scoobysnax83

Thats pretty much the question, thanks....

Cerwin Vega Fan

Waiting to hear the answer myself.

RamAir95TA

Valve "lapping" is a process used to mechanically "mesh" the fit between the valve and the seat. This basically allows a more perfect fit between the valve and seat, sealing the valves against compression leakage.

scoobysnax83

That makes me happy. I just scored a set of port matched mildly ported heads and intake. They have upgraded springs that will go to 530-540 lift. And the valves were lapped. Supposedly they were making 430rwhp with a small procharger and cam. I can't wait to get these.

By the way I got them for $400 with a car sale

Cerwin Vega Fan

Where did you get those from?

scoobysnax83

I just sold my 93 V6 Camaro and worked in a deal to get these heads and intake. My 94 Z (pics below) Just blew a head gasket after a radiator explosion Anyway, atleast I get to throw some awesome heads on there. I look at it as an opportunity to upgrade

Cerwin Vega Fan

Damn your lucky, I need some new heads bad, I think one of my exhaist valves is sticking due to the fact it had rough life.

anaik

I believe lapping was done more years ago than now. Machine technology is much more advanced now. When I worked at TRW's Valve Div. most prints wouldn't allow for more than .0003 seat runout, and we usually kept it at .0001-.00015. A lot of valves required pressure testing to make sure the seats sealed.

scoobysnax83

Well, I'm actually selling my old ones once they are off. The only reason that I'm swapping them out is because I will have them off as it is. And it takes too long to send them off for porting. I was just gonna throw the old ones back on. The car always has run perfect. As soon as I noticed coolant was missing. I parked it. The oil has a tint of milky residue in it. But nothing much. If you want the old heads and intake to send off for porting and such, shoot me a pm with an offer. I live on a Marine Corps base in the barracks, so I have nowhere to put them long term. Maybe we can work something out. Good Luck

Ai

The reason we lap valves is to see where the actual seat cut is on the valve face. Using a fine compound will polish the two mating surfaces together, but it's primarily so we can ensure our seat cut is located where we want & give us a guide when backcutting.

What people don't seem to understand is that using something like the Sunnen VGS-20 seat & guide machine, which is practically racing industry standard along with Serdi stuff, isnt nearly as precise as people want to think. You're locating off of a tapered pilot, and using a tool holder that's adjustable & flexes. Quite honestly, we got into a big thing awhile back on the board about it, and most people didnt want to believe it, but I've been taught that in perf. apps, shooting for a couple thou runout is preferable. Not going to get into why, as most people will just shake their heads & say whatever... but I digress . The stuff isnt that precise, and in a real perf. application, a cylinder head porter will need to lap the stuff together to see what he's got in most cases .

As far as actual performance gains or anything? The end user isnt really going to benifit from the lapping itself, even if the stuff didnt seat properly.. technically it'll hammer itself in in short order LOL

Scary Engine Builder Quote #347, "It'll wear in before it wears out." - Judson

Cerwin Vega Fan

Damn dude how did you get water into your system.

gb95zconv

Have them checked out by a place you trust......I paid $450 for used ported heads and ended up having to put another $350 into them to get them right....port work was good but they needed new valve guides and valves.....

arnie

Hey Phil, we actually agree. (almost... ) However, for me, with a calipher in my hand being second nature, I use it instead. That, and a felt marker pen when necessary. Just as effective, and a little quicker to boot.

I did a little experiment a few....well ok, several years ago to prove a point. With guide clearance at .0015", valve at .002", and a seat out .004" (or more), the seat lapped 100% easily. How much did I improve the concentricity? Guess! Just something about sandwiching abrasive compound between metal surfaces, that rubs me the wrong way. Pun intended!

Ai

Well like I said b4.. not really doing it to improve concentrity or anything like that. Even with the seat cut in the right place, tools chatter occaisionally etc. so aside from an indicator its a nice surface prep. I mean.. the heads etc. are obviously washed prior to assembly, so whats the problem?

Dunno m-ang, we've discussed the pros & cons before, but my local buddy who's doing current TF/FC, ProStock, Cup, etc. stuff along with The Man, Greg Good down in Houston are lapping & teaching race head porters/machinists to do so...

They could be old school I suppose.. but theyre at the top of the current game along with guys like don losito out here in CLT at ultra-pro.. so I dunno, I suppose the DARE officer in school was right, peer pressure is a sonofabitch.