Technical The world's worst valve job?

In the process of prepping for Eagle Field, I attempted a quick tune up on my tow vehicle; a mild custom '55 F-100 with a 302/C4. I found two dead cylinders, very low compression apparently due to burned exhaust valves. So off came the heads. I couldn't believe my eyes.... It looks like they put 260 exhaust valves (1.39" valves) in 302 heads (1.45"). They are sunk an average of .090".
I had a spare set of heads in stock so I disassembled them for inspection, lapped the valves and stuck them on. I also took the opportunity to upgrade from the crappy Ford manifolds to a nice set of stainless shorty headers. So far so good, I got my good old workhorse back.
Has anyone else ever pulled apart an engine, trans or rear end to find someone else's finest work? Have pictures?

 

Wow

 

It's hard to be sure until you take the valves out and look, but I'd be inclined to blame the seats, instead of the valves. If you run unleaded fuel in heads that were built in the days of leaded gas, the valves will recess into the seats, just like what you see in these photos. If you want to run unleaded fuel, you need to install hardened valve seats.

 

At first, I thought about the valve seats not being hardened too, but those valves are really sunk in there quite a ways..

 

Im gonna agree with cowboy ted. It looks like recessed seats.

 

Wow, I've never seen that before.
I put bb Chevy rocker arm studs in a pair of Ford 429 cylinder heads once, lost 10 hp.

 

I've seen the same on a set of 390 heads. Ran on unleaded too long hammers the seats to death.

 

I have never seen the results of unleaded gas on old seats before but I find it hard to believe that they would all recess so evenly. Who knows. Funny thing is, it actually ran OK except for at idle, it shook a bunch - like a booger in the carb, that's why I started looking at the tune up. Doing the old "pull the plug wires one-at-a-time and see what happens" revealed two dead holes. It was all down hill from there.
The new heads have hardened seats, 3 angle valve job and good stem seals. With the exception of the new headers, this was a "no dollar" fix - luckily, I had everything in stock to fix it - even the engine paint.
Anyone else find interesting stuff?

 

Oh yeah on a 'rebuilt' engine from Shade Tree, I found brass? soft valve seats on one head of a SBC

 

OK, Cowboy Ted hit the nail squarely on the head. I pulled some valves and they are the correct 1.43 diameter valves but it is pretty clear that they just cleanly hammered and abraded themselves into the iron. Amazing.
This engine came out of a buddy's Model A. He bought the car with low miles on the build and a complete build book with receipts. He seldom drove it before pulling the engine and installing a SBC. I bought the engine and installed it about five years ago when my other 302 developed an ominous knock. I haven't put on lots of miles but they were almost all towing as I used the truck to move all my junk from L.A. to NorCal. Probably 12-15K towing and highway miles and the seats look like this, yikes. I wouldn't believe it if I hadn't seen it with my own eyes.

 

Thats' interesting, I wonder if they were really brass or some strange alloy. sure doesn't seem like brass would be a material for a valve seat.
I had some BBC heads done once by a local machine shop. I took them apart to change to better valve springs before installing them and found that they had forgotten to grind the all of exhaust seats on one head.
Same shop returned my ground and polished SBC crank with only half of the journals polished. I found another machine shop......
I never take any one's work for granted any more - check and double check.

 

Naaaasty man what else can I say.

Got a story but no pics so I won't waste your time.

.

 

'Beaner, your stories are never a waste of time!
What amazes me about these old Ford heads is that the damned thing ran OK. Other than a crappy idle, it was perfectly drivable. It really didn't give any indication it was hurt that badly.
I was just wondering what kind of strange damage others have found when they tear down their running stuff.

 

Look on the bright side.....now you can install oversize exhaust valves in those heads.....

 

I had a "Harley" expert put the valves in the wrong holes on my old panhead in 1980.it gets worse, I didn't have access to a machine shop at the time and was upgrading to bigger intakes. I brought the stripped down heads in with the valves stuck in the correct holes and he still got it wrong. So the exhaust valves would have been about 3/16 over size and the intakes were about 1/16 undersized. The heads became door stops.

