Valve Seats

HomeBuiltAirplanes.com

Help Support HomeBuiltAirplanes.com:

Tuneturkey

Well-Known Member
HBA Supporter
Joined
Dec 29, 2018
Messages
64
Location
baton Rouge, LA 70816
I am installing new valves on a 1/2 VW build, and the exhaust valve seats re-used heads)are not clean and shiney as are the intake valve seats. The seats have been lapped with the old valves to clean up the seats, but the coating of carbon or corrosion and discoloration did not come off. The valve seats firmly, but does not appear to be leak tight. How complicated is the valve grinding process, and how clean should the seats be?

Johnc
 

BBerson

Well-Known Member
HBA Supporter
Joined
Dec 16, 2007
Messages
12,956
Location
Port Townsend WA
Takes special tools to do the three angle grind process.. Measure the width of the contact ring.
If much wider than .060" consider a regrind.
 

Pops

Well-Known Member
Log Member
Joined
Jan 1, 2013
Messages
7,866
Location
USA.
Takes special tools to do the three angle grind process.. Measure the width of the contact ring.
If much wider than .060" consider a regrind.
Yes, should have a .060" wide contact width.
 

TFF

Well-Known Member
Joined
Apr 28, 2010
Messages
12,559
Location
Memphis, TN
Intake valves are closed during all the hot cycles. The exhaust valve is open in most of the heat generated. So the seats are going to look different. If you have carbon on the seat, not just discoloration, you did not lap the valve enough. If you do see the band of the grinding of the compound, then you did lap the valve. You can always install the spring and pour some mineral spririts in the ports; if it comes out the chamber side it's not a good seal.
 

proppastie

Well-Known Member
Log Member
Joined
Feb 19, 2012
Messages
4,415
Location
NJ
valve grinding compound can be pretty aggressive, putting the tool in an electric drill might help.
 

specter22

Member
Joined
Mar 3, 2018
Messages
13
Location
Rochester, NY / USA
If you want to do it the "right way," I'm a fan of the Neway system. It's a few hundred $ to get set up, but it was going to cost me close to that to ship my heads to someone who would do them for me. If you can lap them and get your valve-to-seat contact width within spec, go for it - just make sure your valve guides aren't worn too much, or your lap job may only make things worse.
 

Hot Wings

Grumpy Cynic
HBA Supporter
Log Member
Joined
Nov 14, 2009
Messages
6,901
Location
Rocky Mountains
If you want to do it the "right way," I'm a fan of the Neway system.
Done right with the Neway cutters lapping is not needed. Check with blue when close, finish with a good touch and then double check with a leak down test. Lapping just ruins a good cut.

Trying to lap new valves into uncut seats is just a waste of good valves because the seats don't wear flat. By the time you have a "good" pattern with the grinding compound you just have 2 nice matched arcs which will move relative to one another when things get hot. The valves may still seal, in the short term, but there is almost zero contact face left resulting in very short valve life.
 

specter22

Member
Joined
Mar 3, 2018
Messages
13
Location
Rochester, NY / USA
Done right with the Neway cutters lapping is not needed.
Absolutely right. I meant, if you *don't* want to use the Neway cutters, you can try to lap and get your contact within spec; not that you use the cutters and *then* lap. However, I re-read the OP and see we're talking about new valves in old seats, in which case I agree: lapping is not a solution. If you plan on keeping the engine around for very long, save up for some Neway tooling; odds are you'll use it more than once. Otherwise, I'd start asking around to find someone relatively local with the tooling you need.
 

Dana

Super Moderator
Staff member
Joined
Apr 3, 2007
Messages
9,107
Location
CT, USA
Just take the heads to an automotive shop that does cylinder head rebuilds and have them do a proper 3 angle grind. Best if it's a shop that specializes in air cooled VWs (there are still some around). That's what I did when I had leaky valves on my Mosler half VW and hand lapping didn't fix it. Ran like a champ after I got the heads back.
 

Tuneturkey

Well-Known Member
HBA Supporter
Joined
Dec 29, 2018
Messages
64
Location
baton Rouge, LA 70816
Thanks to all responders.
One of the intake valve seats is pitted, has a very narrow contact width, and the Seat is worn down. Lapping multiple times has not gone deep enough.
The repair shop is suggesting pressing in a new seat. Per my reading, VW does not condone pressing in a new seat. Needless to say, after all the prep work to cut the heads and install of intakes, etc., etc. Throwing away the heads does not make me very Joyous!
1. Is pressing in a new seat a customary fix.
2. Will the seat remain in place for the long haul.
Thanks,
johnc
 

Hot Wings

Grumpy Cynic
HBA Supporter
Log Member
Joined
Nov 14, 2009
Messages
6,901
Location
Rocky Mountains
1. Is pressing in a new seat a customary fix.
ABSOLUTELY not!

But the shop may just be using improper terminology. ;) At least I hope that is the case.
Putting new seats in aluminum heads is common but requires very good procedure.

The cut in the head is done after measuring the new seat and is sized for an interference fit. Once that is accomplished the head is heated and the seat cooled so it will slip into place. VW then peened the seat in place (that little ring just outboard of the seat). This practice is somewhat controversial. It worked for VW. Others say it just loosens up an other wise good fit.

Look for a shop that has a good track record of doing this with aluminum heads - or just build/buy new heads.
 

Pops

Well-Known Member
Log Member
Joined
Jan 1, 2013
Messages
7,866
Location
USA.
This shop has been all of my VW engine machine work since 1970. Also when I was building VW engines and selling VW Bugs as a slide business. Always good work at good prices. They do mail order. Its a VW only shop. They can do any machine work that you need done. I was there Tuesday and picked up a tube frame kit for a sand buggy, ( mud Buggy in my area). Closed Sundays and Wednesdays. 304-548-7627 and ask for Vic. I have no interest in the business, and they started doing work for me when Vic was 8 years old. Vic has been doing this work all of his life. Great people in the 2 generation family business.
 

Dana

Super Moderator
Staff member
Joined
Apr 3, 2007
Messages
9,107
Location
CT, USA
Dana,
You wouldn't happen to have your old plans for the Kolb Ultrastar?
A rough scanned set, same as the ones uploaded to the Kolbultrastar yahoo group, the paper copies went with the plane.
 

N8053H

Well-Known Member
Joined
Jan 31, 2013
Messages
2,523
Location
Right here in front of my computer
I have a set of heads off a 1/2 vw. They are in great condition. Scott Casler told me there was nothing wrong with these heads. But seeing how I was replacing the case on my engine I went ahead and replaced the heads. If you would like these heads you can have them for 75 bucks each plus shipping. Sent me a message if you want these you can use paypal to pay for them.
Tony
 
Top