strange leakdown effect

Have you already gone to more troublesome extremes to verify the flatness of the head and block surfaces? Is the problem on both sides or just 1?

 

thinking the block is warped or such than when mounted, if that's what more you did from the bench, that there is a slight twist to the seals allowing leakage...


but like I said, 'what do I know'

rik

 

not sure if you make kittay kry or put a smile on face

fun stuff for sure.

 

Hate to say it Brian but that is what you get for working on one of those.

 

Ohhhh, thats cold!!

Agreed.

 

Did you magnaflux the head? You could have a crack that opens up upon torquing the head bolts down. And what about those rings?

 

Geography doesn't seem to change the effects. No good deed goes unpunished...

Did you try leaking it down with the cams out? Bare head bolted to the block? I already know about most of the work done from prior conversations. Was it a central journal worked on or an end?

 

LOL!

 

Thankfully I am not at all familiar with those heads despite the fact I have a pair of them attached to a car in my own garage.

Please don't ask, it isn't my fault.

Anyway if it was me I would be curious to know what would happen if I pressureized one of the bad cylinders and backed off the head bolts a few lbs at a time. In other words, I wonder if something is getting distorted.


I have seen some real butchers rebuild heads like they were from a Massey Ferguson and cause all sorts of trouble.

By the way, does it have standard headgaskets?

I am working on a TR motor now that was butchered with O rings and soild copper gaskets. You couldnt torque it tight enough to keep it from leaking like the Exxon Valdez because the combination of the o rings and solid copper gaskets. The gaskets would not allow the rings to inbed far enough to get anything else to seal and if it got clamped down far enough the head would start to bow down its length distorting everything. Valves would lose their seal on the seats. The coolant jacket sealing was hopeless and it would even start leaking past the o rings because of the head distortion. It was all the creation of an idiot.

 

The head must be distorting when it is torqued down. Are you sure that it is leaking as bad as you say it is, maybe check it with another gauge? You could just run the motor and let the valves seat themselves.

I have never seen an engine builder check leakage or compression on a new engine that hasn't been run, so slight leakage may be more common than we know.

How flat are the head and deck surfaces? We had a horror story motor with a reproduction block and heads. When you torqued the heads down, the crank would bind up. We had to line bore the block with head torque plates on it.

If you wanted to go crazy, you could install the head on the block with no valve springs and the valves in place with lapping compound on the faces, and use a hand cranked drill, to reverse lap them by chucking the valve stems in the drill.

 

I do it on every motor, first with the heads off, then with them on.

If the rings leak more than 3% or so it has a problem. If the valves show ANY measurable leakage they are NFG.

We just did it today on an F40 motor going together and the worst cylinders were 2%. Good quality modern parts and machine work should be able to do that.

 

I figured you for something more like this.
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Thats cool but mine would be rattle can flat black with a skull and cross bones on the hood.

Oh and de-bling the wheels.

 

Dont be dissing the Old Ferguson now.....

Mine has the hot rod over bore kit! I can out pull any Ford N in the valley.... I have been in the country far too long!

One of the few things I own that is older than me and still works.....hmmm, not sure that is a good thing!

 

Typical.


"It'll wear in"


Right Tony. Do it to your own car.

 

Well http://www.cometic.com/custom.aspx these guys will make you a custom MLS gasket. These are all I use now and they have been fantastic. The last ones the owner of the car bought and cometic had the pattern but they still had to be custom made as they were for a special overbore NSX application and I swear they were under 200 bucks. They are worth a look and man do they work nice.

 

I would look hard at my leak down equip.
Is your pressure test of the heads using the same equip.....pressurizing thru the plug threads?
Do you hear the leak or just "see" it on the gage?
Because it is in a lot of places...want to try soap and water..looking for bubbles?
Would be great to find the leak was at the sparkplug holes

Good luck

Dave Bentley

PS hard to magnaflux aluminum!!