Ok, so I have one of the WORST cases of the infamous recessed exhaust valve seats on my ‘00 2.5L. I never experienced any of the intermittent dying after hard acceleration, rough idle for a few seconds when coming to a stop, or random stalling. I just experienced intermittent misfiring at idle that progressed into an almost completely dead cylinder, or so I thought it was only ONE cylinder. I actually had TWO dead cylinders - 1 and 4. Since they were companion cylinders, I couldn’t tell that I had a second cylinder dying as well. Even 2 and 3 had slightly recessed seats so even they weren’t making the power they should have been making. I was basically driving a 2 cylinder 1.25L Ranger which is why it had NO power until I gave it enough throttle and RPM to cause the compression event to happen quick enough that not all of the compression was lost.

Well, I ended up getting lucky and getting a good head off a ‘97 2.3L. I’ve checked the head over and everything seems to be good. I did notice that it looks like cylinders 1 and 2 were not firing on the junkyard truck but the exhaust side plugs are completely worn out and the intake side plugs are iffy. I’m thinking it had a dead coil on the iffy plugs and bad plugs on 1 and 2 on the hood coil. There are no cracks in the head, the valves and lifters all are good. I’ve measured the seat depth on everything and it all looks to be perfect. Either that or it had a bad head gasket between 1 and 2. I’ve checked the head for warping and it’s straight. But anyway, on to the pictures.

Here is one of the combustion chambers of the new head. This is the way everything SHOULD look. Obviously the exhaust valve in every picture is on the left.



Now on to my original head. Pictures are ordered in the order of the cylinders 1-4.







As you can see, ALL FOUR of my exhaust valves were recessed to some degree, cylinder 1 being BY FAR the worst followed by cylinder 4, then 2, and then 3 being the least recessed.

When I measured the lifter height with my digital caliper in mm down to the 10th of a mm measured between the top of the lifter body and the bottom of the rocker arm, the lowest was 15.4mm and the highest was 15.7mm. After that’s calculated out, that’s only 0.0118” deviation from the highest to lowest and that translates to 0.0088” (yes, I am meaning to put that in 10,000th’s of an inch rather than 1,000th’s) at the valve, WELL within manufacturing tolerances. When I measured in 100th’s of an inch rather than 10th’s of mm, it came out to 0.60” for the lowest and 0.61” for the highest which could be even closer than that because of rounding since my caliper only does 100th’s rather than 1,000th’s. That’s why I decided to do mm. Anyway, the OLD head was at 0.42” for cylinder 1 and 0.52” for cylinder 2. I stopped there. That’s a 10th of an inch at the lifter from the worst to the second best already, not to mention how far it was off from a good head! Obviously all of these measurements were done with the lifters bled down. Cylinder 1 was so bad that it would not even show 1psi on a compression test. Cylinder 4 would take a couple seconds after fire for the lifter to pump up before it would start misfiring, and 2 & 3 seemed to run at least ok. This can all be confirmed with the carbon on cylinders 1 and 4 with 2 and 3 being clean. Here is a picture of that.




You can see how badly carboned up cylinders 1 and 4 are. They weren’t making any power at all. I was lucky to be making 60-70hp at the flywheel on this head.

I did have my stock 7.5” rear end with a 4.10:1 gear rot out on me as well and started leaking gear oil. Ford told me the truck had a 3.55:1 stock. Either someone changed it or Ford’s information is inaccurate. Well, I swapped in an 8.8” from a 2001 4.0L 4x4, took the blocks out, and used my original U-bolts. That was a straight forward swap. Everything bolted up with no issue. Well, that IS a 3.55:1 gear. The truck could barely even get off the line from a stop with the head like that and 3.55’s. So, on to swapping the head I went to continue to fix the major issues with the truck. I also have bad leaf spring and shackle bushings but everything is seized so I’m going to have to change the hangers and the leaf springs. I tried to change the bushings and shackles but that wasn’t going to happen. I’m going to have to cut the rivets out and install new hangers and springs in the rear. I’ll probably lower the truck and flip the axle at that time. I just need my truck back up so I can start working again. I’m a mobile mechanic and it was quite embarrassing to show up to a job with a truck that ran so poorly. When the axle started leaking and I HAD to put the truck down, that’s when I decided to go ahead and replace the head as well while it was down.

But anyway, back on topic, I don’t know how many of you have had this recessed seat issue, what year your trucks are, or what cylinders you had do this on you, but there’s my story with them along with pictures so you can possibly identify it if you’re having similar issues. You CAN diagnose it WITHOUT pulling the head. The first trick is the dollar bill on the tail pipe test. If the dollar bill gets sucked up to the pipe, you probably have at least one recessed seat. You can check it by pulling the valve cover when the lifters have bled down and checking the height of the lifter. When the valve seat recesses, it compresses the lifter more than other valves because the stem is now sticking up higher and therefore pushes down on the lifter more. Due to the lack of seat pressure since the installed height of the valve spring is now higher, it doesn’t have enough pressure to compress the lifter once it has pumped up when the engine is running. That causes the oil pressure to push the lifter tip up and hold the valve off its seat roughly where the spring has the tension it had at seat pressure when the seat was in the correct place. So, if you measure it there and you see a lifter more compressed that the rest, you definitely have a recessed seat on that valve.

Mine was bad enough I could see it with the naked eye. I could see both the lifter compressed more and I could also see more distance between the coils of the valve spring plus I could see the stem sitting higher. Little did I know I was comparing it to other valves that were also recessed, just not as much! That means that my worst valve has compressed the lifter 0.180” more than it should which translates to a seat being about 0.135”…OVER AN EIGHTH OF AN INCH!

