Should I lap the valves?
#2485765
04/20/18 08:21 PM
04/20/18 08:21 PM
|
Joined: Jan 2006
Posts: 250
Iceland
BadMoonRacer
OP
enthusiast
|
OP
enthusiast
Joined: Jan 2006
Posts: 250
Iceland
|
Received small block heads from an engine shop today. Had them insert new valve guides and do a three angle vale job. My question: Should I lap the valves? The engine shop did not return the valves marked for specific cylinders. This is a stock 273 ´67 year buildup.
Ragnar in Iceland
66 Charger, 451, .582" lift, 11" conv. 4.10:1. 4118 lbs 11.75@117 mph on regular Firestone Firehawk radials.
Icelandic Champion in MC 2007, 2008, 2009 and 2022.
|
|
|
Re: Should I lap the valves?
[Re: stumpy]
#2485811
04/20/18 09:39 PM
04/20/18 09:39 PM
|
Joined: Aug 2003
Posts: 43,097
Bend,OR USA
Cab_Burge
I Win
|
I Win
Joined: Aug 2003
Posts: 43,097
Bend,OR USA
|
Last edited by Cab_Burge; 04/20/18 09:40 PM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
|
|
|
Re: Should I lap the valves?
[Re: Magnum]
#2485864
04/20/18 11:46 PM
04/20/18 11:46 PM
|
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
RapidRobert
Circle Track
|
Circle Track
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
|
Pour something down the ports and see if they are leaking. Agreed, with the head on its side with ex ports on top then with the intake ports on top pour some solvent in the ports & see if it gets wet at the valve heads. I read/saw something (on the dark web) so it has to be correct! that lapping is old school/obsolete & the article went on to say that the contact area will change drastically once it get hot so it is ineffective but I would think that yes heat is going to alter things but I'd want a perfect seal as I can get in the beginning for a good baseline. It does give a good pattern on the height/width of the contact area.
live every 24 hour block of time like it's your last day on earth
|
|
|
Re: Should I lap the valves?
[Re: Cab_Burge]
#2485976
04/21/18 09:59 AM
04/21/18 09:59 AM
|
Joined: Jan 2003
Posts: 8,667
Buford, GA
I_bleed_MOPAR
master
|
master
Joined: Jan 2003
Posts: 8,667
Buford, GA
|
X 2 If I was assembling new valves and/or heads I always lapped the valves. If the heads were sent out for work, I always inspected them and would leak-check as Magnum and RR suggested. Tim
'71 Charger 383/727 '17 Challenger SXT (Wifeys car  )
|
|
|
Re: Should I lap the valves?
[Re: BadMoonRacer]
#2486012
04/21/18 11:16 AM
04/21/18 11:16 AM
|
Joined: Jan 2006
Posts: 250
Iceland
BadMoonRacer
OP
enthusiast
|
OP
enthusiast
Joined: Jan 2006
Posts: 250
Iceland
|
Thanks for you input guys.
I´ll do some lap dancing today.
Ragnar in Iceland
66 Charger, 451, .582" lift, 11" conv. 4.10:1. 4118 lbs 11.75@117 mph on regular Firestone Firehawk radials.
Icelandic Champion in MC 2007, 2008, 2009 and 2022.
|
|
|
Re: Should I lap the valves?
[Re: BadMoonRacer]
#2486106
04/21/18 03:52 PM
04/21/18 03:52 PM
|
Joined: Jan 2005
Posts: 12,419
Kalispell Mt.
HotRodDave
I Live Here
|
I Live Here
Joined: Jan 2005
Posts: 12,419
Kalispell Mt.
|
I lap them not to get them to seal, a good valve job should get them to seal, but you lap them as a poor mans way of checking to make sure they are touching all the way around and the sealing surface is more than just a sharp edge. Checking with fluid alone does not tell you if it has a good contact area, espercially important on the exhaust for heat transfer. Could also be sealing against the wrong side of the margin, I like to see them seal more against the outside edge of the valve face than the inside but just checking with fluid you will never know. Also if the machine shop assembles them they could have left a layer of oil or grease or something that seals them instead of the metal metal contact (I had a shop in texas do this one time and had to have them re-do a slant six head when I was 17 and they argued with me that they did not have to seal with just metal to metal, never used them again). If you have to grind them a bunch with lapping compound to get them to seal you can end up with a curved sealing surface, I have done this in a pinch on junk yard builds but it aint the right way for a good engine. Just use lapping for checking the machine shops work not grinding.
