CarTalk.com Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

Concepts: What did a "valve job" entail? Valve tapping?

  1. Back in the 1980s and prior, with cams that were underneath the cylinder, what did a valve job mean?
    What exactly went wrong?

  2. Also, what exactly was “valve tapping”? I had a 1965 Mustang 289 that used to have a slight valve tap.

  3. When someone does a valve job today, how is it different?
    I see “top end cleaning” on my service records from the prev. owner.\

  4. Do all modern cars have overhead cams?
    Or do some still use rocker arms and push rods…

A valve job meant decarboning and refinishing the portion of the valves that seats (seals) against the port openings, and resurfacing the openings. If the valves were burned or damaged, they were replaced.
It also meant checking the health of the springs (they get weak over time and can be tested for length and strength), replacing the valve stem seals, and cleaning and inspecting and replacing as necessary the other parts such as lifters, rockers, and even the bushings on the rocker arm shafts.

In addition, the head needed to be removed to do a valve job, so the head itself was cleaned and checked for flatness and damage, and machined if necessary. Typically, carbon buildup was mechanically cleaned from the piston tops if necessary.

And of course the headgasket was replaced upon reinstallation. And the valvelash was readjusted.

Valve tapping means the valve lash needs adjustment. The valve lash is the “free play” in the chain of parts from the cam lobe to the valve.

Today a valve job on an engine with the cam in the block would be the same. On an overhead cm engine, it would include checking the camshaft as well as the components in the system that drives the camshaft, whether they’re belt or chain. Since this string of components also has to be disassembled to get the head off, the front of the engine has to come apart. Everything there gets checked as well.

Some still use cams in the blocks.

Guys, did I miss anything?

Valve jobs were needed to remove carbon and deposits on the valve and heads that kept the valves from sealing properly. Valve jobs became rare when lead was removed from gasoline. Without lead the valves and valve seats had to be hardened to handle the load, lead did a few things one of them was a “lubricant” for the valves. Without lead in the gas car makers had to use harder and different materials to preserve valve function. Essentially, valve jobs of the past just don’t happen anymore.

A valve tap is usually a valve lifter that isn’t holding oil properly and that makes for a metal on metal sound, that tap. Lifters are basically a “buffer” that traps oil in a way to cushion areas so metal doesn’t contact metal. These lifters are fine, but reduce the valves ability to handle high rpm’s. Therefore most race engines use solid valves without lifters that need adjusting periodically. Valve springs also enter into valve function, Ducati motorcycle engines use cams to both open and close valves to allow even more precise valve action.

A valve job meant, pulling the head(s) and cleaning all carbon and debris from the valve seats on the heads. Valves could be cleaned but putting new valves into the head was easier and more effective, so new valves were the norm. Any parts showing wear were replaced, rocker arms etc. The bottom end of the motor was not disturbed (the oil pan stayed on) and the heads were put back on and all was put back together. Cars weren’t driven as many miles per year in those days and valve jobs were pretty standard practice about every 30K miles. A car without a valve job at 50K plus miles was rare. Again all this was back in the days when lead was in all the gas.

The camshaft location is pretty much irrelevant because the valve job itself on a modern era engine is performed the same way as it would be on an older engine.

The only thing I would add to Mountainbike’s comments is that checking the valve stem to valve guide clearance should also be a part of the job.

Regarding Mountainbike’s comment about valve spring tension I have a short story about how critical that process can be.
A Chevy pickup was in the shop and the engine in this truck was a remanufactured unit that had just been installed. The truck ran great except for one problem; it idled a bit rough. The basics such as plugs, wires, and so on were all fine along with compression which was at about 180-185 PSI on each cylinder.

Further examination with a vacuum gauge showed that there was a potential problem in the valve train. Upon removal of the valve covers I discovered that one cylinder on each bank had a weak valve spring. This was easily detectable by prying down on the rocker arm. I aired the cylinders up, removed the rockers, and after depressing the spring with a special tool, removed the valve collars and changed the springs. That fixed it right up and the idle was smooth as silk.
Apparently the reman facility had allowed this one to skate through. :frowning:

Ans. to question #3 - top end cleaning today is joke, an additive is added to the gas. It is nothing really.

Ans. to #4 - most motors use overhead cams, but some still use push rods. Is there a difference? Not really, push rod engines rarely have problems due to the push rod set up. They tend not to rev as high as overhead cams. But, most driver’s freak out if they push their motor to 3,500 rpm so the difference is small outside of racing applications. Push rod engines can be very compact. Overhead cams take up a lot of space and make the heads bigger. This is just an issue for engine designers. In the real world of normal driving either set up works fine.

Hey Used BMW, are you looking for a career change or looking for the meaning of life and starting with the basics?

Work smarter, not harder. Google “valve job” and “valve tapping”.

OK4450, I believe the cam location is relevant only because removing the head on an overhead cam engine requires pulling the front apart and removing the chain and/or belt. And knowing how coscienscious you are I know you’d check the chain, sprockets, a guides for wear and if it were a belt the tensioner also.

I’m guessing that you’d also check the cam lobes and for play in the shaft and matbe even the sleeve bearings.

None of that counts in an engine with the cam in th eblock, but it’ll add tto the dent in the wallet for an overhead cam valvejob.

