Bitter learning curve. Absolutely DONE with carburetors!!!

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PhillH

PhillH

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I started hearing a faint thumping sound on my newly built 360 at idle around the trans hump. Now I know this can't be good but I try not to worry to much because it's just ever so slight, but I'm monitering it and can't stop listening for it. I have about 300 miles on it and it's only been to around 4k rpms so far, it's on it's second oil change. I'm on my way home from work (about 20 miles) and decide to find out if the looming cloud is real, I'm on back country roads and I make a left, I put it to the floor mid turn and WOW! It just lights it up with a big trail of blue smoke coming off the fresh tires, love that smell.
Seems to have more vibration now, but can't really tell, maybe it's in my head from worry.
I still have a few miles before any stop signs, decide we are going to find out if this is a runner or needs torn down again, I slow to about 45mph and nail it a couple times, it shifts to second and sounds fantastic, holds it to about 4.5k rpms, firm shift (trans has a shift kit but definately needs modded) still shifts way to early.
I get to a stop sign and listen closely now, the thumping is definatley more pronounced now, it's not loud, most people probobly wouldn't hear it, but it's there and I know what it is....
The bearings are shot, ruined. During break in I had the carb issue where it was leaking fuel into the cylinders, I found this out when I changed the oil after break-in, about 8 quarts came out of my 6 quart pan. It wasn't driven much at all during the break-in, just about 20 miles, but that gas soaked oil didn't need alot of time to do it;s dirty work. UUUGGH....
I'm done with carbs forever and will have injection and a bunch of new parts before this thing gets fired again.
 
One of the most important things on a new engine fire up is having a known good carb. How did two quarts of gas get into the oil? Electric pump? I wouldn't blame the carb sounds like operator error sorry to say.
 
Just a mechanical pump and my first build, and operator not knowing enough about carbs, hence the title " Bitter learning curve". Do you really have to ask how the gas got from the carb to the crankcase? Thanks for the salt.
 
Well there are a few ways, mechanical pump diaphram ruptures and pumps fuel into oil. Or electric pump was on and not regulated properly and fuel blew past the needle and seat dumping down the carb past the rings. Or the float was set way to high and fuel would dribble past the boosters. The last two should have given a lot of warning before or at first start up. The last one happened to me but I cought it quickly.
 
Check your flex plate bolts, maybe you did not get them tight enough????
 
FI can be tuned wrong and lead to rich or lean problems so seriously, carb or FI is not really the issue. Unfortunately, the issue was not caught in time, but likely due to your just being new to things.... it happens when you are new and are learning, and even experts muck it up once in a while. You had an unusually large amount of fuel leakage there if there was 2 extra qts of fuel in there! The carb had to be flooding or the pump diaphragm leaking as mentioned. With more experience, I am sure you would have caught it sooner and things would have been different.

BTW, we had light seepage from the primary fuel needle & seat in a recent new 340 startup. Drove the new engine 20 miles after break-in... pulled plugs and found the front 4 plugs very rich, which lead to the detection of the issue. A new Holley kit fixed it all up. That is just from knowing what to look for and being aware that we were starting with an unknown carb and to be watchful on that... all just from past experience. I would have been just as wary with a new FI system on a new engine.

Have you gotten to the point of pulling the bearings? You 'know' it is ruined bearings but this is your first build...... maybe jumping to conclusions?
 
67Dart273 said:
You sure it's not a bad fuel pump?
Click to expand...


PhillH said:
Just a mechanical pump and my first build, and operator not knowing enough about carbs, hence the title " Bitter learning curve". Do you really have to ask how the gas got from the carb to the crankcase? Thanks for the salt.
Click to expand...

67Dart273 said:
You sure it's not a bad fuel pump?
Click to expand...


67Dart273 said:
You sure it's not a bad fuel pump?
Click to expand...


67Dart273 said:
You sure it's not a bad fuel pump?
Click to expand...


67Dart273 said:
You sure it's not a bad fuel pump?
Click to expand...


67Dart273 said:
You sure it's not a bad fuel pump?
Click to expand...


67Dart273 said:
You sure it's not a bad fuel pump?
Click to expand...

........
 
sireland67 said:
Check your flex plate bolts, maybe you did not get them tight enough????
Click to expand...
Make sure of simple stupid stuff not uncommon to come out in a handful of hundred miles. Maybe you're as screwed as you think- but sure hate to tear apart the motor and stare at fresh bearings, tighten the flexplate bolts properly when it goes back in, and have it all go away. Been there too often. No fun diagnosing a no start for too many hours before realizing it doesn't have gas. (any is the answer on too many)
 
Demon,... Sir you have shown the light. You are right, I never considered that the fuel could have come from the pump diaphragm, that is one of the only things I reused, it was new but it did sit for years, and I shouldn't have used it.
Flex-plate bolts were torqued and I used threadlocker, so not likely unfortunately.
I still don't consider this a fail, it's been on my bucket list since I was a teen and I rebuilt this myself, all the internals are right and it makes tire smoking power. That is a win! A small setback because of an external part that I did not put together isn't enough to call it failure. I will rebuild, but this time with fuel injection. Then I don't have to learn all the settings, adjustments, choke, jets, secondary's, etc, it is operator error here, but in this day and age I don;t have to learn it.
 
