Hey Eric, Tim here.......i learned cutting seats with a stone (circa 1982), in auto shop class.......wish we cudda had proper cutters, etc.....but in auto shop, you wen't learning hi-perf stuff persay, it was make it useable for a daily driver......and i did ALOT of heads in auto shop, cuz i was good at it......but i always wanted to know more.......now, i've known for YEARS now about angles, chatter, etc.......this vid is CRUCIAL for younger folk, just gettin goin......they MUST learn about chatter marks, and how to address them.....ESPECIALLY for performance work.....what a GREAT vid!!!!!......i just LOVE it!!!!.......content is SUPERIOR!!!.....PEACE to you sir!!

I have a really good set of pilots, stones, and stone holders. I used to do a lot of heads the old way, years ago, and I think I was pretty good at it. On several occasions, I was approached by some car owners, unhappy with the way they're cars were running. On a couple of those engine rebuilds, I diagnosed leaky valves. Both were done by (then)new form cutter machines. I reground the freshly cut heads with my old school Sioux seat grinder, and had them running much better. Now, don't get me wrong, if I had the money for a Rottler seat machine, I'd rather use that. I guess my point is that it isn't just the tool, it's the operator who runs the tooling. He has to take the time, and use proper care to not feed the cutter too fast, or run the cutter speed too fast to avoid chatter and tool deflection. And he's responsible for closely checking his work. I used to check all my valve jobs with a Sioux vacuum checker. I also used an adjustable seat scribe to help get my seats the same height.

Watching this video took me back to my teen years.i remember going to a junk yard and buying a set of coveted 906 heads for my 440. When I got them home and started cleaning them up , I saw they had about a half inch of carbon on the valve stems. So I pulled all of the valves out and wire wheeled them and then putting them back in, in no particular order and lapping them in. The lapping seemed like way too much work to do by hand so I had a bright idea, why not just clamp a drill to the stem and lap the shit out of them by putting some compound on them and giving a good long pull! Surprisingly the car actually ran pretty good! These are the things s teen with no money, little knowledge, tools and a desire to go fast do.

OMG I still have my Sioux stone grinder sitting in my garage. Looks almost exactly like yours. I run an IDL valve seat and guide machine. But certainly cannot cut as much as you just have to go slow. Loved your video Eric. That was a great idea to stone lap those chatter marks 👍🍻🍿

Good video. I worked in a small head shop in the early 90s here in Australia. We got one of the early small Serdi machines and had stones too. We weren't as fussy as you back then but everything you said was 100%.

Great info for a young engine enthusiast like myself. Thank you for clarifying all the misconceptions and providing us with your wisdom

Thank you for making this video Eric. I'm over in Claremore, not far from you, and have always been impressed with your work. I run a sunnen VGS-20 and I have been using 800 grit to check my valves and seats(I know I'm being to picky) and have been very impressed with how well this old machine holds up against the new Rottlers/Robinson machines. I feel like Sunnen, even today, made the best seat and guide machine out there. Great video man, we have been trying to tell people for years that a lap job with 200grit 🤣 just won't cut it. No pun intended. Lol

Thanks for the info Eric this is the stuff we want to see! Not only showing why you do things but showing what will happen if you do things differently!

I was always taught that lapping is for cleaning up / freshening the seat and seal , but , to go ahead and spring for a real valve job after a couple times lapping them . Stones will always have some utility , no matter how good a milling machine gets . I wonder if the chatter is also partly due to variances in the hardness of the seats ? Easy to imagine that the hardening process may not have been done as well as it could have been , and / or the composition of the seats is not as homogenous as it should be . Everything isn't as well controlled and consistent as we would like it to be , even with all the technology at our disposal these days . Really makes you appreciate how good the old guys were , and what they could achieve with what they had available .

Don’t forget about the role the valve seat plays in transferring heat too . . . Arguably more important than the flow aspect

I've been using the Neway valve seat cutters since the early 80's (3 angle)for Atv,Motorcycle and marine Cylinder heads.Seem to work decent and I always leak test my work.i would love to have a serdi,newen or rottler but I'm semi retired nowadays and even if I purchased a nice used machine I doubt I would be working long enough to make it worth my time.ive sent off a few heads to have seats replaced(I do the guides myself)and was very impressed with the work,especially the radius type cut on the exhaust seats,very nice.i enjoy your vids young man,keep up the good work.

