1950 Ford 8BA flathead leak Down Test

[Bustingear]

Having some blow by issues with my 1950 8BA flatty and would like some opinions, advice and recommendations from flathead pros on the test results. Notes at bottom.

TEST IN ATTACHED PDF
1950 Ford 8BA Flathead 239ci
Leak Down Dry & then Leak Down With Oil
Cylinder # PSI Leak % PSI Leak %
1 26 20 26 20
5 23 30 24 23
4 27 17 25 33
8 25 37 25 35
6 25 35 25 40
3 26 15 25 15
7 26 26 24 40
2 25 39 25 34
Compression Test Dry & Pressure Test With Oil
Cylinder # PSI PSI
1 115 95
5 115 95
4 118 95
8 100 80
6 100 95
3 100 90
7 118 90
2 99 95
* The Compression test dry and wet were done with two different gauges So there may be some inconsistency there.
First one ended up going bad so oil test is probably more reliable
* Leak down was done with same leak down gauges both wet and dry
* Gauge quality is cheap import type so reliability is a general question.
* In leak down case air was pushing out of oil fill tube and dipstick during all 8 cylinder tests
No bubbles in radiator fill cap, No air push from exhaust, No air from any cylinders while singles were being tested
No air pushing up out of carbs
While driving I have excessive oil blowby coming up out of oil fill tube and dipstick, along with pan gasket pan leakage

[Bustingear]

bump

[JSeery]

Are you sure yours numbers are in the correct order? On the Compression test, dry should be a lower number than wet.

[Bored&Stroked]

With the assumption that your leak-down gauges setup is accurate and that your engine has "normal" rings, the leak-down percentages are quite high. Heck, on the last column you have 5 cylinders over 30% and two over 40%. I'd expect to see percentages a lot closer to 10% than 20%+ . . . all the way to 40%.

Given that you're hearing air coming out of the breather, this also coincides with your blow-by concerns/observations.

I'd say your rings/cylinders are worn or not sealing well . . .

[Frank Miller]

Your valves appear to be tight. You have two choices if the motor is running well otherwise. Leave it alone until it gets worse or take it apart and put new rings in it. Of course upon disassembly inspection you may find yourself doing much more.

[51 MERC-CT]

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Originally Posted by Bustingear

Having some blow by issues with my 1950 8BA flatty and would like some opinions, advice and recommendations from flathead pros on the test results.

While driving I have excessive oil blowby coming up out of oil fill tube and dipstick, along with pan gasket pan leakage

Install a PCV valve/system and the symptoms will virtually disappear and it will help with the oil seepage also by placing the crankcase in a vacuum condition while running.

[Bustingear]

Originally Posted by JSeery

Are you sure yours numbers are in the correct order? On the Compression test, dry should be a lower number than wet.

In notes detailed two different gauges the first set i deem as faulty gauge

[Bustingear]

The engine was honed and reringed with new guides added about 200 miles ago and a pvc system was installed in the blowby tube outlet same time as rering and it helps only in a minor way. It is being routed to the old brake port in the manifold below the carb as i understand it should be.

[Bored&Stroked]

Originally Posted by Bustingear

The engine was honed and reringed with new guides added about 200 miles ago and a pvc system was installed in the blowby tube outlet same time as rering and it helps only in a minor way. It is being routed to the old brake port in the manifold below the carb as i understand it should be.

Then my guess is that the rings have not seated. Did you take it out and run it hard after the new ring job to break the rings in?

What shape were the bores actually in? How worn, how much taper and how much out of round? You maybe asking for the new rings to solve a problem they can't solve (bore condition).

I don't think I've found a flathead block yet that didn't actually need to be bored and have new pistons put in . . . but maybe that is just my luck (and I'm a bit of a perfectionist ).

[Ggmac]

You didnt use chrome rings , did you?

[40 Deluxe]

Originally Posted by Bustingear

The engine was honed and reringed with new guides added about 200 miles ago and a pvc system was installed in the blowby tube outlet same time as rering and it helps only in a minor way. It is being routed to the old brake port in the manifold below the carb as i understand it should be.

If you reused the old pistons, did you check the side play of the rings in their grooves? The top side of the top ring grooves wear the most, so a new ring will not seal properly. The grooves wear unevenly as well. If you still have the old rings, take a close look at the top sides of the top rings. You most likely will both see and feel the wear.

[Bustingear]

pretty sure from all indications its going to have to come back out for machine work