200 c.i. with auto trans rough idle problem

:D :unsure: You could try your local parts house or Holley through the internet or their 800 number.If you talk to a tech at the 800 number,tell them your cam specs and the vacuum you are showing.They should be able to recommend the proper PV for your application.Oh yeah,be sure to let them know what carb you are using.
Good luck.Have fun.Be safe.
Leo
 
Since my last reply I've replaced the main jet in the carb with a new one from Mike's Carb Shop.
The new jet was .068,assuming it is stock for a holley 1940...and drilled it out to .073. Reset the float level and
reinstalled the carb. Waiting to see how my gas mileage will suffer.

The idle seemed to smooth out but the car had a definite stumble on acceleration.
Readjusted the accelerator pump linkage and now it runs a lot smoother from 0 to
45-50 mph.I believe all along that this was the source of my original idle problem.

Also installed a Petronix power relay to work with the Petronix ignition module and coil.
Can see an improvement in idle quality but don't know if the relay really helped.
Timing is set at approx. 14 btdc...slightly above the timing tab. Dist.vacuum is ported from the carb.
Idle speed is 850-900 rpm in park,and 600-650 rpm in drive. Many repeated attempts to go lower with
the idle have been useless. The car likes these settings and they will stay there.

Looking to see if my harmonic balancer is accurate,as I think it may have moved but I'm not sure.
Also looking to recurve the distributor or replace it if needed. Thinking of going to manifold vacuum
but not before a distributor recurve. The engine is running fine now on ported vacuum but I'm curious
about if it could run even better.

A lot of work has been done on this Holley 1940 since my first post and I've learned a lot from all
of you guys on this site,and I thank you.I'm hoping my progress posts help someone else who has the
same problems.
 
Pulled no.3 plug and found it to be covered with black fuzz..too rich.
Removed the drilled out main jet and measured the original. It measured
.055. I drilled it out to approx. .060 and put in the carb.

Also adjusted the accelerator pump linkage so it will operate smoothly.
This pump operates with it's spring under COMPRESSION when at rest.
Pressing the gas pedal gives the initial shot of fuel and continues to
pump fuel as the car accelerates.This is the reason for the slots in the
linkage. I now have very smooth transition from dead stop thru 35 mph
with no stumbling or hesitation.

Will continue to check spark plugs to determine if I'm still running too rich.
Any opinions regarding what I've done will be welcomed.
 
You need a DS11 distributor with centrifugal & vacuum advance properly recurved for your application. I can supply that for you. With a scv carb you cannot run ported vacuum only manifold vacuum to the vacuum advance with the DS11 distributor.
You also will need a MSD Blaster 2 or 3 coil with low primary resistance. Also A MSD6-AL ignition box which has a rev limiter & supplies multiple sparks up to 3K rpm. Another option is one of my HEI Modules witch is mounted on an AC Delco heat sink.
Another option i also market a Real HEI distributor of course recurved for your application. It only requires a 12V power source, coil & module is builtin the only thing you would need is a set of spiral wound plug wires available from Summit. It also comes with a tachometer outlet.
See the for sale section of the forum. You will also need a full 12V to all units.
Replace your stock torque converter with something in the 2400-2500 area would be a plus. Set your curb idle @ 1000 in park.
Then you can concentrate on your carb issues.
Did you ever get at least 5# fuel pressure??? idling & cruising. You may have a clogged sock filter in the fuel tank. Bill
 
The carb that I have does not have the spark valve port on it. Have considered switching to manifold
vacuum and have tried that,but had knocking at mid-range speeds under load(uphill). Believe dist.needs
mechanical advance recurve. Presently running ported vacuum and it seems to be running well after all
the tinkering I've done on the carb.

In July I dropped the gas tank to see if any gremlins were inside. The sock was clean and
there was NOTHING inside the tank.The tank is new when the car was restored.Not even a speck of dirt.
I removed the gauge and have been running without it ever since. I run premium gas with an octane booster.

Another thing I did was replace the fuel line with one that ran with a slant upward from the fuel
pump up to the carb. Noticed air bubbles appear in the clear filter when I pressed on the fuel line.
The slant is about 30-35 degrees rise from the pump to the front of the engine. No more bubbles.

What you are proposing is way more that I have the desire to do. As it is now the idle in park is set
at about 950 the dropping to 625-650 in drive and runs fine at that setting. I'm considering a new dist.
as I don't know the history of the old one. Will replace cap and wires too.Current wires are stock.
The converter would be another option,but the car is growing old on me and will soon be for sale.
I want to keep the dist. stock as I have power steering and the bigger dist.would hit the pump.
Is the DS 11 dist. any bigger that stock and what would be involved getting one from you?
 
