Technical Flathead runs rough after acceleration and has therewith oil pressure drop

Hi all,
Thanks again for all your input.
I am always very surprised how you all are willing to help a guy who lives thousands of miles away.
That is really, really awesome.
To the questions you asked me.
Video was made after oil change, spar plug and condenser change.
Engine vibrating is horrible under load.
It has still power - that is what I found out yesterday.
Most vibration und load 5th gear low rpm acceleration.
I have to find out what it might be with the pressure relief valve.
To be honest, I am afraid to let it run like that, now.
Don‘t you think I will hurt the crankshaft surface or even too late...?

What really makes me wonder is that the pcv valve open and closes very fast in rythm clicking at idle after warmed up the engine.
Click-click-click-click - very fast...
Again and again - thanks for any further idea, before pulling the engine out.
Michael




The H.A.M.B.

 

When is the last time the valve lifters were adjusted, if ever?

Sent from my SM-G965U using The H.A.M.B. mobile app

 

Reserve 5th for highway cruising, a good flathead will pull from a walking pace to flat out in 3rd ( lets refrase 1 to 1 ) expecting more of it in overdrive isnt a performance option its an economy option .. in my opinion..

You see now this is what I mean by guessing at the problem when not present with the vehicle , We have vibration. where does it emante from, is it a transmission problem, viz an un ballanced prop ? Im guessing its Flathead V8 T5 open drive maybee an open drive conversion rear end.. ?

Could it be a drive line imbalance at certain speeds trying to shake the car to pieces , ?

We can eliminate the plugs since they have been changed and it still misbehaves ..

For this kind of diagnosis, list the drive train and engine spec . Take a video of the car stationary at idle from out side the car , increase the revs gradually if you can to around 2700 rpm You would be into Max advance territory withing that rev limit .. DONT STRESS THE ENGINE THOUGH. if its knocking its nuts off BACK OFF.

Try to do this video in a reasonably quiet enviroment so its your vehicle we are listening to eliminate as much background noise as you can ..

Film from both sides on the engine bay and from the front of the car , Noise is a funny thing..

With that done , jump in the car and do a stationary check start it up with focus on the gauges again..

lets see what happens, raise the revs in neutral and see what happens ,

IF it reaches a certain revs and doesnt shake the motor from its mounts the vibration is comming from some other rotating mass ( Prop shaft perhaps ... just guessing)

If the engine is vibrating badly while stationary with higher revs , depress the clutch and see if anything changes ..

If its still vibrates mady then it looks like an engine area issue, check the engine mounts , If you are running a mechanical fan, SWITCH OFF THE ENGINE and check belt tension and fan mount for play .. Disconect the fan belt and spin the fan manually .. with the fan belt OFF start the engine up Dont run it for a prolonged period , with the fan disconected is the vibration still there ?

Its a process of elimination..

The clikety click could be the lifters as mentioned just prior to this post , If they are way out of whack that would affect the running and can cause misfires and all sorts depending how out of adjustment they are .. If they are just clacking away they need attention but shouldnt create to much of a problem .. Do a compression test ..

and a vacuum check ..

check the fresh oil for metalic debris if none then the issue probably isnt inside the engine .. you are not looking for chunks just glitter .. but even a little glitter is common ..

 

So, the problem is greatest at low rpm under a load. That is when the cylinder pressure is the greatest. This is when detonation happens, but I'm not hearing it in the video. Maybe the sound is being swamped by the wind and exhaust noise. Something that is bugging me is, why did the insulators on the plugs crack? Is the vibration in the engine under a load so severe that it caused the spark plug insulators to crack? Wow, that's pretty bad.

Sorry, I'm just kind of thinking out loud here. This thread is kind of quiet considering all the flathead guys we have around here. I'm not offering much help, but this post will bump the thread back up to the top and maybe catch the interest of somebody that can offer additional ideas.

 

Cracked plugs will definitely cause problems, how’s the plug wires? A lot of times you could have a bad wire or two, will cause a miss or high end sputtering
Simple fix


Sent from my iPhone using The H.A.M.B. mobile app

 

Hi all,
I will do it right - I will pull the engine.
Of course you will get information about the circumstances.
I need the engine bullet proof.
Till soon
Michael



The H.A.M.B.

