The last screenshot I took of it shows .805, it was acting normal. Again that’s a screenshot and not showing fluctuation .
Misfire madness
- Thread starter Frank4
- Start date
So the instructions say a spec and then 90% then another 90%. You did the 90% turns ? If so then put compressed air in that cylinder and turn the crank. Eventually the thing will make a different noise as air rushes out of wherever. I’m questing your going to hear it hissing at the tailpipe. Cause the exhaust valve is stuck in the guide your machinist failed to ream out properly for you.
Terry knows a lot more about that process than me. He was a machinist in a past life. But when we did these things all the time, like back in the late ‘90s I would just lap the valves and run the specified reamer in the guide and clean the valve stem on a wire wheel. Then slam it all together with new valve stem seals. The valves sticking was a pretty common issue right up till about 02 or 03.
Yes, exactly as the RAVE sequence says. both heads are coming off and going back to the machinist.
Our shop was in a “economically challenged“ part of town and we did a lot of work for used car lots. Instead of replacing valve guides more often we knurled them and reamed them to size. We even had a guy that would ask us to only regrind the damaged journal on crankshafts and sell him only one set of bearing shells when an engine would spin a rod bearing. My boss went along with it... I was younger then and allowed that to bother me. This guy also reused head gaskets. He would spray them with that copper spray stuff. He would pay $5 bucks for a can of that but not $20 for a head gasket.
In reference to Skip‘s comments on the valve guide and likely bent valve, I have more recent and relevant experience. Not long ago I acquired a 4.0 Gems engine that had been stored at least 10 years (probably closer to 20) after only covering 27,000 miles. The outside of the engine looked like hell but the inside was like new. I know because I took it apart to inspect it and replace the head gaskets as well as every seal and other gasket. I was surprised that several of the valves were oddly tight in the guides. I opened them up a tiny bit to assure they didn’t get stuck. I do suspect you have a bent valve. if that is all that is wrong, its not too bad. The shop that did the work might even fix it for free. Tearing it down and putting it back together is a bummer but if you have the time to do it at least it isn’t expensive.
if you have a bore scope you can look through the spark plug hole. If you don’t have one they are fairly cheap and is a great tool to have on hand for many reasons. You will have to look very carefully as it doesn’t take much “bending” to cause such a problem,
I had a friend who over revved his old Triumph. It had very thin valve stems. It ran like crap right after. He knew he bent some valves. His solution... drive it. “They will straighten themselves out.” Much to my surprise the problem got better. I’m not saying it was 100% better, but it actually ran pretty well after a while. It was kind of a junker and we were poor teenagers. Our old $300 cars didn’t have ECUs and the only trouble lights were temperature and oil pressure. Ignorance was bliss...
Also, while I did work as a machinist, Skip is actually much more experienced and knowledgeable on this specific issue. I wasn’t aware until I read this post this was a typical Rover V8 issue. If I was having such a problem, he is who I would ask for advice,
I have a brand new set of 4.0 heads I was going to use on my next build. I now plan to take them apart and measure the valve stems and guides.
Also, on lapping the valves, we didn’t do it when we did valve jobs unless it was requested. We also didn’t do it the way you are “supposed to do it.” We used a hand drill on the valve spring side of the stem. The machinist that taught me that, was in his 70s and had been an automotive machinist since his teen years. Never had one come back with or without lapping.
.Lapping does make it a better job, that can’t be argued. . If you are just replacing a valve or two, it works well. It also can reveal if you have a problem.
In reference to Skip‘s comments on the valve guide and likely bent valve, I have more recent and relevant experience. Not long ago I acquired a 4.0 Gems engine that had been stored at least 10 years (probably closer to 20) after only covering 27,000 miles. The outside of the engine looked like hell but the inside was like new. I know because I took it apart to inspect it and replace the head gaskets as well as every seal and other gasket. I was surprised that several of the valves were oddly tight in the guides. I opened them up a tiny bit to assure they didn’t get stuck. I do suspect you have a bent valve. if that is all that is wrong, its not too bad. The shop that did the work might even fix it for free. Tearing it down and putting it back together is a bummer but if you have the time to do it at least it isn’t expensive.
if you have a bore scope you can look through the spark plug hole. If you don’t have one they are fairly cheap and is a great tool to have on hand for many reasons. You will have to look very carefully as it doesn’t take much “bending” to cause such a problem,
I had a friend who over revved his old Triumph. It had very thin valve stems. It ran like crap right after. He knew he bent some valves. His solution... drive it. “They will straighten themselves out.” Much to my surprise the problem got better. I’m not saying it was 100% better, but it actually ran pretty well after a while. It was kind of a junker and we were poor teenagers. Our old $300 cars didn’t have ECUs and the only trouble lights were temperature and oil pressure. Ignorance was bliss...
