This is a video to make you think about it. It’s not about me saying whether it’s right or wrong. One thing is for sure you can make valve seal worse by lapping badly!!
if ya have the guides right and machine dialed in properly you can get get concentricity less than .001" run out. no lapping needed at that point. sadly there are many out there looking to just get it good enough. then again some people can't cut seats properly even with years of experience. feed and speed makes a difference, having the guides right makes a difference, looking at you cat. more goes into it than just cutting seats.
Even when I’ve built multi valve 500-600bhp engines I still manually lap valves by hand with a fine paste exactly the same way you taught me to do two decades or so ago when building mini engines in your workshop :) Good engineering is still good engineering and it frustrates me that for something that ultimately only takes a few minutes a valve people are looking for a short cut that isn’t needed.
I think it’s completely fair to say this is one of the best videos available now on the internet regarding valve seat seat seal. There will be an order on its way in the new year for some of this valve paste. Top top job mister Dodd
@@ACDodd Great video Mr.Dodd. I however didn't understand if you made the lapping paste yourself or bought it from the industrial suppliers. If you did make it yourself, how do you suggest one can do it themselves? Thanks for a great educational video!
@@ACDodd An excellent demonstration, indeed. Now you young people wouldn't know but back in my day, we'd tilt the cylinder head so that the port was vertical, install the valve with a light spring, dust the valve seat area with talcum powder, and fill the port with kerosene or ATF. A beautifully lapped valve will leave the powder dry for hours, a good one will show you spots around the valve in a short time, and an ordinary valve installation will be dripping kerosene. It's all the same -- good sealing (valves, head gaskets, piston rings, etc.) is an absolutely fundamental feature of any good, strong-running engine. A head with valves not properly lapped is a poor head and it indicates a poor job.
Never lapped valves. Seats and the valve face are ground or cut with about 1° difference. Put the valve in the guide and hold off the seat with a finger. Give the valve a quick tap with a couple of fingers so it hits the seat. This will leave a witness mark around the valve face. It should be visible all around the valve face and will show how far up the face toward the margin that the seat is. A very thin smear of grease on the valve face and lightly pushed on the seat will allow measurement of seat width. When this indicates the proper seat position and width, wipe the valves and seats clean and dry. Install the valves with a bit of assembly lube or oil in the guides and the stems. Once assembled, perform a vaccuum test on the ports. With the stems lubed it should hold the vaccuum for a minute. If it does not, there is a leak on either the guide/stem or the face/seat. I never had an issue. Taking care with having good guides and grinding the seats and faces makes the difference. Most of this was on diesel heads that went 100's of thousands of miles.
Also worth mentioning, about half the cooling for the valve head goes through the valve seat. A poorly seating valve also has poor cooling. Particularly important on exhaust valves that are prone to, you know, living inside the flame of a 200psi blowtorch that is the exhaust port... Also also: With a high clamping force cylinder head, some heads will distort the valve seats. So if you're building a maximum effort blown engine with high clamping pressure (probably not a 3-main bearing BMC...) building a torque plate jig for your valve seating can result in longer lasting valves.
Perfectly matched surfaces after lapping are no longer the same in very high temperatures 600C plus. Valves grow up and just are out of the lapping position [pattern] obtained when cold. Race engine builders never ever lapping the valves. Modern valve seat cutting machines give perfect concentric surfaces without lapping.
The same applies when hot. I would agree with you if the the machining action was carried out with a hot casting. The point it both the centre and the diameters will change at heating, meaning both methods are flawed when done cold. I have yet to see an as machined seat that can get less than 2.5% loss on this seal check I use regardless who’s cuts them or what process they use. Valves are not lapped nowadays as the customers won’t pay for it.
Excellent video showing different results from different lapping methods, and also showing how to verify your work. One thing to note - when watching the needle-sweep of leakage, be aware that the leakage/needle sweep is NON-linear, so make sure to compare the same range on the gauge (i.e. from 50psi to 40psi) when making comparisons. Obviously the 1000-grit valve is noticeably different across the entire range.