Thank you for having the guts to talk about chatter and being honest about how it happens to everyone.

Lol. I knew what heads those were before you said. I have seen many of them. YES not perfect, but with a little work, the are great ! Good information. I love your videos !

You are so right about lapping. Another issue with uneven seat is uneven heat dissapation. Good info!

Back in the day I used stone cutters. I did a 3 angle valve job. It took time to do a good job.

Chatter seems to be mainly about cutter angle vs seat hardness, alongside cutter pressure vs edge quality. It is complex, and as you point out sometimes a stone is needed for the final touch. Nicely done.

Lol, had a 454 last week that I installed N series seats into the exhaust side kick my ass. Stones saved my butt on that one at the expence of quite a bit of time. Was getting so angry I almost pawned them off to the neighboring shop😂. I stuck with it though and eventually got them how I wanted them bet dang. Good info you shared👍

Good info here Eric! Many People think wrong about valve jobs and do underestimate their importance. Nor can they imagine how difficult a precise seat cut is. We are using the Serdi Stronik CNC since January. It is a DREAM and to be able to adjust each angle, width or radius makes it priceless. Best „PlayStation“ i ever had. Keep up with your great videos, all the best from germany! Tim

Love watching your videos you have great information on everything you show us thanks.

I ground cranks for a few decades chatter from a stone was usually a wheel that needed dressed.. but sometimes was the machine was getting slop.. make sure the machine bushings aren't getting old when youre on left side.

As a teen in mid 80s we had a multiple auto parts stores , a garage & full service auto machine shop & stones were a way of life for our cyl head guys in those times & one of the guys had it down to a science , we preferred stock & industrial head & block work but 3 of us 16-35 year olds had race cars , we sold out after 30 years & stayed in parts as an independently owned in a box store world , at time of selling the machine shop equipment an older worker said ain’t you gonna keep that stuff & I said nope once you see the 5 angle cutters we had used the last few years in the mid 90s in the Peterson Seat & Guide machine it’s the only way to fly. Never a stone cept to touch up boo boos in our race heads. Excellent video Eric brings back memories ! I’m Saving up for a set of sbc heads to buy from you bare & using your advice on what quality stuff be best to build them to with meet my needs. I was wondering if emailing you be best when I’m ready in a few weeks as I know all about drop what I’m doing & tending to the phone , as I do throughout the day, as Dad told me don’t bite the hand that feeds you. “Appreciate your attention to detail !

great video eric,love your stuff.one thing you can try ,because i did this in the 80s & 90s,with a new mandrell & pilot (which i notice you have)put a spring between the mandrel & the guide which slightly holds it off the seat.use a very fine stone & when you sharpen it go slowly.spin it up & just lightly touch the seat.which removes very little material.i was very good with stones because that is all my shop had but i did drag race & circle track stuff ,then vacuum tested & had good results.even though i dont do machine work anymore im still very interested in it & still occationally do some port work & getting ready to retre from my job now & going to get into racing work as i did machine work for 7yrs.

Great video, my dad was a marine engineer old school where they actually rebuilt engines on the ship. The valve seat width is also important because not enough width will reduce its ability to cool the valve and will burn it out. 1 engine reconditioner told me once all the lapping in is a waste of time because all that hard work the valves and seats get mooshed together anyway when running taking all that work away😄

Lapping has a place today , but it played a bigger role back in the flat head days . Back then , a couple of hours lapping valves made sense . But those were mostly back and forth to work motors , racers pulled the engine and did it , or had it done right . To me , lapping is just lapping . A valve job is an entirely different animal .

Ls cheap guy here. I've been working with some factory Ls7 head for sometime now. Had a couple of machinist look at my heads and none of them said there was issue with my valves. I've dropped 3 valves. Looking at the price of having the work done I'm going to do the work myself. Thankfully with this being a project car, I can take my time. Replace the guides, use a dingle hone to slowly arrive at the right diameter, and lap the valves in. Checking the guides with a bore gauge as I go. I am chasing titanium intake valves dropping. The issue seems to spur from GM not machining the valve seats to be concentric with the valve guides. Causing excessive wear on the guides. Also keepers wearing on the valve stems to the point the valves fall Thank for the quality information! Good luck spreading the good word.

