All Small Six Exhaust manifold leaks

[Stonefree503]

I’m trying to revive a ‘64 ranchero I got from my uncle. I have pretty minimal mechanical experience but am working my way through it with the help of people who do. I have an exhaust leak which looks to be coming from the manifold and definitely where the manifold attaches to the exhaust pipe. My mechanical advisor seems to think I am pushing oil through and that it’s leaky valves or a head gasket. I suspect it could just be a bad manifold gasket seal? I replaced the manifold gasket myself a few weeks ago and didn’t use any RTV sealant or anything. A couple of the bolts were rusty but didn’t seem too bad so I reused those as well. Also, there was no gasket where the manifold attaches to the exhaust pipe but I know they make “donut gaskets” for this connection. I plan to do a compression test before I do anything else but any further advise would be helpful. Thanks.

Also, I wanted to add that the car has been garaged and not running for about 5 or 6 years and that exhaust coming from the tailpipe and the leaky manifold is not clean. Not super black either but is definitely burning some oil up from somewhere.

 

[Frank]

I’m trying to revive a ‘64 ranchero I got from my uncle. I have pretty minimal mechanical experience but am working my way through it with the help of people who do. I have an exhaust leak which looks to be coming from the manifold and definitely where the manifold attaches to the exhaust pipe. My mechanical advisor seems to think I am pushing oil through and that it’s leaky valves or a head gasket. I suspect it could just be a bad manifold gasket seal? I replaced the manifold gasket myself a few weeks ago and didn’t use any RTV sealant or anything. A couple of the bolts were rusty but didn’t seem too bad so I reused those as well. Also, there was no gasket where the manifold attaches to the exhaust pipe but I know they make “donut gaskets” for this connection. I plan to do a compression test before I do anything else but any further advise would be helpful. Thanks.

Also, I wanted to add that the car has been garaged and not running for about 5 or 6 years and that exhaust coming from the tailpipe and the leaky manifold is not clean. Not super black either but is definitely burning some oil up from somewhere.

Welcome!
Leaking exhaust will not cause oil consumption, or an oil leak.
When you do the compression test: All spark plugs out, throttle and choke held in fully open position. If the compression is good, the oil consumption is through the valves, not too hard a fix. If compression is low the oil is from the rings, requiring overhaul.
Keep us posted!

 

[John Ha]

Welcome!
Leaking exhaust will not cause oil consumption, or an oil leak.
When you do the compression test: All spark plugs out, throttle and choke held in fully open position. If the compression is good, the oil consumption is through the valves, not too hard a fix. If compression is low the oil is from the rings, requiring overhaul.
Keep us posted!

Just to add a bit - compression readings can be low because of valves not sealing. Normally, you'll do 2 compression tests on each cylinder. The first one is what @Frank describes. The second one is after squirting a little oil into the cylinder. If the compression increases a lot with the oil in the cylinder, the rings are worn (the oil improves the seal between the piston and the cylinder wall). If the compression reading doesn't change very much but it's still lower than it should be, you probably need a valve job. If the compression readings are within acceptable limits and there's oil consumption, the valve guide seals may be bad. They can be replaced with the engine in the car.

 

[Stonefree503]

Thanks to both of you for your responses. With regard to my question about the exhaust leak. I guess I was just wondering if black smoke in the exhaust could be caused by anything other than oil being pushed through? Just got done with the compression test. All 6 plugs look black and sooty (they are all new as of about a month ago and the engine has been run for a total of about 5-10 minutes. Here’s the results:
1-150
2-145
3-147
4-145
5-150
6-155
I did the test before reading John’s response. Should I do another test and add a little oil to each one? Also how much is “a little”?

Thanks so much!
Nate

 

[Frank]

Thanks to both of you for your responses. With regard to my question about the exhaust leak. I guess I was just wondering if black smoke in the exhaust could be caused by anything other than oil being pushed through? Just got done with the compression test. All 6 plugs look black and sooty (they are all new as of about a month ago and the engine has been run for a total of about 5-10 minutes. Here’s the results:
1-150
2-145
3-147
4-145
5-150
6-155
I did the test before reading John’s response. Should I do another test and add a little oil to each one? Also how much is “a little”?

Thanks so much!
Nate

Hey Nate- no need for another compression test, those numbers look good.

Is it actually using oil? Black and sooty plugs sounds more like a rich carb mixture. Oily plugs are "greasy" black, not sooty black. Blue smoke from the exhaust? Oil. Black smoke from the pipe? Fuel.