I’d like to hear everyone else’s story that has had this issue. I’m feeling alone here since mine has gone way further than other cases I know. And I also posted this to help others figure out what is going on with their truck if they are having similar issues.

I might have the old head overhauled, ported/polished, larger valves installed, milled to increase compression, and have a larger cam grind done. I don’t want to go too crazy with the cambecause I do still haul my tools and things around so I don’t want to lose any torque, but I would like to make more top end power so it keeps up with traffic better. By no means am I trying to build a race truck out of my work truck. I’d just like to see if I can get 150-180hp out of it without throwing a turbo on it! Does anyone else have any experience with the 2.5L and having some head work done?

 

You have a Lima engine, they were first used in a 1974 Pinto so also nick named Pinto engine
They came in 2.0l, 2.3l, and 2.5l(only 1998-2001), all SOHC

2.5l is the stroked version of 2.3l Lima, so used the same head, block and pistons, but different crank and connecting rods

Don't recall any common valve issues with these engines, its an engine so there will be valve issues, lol, just don't recall common issues

As for changes to make for better power look at 2.3l Lima changes as they were used in Mustangs so way more info in those forums vs Ranger forums
Web page here: https://www.route66hotrodhigh.com/2300.html
Never had a 2.3l or 2.5l Lima so up to you on what to make of any changes

2000 2.5l SOHC is listed at 119hp, not sure you can push it to 150hp just with cam/valve work, but some extra power is better than none, lol

 

This is DEFINITELY a common issue with at least the dual plug heads. Google search “Ford Ranger Recessed Valve Seats” and you will find a TON of instances. Most common symptoms are stalling after heavy acceleration or rough idle when coming to a stop for a few seconds, then immediately recovering. Mine was an EXTREME case of it. The 3.0L Vulcan V6’s had the same issue. Not sure if it’s caused by excessive spring pressure, lifters that aren’t holding pressure so the valve gets slammed against the seat, or if there was a manufacturing problem where something was a few 10,000ths of an inch off so the press clearance wasn’t quite as tight as it should have been. But it’s MOST DEFINITELY a common issue with these engines, just doesn’t get much publicity. A lot of it is because people never discover the true cause of their symptoms and they end up getting rid of the truck before they figure it out. Most people replace sensors, spark plugs/wires, and PCM’s with no avail. They just never get to the bottom of it because, in MOST cases, it does NOT show up on a compression test. By the time you pull plugs and do the test, the lifters have bled down and it will make compression. Only in the few extreme cases like mine does it cause a consistent loss of compression. Really the only two ways to actually confirm it is with the dollar bill test on the tailpipe and at least pulling the valve cover and measuring the valve spring installed height.

As for more power, I am considering the SVO turbo set up with a small turbo with a very low exhaust A/R to get it to spool very quickly and make torque down low. The Ecoboost engines are fully spooled at like 1,200RPM or something stupid low like that so they still make good pulling torque. They are designed to make full boost before you hit the stall RPM of the torque converter so you’re not sitting there with no torque coming off the line while towing a heavy trailer. I won’t be able to get boost THAT quickly but I might be able to get 6-8psi by 2,000RPM. Even if I can get 4-5psi at 1,800RPM where the stock converter stall RPM is, it will help with me hauling some things around and maybe towing a small trailer.

 

Didn't see alot and it was odd that I didn't see much in 2.3l Mustangs mostly Rangers???, yes 2004-2006 Ranger 3.0ls did have known issue with exhaust valve seats, was a TSB for it
But regardless glad you found the issue, not sure on the cause, it is possible it was a factory part or installation error

If you think it is a common issue then I wouldn't get a new head, I would machine the one you have so its done right

 

I did get a used head out of the junkyard. I have thoroughly checked it over and it is definitely a good head. If you look at my pictures, on the old head you can see the seam between the seat and the head casting. On the new head, you cannot see that seam on ANY of the cylinders, even in the slightest bit. They are all perfectly flush. You can see the seam on my old head on every single exhaust valve. I’m actually surprised that truck ran at all. I simply cannot believe it still fired up and ran for me every day without failing me. It literally only stalled on me twice and that was when I was turning very sharply and had the steering against the lock. I think maybe once it stalled on me at a traffic light. That is a huge testament to the reliability of these trucks. Even when they run terrible, they still run for you! On the new head I also installed all new lifters and valve stem oil seals. I pulled all of the valves out during the procedure and I looked them over. There was some slight pitting on the seating surface of the exhaust valves, but nothing to cause any major leakage. The intake valves were all perfect. There was only very slight movement of the stems in the guides which you do need some movement so a bit of oil can get in there. It can’t be completely tight or it won’t lubricate at all and it’ll wear out the guide, so that all checked out good. I thoroughly cleaned the deck of the head and looked for any cracks anywhere and didn’t find anything. The truck it came out of was wrecked on the left front which pushed everything back and to the right so that’s why it was in the junkyard. I could tell it was a recent accident because the portions where the paint had cracked and flaked off weren’t even rusted yet. Probably totaled out by insurance which means it was a running truck at the time of the accident. Those are usually good signs when it comes to engine and driveline parts. I would never buy an engine or driveline part from a junked vehicle that was NOT wrecked. At that point you just don’t know what failed to bring it to the junkyard.

Well, I’ll keep everyone posted on how things work out once I get this head installed. Today I was running other errands and I did the work to the replacement head. I’m probably still going to be up a bit so I’m going to get the new head at least bolted to the block and get the new timing belt installed. Maybe I can get a bit further if I’m feeling froggy.

 

I have the same valve seat problem after pulling the head 98 2.5 and the head was a rebuilt unit from the PO... after calling the machine shop i was told they get these heads all the time ... so i will be sending my head in for new valve seats, thats if its not cracked..