Lapping Valves vs Machining

Status
Not open for further replies.
Joined
Aug 30, 2004
Messages
31,869
Location
CA
I am working on a Honda J30 V6 (3.0L from a 06-07 Accord) that jumped time. The cylinder heads have been removed and are currently at the machine shop. The shop spun all of the valves on their machine and advised that I need to provide 5 new exhaust valves and 4 new intake valves. I ordered the parts from the Honda dealer and will be supplying them with the requested valves plus cam and valve stem seals tomorrow. They will also be resurfacing both heads since the said the surface finish has some "shadowing" and is in "fair condition."

The shop also mentioned that they will be doing a "valve job." I recognized that a "valve job" can mean different things. The shop clarified that the valve seats are fine but they will be machining the reusable valves (the remaining 15).

I thought lapping the valves was a common practice but perhaps that is reserved for the DIY crowd? Is there an advantage to machining the valves on a machine versus lapping by hand? He mentioned something about cutting seats but I'll clarify tomorrow.

Also, the cost for the machine shop labor to do all of this work is $540. Not sure what the cost is in other parts of the country, but around here, it isn't exactly peanuts.
 
You can do a three angle valve job on a valve grind machine. I used one many moons ago to do a V8 engine. If the old valve face is pitted or chipped bad, then those valves have to be replaced. From what I remember, it took a long time to do all the valves on a V8 engine...but I was a rookie at it too. Plus I had to use some type of blue dye to make sure the valves had a good seal with the valve seats.
 
When I did Valve Jobs.....I would grind the Valves & then Hand Lap them to their respective Valve Seat using super fine compound along with blue Dycem to check my work.
Lapping alone will not remove Pitting or restore the Valve Seat Contact Area of the Valve.

Of course if the Valve Seats are worn/pitted.....They will need grinding as well.

$540 is a little expensive considering the labor involved in setting the Valve Lash is much easier than "Bucket/Shim" Style set-ups. (Double check the lash before installing the heads!), But....Your in Cali, So that may explain the higher cost.
 
Valve jobs today are a lot different than years ago, back then the iron seals were not hardened and neither were the valves. On those grinding them was the easiest and quickest way to do a valve job. Then came induction hardened seats on the iron head and inserts on aluminum, some of the inserts are very hard materials like stellite.
Using a cutter is the way to do these but in any case hand lapping (mostly done by machine today) is and always was a finishing step or for cleaning up otherwise good seats.

A couple of good articles.

https://goodson.com/blogs/goodson-gazette/take-a-seat-a-valve-seat-that-is

https://goodson.com/blogs/goodson-gazette/valve-lapping-101
 
I've lapped valves on stock replacement stuff and basic rebuilds where it doesn't have to make the most power, just needs to run decent. The race engines though use 5-9 angles with the valves usually on 52-58° seats just .060" wide. There's no lapping compound anywhere near those. The last set of heads I did had 2.35" intake valves with a cam/rocker combo that made .840" lift and turns 9500 rpm with 4.60" bore x 4.75" stroke.
 
I used to do valve jobs with Sunnen stones. I used to check my seat height and thickness with Blue Dykem and then lap them in by hand to finish.
 
When I R+R'ed #4 ex valves, on DIL's '99 CRV , I lapped in the new valves because the old ones burned due to valve seat recession. The other 3 cylinders had good compression so I didn't touch them.Engine ran amazingly well for 75K more miles until rear ended and car driven to JY With the plugs in, invert the head,wedge it level and fill combustion chambers with water or gas. If the liquid doesnt drain , the valve is tight, I went with smooth to the touch and takes several minutes to drain. I used a 3/8 drill. The lapping stick of yore was a wooden dowel with a suction cup to stick to the valve face As Trav said pre- 1970 cars using leaded gas got by with softer steel.I did VW bug head work all the time by just lapping valves by hand.
grin2.gif
 
Disassemble heads, clean heads, check all valves, resurface 2 heads, check valve stem clearance, re-cutting valve seats, install new valves and valve guide seals, re-assemble 2 heads. $540 sounds very, very reasonable to me.
 
When I performed a head transplant on my Mazda (at 476402 miles, due to erosion of coolant passages), I used a rebuilt head from a nearby "head shop" the NAPA guys recommended. Immediately afterward, compression didn't seem to be as good as with the old head (through indirect evidence, not a compression test per se). I assume that means they didn't do the greatest job of lapping? However, it gradually improved with use. One valve stem in the "new" head stuck up conspicuously higher than the others, meaning I guess it was ground pretty severely.

In early 1971, immediately after inheriting my parents' 1954 Chevy, I hired an overdue valve job done (probably due to lack of timely valve clearance adjustments). That surgery cost $35 altogether, including one new exhaust valve to replace the hopelessly burnt one, one heater hose, and labor. Saved the dead valve as a souvenir.
 
