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High compression? or?

Wes Harden said:
Yes you can let it soak. Follow the directions on the can. Then put the other can in a full tank.
Be careful not to get to much sea foam in the engine at one time, Sea film doesn't compress, engine damage can occur
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So I followed the instructions. 10 minute soak, run motor for 10 minutes.

Then I did this:

10 minute hot soak, run motor for 10 minutes.
10 minute hot soak, run motor for 10 minutes.
30 minute hot soak, race the motor on the road for 10 minutes.
10 minute hot soak, race the motor on the road for 10 minutes.


The placebo effect is great!

Motor has more power, its peppier, runs smoother, Don't have to press the gas peddle down as far at cruising speed.

Ya, but once the placebo effect wear off, the original problem still remains...... (inconsistently)
 
78 GMC Jimmy said:
I can check them all. Again..... Once again, I will verify everything with the timing. From the piston to the rotor.

Note: this problem is not consistent. It only happens when hot, and it depends on how long its been sitting before restarting. Restart right away and its not there at all. Wait a bit and its there a little. Wait the correct amount of time and it wont even turn over enough to start. Wait longer and the problem is there a little. Wait long enough and its not there at all.
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I don't understand how the problem can come and go. Its difficult to even demonstrate the problem, because I have never used a stop watch to see how long it has to sit to reach "peak problem". Its just that when I drive it around running errands, if it has been running for maybe at least 20 minutes and then I shut it off for maybe 5 to 10 minutes, it has the issue very bad. Driving for less time or letting it sit for less or more time after driving, then the problem is mild or not there at all.
 
Wes Harden said:
that is Hot soak, most of the time it is starter, battery or wiring related, esp if you are running headers
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You might be right. How do I test the theory? Add a second battery with jumper cables, so there are two batteries rather than one? Further improve my improvised starter heat shield? After stopping, pour water all over the headers and starter to dissipate heat and then test the result? I'm open to any idea, but i need to know how to test/prove the theory.
 
voltage drop tests, starter motor amp draw test, battery voltage while cranking test. If adding a second good battery in parallel enables it to crank normally, that confirms the problem is in the cranking system.

a newer Perm magnet starter might be solution. They are smaller and have higher torque rating. plenty of threads on the swap here at CK5
 
Wes Harden said:
voltage drop tests, starter motor amp draw test, battery voltage while cranking test. If adding a second good battery in parallel enables it to crank normally, that confirms the problem is in the cranking system.

a newer Perm magnet starter might be solution. They are smaller and have higher torque rating. plenty of threads on the swap here at CK5
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A while back, I wanted more power, so this is what I'm "currently" running:

 
So at one point, the fuel inside the carb was boiling. I could see the bubbles coming up though the clear fuel filter when the engine was off. This what before I flushed the cooling system and installed the 160 thermostat. At that time I though the excess pressure in the fuel system was overpowering the floats and flooding the cylinders, resulting in a slow crank. Hydro-locking was not the issue, and the fuel stopped boiling after the cooling system flushes. Wes Harden says it sounds like heat soak. Maybe the oil is too hot and its overheating the starter that sits right next to the headers. Hmm. So maybe I should install an oil cooler. I have no idea if it will help at all, but the issues seems to be directly related to heat, and I cant just run the engine all the time with no thermostat. So an oil cooler it is. My question is this:

Oil cooler in front of the radiator?
Oil cooler behind the radiator?
Totally isolated oil cooler with its own electric cooling fan?
Oil cooler that attaches to the radiator hose (heat exchanger)?
Use the OEM transmission cooler (heat exchanger) that's build into the radiator? (I have a manual trans)

How would be the best way to plumb this oil cooler? Bets oil cooler type?

Run the oil through a cooler in front of the radiator and then through the trans cooler that's built into the radiator? Eliminate excess heat and reduce the amount transferred to the coolant, and also pre-heat the oil on engine warm up?
 
Once again verified the timing marks. Piston, balancer and rotor.

The rotor is slightly off from pointing to number 1, but its VERY close. A slight turn of the distributor an it would be dead on.
 
I didn't read back to what you'd done before I posted, just knew I'd been burned by a mis matched balancer and tab before. And a spun balancer on another occasion.
 
I'd almost bet your starter is heat soaked like crazy then. :dunno:

Unless you already covered that too lol.
 
oil cooler is not going to help with cranking. It is pretty amazing how fast oil cools with the engine off. My air cooled vw, (only oil temp gauge equipped engine atm) drops 20-25° in just 5 to 10 mins.
An oil cooler will help if your oil temps are running over 240-250° and pressure is dropping while driving.

Is that starter you have clockable ? As in can rotate the motor part closer to the block ? If it is I would start with that getting the solenoid and motor part as far from the header tubes as possible.
 
This far in I'd check the cam timing.
A couple of teeth off will screw it up good.
 
