So did some head work for someone who said his car wouldn't hold any pressure during a leak down test on cyl #4, leaking it all out of the exhaust side.

For anyone who thinks its not harmful to install and run even a mild upgrade like a 16g and turn up the boost, here are two pictures. The first is what a valve should look like. Bad macro shot, but a smooth surface.



This valve is out of his head, after attempting to tune his 950's and about 20PSI on his 16g.

So he's bad at tuning then He attempted to no?

Even if he attempted to....

Was he running ecmlink? Even with stock timing & fuel map it should be safe for 20psi if injectors dialed in correctly & fuel is sufficient. You sure engine was not already bad to begin with?

The tuning history seems fuzzy. He has ecmlink but it was dead or something?

He said he had 950's running with it so it had to have been tuned in some way, but also said he saw around a 14:1 afr under boost and it would always cut out. Personally I'm surprised it would even build that much boost running so lean.

Sounds like a lot of unknowns and typical crappy DSM maintenance.

Slide this, slide that, check this, didn't blow up = 16g 400hp, perfect tune.

Meanwhile inside...



I cant understand why people spend money on parts, but refuse to spend money on a tune/drivetrain stuff to actually make use of their new parts.

Whats so bad about the valve in the second pic? I don't get it.

It was all distorted and warped due to dealing with very high EGT's (due to running extremely lean and lots of knock) that the oem valves weren't designed for and wouldn't make a seal because of that.

Have you inspected the pistons? Running lean will usually leave pits in the top of the piston.

I didn't see the engine, he just asked me to replace two valves. Says the other ones held good compression, just cyl 4 was at 0. The other valves were bad too, but I told him to at very least replace the head or have a block rebuilt on the side because I wouldn't trust it to last over a month if he was careful.

Would the valve not burn up before it bent and distorted?

Did you lap the valves?

Unfortunately I haven't been doing this for long enough yet so someone else could possibly chime in, but a shop I talked with about seating valves some time ago told me to make a couple lines with permanent marker across the valve seat, then spin the valve on its seat to cross the line I you draw and back and remove the valve. If the line has a separation, then you know it's making good contact.

These ones wouldn't. I think they only made a decent seat across 1 of 4 lines whereas the ones I put in made a proper seat across 8 of those lines.

That shop told me that they never lap valves on performance engines as it puts a lot of wear on the valve and unless it's properly cleaned afterwards, you will be sending crap through the engine which is very harmful.

Said if it won't make a good seat, then the head has to be machined.

May I suggest that you never return to that shop...

If a Valve does not make a good Seat the Head should be machined... It should be more like if a Valve does not make a good Seat it should be ground, Seat machined and the Valve Lapped into it's respective position...

Ghislain

I forget the shop name, went there with my uncle who's been into racing for a long time and has good connections. Knowing him, if he trusts it, I trust it. According to the shop, lapping valves is what everyone is taught in mechanics school to be the only way of doing it, but isn't the right way to do it.

That's what they said. If you can't pass the seat test that they do, it's got to go for machining.

It makes sense to me, if a valve is making a good seat all around doing their method of testing, why would one lap it anyway.

You must have misunderstood. Lapping is performed after the seat is cut. The seat has to be correct THEN you lap.

You do not correct a seat by lapping it. That is what the shop saying.

Its like honing a cylinder. If the bore isn't round then honing it isn't going to help. Its just going to follow the out of round bore. honing will get you the PTW clearance you want by opening the hole but the oval hole will always stay oval after honing.

Ah, might have been that. I was thinking more like using a MLS headgasket. If the surface is machined and perfect, lapping would be like sanding the block surface with a very fine grit.

Either way in this case, the guy wanted them dropped in as he was in a rush and couldn't wait, so the marker method was the best I could do given only a couple minutes. I told him to message me if the compression was off and haven't heard anything from him. After lapping, it's gotta be cleaned very well to ensure there aren't any metal shavings redesigning the combustion chamber or turbine blades.

The same is true for a head. You machine it flat and then lap the surface finish you want into the head. You can only achieve a certain value by machining with cutters. Anything after needs to be done with stones and abrasives.

Mind you the surface finish requirements of any MLS can be achieved with a cutter. No stone work is needed.

Lapping removes MUCH finer amounts of metal than any kind of machining or even grinding. It should basically just remove any high spots and improve the smoothness of the finish.

Well, still learning in the ways of machining, but point of this thread is I thought I'd share a picture of what leaving your car untuned and beating on it can do. So make sure you take your time to properly tune your car or spend the money on it so you dont do this kind of damage to your engine!

Just as a follow up, the guy just sent me a text message to thank me, as all 4 cylinders checked out at 180 across the board.