The housing is the same diameter. However to take advantage of the DS11 you need an adapter to accommodate the larger cap.
If interested just PM me, email or call after 12 noon EDT. Bill
 
When you switch to manifold vacuum, you should set the timing with the vacuum connected to the distributor. And then set it a little high, like 12-14 btdc. You were probably running 18 or more initial if you didn't set the timing with the vacuum advance hooked up when you were using manifold vacuum. And if it's pinging and you are having problems with idle in drive, you may have a miss issue or a faulty module if you're running an electronic ignition. Maybe combined with a tight torque converter or worn carb body. It's a system and it can get complicated when there's a problem in that idle area. A lot of factors working together and if there are multiple problems with the combination you can fix one and see an improvement, but it still isn't right. And you can chase your tail if you don't look at the whole picture.
 
Econoline":pfox5rsw said:
When you switch to manifold vacuum, you should set the timing with the vacuum connected to the distributor. And then set it a little high, like 12-14 btdc. You were probably running 18 or more initial if you didn't set the timing with the vacuum advance hooked up when you were using manifold vacuum. And if it's pinging and you are having problems with idle in drive, you may have a miss issue or a faulty module if you're running an electronic ignition. Maybe combined with a tight torque converter or worn carb body. It's a system and it can get complicated when there's a problem in that idle area. A lot of factors working together and if there are multiple problems with the combination you can fix one and see an improvement, but it still isn't right. And you can chase your tail if you don't look at the whole picture.
No you set the initial advance with the vacuum line disconnected. When you connect the vacuum hose set your curb idle. If you then encounter pinging the amount of vacuum advance or the manifold vacuum setting needs to be changed.
An engine with a stock cam or a mild cam would probable run better on ported vacuum.
 
I mean alternatively he could set it that way, pull it and see where it is, I'd guess it'll be around 6 btdc, and then he knows he needs to plug it and set it at 6?? And in reality he'll be running 12 deg at idle once he plugs it back in. I know where you're coming from and that's the conventional wisdom, but in this case it just seems more straightforward to set that way to me. Worst case we're walking around different sides of the barn to get to the same place at the end if that means lowering the advance to address the pinging. Outside of having you recurve it.

You're the expert Bill and far be it from me to argue with you about timing curves.
 
Seth, i understand what you mean.
The best thing to do is temporally leave the vacuum line disconnected, yes the idle will be off, but then road test it at WOT & see if the engine pings. On his engine 36-38 degrees total advance would be the limit.
Then hook up the vacuum advance be it ported or full manifold vacuum & again road test at off idle & general mild driving conditions. Not WOT. If you encounter pinging then the amount of vacuum advance is too much or the vacuum settings if adjustable need to be addressed.
Run a cranking compression test with a warm engine & have the throttle wide open.
For example on my present engine with 9.5 CR i get 175#
On my previous engine with 10.4 CR i got 195#
The camshaft plays a big part in those #'s
For street use using 93 octane fuel the 195# is very close to max. For you poor west coast guys with 91 octane you would have to be more conservative if you have the same combo.
 
I tried another approach to this problem by buying 3 different sizes of jets from Mike's carb shop and switching them out,
road testing them,and tuning the accelerator pump. A .073 jet size was way too rich,so I took the stock jet,.055 and drilled it
out to .060. and shortened the acc.pump stroke. Car ran very well with this jet and idle improved with tuning the carb.

Wasn't totally satisfied until I tried the .058 jet.Tore the carb down and installed the .058 jet and road tested the car.
In conclusion the .060 is what this engine LIKES the best. Idles fairly smooth at 650-700 rpm in drive, with timing set at 12 BTDC.
This work is done on the Holly 1940 carb. The same jet changes may work as well with the Autolite 1100. My engine has a mild cam
from Comp Cams installed and I believe after ALL of this,the cammed 200 six needs a richer jet size to run right.

Another discovery is that the Holly 1940 acc. pump is under Compression at rest.The slots in the linkage allow a smooth flow of
fuel into the carb when starting out up to 25-30 mph. If the pump lever sticks in any way during this operation you will experience stumbling during acceleration. The slots in the linkage in the Holly 1940 MUST be clean to allow the pump lever linkage to move.
Took mine off and filed the edges of the slots to improve movement. It works.
 
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