At What Point Is A Valve Job Necessary?

[hoopty5.0]

Unknown mileage on a set of 15-20 year-old Explorer heads and we're debating whether or not to re-cut the valves? I can't even believe its even in question? A good 3-angle valve job is worth it for piece of mind, if nothing else....the added performance is just a bonus.

There are area's you can afford to skimp on and area's you can't. Considering how much cost and effort is involved in removing and repairing/replacing a set of heads, skimping on the valve train is not an area I'd chose to tighten the purse strings on.

Brian, I've been wondering if I should come up with a witty retort to your comment. I've decided against it. Instead, I'll ask the question again, but preface it with a statement.

- Outside of just getting a valve job because it's just a smart thing to do, what physical evidence would you find that would obviously point to you needing a valve job?

Since asking the question, I've learned that there are ways to test for seating and ways to lap the valves in a pinch, should that be your only option in a hypothetical world.

Anything else that should be added?

 

[Gearbanger 101]

Brian, I've been wondering if I should come up with a witty retort to your comment. I've decided against it. Instead, I'll ask the question again, but preface it with a statement.

- Outside of just getting a valve job because it's just a smart thing to do, what physical evidence would you find that would obviously point to you needing a valve job?

Since asking the question, I've learned that there are ways to test for seating and ways to lap the valves in a pinch, should that be your only option in a hypothetical world.

Anything else that should be added?

There was no smart assed intent at all with my reply.

There's more to a valve job than just providing a good seal. The factory valve job on the Explorer heads is very basic and most likely little more than a simple 2-angle grind, with wide cut seats and faces. It's purpose is little more than to provide a leak free seal between the valve and the valve seat and a durable, long service life. A good 3-angle grind (or even 4 or 5-angle if you really want to get fancy) with narrower cuts and shallower angles can greatly improve cfm and velocity and low and mid lift levels and quite frankly should be mandatory for any performance engine.

Also, It's a good bet that if the heads have been sitting in that yard a while, or have been on an engine that has spent the majority of it's life driving short distances without reaching optimum temperatures, they've got a fair amount of pitting around the valve face/seats that should be ground out.

As noted by members previous, if there's any guide wear what so ever, having them replaced and the seats recut will be mandatory.

So while you "could" get away with not having them cut if the guides were in good shape and there was minimal pitting on the faces, I still wouldn't recommend it. You'll not only be leaving some performance on the table (on a set of heads that are only worth about 25hp to start with), but you've now spent $250+ (and presumably an entire afternoon) new valve seals, springs, gaskets, sealant, fluids, etc....to bolt on a set of heads with questionable valvetrain that without a doubt has got more miles behind it, than in has ahead of it.

How bad would it suck a year or so from now to pull your hair out chasing down a rough idle and reduction in performance, only to find out it's stemming from a valve train issues that should have been addressed before the heads went on?

 

[hoopty5.0]

Understood, that makes a lot more sense.

 

[Boosted92LX]

You know with all the talk around here of just tossing a junkyard exploder motor in your Mustang, I'm surprised at the negative responses to diy valve checks/lapping here..The arguement could be made that any explorer motor you put in your car most likely has way more miles behind it than ahead of it..Even though I'm in agreement that when an engine is apart, EVERYTHING feasible that can be reconditioned should be. I however, have been on both sides of the fence concerning having/not having money to go all out. This is why I can say I've pretty much done it all, concerning budget fixes. It is what it is, you have the money to do what you have the money to do...

One thing I can give @Gearbanger 101 is that I didn't know the cfm gains that come with a performance valve job.. I was under the impression they were geared more towards providing a better seal as opposed to flow increase. In my book, that definitely makes waiting for a little more money to do it right. Good stuff Brian.


Here is some supporting data:

John Maher Racing » The importance of the 3 angle valve job

 

[hoopty5.0]

Yeah the DIY porting website tests different angles and has a great low/mid range gain

 

[Gearbanger 101]

Nice find @Boosted92LX I've got a few articles like that collected over the years, still in book and magazine form lol. One thing I didn't notice stated in that article above, is that many race shops will also cut the seat and the valve at slightly different angles to promote sealing and performance gains.

For instance, where the contact face of the valve itself may be cut at 45-degree's, the seat may be cut at 45 1/2, or even 46 degrees to move the contact area to the outside edge of the cut. This will physically increase the diameter of the contact area of the valve and promote more airflow. It will also slightly narrow the contact band width which helps seat the valve for an improved seal.

These more modern shops have it easy. I used to do mine with a 40-year old valve grinding machine, individual stones (which I had to manually dress), while using a micrometer, a digital vernier calliper and a jar of blue machinists dye to take my measurements back in the day. We used to cut the valve and seat faces at different widths too. You could get away with narrower cuts on the intake side, but had to be mindful of the exhaust side to prevent burning a valve. I sometimes even got really fancy and used to back cut the valves on the lathe. I've spent nearly a full day, just on a valve job in the past. My eyes used to feel like I had been watching TV in the dark all night after it was done.

Now with carbide cutters and computer aided programs being all the range, its all done in one fail swoop and is as consistent as it gets.