View Full Version : Cylinder head/valve freshen up (help)
In the past i had a local guy who did any work i required on my cylinder head, however he is no longer in business.
Therefore im going to have a blast myself.
Just a few pointers please, i have head at 73.3mm, and wish to freshen it up, i was going to remove the valves and give them a good clean up, whats the best way of going about this.
Then my plan was to wirebrush/drill spean the cylnder head to remove crud, avoiding teh valves seats, fit fresh stem seals , and then wang the thing back together.
Only other thing i possibly looked at was smoothing out the eghaust ports slightly using the gasket as a template using, and hitting it with 120/240/320 paper.
Please any advice, im a keen learner.
jamie_clioGTT
22-10-2011, 22:25
i used brillo pads on my stuff. wire wool with a detergent in lol.. got rid of all the old oil stains and brought it up like new!
also used some 1200 on my valve faces.. took a while but after a while all the burnt crap etc come off and they looked like new uns!
Tony Walker
22-10-2011, 22:35
Most important thing is to lap the valves in. If they dont seal you'll soon burn them out.
Grinding paste and a grinding suction thing to spin the valve with, if the seats are quite pitted then i personally use a drill on the valve stem. saves hours.
Is there any good way to check the valves seal, like a leak test with petrol or something
Adam 005
23-10-2011, 09:01
Is there any good way to check the valves seal, like a leak test with petrol or something
with the head off turn it up side down and fill with petrol and see if it leaks past the valves.
with every head i rebuild, ive always had it bead blasted.
it may sound harsh, but i simply give instructions to the engineer thats doing the blasting to not go near the valve seats or the head to block mating face.
when i receive the head back, i simply clean up a little more around the valve seats with some wet n dry paper and it comes up nice and clean. from here i go about lapping the valve into their seats.
ive never had a problem, and the result is a fresh clean bare cylinder head:agree: which has not been painted (i hate that:disagree:)
http://www.rtoc.org/boards/picture.php?albumid=25&pictureid=227
http://www.rtoc.org/boards/picture.php?albumid=30&pictureid=268
http://www.rtoc.org/boards/picture.php?albumid=1428&pictureid=3003
http://www.rtoc.org/boards/picture.php?albumid=1428&pictureid=2999
do not use a wire brush attachment on a drill anywhere near the head.
the wires are steel, which is harder than the aluminium. - it will score and wear away areas of the head quite easily if u start pushing hard.
i cleaned up valves by putting them in a drill and using very coarse sandpaper to remove the baked on crud.
i cleaned up valves by putting them in a drill and using very coarse sandpaper to remove the baked on crud.
thats what i do too:agree:
sweet thanks guys thats the kind of info i need, ill probably tackle the valves tonight.
At what point do valve guides need replacing.. all the valves have very slight play.
speant a lil bit of time cleaning up the valves.
http://i3.photobucket.com/albums/y98/djinuk/IMG_1968.jpg
http://i3.photobucket.com/albums/y98/djinuk/IMG_1971.jpg
http://i3.photobucket.com/albums/y98/djinuk/IMG_1972.jpg
going to send the head off for a skim as its got quite bad signs of det i think.
http://i3.photobucket.com/albums/y98/djinuk/IMG_1969.jpg
i done the same damien,just cleaned them up with 1200 wet and dry an polished with paste,also polished up my piston crowns to whilst head was off..:D
ah i used a wire brush on a drill on teh valves.. on the head ill probably ask whomever does the headskim to clean it up for me :)
There is a chap in measham that pressure tested and skimmed mine. I can find the number if needed!
hehe i know the one.. looks like an arms dealer, rc performance, ive used him a lot in the past, just gave him a tinkle and left a message :).
Quality guy he is.
Matt Cole
24-10-2011, 21:47
Wasting your time unless the guides are checked and if worn need to be replaced. I used a medium and then fine grinding paste with the valve on a suction cup placed in a battery drill. Grind the seats untill the paste goes greyish.
Do not use a wire brush. :agree:
only used a wire brush for cleaning the carbon from the valve faces, for the seats i used course and fine grinding paste on a wooden suction took and have done it by hand.
Im not entirely sure how to check valve guides, i checked them by using a valve and they all seem uniform and have next to no play.
Ha ha, that's the guy! Very quick turn around and not a bad price!
only used a wire brush for cleaning the carbon from the valve faces, for the seats i used course and fine grinding paste on a wooden suction took and have done it by hand.
Im not entirely sure how to check valve guides, i checked them by using a valve and they all seem uniform and have next to no play.
paste on valve, fit into head.
attach drill to bit of valve that the collets usually fit to.
set at low speed and gently push down on the middle of the valve with your finger .
then reverse the drill and repeat.
then lift off the valve seat and push a bit more paste in there.
alot quicker than doing it by hand.
i was thinking about doing that sparkie , but was a bit worried about the chuck scratching the top of the valve , but i guess its only where the collect fits so it shouldnt bother it.
im going to be taking the head to my local machine shop soon to have it skimmed, Ive noticed this marks in the combustion chamber area, should i have these machined out ? i presume these are signs of past detonation, there only really visable on the 1 cylinder.
http://i3.photobucket.com/albums/y98/djinuk/IMG_1973.jpg
there seems to be quite a bit of head thickness so hopefully they can be removed
http://i3.photobucket.com/albums/y98/djinuk/IMG_1974.jpg
http://i3.photobucket.com/albums/y98/djinuk/IMG_1976.jpg
whats the minimum head thickness i should be aiming for, ideally i want to be able to run 22psi or thereabouts on a t25 when im done.
Markey Mark (BD)
26-10-2011, 16:09
Yeah that heads got abit of det marks on it around where the gasket firering seals, if the skim doesn't remove them then i wouldn't be using the head.
I wouldn't take the head any lower then 73mm, if needs to go lower then that the comp will be abit high. To over come this either different head, skim piston tops or machine the combustion chamber out abit to lower comp back down to safe level.
papula :(,
Well ill nip to my machine shop and see what he thinks is possible, id sooner keep the bottom end as it is, so maybe ill see if he could machine the combustion chamber a bit if thats whats requierd.
Is it not possible to weld up the det marks and then machine back ?
Just thinking ideally id like to get this head right , purely because they seem to be getting hard to get descent ones.
Markey Mark (BD)
26-10-2011, 16:31
Check how deep the det marks are first mate, you may be ok with just light skim.
I thought that, just not sure how the bloody hell to check how deep they go.. was trying to work it out yesterday lol
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