14 years cutting seats on a serdi, never have I even thought about using lapping past. If the valve doesn't seal when cut, the cut is wrong simple as that. Also note when Eric dropped the valve onto the seat, the valve bounced. This is because the seat is perfectly round and in line with the guide, if your valve doesn't bounce when dropped, there is an issue. Exception to that rule can be Klines and the close clearances Kliners allow you to run.

I bet if you have a lathe you could make an aluminum or brass lap that would thread onto that Sioux stone holder. If your sealing angle is 45 degrees make it 45 degrees. Then load it with lapping compound and it might do a super nice job touching up chatter like you showed. It would of course have to be machined while on the Sioux stone holder so that it runs true within a .0001" or so, and it would probably need to STAY on the arbor at all times. It would probably last a long time before needing refaced. When lapping the "lap" should be softer than the material we are lapping that way it picks up the abrasive by embedding it in it's surface. Aluminum usually works great :-).

Very informative video, thank you.

Fantastic video & information!

I believe each tool has its proper use, it’s strengths and weaknesses. Eric, like you I struggle with certain seats in certain heads on my seat and guide machine, it’s an older 046 Kwik way, not nearly as nice as your Rottler. There no rhyme or reason, I find it best to move on and fix it with stones, I have a Sioux wet grinding bench I use for that type of work. I also use that for touch ups during between season rebuilds on heads I’ve already done. My philosophy is that a round seat with a reasonable amount of runout will seal, but an out of round seat from some of these cnc seat machines will never seal. I always strive for minimal runout, but I always wonder what those number actually look like at operating temperature.

Yep.years ago I went to a seminar AT UNOH in lima Ohio. Learned alot about the importance of valve jobs and wet flow from Darren Morgan and Joe Mondello.The Engine masters Challenge

Good video Eric. While I like the form tools for seat machining. I believe you still have to have stones. I have done 3 angle, 4 angle and 5 angle valve jobs for years. The difference is time, grinding takes alot of time. And you need to wear breathing protection. Hearing protection also. Most us old guys did not take care of our selves like we should have. Machining is faster and healthier. IMO. There will always be a need for grinding. While machines are awesome, you have to have a back up plan when things don't work out. The valves must seal. Thanks for sharing Eric. Take care, Ed.

Only used stones for seats. Generally Sioux seat and valve machines, for heavy duty heads. Always checked seat location by dropping the valves in, holding one valve at a time off the seat and giving a little smack onto the seat. This leaves a shiny contact mark close to the margine. If not contacting all the way around there will be an area without a witness mark. Then a bit of light grease on the stems before final installation. A hand vaccum pump will show real quick if the seat seals well or not. Being careful during grinding shows in the results. Dress the stone regularly also helps consistency.

... Lapping with a600 grit compound is the last step in my valve job. It indicates seating and contact between the seat and the valve ....... IMHO. Thank you for your sharing good info and knowledge.

Another great video….thanks

The way it was explained to me decades ago. Think about the valve job like your fingers releasing a football. Or the crown of your barrel they very much influence the direction and speed.

Machining anything has the potential for chatter. Having the item securely mounted and operating the cut at proper feed and speed will mostly remove any chatter, but a machinist must also use the proper cutting bit for the application. If you still see chatter after all this is done and confirmed then you likely need another machinist or more practice.

Very good information here.

Great video superman!

The 7 angle valve job they just did on my Tesla really made a difference! So pleased with this performance!

13:30 was my day at work today. Just fighting to get good seats with the old worn out Peterson the shop I work for has. Stones come out in the morning. I do have a question for you though. Do you have any recommendations for books on seat geometry? I’m to better understand the changes associated with different angles and widths of each angle. Also porting book recommendations would be appreciated as well. Thanks for the videos, I just found your channel and love the info you put out. I work in a small town shop on ancient worn out machines doing mostly stock rebuilds. However, I’m going to be starting my own head shop that will hopefully grow into more.

Huge facts in this video Eric, thanks for shedding some light on the subject for the Ill informed.

i have always laped with compound (small wood laper) never used water to chek leaks just compression test leaks

thanks for the great video man ! great stuff....FINALLY ! somebody that calls a "Spade" a "SPADE" !!....OnWard......

I believe the lapping compound is a guide marker..

That's exactly what I use my stones for now also. Just to clean up any chatter if I get it with NY full form seat cutter

What valve job would you recommend for out of the box Brodix RR270 heads with CNC chambers?

