Rant 1

Hello All,

More rantings from me about another problem. On automotive heads is any leakage past the valves acceptable? And if so how much?

(incredibly long boring story follows)

I bought a brand new set of Edelbrock 6005 heads (come complete for hydraulic roller) and installed them first time round on the FE engine, after ironing out the new ignition system and the new carburetor the engine idled extremely rough (shaky) and the vacuum gauge on the intake was bouncing from roughly 2-12 (in other words it was pretty spastic).

I did a static compression check (leak down) and I found 9 of 16 valves leaking air, the two biggest offenders were the intakes on #1 and #2 cylinders, not only could I hear air but I could feel it in my ear from the intake port.

So I boxed the heads up and sent them back to Edelbrock, where upon they tested them and found nothing wrong. (very big sigh)

Now I tested these heads without the rockers even bolted on, so there was no question of lifter loading the valves for whatever reason. They told me they test them with a vacuum test and it meets Fords test -blagh blaugh blaugh.

I asked how much leakage is acceptable past intake valves, of which the only answer I received is there is no such thing as a perfect seal. (another big sigh). I then told him in performing the leak down test on small piston powered air G.A. aircraft any audible leaking past the valves on a hot engine is a failure and if it can't be stopped by lightly tapping the valve (carbon deposit) then it needs a valve job or a new cylinder. Of which I was told I wasn't going to get that kind of quality in the automotive world......

huh....

This is the first time I've bought new cylinder heads for an automotive engine so now I'm wondering is he correct or did it just get deep in here.

So the heads shipped back today and I thought I'd pop the valves out and see if maybe a good lapping would seal the brand new heads up.

I just finished that and bolted the one head back on the block and did the static compression (leakage) test once again and it's an improvement. All the exhaust valves are quiet now but I still have 3 intake valves leaking. I can hear them but at least I can't feel them and this is the head where the two worst offenders lie.

An interesting note on the quality of Edelbrocks heads. Here's some pics, as they are worth many many words.

So this is the intake valve with 30-40 minutes of run time. You can see the actual contact area is not the entire face of the valve just a small hair or two worth of actual contact area..... no wonder why these things leak.

After lapping, now most of the area is contacting and it's better but still leaky.

For those wondering about the leakdown numbers, using a leak down tester with a 0.078 orifice, the leakdown is 80/80. Which is what I would expect from a fresh rebuild with gapless top rings. Actually there is more noise coming from the intake valves than coming from gapless rings with 80 psi.

My instinct tells me I should unbolt the head and take that one and the other one down to my machinist and have him fix the valve seat interface, pretty much a valve job without the fuss of guide work.

Rant 2

Everything that the tech manager at Edelbrock was telling me was going against my better judgement. I'd been mulling it over earlier this evening and the heads are boxed up once again and I'll run them down to my local machinist and have him see if he can reface the valves and seats, hopefully there's enough material to do a clean pass without needing to replace the valves and seats, which are brand new.

It's a shame Edelbrock will not fix their brand new heads. These are aluminum FE heads, stainless steel valves and seat inserts.

Boy oh boy I swear this 390 out of the '66 LTD is just jinxed.

Rant 3

I hope you didn't infer from my waffling on that it's the cars fault, I meant in general this engine is jinxed. I just stated it's the '66 LTD engine because I'm also working on the '68 LTD and one other '66 galaxie, so it helps to keep things straight, otherwise when I whinge about a 390 my friends say, which damn car are you working on now .

The problem really lies in the aftermarket. Had this been a stock, albeit sad rebuild, I'm sure it would have been doddle. Bloody hell I bet I could grab the old heads off the shelf, tank, walnut blast and just lap the original valves to the old seats, install new stem seals and they'd probably be just fine. The engine never smoked when I started it in original trim and idled smoothly even with a broken compression ring on #1.

But back to the heads, the heads I bought are 60065. http://www.edelbrock.com/automotive/mc/cylinder-heads/ford/performer-rpm-fe.shtml

Everything about these points to just being a streetable aluminum cobra jet head version of the original.

If it's one thing I am sure of I do have intake reversion at idle (bouncy vacuum 2-12 inches) and a shake like it has Tourettes syndrome. But being told that a perfect seal was not possible and I wouldn't get aircraft quality work in the automotive world by Edelbrock I wanted to keep an open mind just in case. After all Edelbrock has been around for quite some time.

Of course after this, I think I am done with them. Although I don't know if anyone else makes a reasonable dual plane aluminum intake manifold for the FE? Might be forced to concede to still buy those.

At least others are making cylinder heads for FE. I'll be investigating those for the other 390's.

Hopefully the machinist can just cut the intake valves and seats on these and save them.

Rant 3

I do not have the specs from Edelbrock on guide clearance. They are tight though, tighter than an aircraft engine. Of course most aircraft engines are air cooled only so running a head at 400 degrees is normal. Running a liquid cooled head at 400 degrees would be a quick death, mostly because at 400 degrees there would be no liquid left to cool.

There's a possibility about leaking past the seat to head interface. It's definitely a possibility. I'll rule nothing out at this point. However I think it's more probable it's the seat cut or valve cut.

The reason I say this is because the exhaust valves look like the entire contact pattern is on the face, as it should be, especially as noted it needs virtually the entire face to transfer heat from the valve to the head. The head I lapped, after that all the exhaust valves on that head were totally silent. Not a peep. Now all the intake valves have the narrow band contact pattern.

In reading, intake valves shouldn't need the entire face for contact. In the second pic where I had left a little lapping compound on according to articles and books that's right for an intake valve to have about that much contact area regarding the face of the valve.

In pure speculation I think either seat cutter has a chip in it or was at the wrong angle (if adjustable) . It's possible the valves could have been cut on a wrong angle too I suppose.

Whatever the cause the cut was close and lapping helped, but it's far enough off that it won't cure it. I'm kind of done spending money on head and other gaskets as well as wasting time on them. Off to the machine shop they go.

Rant 4

I had an interesting trip into town, specifically at the machine shop. Soooooooooo I brought the heads down and they took the head that I had not done the lapping to (this was straight from Edelbrock testing) and they had a look at the valves, seats and such. Here's where I learned a thing or two. So even though online articles say mostly you want a band of contact area on the intake valve, my machinist says he's seen this singular concentric point of contact too that's on these intake valves.

OK, so it's 6 of one half dozen of the other sort of thing. But then they notice a kind of chattering on the intake valves and one of the exhaust valves was showing signs of galling from the guide being too tight. That'll need a slight reeming bit of work too. They reassemble the valves and do a vacuum check, on one section the pad fell off a few seconds after the pump was shut off, the other 3 three sections the pad stayed on for some time.

With that they took apart those two valves and I got to watch how they dress the grinding wheel for the angle needed for the seat and also how they grind the valve. They did both seats and both valves. The exhaust valve cleaned up evenly with the lightest of grind and so did its seat. Which is what I would expect from what I've seen. Well done Edelbrock they were bang on the cut for the exhaust. However the intake wasn't all that and a bag of chips. Took a bit of grinding there to get a concentric mating surface with a decent width.

As a result, they both need a valve job. It was nice they let me watch as they basically did one cylinders worth to find the problem. I received quite an education actually watching the whole process.

Since they are swamped, I'm sure it'll be a few days or early next week before I see them again. Which is fine have to order another new head gasket anyway. Plus I need to order one of those adjustable push rod measuring tools to determine the correct length of the new push rods I need to have made for the new lifters.

Agh the fun never ends....

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