I pulled a stock 305 down once that all the valves were the same size, all were exhaust valves. I still chuckle about it we just put oversized intakes in the intake holes and called it good enough. They must have been Monday morning heads.LOL

 

Valves recessing into the seats is more common on engines that are worked "hard". Like towing/hauling heavy loads, or sustained high speeds. Good you had the repair parts on hand.
-Dave

 

They may have been door stops in 1980, but they would have still brought good money back in the nineties when we were trying to find early stuff to build "traditional" choppers in L.A. Real Pan and Knuckle parts got real scarce.
I'm not surprised at anything I see when it comes to the "corporate & smog" motors they resorted to in the eighties. Those 301" Pontiacs had some dinky valves and ports too IIRC.

 

It pulled the trailer that hauled all my boat, cars, furniture, shop machines, hoist and my vast collection of useless junk over the infamous Grapevine from L.A. to NorCal. I guess it worked harder than it let on.

 

that explains it.

 

wow. Gotta say, I have seen some sunk exhaust valves, but I have NEVER seen them like THAT, thats like 1/8"!! I have heard that recession is worse on motors that see a lot of load, like towing, but WOW...

 

I"ve seen some like that.

 

I've seen them sunk like that before too. I guess that's why I guessed right!

I have a friend who has several running, driving "survivors." Model Ts, '26 Dodge Brothers, and a '39 Lincoln Limo. While he was sick for a couple years, I took on the duty of driving them all regularly. He studied the problems of unleaded fuel and valve recession, with an eye toward keeping his survivors all original, but still using them regularly. He's convinced that valves aren't likely to recess unless the engines are run hard, so his instructions were to use pump gas, but never accelerate hard and keep top speeds down while driving. I'm glad he healed up and is able to drive his own cars again, but I sure had a good time "exercising" his toys for a couple years!

 

I've seen heads with valve seat recession that bad and worse, all V8 Chevs from the early smog era, early - mid 70s. The same motors that had all the trouble with cam wear.

The worst was an engine run on propane. The valves were sunk in so far they barely opened.

 

I thought the "recession" was over? But seriously, I've not seen anything that bad either. Are you going to attempt to redo those heads for future use, or wait for the price of scrap to go up again? I am Butch/56sedandelivery.

 

they may be salvageable with inserts at least then you'll have one less thing to worry about

 

Can anyone explain what causes unleaded fuel to cause valve seats to sink? I've always wondered and never asked.

 

As I understand it , the lead in the fuel provided cooling of the valve seats..

dave

 

The lead acts as a lubricant on the valve face without

The lead acts as a lubricant on the valve face. Without it under heavy loads the valve will get hot enough to try to weld itself to the seat when closed the valve opens a very small amount of metal is pulled off the seat and is lost.

 

That's my understanding too.

If you look at the photos above, you'll notice that the valves that are most recessed are all exhaust valves, and they are lighter colored, a result of the excess heat burning off the black carbon deposits, leaving them looking white or clean. It's possible that the cylinders that are most recessed are also running leaner than the rest. Some induction systems result in one or more cylinders running lean, and lean running cylinders run hotter than richer ones.

It's an important reason why you should "read" your plugs periodically, to tell you whether you have one or more cylinders running too lean. If you do, you need to richen up your carbs, or that lean cylinder will fail first because of excess heat.

 

I never had the heads off it but it had been rebuilt in a time frame that made me believe they would have installed hardened seats during the rebuild - I guess not. I always thought that the stories about running unleaded without hard seats were overreaction - again, I guess not!
I've torn down some used up motors over the years and I've never seen that kind of recession, especially across the board, all of the exhaust valves were sunk. The worst was a little over .090".
I'm guessing the heads are salvageable but why bother, they are nothing special.
I spent the afternoon hooking the mufflers up to the new headers today and took it for a short drive - Yeay... my truck's back to it's old self again!