Does the 5 angle cutter leave the proper ~90 percent throat diameter?

I have an engine that failed a leak down test and had some bad leaks on the valves. I took the head off and poured water into the chambers. The chambers would hold water but slowly leak and if I blasted compressed air into the ports, I would get lots of bubbles. Yeah, it could have definitely used a valve job, but I just wanted the engine to run right so I lapped the valves using the 3M lapping compound. I noticed that this compound was very coarse and left some deep scratches as was observed under magnification. The water test revealed little tiny air bubbles when I blasted compressed air in the ports. I researched this and found that there are lapping compounds that get very high in grit, like 2000 grit. These lapping compounds were very expensive though and I didn't want to spend so much money on them so I made my own. What I did was I bought some white metal polishing compound from Harbor Freight that comes in a stick for a few dollars. I scraped some off with a razor blade and mixed it with WD40 to form a paste; which worked out quite good after experimenting with many other solvents. After lapping with that stuff, I was able to blast air at 150 PSI into the ports, right up to the back of the valve and not a single tiny little bubble was observed from the pool of water in the chambers. Long story short, the engine now runs like new.

Great video Eric 👍🏻🇦🇺

i came here with an open mind, with the ability to learn. currently building a small engine, but the knowledge is all the same.

Is the bouncing valve test, when inserting into the guide, for motorcycles as well? Seems like if the valve stem slides so easily through the valve stem you have more play in your guide? My motorcycle valves need to be pushed through the valve guide and seal in order to seat.

Yepp, I seen it many times where people lap Valves, it drives me nuts. No Lie when I didn't klnow better I use to do it I hate to admit it but yes, I was poor and did what I could. I have used a "ball Stone" on a drill when I was like 15 or 16 on a small engine head and had "good to me" results lol. What I learned is that A "mirror" finnish on the Valve Guide and as you said the Valve Bounce is a good valve job.

One of the best tech videos ever.

I paused the video in the middle after you explained the valve seat angles you can cut. In a diesel head, a three angle cut, I assume now, is all that is needed correct?

Guys do not realize how much power can be lost or gained by the valve job. Thanks for sharing !!

Razorblade rebuild I reckon. When you're in a pinch during a rering/ bearing job for an engine that will be driven as intended....it'll run. Machine shop trips add up quick and milks $5 a gallon.

Always enjoy your videos. You didn't mention Neway cutters, any thoughts on them? I suppose they present the same problem as the stone in regard to height. What's the proper way to measure height? Do you ever use Neways or are they more of an amateur DIY tool? Thanks for the videos.

interesting vid', i've lightly lapped leaky valves forever and it works for me . On balance trusting this vid' from a guy with such clean, soft skinned dainty hands and carrying on as usual i think i'll acknowledge his thoughts on seat angles but carry on lapping when justified as usual.

I noticed with the single point cutter it's performance in producing a round (centric) and chatter free is the valve guide clearance . I had used the serdi valve cutter and it was tough to get a even cut . Seemed to want to dig in,and messing things up on me.

Is there a horsepower difference between 2 identical cylinder heads except one set of heads is 65cc combustion chambers and the other set of cylinder heads are 76cc combustion chambers? Both engines have different pistons but both are 11 to 1 static compression? Is there an advantage to using 65cc over 76cc combustion chambers or vice versa?

I'd love to see a video with before and after flow numbers on an LS head with no changes other than the valve job.

Hypothetical question... hypothetically speaking, if a person had an engine, rebuilding it on a stand. The engine is mostly stock with minor upgrades (0.030 over + torque plate hone, ceramic coated pistons, rotating assembly balance, a few lbs of boost, head studs, main studs, camshaft replaced with one profiled for low rpm torque) but the engine isn't meant for a few 1/4 mile passes, the engine is meant for 350k miles to 500k miles of heavy and hard towing. If I wanted valves to have maximum sealing during the service life of the engine, should I get a valve job? And which would be best for longevity, not short-term performance. Do 3 angle and 5 angle last the same? Or will one wear out faster than the other?

