Technical Back again with more bird issues...

So as some of you who have been around for the last two years may remember, I have a 4th Generation Thunderbird that loves to cease motion for unexpected reasons (head gaskets, bad bearings, fueling issues, etc). I just finished the third engine overhaul (2 rebuilds and a bearing job) recently, and dropped the 390 back into the car. It’s stock except for the edelbrok intake and carburetor. Last round I had killed the bearings within a dozen miles of first fire, and I didn’t even get a mile into the break in this time before she started kinda knocking. I’m getting 55PSI of oil pressure cold, 30-35 warmed up at idle, so I don’t think it’s a low oil pressure issue. When we put her together the crankshaft and bearings were just over two thousandths apart, towards the high end of tolerances, but not outside of them. Stethoscope confirmed bottom end doesn’t sound iffy. I don’t know what to make of it, as it sounds like a knock still. Only think I can think of is the exhaust manifold leaks, and it just leaks that bad, but I don’t think that’s it. Help?

 

We used to have to align hone the mains on a lot of FE engines during rebuilds. Probably not your issue but something to be aware of.

 

Did you verify crank runout or line bore?

 

I’m going to plead ignorance of those, but I will say the block and heads were machined and the crank and cam polished by a reputable shop a few towns over.

 

Could it be coming from your torque converter?.

 

use a hose as a stethoscope, and try to localize the noise, first...

 

It’s possible, but the bellhousing or dust cover didn’t sound bad when I was poking around and listening with the stethoscope.

 

Clay, I hate to be the bearer of bad news, but if you’re overhauled your engine three times and it still has trouble and the previous builds scrapped bearing and such, you’ve got something horribly wrong or are doing something wrong.
Time to bring in another set of eyes.


Bones

 

You’re probably right on something being hella wrong. I know the first two rebuilds were plagued by trash, I’m hoping this one hasn’t suffered the same fate. If it has I may end up going to the dark side and swapping in an OT motor.

 

Doing the lower end assembly yourself or is a shop putting it together?
If it’s you then the problem has been identified.
If its a shop find another one.

 

It’s been me. First build we had trash in the cylinders. Second, oil pump went to toast, then shot a bunch of crap into the bearings. This one seems to be a top end noise that sounds bottom end

 

Hello Clay: some cars fight you every step of the way. Not sure why. Suggestion: GET a Harbor freight mechanics stethoscope, they're only a few bucks.
If the lower end knock is from a rod bearing, pull off a plug wire one at a time, then start it, if one cylinder has a bad rod bearing -then the pulled wire will silence the knock.

these 390's can also make lots of valve /lifter noise ---might be a lifter or pushrod.

 

Loose flexplate bolt? Like squirrel said, listen close.

 

Do you have aftermarket valve covers on it? I had a 390 that had a knock sound and it turned out to be the rocker arm hitting a baffle in the aftermarket valve cover oil fill.
Those old FEs are great engines, I have had a few and every one was great and easy to work on except the godawful intake so I think you need to be meticulous in putting it back together.

 

They don’t appear to be aftermarket. They’re tent shaped sheet steel valve covers. I’ll have to try pulling the plugs, hadn’t tried that. Just listened and redoubled my efforts on tightening the exhaust manifold.

 

Make sure the correct rocker stands are in place for the oil feed and they have the necked down bolts.

 

As Squirrel mentioned use a rubber hose to pin point any exhaust leaks if you have any. I gotta agree with the above statement based on this, ; "First build we had trash in the cylinders. Second, oil pump went to toast, then shot a bunch of crap into the bearings." These are all builder errors. Then this comes to mind. When was the last time the Micrometer your using re calibrated? Are you using a Micrometer or Plastigauge? There is a fine line between being a Good motor builder and the Aww Crap group. Getting there can be a tough lesson. Sorry your having a Tough go.

