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valves- when is it a good idea to replace them?
#1

I finished disassembling my spare head today. Everything looks pretty good for the most part. However, I was wondering about the valves. The intake valves have a lot of carbon on them but look pretty good for the most part. Can I just clean them up and reuse them?

However, a couple of the exhaust valves look like they have rust on the bottom of the valve. Also, one or two have crater-looking indentations in the bottom of them. Is this a sign of detonation or something?

A few of the valves look like they have some kind of scratches or something on the stems.

Also if you have a valve job done on your head you have to give them your valves too, correct? Should I get the valve guides replaced?

(sorry for all the questions, this is the first engine I've built)
ABS to Vac-assisted brakes conversion
2005 Mustang GT-cams, intake, longtubes, lowered, Brembo swap
2016 F150 5.0 Sport
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#2

Look up the shop manual for the margin (edge) left after the pits are removed. It SB greater than .032", the bigger the longer the valves last. The turbo exhaust valves are $40 ea., intakes are $10.50 ea. Unless you can grind the new valves at a 44 degree angle ( 1 degree less than the 45 seat grind angle, you need to supply the M/C shop the valves to resurface. The carbon can be removed with a wire wheel. It's the pits from the unleaded gas that need to be ground out.
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#3

Wire wheel for that stuff?! Didn't work when I tried it, because it was really baked on there good. I tried just about everything to clean those exhaust valves and nothing worked until I just brought them to get hot tanked.

You can check the dimensions of the valves against the specs in the shop manual, like qhap said. This is very helpful when you're playing with seat angles and stuff, because I noticed that after I got my 3 angle valve job, the seat contact area was a lot more narrow. But it was within spec, so even though I was concerned, I assembled it and it has been fine.

For the most part, turbo valves are pretty rugged. The set I have in my car had a lot of crud, but I noticed that that stuff accumulates quickly when the valves stem seals are on the way out. They did clean up just fine, and I put them in without messing with the valve guides or anything. The head that they went into was not the head they came from, too.

I basically got and oval port from the junkyard, pulled a set of used valves out of a box in my garage and sent it all to the machine shop. I had them hot hank everything and do a 3-angle valve job, like I said. They redid the seats on the valves and even hit the stem tips to compensate for the removed material. I didn't have them touch the guides, like I said, and the total cost was only $60 (I did not have them assemble anything for me).

Hope that helps some.

-Mike

EDIT: To quickly answer your question, I would reuse turbo valves unless there is physical damage. If they're not cracked, burnt or bent, I'll put them in.
I'm just the driver! Tongue
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#4

The wire wheel I used was one at the college auto shop. It was one of those twin rotors, with the std 5" grinder on one side & a 5" heavy duty wire wheel on the other side. I took about 3 head's worth of valves there to grind out the carbon. It took some doing at some points.
You may be able to do this with the 2" wire wheel brush in a column drill, but definitely not with a hand-held drill unit.
The piston head carbon was gotten rid of with cleaner (purple cleaner took just the top surface off). For the baked in rest of the carbon, I had to use the std 2" brush wheel on the hand-held drill unit. When I came time to balanced each Piston head, this was the time that I thought that I might have taken off more Al than Carbon!
$60 is a good price!
I measured the valve stem heights of a std valve in a head before the grinding. Since there is no specs for the stem heghts, I measured the tip to valve base (removed spring - used caliper), and copied the height to the reground head. The stem height pro-trudes higher up because of the grounded valve & seat, so to re-adjust, I took my reference stem & made my measurements on each valve and with the help of the home 5" grinder. I took off about .010 to .015 off the stem tip depending on the valve location (use flat side edge). Once the valves were re-assembled and rotated with the cam, the recess valve location of each edge varied slightlly at different levels. To re-adjust, and make them all come up to the same level below the head base, shims are available to add under the hydraulic lifter (moves valve edge tip towards head base).
One new exhaust valve was about 2 mm above (without shim), but since it was for a Ranger with the valve cupping on the Piston head and with the extra thickness of the head gasket, I thought it would be OK! This process, I believe adds more lift to the valve. The limit would be that the valve spring is able to close the valve at it's seat.
:cheers:
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#5

The stock turbo exhaust valves can take alot more than the stock exhaust valve seats. I just took my head off after wrecking my new cam because of two sunk exhaust valves.
11.42@120 no wideband.
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#6

Quote:Originally posted by SpyVO:
This is very helpful when you're playing with seat angles and stuff, because I noticed that after I got my 3 angle valve job, the seat contact area was a lot more narrow. But it was within spec, so even though I was concerned, I assembled it and it has been fine.
When you do a 3 angle valve job only one of the faces of the 3 different ones will actually touch the valve...You do the 3 angle (or more) to create a radius on the seat, instead of a sharp angle, to help flow..

btw..I clean my vlaves with a glass bead blaster...

b Smile b
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#7

Just get a new set of valves.i beleive I paid under $100 for a whole set of big turbo valves from Racer Walsh.
84TC-gutted intakes-80mm maf-944 FMIC Greddy BOV 72lb inj
PPbig valve head-255LPH kirban-20psi-17"cntlines-65mmTB full 3" exhaust-on the way to 400hp
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#8

The more money I can save, the better. I'm working on a budget.

I think I might reuse the intake valves and replace the exhaust valves.
ABS to Vac-assisted brakes conversion
2005 Mustang GT-cams, intake, longtubes, lowered, Brembo swap
2016 F150 5.0 Sport
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#9

Sign up for a Eng Restoration & Rebuilding Course at your local college next semester & do it all yourself. The money I wasted was on a JY TC Head that when I used the magnaflux on (free at the college), showed up the cracks. Other than that $45 that I wasted, & if you already have a head, it should cost you no more than class fees and a gasket set. I cleaned up a bunch of head bolts (saved more than the $45, rather than buying those new T-Y bolts), parts, Upper & Lower Intake manifolds with the sand blaster there.
The other monies I spent was on the short block re-ringing, bearings & rebalancing the engine assy.
Under $100 is a very good price for the exhaust valve set.
:cheers:
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#10

I don't have time to take ANOTHER class at school, I'm already in school and trying to finish my degree ASAP.
ABS to Vac-assisted brakes conversion
2005 Mustang GT-cams, intake, longtubes, lowered, Brembo swap
2016 F150 5.0 Sport
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