Spot on as usual, was doing this in the mid 70s when I served my time on jags, the garage had a name for head work, coarse paste was banned from the workshop as it would pocket the valve seats, a good valve job would cure most hot starting problems ,but not a quick job on a jag though.
R.KO...fine work....result under ambient temps......which obviously transcends under heat or load.....now that leaves exacting surface material....expansion contractions.....after this polish method obviously is LEGIT.....that leaves material choice.YES not all LAPS are TIGHT.
Good video. I agree pressurizing the head to test is a good way to test the seal. This is how a good shop would do it. That said, you mentioned in the video the reason you don’t use vacuum for test is because of leakage around the stem. But there is a solution for this. I use surgical tubing on the stem and valve to create a 100% air tight seal and it works perfectly. I have a video showing this method.
this guy is right, i have had a VW head back from the machine shop lately, the ones with the soft exhaust guides, it was badly leaking with new valves and fresh cut seats on more than 1 seat, i do a liquid test before i fit the head, the head is upside down the valves and springs are in and so are the spark plugs, now fill the head pockets up with a low viscosity liquid and if any valve leaks you will see which port it flows from. i have never fitted a head which i didn't lap all the valves in on, but who does that anyway?
My 1996 Suzuki GSXR750 SRAD manual for example says "Cut the valve seat with a 30 and 60 degree cutter( I can't exactly remember the degrees), then leave the seat with a smooth velvet finish. Don't lap the valves as the valves will seat properly within a few seconds after engine is running". Therefore I think since you are using new valves that have not been seated, it makes the method used to draw the conclusion completely flawed.
Never thought I would watch a 20 minute video on valve lapping but here I am. Always good to see a science based approach instead of old wives tails or going by "passed down" knowledge. One question: This makes sense for new valves, but lets say I have a used Toyota head with the original OEM valves. If I take them out & clean them, and they are to spec, is lapping still necessary or is this something that would have been perfected at the factory?
Did you work down through the grits in order, or was each cylinder lapped in with the single listed grit? Also do you have any data on how a "broken in" engine seals? Would the freshly machined surfaces eventually mate together through run time to approach the leak down from a lapped in valve?
@@ACDodd I also ported them for performance. next pair of m113/m112 heads I get my hands on I’m going to go up even finer , spend less time on the begging grits so they don’t cut away to much to soon work my way up to 1.5k / 2k / 3k / 4k paste . It’s diamond paste btw . I’m very careful with it . Light pressure & use very little to get the job done . you can feel each grit cut down & when you feel how it gets smoother that’s when it’s time to switch grits & the colorful paste turns black quickly so that’s also a sign to stop .
Shame the seats are soooo wide. Not that you need performance/narrow seats and that the heat transfer with wide seats is better, but wide seats don't crush out the carbon deposited.
One question! If the valve seats have been replaced with hardened type, it’s almost impossible to get a perfect seal, because, air could escape under the new valve seat, between the head?
Well done on the modern " just machined Cut only" or the older, traditional finished, fine compound Lapped valve job controversy with Precision Leak down Measurments directly linked to valve job finishing techniques.....The 4 different valve job examples dramatically demonstrate how just the Slightest valve seat Irregularities produce measurable, significant Leakage differences.....Assuming, at hot engine running conditions, with valve & seat at Different but extremely Elevated temperatures, Is the Lapped, room temperature performed valve job sealing good as it could be ?? How can the hot, running engine valve sealing be Improved by changing to a temperature compensating procedure,...maybe using a slightly Larger OD valve for lapping & Leakage measurments ??
I'm just learning about this process in my work on small engines. I'd very much appreciate a video demonstrating your technique using the drill press (pillar drill) and the oscillating thing you mention, as well as a link to the oscillating item and why you use that as opposed to mounting the lapping tool directly in the chuck. Is that tool oscillating or automatically reversing? Thanks! (Cheers, that is, from a Yank who lived for a year in Guildford and another year in London back in the '70's - I recognize that accent!) All the best!