Also, while I did work as a machinist, Skip is actually much more experienced and knowledgeable on this specific issue. I wasn’t aware until I read this post this was a typical Rover V8 issue. If I was having such a problem, he is who I would ask for advice,
I have a brand new set of 4.0 heads I was going to use on my next build. I now plan to take them apart and measure the valve stems and guides.
Also, on lapping the valves, we didn’t do it when we did valve jobs unless it was requested. We also didn’t do it the way you are “supposed to do it.” We used a hand drill on the valve spring side of the stem. The machinist that taught me that, was in his 70s and had been an automotive machinist since his teen years. Never had one come back with or without lapping.
.Lapping does make it a better job, that can’t be argued. . If you are just replacing a valve or two, it works well. It also can reveal if you have a problem.
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I’ll look for the reamer that we used to use. I know I’ve seen it lately. There’s an old bulletin out there somewhere that gives the actual micron spec and I’ll try to find that too.
I was shown how to lap valves that by a guy who said I didn’t show you this or do as I say or some shit. But that’s how I do it. You don’t need to go crazy. Just spin it up and knock it on the seat a few times. So I was about 30 yrs old and doing one of my 4 hour valve jobs. Heads were on the floor in just over 1 hour. Going back on the car after 2 hours, back together and running in like 5 hours total. But we where doing at least 2 and usually 3 a week. Heads coming off for leaks or stuck valves. So I was doing that deal with the drill, lapping all 8 exhaust valves in like 5 min. Our old boy service manager/ service writer / our fearless leader. Awesome dude. He starts in with how that’s not proper Yada Yada you should do that with a stick and Yada Yada. So when he got done with his rant I said “lap my bag old man” Wow did that piss him off.
I was shown how to lap valves that by a guy who said I didn’t show you this or do as I say or some shit. But that’s how I do it. You don’t need to go crazy. Just spin it up and knock it on the seat a few times. So I was about 30 yrs old and doing one of my 4 hour valve jobs. Heads were on the floor in just over 1 hour. Going back on the car after 2 hours, back together and running in like 5 hours total. But we where doing at least 2 and usually 3 a week. Heads coming off for leaks or stuck valves. So I was doing that deal with the drill, lapping all 8 exhaust valves in like 5 min. Our old boy service manager/ service writer / our fearless leader. Awesome dude. He starts in with how that’s not proper Yada Yada you should do that with a stick and Yada Yada. So when he got done with his rant I said “lap my bag old man” Wow did that piss him off.
It takes me 5 hrs to find my wrench now. And when I do I can't remember which one I needed. Or possibly, why?
There is no way I could do it that fast now. I don’t do anything fast. But back then it was 2 or 3 a week. And again I was 30 something and now I’m almost 60
“Awesome dude. He starts in with how that’s not proper Yada Yada you should do that with a stick and Yada Yada. So when he got done with his rant I said “lap my bag old man” Wow did that piss him off.”
An old friend and mechanic once told me, “We’re not building pianos, stop being so anal.” (I’m still a bit anal about such things but when I get frustrated when I am working on something that doesn’t go quite as perfect as I want, I remember that conversation.)
Later he became the service manager at the largest Honda dealership in the area. He didn’t like being in management and took a job as a mechanic at an independent BMW shop. 30 plus years later and he is still there. Many customers only want him working on their cars.
He is the smartest mechanic I have ever known. He could repair anything and it is uncanny how fast he can look at anything mechanical and know what is wrong.
An old friend and mechanic once told me, “We’re not building pianos, stop being so anal.” (I’m still a bit anal about such things but when I get frustrated when I am working on something that doesn’t go quite as perfect as I want, I remember that conversation.)
Later he became the service manager at the largest Honda dealership in the area. He didn’t like being in management and took a job as a mechanic at an independent BMW shop. 30 plus years later and he is still there. Many customers only want him working on their cars.
He is the smartest mechanic I have ever known. He could repair anything and it is uncanny how fast he can look at anything mechanical and know what is wrong.
We had a guy around my shop a while back who came in on the military program. He was a crew chief for one of the fighter jets. I used to tell him “ it’s not a plane, it’s not going to fall out of the sky”
I am that guy that treats everything automotive like a piano! Very challenging on Bosch motors due to limited choices for parts. I suck at choosing what is good enough so everything gets prepped for 8000rpms. Lol