Foundering flathead
 

Greetings. I haven't posted much but have been reading for several years. I bought a 1951 F1 with a 8BA several years ago out of an estate. The engine appeared to be a new build, clean in and out with many new parts. The entire restoration looked good, but was unfinished as the builder/owner died. It wasn't his first build. I bought without a single wire in the truck, so have been building a wiring harness over time.

This is my first flathead. I finally got around to firing the engine recently. Had 50# oil pressure turning it over. Finally got the fuel pump (new) pumping and put a Holley pressure regulator at 2.5 PSI on it. Went through the Holley 94 and checked everything, fresh rebuild in there too. Has a Pertronix kit in the Loadamatic. It is 12v. It fires up and runs somewhat. I have a very rich condition, some back firing in the exhaust. Vacuum guage shows a steady 12 inches. I checked the power valve and no leaks. Checked the float level. Valves all appear to be opening and closing. I have read that the vacuum should be around 18 inches. Changing the idle mixture screws doesn't have much affect. Next step is checking the intake manifold for leaks. Not sure where to go on the rich fuel problem. Timing is set by ear for now. The only timing mark is the raised dot on the front pulley. It sounds somewhat like it might have a more radical cam than stock, but I really don't know what is inside.

Re: Foundering flathead
 

As a point of reference, I have a fresh built 258" 8BA with an Isky MAX-1 cam that makes 20 inches of vacuum. It sounds to me that there is something else wrong besides the carburetor. There was a guy on here a few years ago that had a similar problem and found that the cam had been installed wrong (a tooth or two off as a result of a mis-marked crankshaft or timing gear).

Re: Foundering flathead
 

I read that late valve timing could cause low vacuum pressures. I'm hoping I don't have to pull it apart.

Re: Foundering flathead
 

It's a real long thread, but if you have some time to spare, you might want to look it over : https://www.fordbarn.com/forum/showthread.php?t=235272

Re: Foundering flathead
 

Good read. Tomorrow I'll check the valves in number 1 against the dot on the pulley. That's a start without taking it apart. If it looks off, I'll pull the front cover.

Re: Foundering flathead
 

Pull all of the plugs to see if any of them look different, like oily or black or wet. Then run a compression test (throttle held open). For a new build that sat for a while, there is a fair chance you have some sticking valves. The fix may be as simple as running a pint of MMO through the intake, and putting some in the gas tank.

Re: Foundering flathead
 

So far they all look black and a little oily (right bank). I'll check the rest. I have watched all the right bank valves through the plug holes.

Re: Foundering flathead
 

Is the vacuum fluttery or just low. Rings. Flutter is maybe stuck valves.


Not to say a vacuum leak or other can give the same low readings.


Run the heck out of the motor, it's not going to hurt. Fatheads need to be run to really diagnose, problems work them self out. Your not going to harm it if it has oil pressure 99.9 times out of 100. If after something is problematic, stick a vacuum or compression gauge to it. Fuel would be next, then timing/spark. Back fire is too much, pre-fire is to little... granted timing is set right.




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Re: Foundering flathead
 

Vacuum is steady, just low. Will check for leaks this weekend. Compression check soon.

Re: Foundering flathead
 

Even rings on a new engine will need to run hard to seat. An engine on a stand does not constitute a brake in, it needs load. pour some MMO down the carb and run it. See if it improves. Obviously if you hear metal on metal noises, knock, or other, pull over.


Kinda sounds like timing but.... run it hard underload for a bit. Only thing that will kill it is no oil and high rpms...





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Re: Foundering flathead
 

Tinker, he says it appears to be a fresh build. If it is, "run it hard for a bit" might not be the best idea. If it is a fresh build, I'm afraid it will have to be taken apart and everything checked. To the O/P; do you think it is a fresh build or do you know if it had been running well in the past?

Re: Foundering flathead
 

Tub not necessarily, New rebuild sitting has never really ran. It needs to run. I'd be really less concerned about low readings if it sat in a garage and never was run? Concern was not about knocking the heads or other. Just my opinion. Probably a good build but it sat, i'm not conditioned to believe the worst.


Tearing an engine apart that has never left a garage or run a mile seems premature. or not. Good luck





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Re: Foundering flathead
 

It appeared new from looking at the valves through the spark plug holes. It sat before I got it for an undetermined length of time, and for 5 years after I got it. No strange noises from the block, oil pressure is still around 50#. All run time is static right now as the rest of the truck is still in work.

Re: Foundering flathead
 

Get some load on it. There are conditions that run great at idle and fail under load.

Re: Foundering flathead
 

Tinker, I guess we'll have to agree to disagree. With the cost of building a flathead what it is today, I'd probably go to great lengths to make sure that no damage would be done to a fresh engine.

Re: Foundering flathead
 

If the powervalve in the carburetor is old...it may be stiff as--- and not close giving you a rich condition...
It still don´t leak but carb runs rich all the time.
Put in a good powervalve and check timing with a strobelight to start with.

Re: Foundering flathead
 

What exhaust ? A blocked exhaut could result in low vacuum. Just another place to look that's easy .

Re: Foundering flathead
 

New exhaust, stainless pipe and straight mufflers, pretty loud.

Re: Foundering flathead
 

MOT, you mentioned that the timing is set "by ear" and that the loadamatic distributor is equipped with the Pertronix ignition. I am presuming that the vacuum connection between the port on the carb and the distributor is in place. You have not mentioned the idle speed, i.e., fast or slow or how the engine reacts when you "goose" the accelerator. Is there hesitation/stumble or a quick run-up? Have you measured the vacuum while rotating the distributor to advance/retard the timing? This will have an effect on the vacuum.
Richard

Re: Foundering flathead
 

I may have missed it but what port are you using for the vacuum gauge ?
What's your location , I'm in lake worth , fl. If your close I'll help !