Glad I found this. Just lapped valves into a Mini Cooper S. With the head upside down each pod of 4 holds water with no leakage after 2 hours. With paint thinner ever exhaust valve leaked. Permatex grinding compound is supposed to start at 120 and end up at 200. I've ordered Loctite Clover 280 and Wheeler 600. Only choices i could find. This video really helped in understanding how smooth is perfect and what to expect at 200. If i can make the jump from 280 to 600, i will do a leakdown test with oil in the piston and report back.
I have to disagree. If you leak test any modern road car engine you`ll find around 4% leak from the rings.Nothing at all from the valves and they have ZERO lapping. We also have a similar test rig to yours whereby we turn off the air supply on our race heads but use vacuum down the ports. If your seats and valves are concentric and the angles are the same they will seal 100% WITHOUT SPRINGS FITTED just a bit of grease on the stems.You have to remember when the engines at full chat those exhaust valves are around 600*C and have grown in diameter. That perfectly lapped valve is no longer the same diameter and so wont seal when hot.There will be an imperceptible ridge on the valve from lapping which will no longer match the seat. We did however have to modify our very expensive seat cutting machine to achieve perfectly concentric seats .
How do you differentiate leak from the rings, from leakage from the valves? Are you suggesting that exhaust valves operating at working temperatures, do not seal properly, even onto perfectly concentric seats? Why can't the very expensive seat cutting machines compensate for the thermal expansion? What would you suggest the DIY engine builder does, in regard to valve seats?
Can you show test data ? Most of the heat from the valve is going out through the valve and seat contact patch, so they both heat up and both expand, also expansion will not suddenly stop the system from sealing it will just move the position at which it seals at ! also if you understood the lapping process you would also understand that the grinding paste adds a thickness that raises the valve away from the seat. that reduces as the grind paste wears, ie no lip/step or whatever
@@andrewleonard9257 you don't need to compensate for heat, it is automatic within the system, ie a cone (valve) within another cone will simply move in Z (along centreline) but will still seal.
Hello sir, where can I order some of your valve cream? I thought your video was spot on and I really would like to have the lineup of the various grits for my current CR750 build.
Great video. One question regarding valve lapping paste: I was discouraged from lapping at one shop I worked at because the boss-man insisted that once you lap you can't completely remove the paste/grit and that causes problems. Is there a cleaning procedure you follow to ensure the valve and seats are perfectly clean?
Excellent question, I have only ever had issues using diamond lapping paste, in those cases finishing using normal silicon carbide paste cleaned the seats sufficiently. After all lapping I clean with thinnners or brake cleaner, both the seat and the valves
You are the man. You are one of the two people on the Mini forums who's reply i rely on. Hourly rates for skill and good knowledge has always demanded a fair price. Thank you.
You're great mister the explanation was perfect and the amount of information you shared are countless please accept my full respect and thank you for you time and for every think you shared good luck in your job and on your life
I've got an electric valve lapper made by Black & Decker. I'm guessing it's from the early 50's. I never used it I got it with a bunch of valve grinding equipment I bought when an old garage went out of business. It's in nice shape but it needs a new cord and a good cleaning, lubrication, etc
If you want better performance I suggest you do some reading. Service manual will give correct seat width and usually position on valve head (top one third is a reasonable generic setting) For racing you can actually work out correct valve seat width, it will be narrower than production specification. Every single seat you showed is far too wide for good sealing A good generalisation for automotive use, 1.5mm (0.060") for intakes and 2mm (0.080") for exhaust seats. Seats too wide are likely to get a carbon build up and cause a leak, particularly if your valve guides are a bit worn and don't have seals. The vast majority of 'modern' engines (since at least 1980's, probably earlier?) don't have valves lapped because they use interference angles, often 45 degree valve face and 46 degree seat. May not be 100% seal if you check before starting engine but it will be 100% after first start. There is a lot, lot, more to know about valves, 4 months watching You Tube video's won't tell you an awful lot of useful information. I've watched way too many video's where people don't know what the hell they are talking about (forget name, mushroom, tomato or something weird) was going on about high revving Honda car engine but didn't even know valve springs were fitted upside down (that's bad and severely limits max rpm) David Vizard has several video's, mostly on small block Chevy, but, the information on valves and porting is applicable to any engine that uses poppet valves. Personally, if I need to lap valves I feel I cut something wrong, width or position. Solvol Autosol works fine to get an accurate measurement of width and position on valve head if everything is right, there are also several 'classic' tuning books you should probably own. Oh, since I retired, I really don't have anything better to do 😂