Lapping is only a check to make sure the valves 45 is contacting the seat’s 45 properly. By rubbing (spinning) the valve against the seat with the compound (or dye or sharpie) smeared around the seat you will be left with an exact mark of where the two touch (contact patch) hence you can visualize with the naked eye if your valve job is in the right place and concentric on the seat and valve itself. Like you said lapping can not really correct anything other than maybe clean some staining or stubborn carbon off. Maybe polish out some extremely fine lines or groove on the micron scale but it just doesn’t remove enough material to correct anything. Anyone who have ever ran a mill or lathe knows that even a .001 cut removes visible chips. When lapping valves there’s no chips so to say. Maybe a few microns of metal dust is left and mixed with the abrasive but not an appreciable amount to correct a wonky VJ. Do you ever do any motorcycle heads Eric? What’s you thoughts on full radius cutters versus putting angles on the seat versus Newen’s cnc single point cutter system?

TO BOWL OR NOT TO BOWL... That is the question. I would love to hear more about whether we need to dig bowls on nearly-straight ports. Is there a recipe? Bigger turn, bigger bowl? I have a 1996 Mustang Cobra with DOHC heads that is notorious for flowing TOO much--killing low-end torque but is crazy good up top and ideally suited for blower. In fact, Ford had to install IMRC plates to compensate for this (closing one of the two ports until 3250 RPM) just to get some velocity and help low-RPM torque. But my concern is that digging a bowl in the intake ports near the valve stem and before the seat will make it even worse... or will it?

Great video

Shouldn't all aftermarket head's be checked for runout and for sealing? I've heard of people's nightmares with assembled head's

Ive done small engine repairs with a sharpie, a stone on a dremel and lapping compound, im lazy so i grab the valve in a dewalt drill and pull it into the seat. But thats also on a twin cyl mower not a performance v8.

Use the five angle insert for a semi rough, so to speak, and then come in and just kiss the seat with a single angle insert of your choice. That deflection due to cutting force is why you get the dip at the spot the two valves are close, a little less material lets the cutter dig a little deeper.

Hi Thanks for this. Very informative. what is your opinion on new valves on old valve seats? I understand that if the guides are worn and the valves have been jumping around and is not sealing 100% if the seats are OK can the new valves and seats be married together if you work the new valves to the old seats. i guess what i am saying is ,is this possible to tidy up the seats lightly with the stone.

Heads that flow well one way will also flow well in reverse. On newer, small, multiple valve per cylinder, light springs, this can be a real issue. The old vacuum test may show a good seal...but it's not. There's a better way. Besides the headaches this will give you...there could be some things worth testing and studying.

I've never used lapping to fix anything, only to confirm how wide the sealing surface is against the valve, and to confirm it's position relative to the valves outer edge

I remember in high school shop class we got to tear down lawn mower engines and one of my valves was burnt. I lapped that valve for the whole hour to try and get it to seal. Mine ended up being the first to fire up. lol.

Nice thanks fron Brazil

I'm still in the stone age, and it does take much longer I agree. Never the less I still have some scarry monsters out their prowling the earth.

Before the Serdi Machine and some of the later machines that you could actually do a valve job with all the high end shops used the Hall Toledo Orbital Seat Grinding Machine and the radius dresser ---

On my Tobin Arp its almost always scattering on the left.

Can you do more valve job tech videos. All videos great.

Hi Eric, I just watched your video. Thanks for the great info. I have a new set of AFR 195cc SBC heads, still in the box. I'm planning to do a leak test on them, and lap them if necessary. But after watching your video, I'm not sure I'm headed in the right direction. I live in a big city and I'm sure there are lots of shops that I can take my heads to. But I have a hard time trusting people I don't know, s I'm reluctant to turn my new heads over to someone who may damage them beyond repair. I like to do as much of the work myself if possible I am not a professional, I'm just a guy doing a restored project in my home garage. What would you advise me to do with these heads? Please help . Thank you. Don P.

Eric in a previous video you said you liked to radius the intake valve job into the 60. Are you saying now you like to leave the sharp edge into the 60 or the 45?

I noticed in another guys shop, he had a strap running over the center of the head, my guess to help with chatter. It’s hard to stop chatter when your removing so much material with a single face cutter.

I want to buy a valve seat cutter head for use with my cincinnati mill. Its kind of like a bridgeport but heavier duty. I just want to use it on tractor heads and these for the most part have valve stems 90 degrees to the deck. I notice some have a ball drive system while some fit right in the spindle with a morse taper or a milling machine taper. Which would you recommend.

