I did a leak down test on my engine because the car slowed up a bit with out explanation, about a tenth. No mis-fires or any thing obvious just slower . It is a 440 topped with trick flow 270 heads. What I found was cylinder #1 and #8 have 30-35% leak down #4 has 15%. The rest of them are less than 5%. The air is escaping passed the exhaust valve. Tried tapping the valve with mallet and and adding a shot of oil with no change. I'm surprised with this as the engine only has 75 runs on it. Has anyone seen an issue like this with the trick flow heads? I don't have the heads off the engine yet, that is going to be my project this weekend so I can get a close up inspection of what is actually going on with the valves.

Did you back off the rockers on those cylinders for the test ?

You said the car slowed down, so I suspect the leakage wasn’t present initially.

Until the heads are removed and inspected it’s all speculation, but my guess is the valves got tagged and are now tweaked.

Yes, I removed the rocker assemblies altogether.

Yes , you are correct there was no leakage when the engine was assembled

That is what I am suspecting too. But why only the three valves? If I remember There was .090" piston to valve clearance. I used the clay method of checking clearance.

Those valves might have gotten a little hang time and made light contact.

When my timing set came apart all the valves held water but when I pulled them 12 were bent. 4 survived. All the pistons had tiny eyebrows.


The tiny tolerances stacking up can make all the difference.

I’ve inspected a few TF heads that had pretty minimal guide clearance.
If yours are like that, it might have pinched the valve a bit and allowed contact.

At high rpm, it doesn’t take much contact at all to tweak a hot exhaust valve.

What rpm, and what valve spring?

You wouldn’t be the first person to get fooled by that.

Please expound on the issue - Thx

Engine assembler used clay, came up with .060” intake clearance.
Breaks new Ferrea 6000 intake valve in burnout box of first pass.
Post blow up inspection reveals all intake valves making hard contact with pistons

I mock everything back up and manually measure with checking springs, with lash set.
I get “zero” clearance.
He kept good notes during assembly. The notes showed .060 , checked with clay.

I only use clay to check for radial clearance in the pocket.

I watched this one a few weeks ago, and he goes over how the valve is not always where people think it is relative to the piston when it's near the top of the cylinder.

https://youtu.be/o_Oln_ik0vw?si=H-vxgkMQwL59kqsb

Did you check all 16 valves for piston to valve clearances and valve to block clearances with checking springs? I do

Then that guy was an idiot, he probably did it with a hydraulic lifter or something stupid like that.
I use both methods for different reasons and have run engines twice in the .050's(using checking springs) and we never hurt a thing. That being said I am not suggesting everyone go out and do it for the reasons above.

If the heads are off you should already know why and what happened. There should be contact marks and bent valves, next would be look at top of valves for x pattern wear for valve float, then stem clearance.

My point being .090 with clay would be fine(clay always shows more) ., but now that I read the post he says I think it was .090

And yes after typing this I can see where .060 with clay could be trouble. Takes me a second. Clay usually adds about .030 or more. (deflection in valvetrain).

If the rocker shafts are off put a straightedge across the valve stems to see if they are all the same height?

Greg how much did you pick up changing from the 240s to the 270s?

The car went from 10.7s to 10.4s and 124mph to 128mph with just the cylinder head change. I am quite happy with the results.

I got the heads off the engine and checked the valves and to my surprise the valves are not bent but the seats are deformed on the high leakage cylinders #1, 8, and 4. I can see light behind the valve. When checked with bluing dye there is a gap on the seat. I have no idea what could have caused this , I'm going to call trick flow tomorrow and see what they have to say.

Time to put that warranty to the test.