Thanks for the post, but having cut heads before that have passed the 130hp mark using only the stock exhaust valve sizes, and having many customers who have had heads cut by me can vouch for my experience with porting 5 port castings.. As for seats being too narrow, the a-series runs at high seat temps and will simply pound the seats out when used for typical road mileages. The narrowest I use is 1.7mm inlets and 1.8mm on modified heads. Any less than that will deliver unacceptably short service life. For further information, you might want to watch this 6 part series on rebuilding a 1275 cylinder head; ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-XtR1fOWdh70.htmlsi=PWAmOZ6cSeqOxzWZ
@@ACDodd Haven't worked on Mini's since I was 17 or 18, quite a long time ago. Never said anything about seats being too narrow, 1.5mm in. and 2mm ex. were generics that work on just about everything. I only said the ones you showed are too wide. Have you read Vizard's book on tuning the A-Series? He is an engineer who wrote tuning articles in many publications in the 1970's (probably before your time?) He did development work for many car companies. Here'sa You Tube video, it's actually much older than 12 years ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-ow5cGV7bXCw.htmlsi=bQhkJWFtzT3msiCZ
@@1crazypjI am well read and am fully aware of MrVizard and many others. I am also aware that a lot of information in books is old. The idea of this video is to give my view, nothing else. Things have moved on a lot since the information that have been written by many authors on the subject of A-series tuning, especially camshafts and cylinder heads. Thankyou for taking the time to write an extensive answer it is appreciated.
Top notch. I always knew there was something wrong with average auto parts store "lapping compound" [which is always on the coarse side]. Grinding paste is a better description. Your test method shows why. Tricks learned from steam applications?
@@ACDodd Dear Sir, The exhaust valve seat will have an expansion during operation because of high temperatures. If the contact is full contact, then the contact profile will be different during operation due to heat load. Hence, in my opinion a line contact will suffice.
My cars workshop manual says that you can recondition valves by lapping them but if you need to use new valves then do not lap them under any condition and you must have the seats in the head ground to spec. Also valve seats on the valve are supposed to be at 45 degree angle and on the head at 46 degree angle. I assume this is necessary for proper seating once engine warms up? On top of this according to the workshop manual, actual seating area is supposed to be less than a millimeter in width.
Thanks ! I never knew the fine paste I have used for years was not fine enough . Ta muchly . And vacuum testing .... damn , you are worth listening to !
Hello, great vid. I was wondering your thoughts on a 3 angled valve job compared to just the 45⁰ being lapped tightly. Also I looked up the 1000 grit clover paste wheweee! That is pricey. They have a diamond tech brand with 600,800,1000,1200 grits. Any good? Cheap compared to clover. Anyway, great stuff and excellent food for thought.! Thank you for this.
I had a bad experience with diamond paste an now use silicon carbide water based product from Kemet. However it’s very expensive to purchase as it only comes in relatively large sizes.
What is the outcome of using finer than 1000 grit? The more seal the better the sound of the engine? More power? I'm just curious because I'm gonna lap valves and since you have years of experience maybe you could know
Always nice to learn something new, I’d only watched the first half of this before I saw you yesterday, definitely going to check what paste I have and find something better
I was gobsmacked to see the 4% meant roughly half of pressure was lost in just under a second. Granted, its only chamber volume - full cylinder would take longer. That makes an engine wheeze on down the road. The description of good valve seats making a running engine sound "digital" is pretty good: things are popping along with clarity and distinction.
@@ACDodd I tried 3m compound for car surfaces. Yellow squeeze bottle. Not sure the grit . I lapped all 16 valves with normal lapping compound . Then cut with oil and lapped again. Then cleaned off all surfaces and used the 3m compound. I even did another final lap adding tiny bit oil again. Deff noticed a difference in the steel looked more shiny like yours. Redoing heads and 350 for 72 c20 step side. Just a driver . But want to practice lapping for my GTO. Will test soon when the valve o rings come in .