Been a machinist over 20 years now, mostly large industry but always been a gear head mostly BBC. I do most of my own work now and I get by with an old Sioux stone grinder. I’m expanding and would love a real valve seat machine but it’s not justified yet. That said, I can achieve seal without lapping with those tools. I just had to correct concentricity on a pair of Harley heads, the weight of the valve held lacquer thinner with no spring for hours. It just takes more time and dare I say skill?

Chatter is caused by a 'flexible' set up or actual lightweight machine. The tool 'digs in' flexes and bounces out leaving rhythmic 'waves', dull cutters can often make things a lot worse The SERDI style cutters will always be pretty flexible as they have a huge cutting surface relying on a rather small diameter pilot. The style of cutter has been around since 1970's but was at that time designed to be used in a vertical milling machine and required a much longer set up time to get head properly aligned. Original factory cast iron heads were done on multi spindle machines specidfically designed to do valve guide and seats in one operation Very few production engines have ever used a fully radiused valve seat ( the only one I have any experience with is 1960's Royal Enfield motorcycle) It was a very long time before I found out air doesn't like to 'turn corners' and anything more than about 7~8 degree angle leads to flow separation from surface (why most multi angle seats are cut at 15 degree angles,( 75,60,45,30, 15) This is not the most efficient for flow but is a reasonable compromise. In flow tests, the 'best' seat shape( for intake) was a parabola but I have no understanding of the math involved calculating it for different venturi sizes. BTW, I found an Engine Masters magazine with you in it, 540 big block 800+BHP, forgot to check date but I'm sure you remember.

Going to build a blown 427 bbc. What head would you recommend? Want to start with an as cast head on gas. Oval port or rectangular. Will be running a solid roller cam.

what about using a drill with the 120 grit lapping compound because that suction cup thing was taking way too long?

On a Gen1 (what I'm working on) is there any real comparative hp difference to doing a 3 vs 5 angle. 350 sbc 9.6 to 1 compression Started life as a 290 gm performance crate engine. Have a used set of Promaxx alum heads. They look brand new BUT, going to the machine shop be be checked and a valve job done just for surety. Q is 3 or 5 angle and the value of the expense vs gains.

Will lapping take out e few spots of minor scuffing of the seat, by a 100 grit cartridge roll? Lesson learned. 1st time 😢

Thank You Good Tech. To Know

Paused... Valve jobs have three functions: seal, air flow, and heat management. The basics needs to be able to transfer heat into the head to stay cool. Maybe more important with diesels, but it's still a function of a valve job. To be fair, I'm far less experienced with all of this than you. Also, is there any benefit of drawback to using higher grit laying compounds? I have diamonds polishing compound and I've found myself wondering if I could lap a valve to 12k grit. Mostly just morbid curiosity, I kinda doubt it would really seal any better.

I like to just touch the seats with a trued stone after using a form cutter. Never seen a form cutter seat quite good enough. Single point cutters are so much better, but like all machining you can mess things up if you're hurrying or not paying attention. Just night be a seat needs 2 passes to cut right instead of one heavy pass. Eric I'm happy to hear you cringe over the junkyard LS build stuff. %0% of those engines from junkyards around here need bored out from condensation rusting bores. A turbo on an engine with 150,000 miles is STUPID for one thing.

Thx Tex

Neway was the best. Interference angles seal 100% . And fast. Great for production. 16 seats 15 minutes, floor to floor. As far as valve height, level them up on the spring side. Clip the stem tips,. All valve refacers have a srem cutter. And set the spring heights. You'll never make any money if it takes all day to do valve job. All valve jobs are the same hi po or street. Do them both right. Not an inferior job ona street. Did it 50 yrs. Many engines, many heads. If we took all day doing a valve job we'd get fired. Do it right do it fast! Just my opinion.

I don't see how the stone can be blamed for the seat being inserted crooked... if the seat is croocked and one cuts as many angles with stones than with a machine cutter the result will be the same, as both are center on the valve guide. Only difference will be the time it takes if one needs (and the cost of the equipment)...

Where does the oil get past a Valve, and what fails to cause it, making the cylinder consume oil ?

Hello thanks for the education question i have is should i have had machine shop do valve job on the new 200cc promax heads before using them. THANKS MUCH

Do you cut dry? Or do you use a coolant or cutting fluid?

If you lap it enough, it will seal. They do it all the time with industrial valves.

Have you ever done stock Mopar 906 heads?,thanks !

How many CFM is gained by going from the factory valve job to the latest high performance valve job??