 

Hi you all,
I pulled the engine, what was a pain in the ass.
But I did it.
Looking to the oil pump, I can not find an issue.
Also bearings seem not too bad, but have not opened them till now.
I will forward the engine to Cheater Pete, a friend of mine, who is a great flathead guy.
He will check everything in detail an will make it bullet proof.
I will let you know what the problem was. as soon as I know it.
Thanks a again for all your support.



The H.A.M.B.

 

Looks like a really nice engine,,,,and hot rod,,,,good job .


Tommy

 

Hi all,
Please hear the noise of the turning assembly.
Look hear:



Sounds not good!
Your Opinion..?



The H.A.M.B.

 

Hi all engine will be checked completely today.
I am wondering what it will be, but sure it is a bearing or even worse, the crankshaft itself.
I will let you know.



The H.A.M.B.

 

Hi all,
Here is what we found!
The answer to the question.
Broken Main Bearing!!
So this is why the pressure decrease in high gear - the crankshaft moves beside than...
And without gear and heavy load there was still pressure..
Thank you for all help and opinions!
Crankshaft is ok and healthy!





The H.A.M.B.

 

Geez - these things are tough as nails!

 

Wow....well done Glad you found the problem before it got worse !

 

Holy $hit! Good thing you took it apart before it grenaded


Sent from my iPhone using H.A.M.B.

 

cool, you cracked it pun intended.

 

That could of been nasty. glad you took the right route.

 

How did the bearing look? Any signs of heat?

 

Didn't see your video from the a week or so ago, just saw the thread again today. Wow, that bearing cap! Well, that goes along with our guess about what was happening, doesn't it? When placed under a load the cap would allow increased clearance at the bearing, allowing oil to escape, and pressure to fall. This is a good one! Thanks for coming back and showing us what you found.

 

Good decision to pull and inspect. Good Luck.

 

Question now is, what caused the cap to crack ? defective part, ( bad casting) previous poor assembly, ? serious detonation or wierd load stress loading it up from slower speeds in OD ? Will you be line boring the mains since your fitting a replacement cap ?

A buddy on mine suffered a catastrophic crank failure on his French flathead, the crank broke at the mains journal, slow speed in O/D ( columbia) .. These engines will pull from walking pace in top 1:1 but the stress to pull from 10mph to running speed while in OD must load them up pretty bad .. Its just a theory / question ive pondered . I have no technical experience of loads and stresses..

 

wow thats great you found out the issue, let us know if the crank can be saved, or if has been reground too much already/ just curious if the movement did more damage to the caps and crank.

 

Now I see why people add supports to the center main cap. Good luck on the repair. If the crank is still true, main and rod bearings and an align bore and hone should get it done. Here's hoping.

 

Hi all,
I am back with more info.
Please see the picture.
We found a matching bearing cap from a french flathead, which makes it much stronger!
Bearings and Crank were ok.
I will take the engine back on its place soon..





The H.A.M.B.

 

Something different about FHs that don’t need to be align bored with different caps?

 

I wondered that too.

 

Well that’s A Lead foot Louie break right there, never would have suspected that one, great diagnosis @soonrodder
Not being a machinist but I would have thought when you swap main caps from something else It was essential to align bore all the main caps . Well I for one would , to be sure of no bind. French cap looks great.

 

I suppose you could check cap alignment and bore diameter with a dial bore gage and then have the block "touched up"
with an align hone. I had a block squared once and the first thing he did was to check the mains by just touching the block with a hone. In your situation, I'd have it align bored and honed. JMHO

 

Sounds like what Brad Penn oil was doing to my Pontiac 455 and Chevrolet 454. I changed the oil to Mobil 1 5-30 and it all went away..

 

I have torqued mains on a Cummins laying on my back, and Caterpillars, Internationals, Macks, and Detroits. Never fun, that’s why I always do the mains first, get it done and out of the way.


Sent from my iPhone using The H.A.M.B. mobile app

 

It used to be a regular maintenance item, after so many miles you roll in new bearings. I don't think they do that any more, do they Andy?