“Valve Jobs” are rare today because of;

Lower compression engines put less stress on valves.
“Smog” valve timing keeps valves on their seats longer, cooling them better.
Big advancements in metallurgy provide much better valves (and valve seats)
Fine mixture control eliminates “lean burn” which is a valve killer…

Mountainbike, I totally agree with you and my comment about the in-block cams and OHC engines was only to mean that when performing the actual valve job itself (the physical grinding and fitting of the valves and seats) the process is the same but all of the peripherals are different.

Until about 15 years ago I used to do all of my own cylinder head valve work and finally just gave it up. It’s kind of labor intensive to do it right and it’s cheaper and easier to send them off to the auto machine shop where they do it for 5 dollars a hole.

I put all of my valve grinding equipment up on eBay because it was just rotting away and I was a bit stunned to find that the guy who bought it was from Canada and wanted to pick it up in person. He was a long haul truck driver going back and forth from Texas to Alberta so he swung by one evening and we wrestled all of it into the back of his trailer. He was going to use the equipment for some engine project work on hobby cars and so on.

You’re a good man, my friend. And a great mentor. I’ll be the first to admit that I’ve learned a great deal from you. And I’ll be forever grateful.

I’m in agreement with Caddyman that valve jobs are not as prevalent as they used to be and unleaded gas has a lot to do with that. The reason I got into it was because the bulk of what I worked with are solid lifter engines and valve sealing problems due to tight valve lash or mushroomed valve stems and noise was not that rare a thing to occur; something not very common on hydraulic lifter motors.

Better the money in my pocket rather than the machine shop was the way I looked at it but doing a valve job is a bit tedious and eventually it just interfered too much with everything else.

For a while there, this area was pretty skimpy as far as machine shops go. One was reputable and after botching a few things (who turns a crank .010/.007 and .020/.002?) I avoided them like the plague. The other was part of a national auto parts chain and after the franchise manager apparently decided to loot the corporate bank for a 100 grand that was the end of the machine shop and parts house.
The current one I use is very good and downright reasonable on prices; plus they have a pretty nifty blown Corvette down there I like to drool over and which churns out about 1500 or so horsepower. :slight_smile:

When the lead was removed from gas, circa 1975, engines had to use hardened valve seats, or else there was accelerated seat wear. The valves themselves may have needed to have been hardened as well. The lead acted as a cushion on the valve seat every time the valve closed.

However, the lead did result in a dirtier combustion chamber over time. Today’s combustion chambers are definitely cleaner.

I’ve never understood how the lack of lead results in longer valve life, though I am interested in hearing feedback on it.

My opinion is that valve life is improved as compared to the old leaded gas engines because most valve problems start out as something microscopic in nature. Lead deposits may not allow the valve to seal completely and this in turn leads to microscopic pitting on the valve face and seat. While there may not be any obvious symptoms at first, over time hot gas turns the pitting into a microscopic squiggly trail and then into full blown leakage.

Examination of some valve faces and seats with a magnifying glass will often reveal that pitting or trail and those symptoms can also be created by tight valve lash, too much advance in ignition timing (when applicable), and coolant leakage into the combustion chambers.

Many older engines will run for a long time on unleaded but it varies by era, engine type, if the valve seats are integral with the head, and so on.
Many older engine blocks had a high nickel content in the cast iron and will stand up to unleaded just fine.

I too agree with Caddyman. I cannot recall of a valve job being done on any engine manufactured within the last 20 years except perhaps in a case of a damaged camshaft or such.

For that matter, ring jobs are no longer common either. Engines have come a long way.

@Caddyman

Caddyman, I agree with parts of your April 26 posting about valve jobs being rare these days. for example, I certainly agree with you on big advancements in metallurgy, that much better quality in metals is now possible; I also agree that fine mixture control, courtesy of electronic sequential fuel injection and valve timing, to eliminate “lean burn”. As far as “smog timing” that kinda sounds like 1980s technology to me. And I have to respectfully disagree with you that today’s engines have lower compression; that is simply not true. Today’s modern electronic engines have considerably higher compression ratios than engines had in the 1980s; From the late 1970s thru at least the early 1990s, most engines had compression ratios ranging from 8:1 to 8.5:1; from the late 1990s up to now, most engines have at least a 9.5:1 compression ratio, and some engines even have a 10:1 ratio, with some slightly above that. Before the late 1990s, 9.5-to-1 and 10-to-1 compression ratios hadn’t been heard of since the late 1960s Muscle Car Era; in the early 1970s about the highest compression ratio available on some of the period’s cars was 9-to-1, dropping to 8:1-8.5:1 later that decade. Automotive engines these days can run higher compression ratios without “knocking” or “pinging” due to vast improvements in fuel flow control and ignition control; ignition and fuel delivery are SO MUCH more precise than ever before.

Just my humble opinion, but valve problems on unleaded gasoline engines might be considered to be less prevalent as compared to the old days but it’s not what I would consider a rare thing.

I just tore down a Ford V-8 (5.0 with hydraulic lifters) recently and it was losing compression across the board with most cylinders in the 120-130 PSI range but 2 of them were in the 60-80 range. Testing showed there were valve problems on those 2 cylinders. Once the heads were removed and the combustion chambers were filled with gasoline the intake valves on both cylinders would leak almost all of that gas out inside of 5 minutes. This was due to oil consumption from the valve seals and piston rings which was caking up the valve seat area and not allowing them to seal properly. A few others showed some leakage but it was not as severe as the 2 I mentioned.
This engine has about 100k miles on it and it should be pointed out that it looked to be rode hard and put away wet as the saying goes. That’s just a recent example and not indicative of the majority.