Nice demo, thanks for sharing/teaching us knowledge ... Would be nice to see how you lap by hand and how to make a finer paste .. Its a wonder you dont provide a link to purchase your 3 home made grades ... Im sure they would sell ... 👍
Hi, I watched and listened and it all makes perfect sense given the results and comparisons between valve paste grades. These findings only ever come from someone like you who has done lots of homework! Great stuff 😊
Great video! Thanks for the testing idea using the press and rubber mat. I was able to do that today and it's nice to know that it's going to be OK before going to the trouble to put things back together. Thanks.
That's pretty interesting. Didn't expect to see such a difference, especially between different grits. What I wonder, though, and can't seem to find an answer to, is why do we need oscillating action when lapping valves? Why can't we just chuck them up in a drill and spin away?
Exellent video. I wish I'd had known this 9 months ago when building my engine! I'll be forever wondering what potential HP is wasted. I was told by the machine shop not to lap the valves but I couldn't help myself and used the bog standard fine paste. Next time I'll go all out. After the 1000 grit could you use something like autosol metal polish to finish?
Great to see a guy become an expert in a specialised field through hands-on research and data collection. Particularly like building your own tools to test, and making your own paste. Thanks for sharing, it all makes sense to me!
A valve job done with quality valve and seat gear does NOT need to be lapped. If the seat is a poor fit (checked with bearing blue) and needs lapping it reflects on the quality of the gear being used. Do people really think a brand new vehicle had the valves lapped into their seats when the engine was manufactured???
@@ACDodd If quality equipment is used to face the vale and cut the seat, a vacuum proven non lapped valve will achieve a "perfect seal" within seconds of starting the engine as the valve impacts the seat a couple thousand times a minute. That would be around 6000 times a minute on my race bike.
@@ACDodd Take a hi performance engine valve, lets say a coated titanium valve, stick glorified beach sand suspended in paste on its face, and manually grind it into the valve seat. Is this (a) going to improve engine performance, or (b) demonstrate the person who did that hasn't a clue. Many high performance engines these days uses 'exotic' engine valves and NONE of these should ever be lapped (or even resurfaced). Perhaps you should write to Porsche, Ferrari, Mercedes, Suzuki, etc, etc and advise them they should be lapping their exotic engine valves to improve performance. They may appreciate a good laugh!
@@johnwoodrow8769perhaps you should look at this video from the point of view of the diy person who it is aimed at. Mainstream manufacturers have access to much more expensive and higher accuracy machines, the home mechanic does not. If you listen to the video properly you will understand that, and also the opening minute explains this.
An explanation of 1970's technology that made valve lapping basically obsolete. This equipment can still be purchased today from Warren and Brown. The W&B stone carrier is unique in that the pilot of various sizes is locked into the stone carrier, and spins freely in the valve guide (exactly how the actual valve behaves). "Synchro-seating valves A process known as synchro-seating can be used to produce valve seats with a fine finish and at exactly the same angle as the valve faces. With this method, the valves are refaced in the usual way, and the seats in the cylinder head are rough-finished to the correct angle with a stone. After rough-finishing the seats, the carrier with its stone and pilot is mounted in the valve refacer in the same way as a valve. The grinding wheel is then used with a very light feed to dress the stone, just as if grinding a valve. The stone will have a fine finish at exactly the same angle as the valves. The seats are then given a finish grind with the finely dressed stone. With this method, the seat angle will match that of the valves. The valves can be checked for correct sealing with bearing blue, but lapping is normally not required."
@@ACDodd If you truly want to do a worthwhile test, take say 6 a cylinder head from a decent motor. Get all the valves and seats professionally and quality cut. Fit the valves to cylinders 1 3 5 lapped, fit the valves to cylinders 2 4 6 without lapping them. Reassemble motor and drive the vehicle for say 50 miles. Now do a compression test. I'll say there will be no material difference or pattern in compression between the cylinders lapped, and those that were not There is your challenge.
I really don’t understand how people can say that two parts machined separately, albeit to tight tolerances can expect them to seal anywhere near as good as if they were lapped together correctly. The internet makes my wee wee boil 🤣
