You also need to see what your maximum timing is at. I use a digital timing light with adv/ret feature to know where it's at and at what rpm
All Small Six Chasing vacuum leaks..the saga has ended.
- Thread starter ActionYobbo
- Start date
This relates to all small sixes
How are you determining when to stop adding coolant when it's cold? Normally the Mustangs like to have the internal radiator fins covered by about 1/4 inch of coolant. Much more than that will end up spewing out the overflow. Have you run it for a while after you see the coolant circulating with the radiator cap off and added coolant as needed? This will eliminate air pockets in the system.
As far as the "sat at just below boiling", remember that it's a pressurized system and that being under pressure raises the boiling point of the coolant. As long as your gauge is steady, it sounds like the system is working like it's supposed to.
As far as the sluggishness, what is the distributor vacuum advance connected to - full manifold vacuum or ported vacuum?
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ActionYobbo
Well-known member
I have the original carburetor rebuilt and back on the motor and the original distributor and coil. I have the radiator out getting ready to put the original radiator back in when I finish cleaning it. I started flushing the coolant system last night. I should have it ready for another drive soon.
To answer some questions
I assume it’s full of coolant when it can’t take anymore. I had it running and kept adding coolant when there was room.
The vacuum advance was not hooked up when I was using the electronic distributor now it has the original distributor hooked up like ford did it. I have it running but have not taken it for a drive since changing back to the original parts.
To answer some questions
I assume it’s full of coolant when it can’t take anymore. I had it running and kept adding coolant when there was room.
The vacuum advance was not hooked up when I was using the electronic distributor now it has the original distributor hooked up like ford did it. I have it running but have not taken it for a drive since changing back to the original parts.
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Small Block inline sixes are known for timing chain stretch. There is a simple way to check if the chain is still within spec. I don’t have the procedure saved to check. Maybe another member can assist. This should be checked on any Small Block inline sixes.
It can be difficult figuring out if you're solving it or causing it whenever changing more than one thing at a time.
ActionYobbo
Well-known member
Another update. I found the bottom hose was sucking flat behind the power steering bracket. So I have replaced the hose and filled the radiator with what it could take then ran it for a bit and now I am waiting for it to cool off a bit before filling the radiator with more coolant then I hope to go for a long spin with out any more problems.
rickwrench
Famous Member
Might be a good idea to back flush your new radiator with as much flow as you can manage, then install a Gano type inline radiator filter in the top hose. The blocks are 50-60 years old now, and full of flaking crap that comes loose, flows to the radiator (or heater core), and plugs up core tubes.
Running a spring reinforced lower hose is also a good idea. Overflow jug is needed, blown coolant gets sucked back as when the system cools off.
Already mentioned: Advance 'till ping, back off a bit from there.
I've pulled a surprising amount of crap out of the radiator filter over the years.
Running a spring reinforced lower hose is also a good idea. Overflow jug is needed, blown coolant gets sucked back as when the system cools off.
Already mentioned: Advance 'till ping, back off a bit from there.
I've pulled a surprising amount of crap out of the radiator filter over the years.
ActionYobbo
Well-known member
All is good. Have taken a few drives in this heat and it’s running good and not getting overheated. Just need some wheels and tires and lower the front end a bit to get it from takeoff to flying level and it can be my daily driver for a while.
Glad to hear you got that handled. There's a big difference in driving mine in the Spring and Fall from the Summer, especially when I'm stuck in bumper to bumper traffic. It hasn't overheated yet and I have a new radiator and my block was tanked and cleaned but it sure gets unhappy in traffic; runs rough and shakes at idle more than normal.
So can you narrow down what you did to fix it??
ActionYobbo
Well-known member
ActionYobbo
Well-known member
So I went for a 15 mile each way drive.
So let’s start out with the settings. Cold it starts and will idle with a bit of (manual) choke and after a few minutes idle with no choke. High idle in park is 800 low idle in drive is 650. It runs good and can keep up on the hiway but after driving a while thd low idle goes up to 900 and thd high idle is 1400 so when I got to where I was visiting it was reving a bit high. Left it sit for 2 hours while I was visiting and it started just fine with idle back down at 650/800 and after driving the 15 miles back home it was 900/1400. AFR is 12 to 14 I did the timing by advancing it til it pinged on acceleration and backed off a few degrees. Other than that it runs good. I have been shutting it off in drive then putting it in park just so it not reving hard when I shut it off.