I am not causing global warming, I am just trying to hold off a impending Ice Age!
|
|
|
Re: Should I lap the valves?
[Re: HotRodDave]
#2486169
04/21/18 07:44 PM
04/21/18 07:44 PM
|
Joined: Jan 2003
Posts: 25,729
Rio Linda, CA
John_Kunkel
Too Many Posts
|
Too Many Posts
Joined: Jan 2003
Posts: 25,729
Rio Linda, CA
|
My shop teacher taught that lapping doesn't guarantee a good seal because the valves expand a little when in operation and don't contact the seat the same as when lapped cold.
The INTERNET, the MISinformation superhighway
|
|
|
Re: Should I lap the valves?
[Re: HotRodDave]
#2486268
04/22/18 01:33 AM
04/22/18 01:33 AM
|
Joined: Jan 2005
Posts: 3,699
Newport, Mi
Evil Spirit
master
|
master
Joined: Jan 2005
Posts: 3,699
Newport, Mi
|
I lap them not to get them to seal, a good valve job should get them to seal, but you lap them as a poor mans way of checking to make sure they are touching all the way around and the sealing surface is more than just a sharp edge. Checking with fluid alone does not tell you if it has a good contact area, espercially important on the exhaust for heat transfer. Could also be sealing against the wrong side of the margin, I like to see them seal more against the outside edge of the valve face than the inside but just checking with fluid you will never know. Also if the machine shop assembles them they could have left a layer of oil or grease or something that seals them instead of the metal metal contact (I had a shop in texas do this one time and had to have them re-do a slant six head when I was 17 and they argued with me that they did not have to seal with just metal to metal, never used them again). If you have to grind them a bunch with lapping compound to get them to seal you can end up with a curved sealing surface, I have done this in a pinch on junk yard builds but it aint the right way for a good engine. Just use lapping for checking the machine shops work not grinding. This. And food for thought - many machine shops have went to 3 angle cutters to do their "production" valve jobs instead of using stones, to save time dressing the seats in the heads. While the cutters are great to remove material for larger valves, IMO they are not intended to be used as the sole method of dressing seats. IMO it is absolutely necessary to lap in the valves on heads that have had cutters used for the seats, to smooth out the inherent chatter bumps from the cutters.
Free advice and worth every penny...
Factory trained Slinky rewinder.........
|
|
|
Re: Should I lap the valves?
[Re: Evil Spirit]
#2486312
04/22/18 06:36 AM
04/22/18 06:36 AM
|
Joined: Feb 2005
Posts: 20,151
PA.
pittsburghracer
"Little"John
|
"Little"John
Joined: Feb 2005
Posts: 20,151
PA.
|
I use blueing on every valve seat I cut and lap them in. Then it’s time for a good cleaning.
1970 Duster
Edelbrock headed 408
5.984@112.52
422 Indy headed small block
5.982@112.56 mph
9.42@138.27
Livin and lovin life one day at a time
|
|
|
Re: Should I lap the valves?
[Re: dogdays]
#2487769
04/25/18 01:33 PM
04/25/18 01:33 PM
|
Joined: Sep 2003
Posts: 19,310
north of coder
moparx
"Butt Crack Bob"
|
"Butt Crack Bob"
Joined: Sep 2003
Posts: 19,310
north of coder
|
your statement is generally correct, however, since the valves rotate, i use the "apply very light pressure, while twisting the valve with your thumb" process to see what the contact looks like. then, if not the whole way around the seat or valve, apply a little amount of compound to get a perfect pattern [one i'm satisfied with], then as a final test fill the chamber with solvent for a leak test. i do very few heads, and only have very old equipment at my disposal. this works for me, it appears your method is the "correct" way, and should be the followed practice if one does way more work in this area than i do. no disrespect intended toward you [or others] in any way. please accept my apologies if offended. 
|
|
|
|
|