Wes Harden said:
oil cooler is not going to help with cranking. It is pretty amazing how fast oil cools with the engine off. My air cooled vw, (only oil temp gauge equipped engine atm) drops 20-25° in just 5 to 10 mins.
An oil cooler will help if your oil temps are running over 240-250° and pressure is dropping while driving.

Is that starter you have clockable ? As in can rotate the motor part closer to the block ? If it is I would start with that getting the solenoid and motor part as far from the header tubes as possible.
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I don't think the oil cooler will help either. But I'm running out of ideas here.

Checked compression
Tried every possible timing setting
Tried 3 different carbs
Tried complete brand new distributor
Tried Checked the plugs for proper type/condition/gap
Checked for intake leaks
De-carbon the cylinder multiple times
Flushed the cooling system 8 times
Tried all the possible settings and configurations on the vacuum advance
What else... There is more, I'm sure.


ONLY cranks slow or stops turning over when it has spark. ONLY cranks slow or stops turning over when the engine is hot.

I have the starter clocked away as far as possible, with a fab'd aluminum heat shield protecting it. The rig had the same issues with the stock starter. I don't think its the starter, but I could be wrong. Removing the Thermostat eliminates the issue, which would have minimal impact on the starter temp, I assume.

Since heat is the only thing I have left to try, all I can think of is cooling the oil down. I can t cool the engine down any lower than it is. Its already running too cold as is with the 160 T-stat.

Normally I use 87 octane. I just put a fresh tank of 92 octane fuel (30 gal) with enough octane booster additive to treat 40 gallons.

Too soon to tell if that helped. Its not starting perfectly, so there is still an issue. I will have to drive it more to see if the worst of the symptoms are gone with the octane thing. It take a lot of starts to finds that "sweet spot" in temp and time for it to not start at all where it just grinds to a super slow crank.
 
So my final plan:

One more coolant flush with a new type of radiator cleaner.
Super high octane fuel
Heat shield blanket for the high torque mini starter.

I will try all 3 at the next test.

If the problem remains, I will either hire someone that is a better mechanic than I am to diagnose it, or I will replace everything between the firewall and the cooling fan. Just do a complete engine swap without re-using any of the old parts. Starter, carb, intake manifold, etc works. Hell, I wont even reuse the damn dipstick or air filter! I will solve this problem, one way or another!


Maybe it just needs a quart of oil?

Cars Fail GIF
 
high octane is more difficult to ignite than low octane. That's is what helps with pre ignition. Still say look to your electrical system. SBC 400 needs the best possible cooling system, even new they were marginal on cooling, siamese cylinders.
 
With your body mounts being shot the engine is sitting lower, therefore your cooling fan isn’t sitting properly in the shroud making it less efficient. For all I know you could even be missing the lower half of the shroud if it was rubbing or if you have a body lift.
 
rampage said:
With your body mounts being shot the engine is sitting lower, therefore your cooling fan isn’t sitting properly in the shroud making it less efficient. For all I know you could even be missing the lower half of the shroud if it was rubbing or if you have a body lift.
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The previous owner removed the stock fan and shroud, and installed a chrome upper shroud with no lower section. They had it set up with a shitty flex fan. The fan was super loud and WAY too far away from the radiator. On top of that they must have put 10 bottles of stop leak in the cooling system.

I flushed the cooling system multiple times, replaced the flex fan with a larger clutch fan and installed a spacer to push the fan up closer to the radiator. I also added a section of molded plastic to the lower section to improve the shroud.

The way it runs now, the clutch fan is almost always freespining, the clutch never engages much. The temp gauge used to be at 50%. After my mods it runs at about 15 to 20%.

If I can ever get the starting issue solved, I will take the 160 thermostat out and put back in the other one. I think that one was a 190.
 
So the plan was:

One more coolant flush with a new type of radiator cleaner.
Super high octane fuel
Heat shield blanket for the high torque mini starter.

None of that made any difference, because for the first time ever, the issue happened when the engine was cold! That have never happened before. Ever.

What changed?

I had driven the truck a short distance and when I shut it off, I left the headlights on (intentionally). After about 3 minutes, I jumped back in the rig and tried to start it. The age old problem, it barely turns over and wont start! So I flip the headlights off and try cranking it again and it cranks fine and starts right up. So I shut it off, turned on the headlights, and tried to start again. It started fine. But It seems like it was definitely some sort of voltage issue.

Already done, weeks ago: replaced battery, checked grounds, checked the connections and main starter wire from the battery. I have already been through the electrical long ago.

But electrical seems to be the issue.

I think Wes was saying something about the distributor switch allowing more power to the starter.

So...

When cold it works fine. When hot it lacks power to turn over.
When the battery is not at absolute 100%, it lacks power to turn over.
When other electrical draws are turned on, it lacks power to turn over.

Hmm.

Or maybe today was a fluke, I don't know. But I going after the voltage for now. pointers?

Whats up?
 
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