Originally Posted by Trav
Valve jobs today are a lot different than years ago, back then the iron seals were not hardened and neither were the valves. On those grinding them was the easiest and quickest way to do a valve job. Then came induction hardened seats on the iron head and inserts on aluminum, some of the inserts are very hard materials like stellite.
Using a cutter is the way to do these but in any case hand lapping (mostly done by machine today) is and always was a finishing step or for cleaning up otherwise good seats.

A couple of good articles.

https://goodson.com/blogs/goodson-gazette/take-a-seat-a-valve-seat-that-is

https://goodson.com/blogs/goodson-gazette/valve-lapping-101



Thanks Trav....Been a long time since I've done a Valve Job. Though I have ground hardened Valves & Seats. The Valves aren't really that bad......Some seats on the other hand can be impossible with stones. I found that out the hard way on a buddy's Toyota 2JZ-FE.
 
Yes, some of the materials used for seat insets is as hard or almost as hard as grinding wheel dressers. The other problem today is with later iron heads and their induction hardened seats, it doesn't take a that much grinding to go through the hardened layer into the soft iron.

On these unless the seat is badly damaged I just used an egg beater drill with paste to clean them up.
 
Price sounds good for the Bay Area. Check all the keepers before installing the heads. Machining May be done by a pro, but the assembly is probably an apprentice or young kid who
might leave you some loose keepers/retainers.
 
Originally Posted by clinebarg


$540 is a little expensive considering the labor involved in setting the Valve Lash is much easier than "Bucket/Shim" Style set-ups. (Double check the lash before installing the heads!), But....Your in Cali, So that may explain the higher cost.

He is in the highest priced part of California!
 
I spoke with the shop this morning. It appears that they are doing a 3-angle valve job; the person specifically stated that they will be doing a 3-angle cut to all of the valve seats.

Originally Posted by Trav
Valve jobs today are a lot different than years ago, back then the iron seals were not hardened and neither were the valves. On those grinding them was the easiest and quickest way to do a valve job. Then came induction hardened seats on the iron head and inserts on aluminum, some of the inserts are very hard materials like stellite.
Using a cutter is the way to do these but in any case hand lapping (mostly done by machine today) is and always was a finishing step or for cleaning up otherwise good seats.

A couple of good articles.

https://goodson.com/blogs/goodson-gazette/take-a-seat-a-valve-seat-that-is

https://goodson.com/blogs/goodson-gazette/valve-lapping-101


Thanks Trav, this is good info.

Originally Posted by clinebarger
When I did Valve Jobs.....I would grind the Valves & then Hand Lap them to their respective Valve Seat using super fine compound along with blue Dycem to check my work.
Lapping alone will not remove Pitting or restore the Valve Seat Contact Area of the Valve.

Of course if the Valve Seats are worn/pitted.....They will need grinding as well.

$540 is a little expensive considering the labor involved in setting the Valve Lash is much easier than "Bucket/Shim" Style set-ups. (Double check the lash before installing the heads!), But....Your in Cali, So that may explain the higher cost.

The shop did advise me to re-check the valve clearances after installing the head.

Originally Posted by mehullica
Price sounds good for the Bay Area. Check all the keepers before installing the heads. Machining May be done by a pro, but the assembly is probably an apprentice or young kid who
might leave you some loose keepers/retainers.

Will do, thanks.
 
Originally Posted by andyd
I lapped in the new valves because the old ones burned due to valve seat recession. :

That's one more important thing to mention - many people with Hondas don't adjust their valves per the maintenance guidelines(30K for the older models). Honda claimed the K/R series I4s can go up to 100K before a valve adjustment which was hit or miss.

The V6s can go a lot longer before a valve adjustment is needed - but they call for one at the 105K mark.
 
Originally Posted by nthach
Originally Posted by andyd
I lapped in the new valves because the old ones burned due to valve seat recession. :

That's one more important thing to mention - many people with Hondas don't adjust their valves per the maintenance guidelines ...
Not the first engines with that tendency. I alluded to it earlier for the old "stovebolt" Chevy I6. Conventional wisdom was that if the valves become too quiet, you have a problem.
 
On the Triumph twins, they would be noisy when tight too. ''Ramp'' cams - too loose, or too tight, they miss the ramp and make a noise.

Machining and lapping...we stopped doing that early this century. A case from the files - headgasket on a dohc Mazda after an overheat, we had the head skimmed, cutting the valve seats which took more than usual. I stopped by my mechanic as he was lapping in the valves, as he seemed to spending a bit too much time on the job. He's smacking the valve down on the blue pretty hard to get a good mark, but he does get a seating mark. All back together and it's not running well...and a leak down test shows leaky valves. The modern (to us back then) 4 valve heads have very thin stems - he was forcing the cutters into the deformed seat, and a hard smack on the blue test would flex the stem enough to show a good seat. So, we are not going there again, and sold my valve and seat cutters and let the engine guys do the whole job....and then we stopped doing heads, it's just not worth the time, we put another engine in now.
 
Status
Not open for further replies.
Back
Top