Now you have taken it for a stomp better check the oil level again.

If that fuel pump is leaking into the crank case.........IT WILL TAKE OUT A 2nt set of bearing as well.
 
PhillH said:
Demon,... Sir you have shown the light. You are right, I never considered that the fuel could have come from the pump diaphragm, that is one of the only things I reused, it was new but it did sit for years, and I shouldn't have used it.
Flex-plate bolts were torqued and I used threadlocker, so not likely unfortunately.
I still don't consider this a fail, it's been on my bucket list since I was a teen and I rebuilt this myself, all the internals are right and it makes tire smoking power. That is a win! A small setback because of an external part that I did not put together isn't enough to call it failure. I will rebuild, but this time with fuel injection. Then I don't have to learn all the settings, adjustments, choke, jets, secondary's, etc, it is operator error here, but in this day and age I don;t have to learn it.
Click to expand...
Not a fail, practice.
 
Have not torn it down, just drove it home tonight when this happened. I checked the oil and the level has not changed, but, when I wipe the dipstick there is clean new oil and a slight film of grey film on the white rag. I'm assuming this is the babbot from the bearings??
Also the oil pressure is low, 5 pounds at idle after warm, 23 at 2k rpms, 32 at 3k rpms.
 
PhillH said:
5 pounds at idle after warm, 23 at 2k rpms, 32 at 3k rpms.
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still reasonable. Diagnose it, and/or drive till it fails.

Replacing bearings in the car ain't too tough.
 
What are opinions on driving it? Will it get worse if it is bad and let me know? Or will I destroy the crank? Theres no way I can get the oil pan off without pulling the motor, it has a Kevco race pan on it.
 
PhillH said:
when I wipe the dipstick there is clean new oil and a slight film of grey film on the white rag. I'm assuming this is the babbot from the bearings??
Click to expand...

Any chance you're not running a PCV.? That'd be the grey film, - condensation..

I wouldn't be too quick to assume it's a bearing.

Can you post a vid with the noise?

Consider buying/borrowing a Lisle stethescope for better analysis and area of noise, cost is <$20 at most parts stores. http://www.amazon.com/dp/B0015DLMOO/?tag=joeychgo-20

Consider taking it to a knowledgeable mechanic, for a second opinion.

I've often found a bad bearing will "squeal" for a while before it truly starts knocking.. Any squeals?
 
I'm running a PVC valve from the rocker cover to the carb. I do have acheap version of the stethoscope but haven't used it yet. It did squeel one quick second when I revved it yesterday, it's never done that before but it sounded lke a belt. It would be hard to record the sound over the exhaust, I'm going to start it this weekend and record what happens. I'd still like to hear opinions though. The grey film isn't moisture, but it could very well be just a new motor breaking in. I'll get some pics or videos I know it's hard without them to diagnose.
 
PhillH said:
Have not torn it down, just drove it home tonight when this happened. I checked the oil and the level has not changed, but, when I wipe the dipstick there is clean new oil and a slight film of grey film on the white rag. I'm assuming this is the babbot from the bearings??
Also the oil pressure is low, 5 pounds at idle after warm, 23 at 2k rpms, 32 at 3k rpms.
Click to expand...
As inertia says, this grey film can be water/condensation. Not sure how you can say it is not.... grey scum under the valve covers is indeed one of THE common results of a non-working PCV or moisture not getting driven out. It aslo can be brownish.... How does the coolant level look in the radiator? I don't think I have ever seen bearing materials show up on a disptick, even with a temporarily seized crank and another case of totally wiped out and spun main bearings; it all went to the bottom.

Those oil pressure numbers do seem low.... how were the pressures when the engine was breaking in? What weight of oil are you using? FYI, our new engine with 200+ miles on it has no less than 35 psi idling, fully warmed up, with 10W30. The clearances were all in the middle to upper end of spec range. Pump is an HV pump. Any reason to think your oil pressure gauge could be off?

BTW, I would not be driving it at all.... that never makes things like this better.... unless it is carbon'd up plugs.
 
41 years of using carbs and never had or heard of a carb doing that.
But regardless my next one is going to be efi because turbos will be used and the tuneability of efi is a perfect match for boost.
 
...after you figure out the knocking sound, adjust the kick-down lever for the transmission. Make it longer until the lever on the transmission won't go back any farther, then begin to shorten it to suit your shift preferences. Lengthening it will raise your shift points.
 
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