Engine Mechanic Says Sticking Valve Guides

Discussion in 'Fox 5.0 Mustang Tech' started by JasinC19, Aug 26, 2013.

  1. As some of you know, I've been struggling with a really bad idle issue after installing my TFS top end kit.

    A local mechanic with experience in the performance fox body game diagnosed it with sticking valve seal guides. He said that sometimes in new heads, the valves heat up in such a way where the guides fuse to them and they won't seal properly.

    I am not sure this is the issue because my compression check didn't yield terrible results. But if it is, what would the typical fix for this be?

    He recommended removing heads and sending to a machine shop to do the work, but unless the valves themsevles needed to be replaced, couldn't the job be done easily with the heads on the car?

    I just want to be educated before I go in there tomorrow.

  2. interested as well. I have a miss but cylinder balance and compression tests show everything as good.
  3. How are the rockers adjusted. If they're too tight, they'll hold the valve open, causing a slight loss in compression and a rough idle. If they're too loose, they'll make noise.
    #3 Gearbanger 101, Aug 26, 2013
    Last edited: Aug 26, 2013
  4. Ok. Couple of things. First, are the rockers adjusted too tight? Correct length pushrod? What kind of swipe is there on the valve stem tip? If the valve train geometry was not right then that would cause premature/excessive wear on the guides and seals, but IMO you would see more oil consumption and smoke. Are the valves noisy? What was your compression reading in all 8 cylinders?

    Second, did he say valve seal or valve guide? Valve seals can be replaced with the head on as they are on the valve stem under the spring. Valve guides are what the valve stem rides in. The only way to replace/repair them is with the head off.

    That being said, If these were brand new in the box TFS heads and the the seals or guides are faulty, I would not be paying for any work. I'd be on the phone with TFS. On olderTFS heads, they had problems with the valve guides but I haven't heard of that problem in years.
  5. I had the pleasure of being informed of my problem by a woman who was relaying the information so I am not 100% sure if it was correct, but she did say guides.

    The rockers were adjusted a quarter turn past zero lash.

    The swipe was within spec. The valves are not noisy and there is 0 smoke and no oil consumption. The valves are not noisy.

    There was a period of time where, being a noob, I did not know i needed different spark plugs with the TFS heads so I had OEM style in there. Not sure if that could have caused a poor combustion environment that could have caused this problem.

    And yeah, they were brand new heads, preassembled from the factory (valves/springs/etc already put together on the head)

    Compression check was done hot and the results were something like:


    If memory serves... (paper that I wrote it down on is in the car at the shop)

  6. Valve seals are certainly not the problem, I have no valve seals on all of my exhaust valves and have no trouble. I have never seen a problem with TFS valve guides with a head new out if the box. I personally think your issue is somewhere else..
  7. Well I'm going to pull the heads and take them to the machine shop. If anything is wrong with the valvetrain they'll find it. I've had more than a few people tell me this problem is indicative of a burnt or sticking valve and I've basically eliminated most of the other possibilities.

    If anyone has any ideas before I tear the heads off, I'd appreciate it. Thanks for the input so far.
  8. First pull your valve covers and rotate the engine by hand. Check and see if the valve-train looks like its running smoothly.

    I may be wrong but I suspect shenanigans. I did a quick search of this specific issue with tfs and cant find much.
  9. I may be wrong. I went back and read more of the thread. I missed some stuff.
  10. I also haven't had an issue with them out of the box but the only way to know is pull them.... before any work is done to the head is personally call and talk to TFS. They will stand behind their product but maybe not once you take them apart......

    TFS uses a good Vinton valve seal....

    Sent from my XT907 using Tapatalk 2
  11. To the OP, if I were to guess, I would say something went wrong in the install. I agree with Rick. Have you called TFS tech yet? I would do that before proceeding any further.
  12. if you have a burnt valve it would pop..you could put your hand on the end on the tail pipe and it would suck on it...i would do a visual with the v/c off and running
  13. you need to go over your rockers again and lossen them by a 1/4 turn to start..do you have the right push rods for heads?
  14. I had called TFS before about the general issue and he didn't mention anything about checking valves other than for clearance issues.

    Last time I adjusted the valves, I made sure all the lifters were pumped up fully and then adjusted 1/4 turn past 0 lash. I am not a professional, but I'm fairly sure they are not too tight. The push rods are the ones that came with the kit. I measured the swipe on the valves and it was within the proper range so I think they are ok.

    However, if they were too tight in the past, is it possible that my cam lobes have been worn down and damaged to the point of affecting the running condition?

    I'll try the burnt valve test at lunch time. :)

    Thanks for the feedback!
  15. Have you called TFS about this issue and told them what the mechanic said- the brand new heads had sticking valves?

    Sounds like there is more to the story here.
  16. I'm give them a call today and ask.

    How likely is it that cam lobes for wiped? Like how tight would the valves had to have been?
  17. Not likely at all. The lifters would have failed before the camshaft lobes wore down. Remember....the lifters are roller....very little friction.
  18. That is what the TFS guy told me too. All my lifters are fine. He did explain that he's seen a lot of valve springs get weak from the car sitting too long without being started.

    This is possible I guess because it did sit for a while after being assembled due to me putting incorrect plugs in it.

    Wouldn't a weak valve spring only have symptoms at higher rpm's though?
  19. I highly doubt that is the case. How many of us have heads sitting around for months or sometimes years on a project and never have an issue. I agree that it could be an issue with high rev springs and a 600+ lift cam but you have the TFS1 which is a mild/moderate cam.

    what about the sticking valves/bad guides or seals?
  20. Meh....I doubt springs are you problem (unless they're binding, or broken). The TFS Stage 1 camshaft isn't all that aggressive and I doubt is putting that much stress on your springs.

    Besides, I've seen cars sit for decades and start and run just fine. Putting the wrong spark plugs in your head aren't going to have any effect on your valve train.