So let’s start out with the settings. Cold it starts and will idle with a bit of (manual) choke and after a few minutes idle with no choke. High idle in park is 800 low idle in drive is 650. It runs good and can keep up on the hiway but after driving a while thd low idle goes up to 900 and thd high idle is 1400 so when I got to where I was visiting it was reving a bit high. Left it sit for 2 hours while I was visiting and it started just fine with idle back down at 650/800 and after driving the 15 miles back home it was 900/1400. AFR is 12 to 14 I did the timing by advancing it til it pinged on acceleration and backed off a few degrees. Other than that it runs good. I have been shutting it off in drive then putting it in park just so it not reving hard when I shut it off.
Not bad
As for the idle, it should be set when it is hot. Then, when it is cold, you might have to run the choke a little longer. Your idle speeds are good, just set it when hot. At that time adjust your mixture with the meter as well/ it might change with the idle speed change
Oh! And go drive it some more
As for the idle, it should be set when it is hot. Then, when it is cold, you might have to run the choke a little longer. Your idle speeds are good, just set it when hot. At that time adjust your mixture with the meter as well/ it might change with the idle speed change
Oh! And go drive it some more
Because choke is required after cold start for more than a half minute, and because of the idle speed difference cold/hot, either the idle circuit on the carb is too lean or more likely a vacuum leak. One way or other, idle is too lean.
Glad it's running good though! You've come a long way from where you started.
I think that a faster idle after it has become fully heated up is normal for these cast iron on top of cast iron engines with the less than optimal log intakes. Mine likes the choke for cold starting, even on a blistering hot day with a cold motor until a minute or two of fast idle and then it drops to a choppy idle of around 750. That’s just a function of the choppy cam and not quite warmed up state. After a few blocks of driving, the idle picks up to a smooth 900 and remains there. I can drive for 10 minutes or an hour and that is the constant about 900 RPM and fairly smooth.
Being a manual, stick-shift car, 900 RPM is fine for mine. I’m not sure that it’s optimal for a car with an automatic though. With a high enough stall on the torque converter it shouldn’t be a problem. It sounds like you’ve got the A/F ratio pretty bang on as well as the timing, so that’s awesome.
What I don’t understand in your description is that after driving the 15 miles home you describe a low idle of 900 and a high of 1400. Are you saying that it has a high idle as well as a low idle after it has warmed up. Is It hanging high?
Being a manual, stick-shift car, 900 RPM is fine for mine. I’m not sure that it’s optimal for a car with an automatic though. With a high enough stall on the torque converter it shouldn’t be a problem. It sounds like you’ve got the A/F ratio pretty bang on as well as the timing, so that’s awesome.
What I don’t understand in your description is that after driving the 15 miles home you describe a low idle of 900 and a high of 1400. Are you saying that it has a high idle as well as a low idle after it has warmed up. Is It hanging high?
ActionYobbo
Well-known member
Yes
When after driving a few miles the idle goes up and stays up until the engine cools then it will resume at the correct idle speeds until it “gets hot”. There is no adjustment left in the carburetor to lower the idle. The throttle shaft had no more movement and the throttle plate is as closed as it can get. There only way I am able to bring the idle rpm down is to back off the timing.
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Oh, ok... So it goes up to 1400 and stays there. Going from 750 to 900 and staying at 900 is the normal thing on mine but if it's shooting up to 1400 and hanging, that does sound like some kind of vacuum leak especially if the carb is closed. It sounds like something is changing shape due to heat and allowing the vacuum to pull in extra air.
It's unlikely that it's at the accessory port on the intake log below the carb but it might be a good idea for testing purposes to remove anything attached and block it off. I don't know if you've got power brakes or something connected to it but I'd look there first if there's something that could be pulling vacuum through it. You may need to run it until it gets to that hot high idle, shut it down briefly, disconnect and block the port and start again to see if it changes it.
Aside from that, I'd block the ported vacuum at the carb when it's hot to see if that changes it. If it's running fast and your ported vacuum to the distributor is on a flexible rubber line, you could bend/kink the rubber line to prevent it from flowing and see if that affects the idle speed.
vacuum leak.
Verify the PCV valve is not over feeding: With engine idling hot remove the valve from the valve cover and put your thumb over the orifice to stop the airflow. The idle speed will drop, how much is the question.
