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Replacing broken valve stem

5K views 12 replies 5 participants last post by  TruBlu351 
#1 ·
Hi I need some pointers, I broke an intake valve stem on Friday when I was dicking around laying rubber in my driveway. I want to rebuild the engine in about 4 months when I can aford to do so. But in the mean time I want to just patch the problem. Can I just relace the one valve for now? where can I get just one valve and how do i replace the valve(redoing heads is unknown to me, Im a bottom end and block kinda guy)
 
#3 ·
Keita said:
I have found out that you can buy just 1 valve so theres that part solved, still can any one tell me how to replace it?
If you dont want to remove the head, just remove the sump, crank, rods and that one pistin, and insert the valve :priest:
Seriously, was it just the valve stem itself that broke? How, did you
drop a valve? Did it damage the heads where the valve slides?
 
#4 ·
Let me guess, stock valves and revving over 5500? Was it valve bouncing at the time too? These are good insurance things to keep in mind to avoid busting parts.

Wouldn't removing the head be 100 times easier than removing the sump and piston in the car?

I'd be pulling the head and just inspect the top of the piston - if its OK, then just do the valve. Did the valve drop into the cylinder and mash the piston, or did the valve stem seal hold it up?

Are you sure its a busted valve and not the locks or retainers failing?

So, remove the head........

With the valve stem broken, the retainer would have fallen off the top of the spring with the 2 locks lying around too (you'll see this with the rocker cover removed). This negates the requirement for a valve spring removal tool for the strip down.

Not sure if you'll need some cutting compound to seat the valve into the seat? Bueller?

Give it a thorough parts clean, insert valve, valve stem seal, spring and retainer. Squash it all down with a spring compressor tool and the insert the 2 valve locks and then release the compressor tool slowly. Refit head.
 
#7 ·
Keita said:
I have found out that you can buy just 1 valve so theres that part solved, still can any one tell me how to replace it?
Keita, just disregard some of the stirrers on here who have usually had one too many :beerbottl

before they get on here.

You will have to remove the head. after removing carby, inlet manifold, exhaust manifold, and rocker cover. When removing the rocker gear and pushrods, keep everything in the same order from front to back for re-assembly. There may be shims of different thicknesses under the rocker pedastals. You will need a breaker bar or a lenght of pipe for leverage to crack the head studs for removal. The head needs to be levered up off the locating dowels to remove it. Take it to a head re-conditioner to have the valve put in unless you know what you are doing and have a valve spring compressor.

Re-assembly is just the reverse but you should oil the thread of the head studs and tension them in the correct order. Buy a manual for guidance.

xdclevo
just how were you going to get the ring compressor up onto the bottom of the bore and slide the piston in there? :priest: :priest: :priest:
 
#8 ·
if you just buy a valve spring compressor its pretty basic in theory. i would get some valve grind compoud from the local autoparts store and put a liberal amount on the valve and seat and slide the valve in and put the end of the valve stem in a drill and pull up gently to seat the new valve so it doenst leak. then clean the port, valve and compustion chamber before re-istalling the valve, if you decide to go this route you can ask more questiond on how to exactly do it, many on here could help you out with any questions. and anyone that tells you that using a drill doesnt work, ignore them, it works just fine. its not the 100% best route but it does get the job done. i've done it myself on different occasions and know many others that have done it aswell
 
#9 ·
musclemustang8 said:
if you just buy a valve spring compressor its pretty basic in theory. i would get some valve grind compoud from the local autoparts store and put a liberal amount on the valve and seat and slide the valve in and put the end of the valve stem in a drill and pull up gently to seat the new valve so it doenst leak. then clean the port, valve and compustion chamber before re-istalling the valve, if you decide to go this route you can ask more questiond on how to exactly do it, many on here could help you out with any questions. and anyone that tells you that using a drill doesnt work, ignore them, it works just fine. its not the 100% best route but it does get the job done. i've done it myself on different occasions and know many others that have done it aswell
I am not a qualified mechanic but my Dad was and he never taught me to seat valves using a drill. I doubt they would teach this method at Tech but enlighten me if they do.

As musclemustang8 says its not the 100% best route to take. I would suggest that this method could lead to damaging the valve tip and may wear the guide if pressure is inadvertantly put to one side by not keeping the drill absolutely square to the seat face.
This approach seems a bit rough and reminds me of a kid I used to know who could fix his pushbike with only two tools. An open ender and a hammer. Needless to say his bike looked like it too!
 
#11 ·
well the wear on the guide would be very minimal for the amount of time spend spinning
the suction cup on a stick would take you about an hour to seat the valve as the drill would take about 2 minuits.

#1 lightly oil the valve stem for best lubrication and least wear on the stem.
#2 take the tube of valve grind compound and run a thin bead on the valve seat face.
#3 slide the valve into the head
#4 put the valve stem in the chuck of the drill and pull up lightly and as straight up as possible, the taper of the valve seat will center the valve perfecty when you pull back on the drill.
#5 start slow til you get the feel for it, you will hear a light grinding noise like there is sand between the valve and the seat. the faster you go the faster it will seat the valve, but you'll will know if you go to fast b\c it will vibrate and squeal a low tone, just back of the drill rpms and keep goin for about 1 minuite.
#6 now the sanding noise will come to a minimum and pull out the valve and wipe it off and re-apply valve grind compound again, this time when you pull on the valve with the drill, pull slighly harder(just before you start to put excess tension to the head) and go a little slower this time as well. do it again for about 1 minuite.
#7 now pull out the valve, clean it off, and you should see the shiny contact area on the seat on the head. the conatct area should be roughly an 1\8th of an inch wide all the way around. if not, add more compound grind more as needed.
#8 now take out the valve, clean it well with a solvent, clean the port well and the combustion chamber
flip the head up-side down (block contact side up) so you can drop the valve in and fill the combustion chamber with gasoline (gas is thinner than water so it will give you a better reading). it should have no leaking from the valve, if it does, grind more, less tension pulling back on the drill and a slow speed to fine tune the seat.
#9 once it hold gasoline its ready to put back together, your valve is seated.
if gasoline seeps VERY very slowly it will be ok as it will seat itself when it hammers on the seat while running and the spring wil pull it tight.
but it should hold gasoline without tension and it will as long as you work with it, it doesnt take much to get it to seal. i have had much luck with this method

if there are any more questions on this let ne know. -Ryan

























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#12 ·
Thanks all for the help. Yes you were right I did brake it at atleast 5500 rpms whilest resurfacing my driveway black with standard valves. I have just done a pach job for now and just replaced the one valve that broke. I think in about 4 months it may come out again and rebuild the hole thing with better nonstandard parts. It has been fixed, but i fergot to get a rocker cover gasket so I didnt start it last night, I will be picking up one today and will let you all know how I went over the next few days. Once again thanks for the help.
 
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