 

[Stonefree503]

The carburetor is a brand new Chinese knockoff autolite 1100 and has never been tuned at all. I installed a choke tube/stove as it has an auto choke but other than that it was plug and play and fired right up. My mechanic friend came over to help me tune the carb and once he saw the black exhaust out the pipe he started thinking it was burning oil which led to the compression test. I always suspected that the carburetor could at least be part of the problem.

After the compression test today I plugged everything back in and started it up. Definitely black exhaust when you first start it but then it mellows out and changes to a more blue color…and there does seem to just be a lot of exhaust in general. I ran it for a total of about 30 minutes, mostly at an idle with the occasional throttle and a couple laps around the block. No misfires at all and it sounds pretty decent when given some gas. At idle it putters a little bit and I would say the black exhaust is intermittent.

Thanks for any advice on what my next steps should be.

 

[John Ha]

Usually, black smoke is fuel, blue smoke is oil, white smoke is coolant.

Black smoke at startup isn't uncommon and may indicate that your choke needs to be adjusted (it is closed too far too long) if there's smoke for very long after it starts. You could adjust your idle mixture using the vacuum gauge method after the engine is warm. Also, since it's been so long since it's been run, it's at least likely that the valve guide seals have aged badly and are leaking. As mentioned, those can be replaced with the engine in the car. Your local chain auto parts store tool loan program may have the tool you need to compress the valve springs.

I'm offering this as something to keep in mind - my experience with the Chinese carbs is that they aren't worth doodoo, although your engine runs with one (mine wouldn't even start). You can get remanufactured original equipment carbs from RockAuto. They're not terribly expensive and in my experience, work well.

 

[Frank]

Mr. Ha's above post is on target.
Choke: with engine cold, check the choke blade tension: Air filter off of course. Looking at the choke, move the throttle lever by hand and release, the choke should move to fully closed. Use your finger and see how tightly the blade is held shut. It should take very light finger pressure to move it. If the blade has high resistance to open and snaps back shut, the choke coil is set too tight. Loosen the 3 screws and move it 1/8th turn leaner. I recommend using a marker and marking the relative position of the choke cover-to-housing before changing it, as a baseline reference. Repeat this process (engine cold every time) until the engine starts and stays running, but does not begin to "chug" or black-smoke. After the adjustment, run the engine, watch the choke blade, it should be fully vertical in 3-5 minutes, if not it's too tight OR your hot-air system is not correct. Out-of-box chokes are rarely correctly set.

Valve guide oil consumption: it's "normal" for old engines built during the leaded gas era to begin using oil through the valves. The space between the valve and the channel it rides in (valve guide) gets wider from wear, and oil lubricating the rockers runs down the stem and into the combustion chamber with the incoming fuel/air charge. When manifold vacuum is higher, more oil is draw in from the suction below the valve pulling it down the stem when the valve opens. So worn valve guides the pattern is this: after a period of idling, a puff or stream of blue smoke is emitted at acceleration, then diminishes. Hard acceleration will start smoky, and clear up in a few seconds. The longer the engine has been "babied" the worse these symptoms become. This pattern gets worse when the engine is hot and oil is thinner.

So to verify valve oil consumption, go out and run the engine hard, do several hard take-offs up to legal speed, watch the mirror for smoke. It should clear up. then idle a few minutes and take off hard again. If a puff or several second stream of smoke occurs then clears up, it's valves.

All of the above assumes your choke is fully open- important!

 

[John Ha]

I forget to mention - the later model Mustangs (I think starting in late 1965-ish) had a bracket that bolted to the engine block and clamped to the head pipe that comes off the exhaust manifold. I have read elsewhere that Ford added it because the engine could move but the head pipe either didn't move at all or didn't move as much, which caused the donut gasket between the manifold and head pipe to fail prematurely. It's called a "head pipe hanger bracket" and I have seen it for sale on the CJ Pony Parts website and it's possible the National Parts Depot also carries it. You could probably make your own quite easily. I'm attaching a screen shot - it's from 2024 so the price has probably doubled since then.

 

[Otto]

I forget to mention - the later model Mustangs (I think starting in late 1965-ish) had a bracket that bolted to the engine block and clamped to the head pipe that comes off the exhaust manifold. I have read elsewhere that Ford added it because the engine could move but the head pipe either didn't move at all or didn't move as much, which caused the donut gasket between the manifold and head pipe to fail prematurely. It's called a "head pipe hanger bracket" and I have seen it for sale on the CJ Pony Parts website and it's possible the National Parts Depot also carries it. You could probably make your own quite easily. I'm attaching a screen shot - it's from 2024 so the price has probably doubled since then.
View attachment 26239

I can recommend this little bracket. This was suggested to me in my van project to steady the exhaust. I didn't know it was supposed to be there, but it really solidified the exhaust- should help the donut last longer. I just made my own bracket.