Interesting read... Just curious, Last year my car was running an AFR in the low/mid 10's at WOT, stock timing map, no knock. Obviously this is a very conservative tune, but would their be any long term ailments the engine could see if running rich for pro longed periods? I'll be switching to speed density for this year so the tune will be starting from scratch, I intend to keep it on the richer side of things...

Just carbon build up is all I could foresee. However be sure to run more advanced timing if you are running rich to ensure a complete burn.

A safe way to tune is to go for an 11-11.5 afr, then increase the ignition timing until you see the ECU pulling ignition timing due to knock, then back it off by 2* in those area you were increasing your timing.

Who's head is that?

Some dude off of Kijiji.

You are kijiji tuning now? The dude probably has endless issues.

Probably. However he ended up buying a Subaru and has since decided to part out his Talon. I'm just glad that the valve replacement I did for him left him with perfect compression in that cyl.

I would of done a leak down test.....compression test arent that accurate for valve seatment. Even a vaccuum test is better.

Sand blast and valve job and I'd reuse that valve all day. I don't see what's wrong with it. This thread doesn't make sense to me, pointless IMO.

Haha is this how technical we have gotten on ca.dsm?

You'd just sand blast and reuse a valve that was warped?

The bubbling on the valve is not carbon buildup. Just wanted to show my findings... Definitely a more useful thread than most that get posted here.

Sadly yes. This thread is filled with misinformation.

Valves don't warp! Valves are steel, head is aluminum. aluminum deforms before steel does.

A valve does burn up because it does protrude into the combustion if too high of combustion temperatures are reached. This is an erosion process.

I agree with Mike, valves don't just warp they burn. The pic you posted looks like a layer of carbon build up which could be removed by sandblasting. You would really have to show us a close up pic of where you think it is warped from. I have seen many ugly looking valves from DSM heads which my machinist is easily able to clean up and after a 3 angle valve job, as good as new.

Either way, tune has nothing to really do with that, that didn't happen in a matter of days or months. You ever see a stock DSM AFR map all in the 9.x range? 14b's running 12-14 psi pumping out 160WHP on stock DSM's. Running that rich is not gonna kill anything at all, it will not damage any valves or your motor, and Mitsu engineers knew that back in the 90's

I originally decided to stay out of here, because it seemed like another head-against-wall type argument brewing. But I agree, this thread should be taken out back and shot.

Valves don't warp. They bend if they make contact. And for what it's worth, I showed perfect compression in two different cylinders, each which had 2 bent valves, doing a standard compression test. Leak down test is your friend.



But dude... performance shops NEVER lap valves

Was running mid 13:1 to low 14:1 afr's, so apart from super hot EGT's, I'm sure the timing retard due to knock wasn't helping their case.

I tossed the valves unfortunately so can't sand blast them now to see what the bubbles on them were for sure, but when I checked for a seat, they wouldn't create a seat all the way around the valve, whereas the replacements did.

If it wouldn't hold anything on the compression test the first time, but held 180PSI with the new valves in, that is fact that they worked.

I'd say call some high end machine shops and engine builders, or even just look online about valve lapping if you don't believe me. And if you come back saying that all the engine builders say they lap valves, that means you didn't bother checking.

Personally, I'd rather listen to the recommendations of a shop that builds engines that make more power than any of us ever will rather than some people on a DSM forum. But to each their own. Right?

But lock it up and delete the thread, I agree. Can't teach an old dog new tricks .

I don't need to call anybody; I talk to high end machine shops on a weekly basis. Not that I would ask them anything, anyway. I know when and why a valve needs to be lapped. So does Mike. So does Reza. So does Ghis. So does everybody else who does their own engine work, who probably pissed themselves laughing when they read this:



Or when they read that turbos are mufflers according to the MTO. Or any of the other sh!t you spout as truth.

Head, meet wall.

You two have been bashing each other far too long. There's only one way to decide this. Good old 1/4 mile drag race. Winner gets bragging rights on the other. I'm sure the rest of the board agrees.

I'd be happy to race, but if I lose, you certainly shouldn't expect me to sit back and embrace half truths and full out lies.

I don't bash people, I bash bad information. I like Stephan; he's a good guy. I have NOTHING against him, which was why I wanted to leave this thread alone. The fact you think I've been specifically bashing him just means you've noticed the same pattern that I did: Stephan posts a lot of bad information.

Please don't take this as an indication that I believe I'm infallible; those who know me, know I think the opposite of myself. I've posted tons of bad info on various boards in the past, but I never claimed I was an expert. Point is, everybody should be double checking ANY info they receive, about ANYTHING. Just because you read something in a Google search doesn't mean you should post it as scripture.