2012, 06:08 AM
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Originally Posted by KSL '67 101234 View Post
So X2, your comment leads me to believe that you are advocating a higher torque stall converter.
I believe he is agreeing to check the timing when you pull the car in gear to make sure timing is not dropping out and causing a loss of rpm in addition to the drag of the converter.
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Old 10-26-2012, 07:53 AM
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are you running ported vacum advance at idle. if so try unported and adjust idle at 700 750 and road test .
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Old 10-30-2012, 12:59 AM
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Originally Posted by steampunk c1 View Post
are you running ported vacuum advance at idle. if so try unported and adjust idle at 700 750 and road test .
What do you mean by "running ported vacuum advance at idle?"
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Old 10-30-2012, 01:10 AM
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Originally Posted by MikeM View Post
I believe he is agreeing to check the timing when you pull the car in gear to make sure timing is not dropping out and causing a loss of rpm in addition to the drag of the converter.
Mike, thanks for clarifying. My buddy loaned me his Sun Diagnostic tune-up kit, so I plan to perform the various procedures recommended in these posts. I'll keep you posted.

BTW, I described the stall problem to a long-time hot rodder who also builds custom hot rods. Without hesitating he recommended a higher rated torque stall converter. I like to study problems, so before jumping to a fix I figure I have a lot of diagnostic work to perform.
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Old 10-30-2012, 04:25 AM
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Originally Posted by KSL '67 101234 View Post
Mike, thanks for clarifying. My buddy loaned me his Sun Diagnostic tune-up kit, so I plan to perform the various procedures recommended in these posts. I'll keep you posted.

BTW, I described the stall problem to a long-time hot rodder who also builds custom hot rods. Without hesitating he recommended a higher rated torque stall converter. I like to study problems, so before jumping to a fix I figure I have a lot of diagnostic work to perform.
The high stall converter could be addressing a symptom and not the problem but it is an alternative if nothing else works.
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Old 10-30-2012, 07:09 AM
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The whistle sound you hear could be a vaccume leak. Check for leaks , be sure to check between the carb body and the throttle plate . Holley carb body,s warp due to over tight throttle body screws .
If it is warped it needs to be surfaced .

Bill
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Old 11-04-2012, 10:52 AM
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Originally Posted by Rokndad View Post
Before you start a wholesale changeout of items that may not need changing, start with the basics like you seem to be after: timing, dwell, plugs, condition of distributor cap, rotor, vacuum advance canister (does it hold vacuum and is it the correct profile for your cam), richness setting of your carb at idle in neutral vacuum plugged, fuel filters plus other items I'm sure some of the other guys will chime in on.

Once you have those set up at an idle speed you're happy with (stock 300hp is about 550-650), richness mixture leaned per spec, reconnect the vacuum can and adjust to the rpm you like at that config. Now put it in Drive (with a helper stepping on the brake) and adjust to the idle speed you like there (most likely will have to raise it again). My 300hp Powerglide shows about 850 rpm in neutral no A/C on. When I put it in gear, it drops to about 650 rpm and then adding the A/C it drops further to about 575-625 depending on whether I'm in stop or go traffic. It's a trial and error step by step process. You'll eventually arrive at the setting that works best for you. Wait till you get to the hot starting fun with what I presume is a Holley. A real hoot of a good time.
I found the reason for the engine stalling at idle. During the removal and replacing of the spark plugs I found 3 plugs that were less than finger tight, two that were finger tight, and the remaining that took a socket wrench to remove. I also installed a new rotor. I started it up, set the idle at 850, adjusted the air to fuel mixture, reset the idle to 850, checked the timing and dwell - they were at 4 and 28, respectively, so I made no adjustements, closed the hood and placed it in gear. The engine RPM dropped to 650-575, but gave no indication that it wanted to stall. The engine purred like only a 327 can - IN GEAR! So for less than $30 the problem was fixed. The Berryman's Chemtool fuel treatment cleared the jets so the carb no longer whistles. That was another $5. Total cost to fix $35!

Last edited by KSL '67 101234; 09-29-2013 at 09:14 PM.
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