 

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When going through the motor when rebuilding/overhauling, do not be afraid to look at and check everything. That means everything, like the oil pump, rocker shafts, arms and stands, everything. Do you have a manual that gives you all the clearances and specs? Remember, you need to remove every plug in the oil passages and make sure the are clean and clear. Check bearing hole alignment to make sure oil is getting through, cam bearings included. Take absolutely nothing for granted. If you have questions, and you should, right here is a great place to ask them. Locate the noise, and let us know what you find and think. If it comes to tearing it down and doing it again, you have all the help in the world here, use it.

Edited; I forgot your oil pressure readings were in your post.

 

There are 3 things that need to be done when doing a rebuild. First, excellent machine work.
Second, high quality parts.
Third, careful inspection of parts and machine work. Followed by careful assembly in a clean invironment.
Any short cuts to those 3 items WILL end in disaster. A correctly built FE motor will give many years of dependable service. Each of those 3 items must be taken seriously always. Good luck.

 

Sounds like you might have assembled it dirty again. I was always taught cleanliness is next to godliness when assembling an engine. Did you pull the oil plugs and clean the oil passages? Clean the oil passages in the crank? Like was said above the Ford FE is a good engine. Was used in cars and trucks from 1958 till 1974.

 

Wish I could tell you where I bought my Brush set. I have a set of brushes made to clean out oil passages. I think 1/8" is the small one up to like 3/4" and I believe there are 10 of them. They are on a long spring type shaft so they bend and flex. You push them through with some cleaner. You do every passage then use a light and look through just like cleaning your Rifle barrel. Never use a Rag or paper towel for final wipe on anything, they leave lint behind and enough of that and you have another blockage. Wash your hands a lot!! Ya, I know, everything is clean and new but wash your hands anyway, often. Don't ware Rubber Gloves, they snag on everything and a little piece of that floating and guess what.

 

Before going too far, listen to the fuel pump with that stethoscope thingy. I've seen many of them knock on FE engines.
Eddie

 

Another for, If the plug's an brushes didn't come out between rebuilds, That definitively is your problem .. Look at it as hardening of the arteries with particulate in metallic form... Bad candy

 

We used plastigauge when we redid the first one, we hadn’t touched it since as there didn’t appear to be any wear on the crank since then. Rockers have their oil coming in the right place, but other than the crank we didn’t clean oil passages this go around. Fuel pump is brand new and installed correctly, as we thought it was the problem initially. Clean environment seems to be the biggest issue, as the first two engines were built in the machine shop where we had the work done and the bearing job was done in the garage I share with 3 dogs and a horde of crap.

 

I'm going to assume at one point new pistons were installed... A bad wrist pin can make ya chase your tail Also, An doesn't effect oil psi., It is a double knock an also if the knock change's from double to one when pulling plug wires running...

 

say it sounds top end? how did you break in the cam? i may be in left field, but i pulled a small block because of a loud knock. it turned out to be a wiped cam.

 

Have you narrowed down the location yet? Are your cam and lifters new? Timing set?

 

We reused as much as possible in the builds. Pistons are old, but new rings. Block was machined, crank and cam polished, heads machined, old timing set as it was a metal aftermarket one that didn’t have much stretch to it. We reused the lifters as they didn’t have any obvious wear or damage either. Seals are all new, distributor, fuel pump and power steering pump are too. Would have liked to do more, but I’m doing what I can with a college student’s budget. Rocker arm shafts were a little on the worn side, but I’m going to inspect them when I can get away from the Christmas festivities and back into the driveway.

EDIT: noise isn’t as loud this time. When I got the exhaust a little tighter than almost falling off last time I was under there, I didn’t get a chance to start it and see. Now that I have, I’m thinking that I just have been played by my exhaust leaks

 

Did you put the lifters back on the exact same cam lobs they came off of? If not that could be your problem.
Clay, an exhaust leak, usually has a distinct sound, that changes dramatically with engine load that kinda works opposite of a bearing knock.



Bones