1-MM Oversized valve install

[MXD]

Hey guys i just got back my head from the machine shop. I had a port and polish job done along with a set of 1mm Oversized valves. This is probably a dumb question but here goes... The valves are seated at the moment (No cams), and in their seats, they seem to be above the head surface. In other words, if i put a straight edge along the head, i would touch the valves more than the head. They stick out about 1 mm. I was wondering will i or has anyone had any clearance issues after installing 1mm oversized valves? Im worried that the head will not mate perfectly flat with the block? Should i worry?

 

[MXD]

never mind guys, i mounted the head on the block and clearance is fine. Thanks for reading, sorry

 

[RoasT BeeF]

I believe you have to punch out the seats for them to fit because mine fit flush...

 

[1fast97gsx]

they don't need to be flush ... how much you will the head also makes a difference. Mine also pop out a tad and I have no problems. My timing belt actually skipped a few teeth and no valve / piston contact even then. Just check the clearance between piston / valve and you'll be fine.

 

[hennessey1104]

Hey I just got my head out of the shop myself, I had the same exact mod done. I got the valves off E Bay. So I have a question, how much difference did it make in power and fuel economy. Thanx brother!

 

[MXD]

i haven't ran the head yet to know power numbers. But for the rest of the posts, i mounted the head on the block with the pistons still out to see the size of the combustion chamber inside the piston bore and the combustion chamber is smaller so im ok. the head was milled considerably so i think thats why the valves are raised a little. And they are seated perfectly

 

[defrag010]

Mine stuck out a little bit. I took .011" off my head surface , and cut my seats wider to fit the oversize valves, but they still stuck out a bit.

 

[Suparata]

... cut my seats wider to fit the oversize valves...

You may want to reformulate that so guys do not get more confused than they already are

 

[defrag010]

Pardon me,
I removed the original seat, and used a drill press to widen the valveseat pad just a tad. I placed a new SBI seat which had a larger outside radius, yet the same inside radius. I used the surdi to cut the seat at a 44 degree angle until the contact patch was about halfway up on the valve face.

 

[gixrman]

Hey I just got my head out of the shop myself, I had the same exact mod done. I got the valves off E Bay. So I have a question, how much difference did it make in power and fuel economy. Thanx brother!

Not to sound like a meat whitsle, but why would you do this mod without knowing wether or not its going to give you any significant gains? Unless you already ported everything, installed bigger cams, and are flowing hugh amounts of air, do 1mm oversized valves really make a difference and where?

I've read of plenty of people with stock heads making very fast, high HP motors.

Who's to say that just adding 1mm oversized EX. valves make better gains? Or vis-versa

 

[92awddsm]

Pardon me,
I removed the original seat, and used a drill press to widen the valveseat pad just a tad. I placed a new SBI seat which had a larger outside radius, yet the same inside radius. I used the surdi to cut the seat at a 44 degree angle until the contact patch was about halfway up on the valve face.

Why did you replace the seats? 1mm os valves work fine with the stock seats. And I hope you lapped the valves after cutting the seats with a serdi. They usually leave fine chatter marks that keep the valve from seating fully.

 

[92awddsm]

Not to sound like a meat whitsle, but why would you do this mod without knowing wether or not its going to give you any significant gains? Unless you already ported everything, installed bigger cams, and are flowing hugh amounts of air, do 1mm oversized valves really make a difference and where?

I've read of plenty of people with stock heads making very fast, high HP motors.

Who's to say that just adding 1mm oversized EX. valves make better gains? Or vis-versa

You do realize that 1mm oversize is actually .03937", right? If porting was done properly, they will flow significantly more than a stock valve.

 

[defrag010]

Why did you replace the seats? 1mm os valves work fine with the stock seats. And I hope you lapped the valves after cutting the seats with a serdi. They usually leave fine chatter marks that keep the valve from seating fully.

Because I cut the stock seat with a serdi, but it took too much material off to get the valve where I wanted it. I did a 3-angle on the valve, and with the cut stock seat, my contact patch was on the transition from 30 to 44 degrees. It might not be the same for people who just buy the valves and throw 'em in.
That's not true about the surdi. I've Never had to lap in one valve out of the thousands i've cut. Fresh cut on the surdi, fresh grind on the valve face, and it will seal perfectly If done right. I've trained people to use it, but they don't lube the seat and it always ends up like you say. All you need to do is kiss the seat lightly with the arbor for a few revolutins (at about 400 rpm), and the lube will give off a short puff of smoke and that's it. Yeah, if you grind the heck out of the seat for more than a fraction of a second with lots of pressure, it will etch the seat no matter how much lube you use. I've had trouble before with the serdi leaving waves in the seats, but it was because the seats were hardened, and needed to be replaced with new softer seats. You shouldn't Ever have to lap a valve in to get it to seal. Lapping should Only be used to check the consistancy of the contact patch for any imperfections in each face. If you have to lap in a valve to get it to seal, then you've done something wrong and it needs to be machined again. The compound does nothing as far as changing the surface contour of the valve and seat.

 

[gixrman]

You do realize that 1mm oversize is actually .03937", right? If porting was done properly, they will flow significantly more than a stock valve.

I'm just trying to understand at what point does going to 1mm larger become benifical.

 

[92awddsm]

Because I cut the stock seat with a serdi, but it took too much material off to get the valve where I wanted it. I did a 3-angle on the valve, and with the cut stock seat, my contact patch was on the transition from 30 to 44 degrees. It might not be the same for people who just buy the valves and throw 'em in.
That's not true about the surdi. I've Never had to lap in one valve out of the thousands i've cut. Fresh cut on the surdi, fresh grind on the valve face, and it will seal perfectly If done right. I've trained people to use it, but they don't lube the seat and it always ends up like you say. All you need to do is kiss the seat lightly with the arbor for a few revolutins (at about 400 rpm), and the lube will give off a short puff of smoke and that's it. Yeah, if you grind the heck out of the seat for more than a fraction of a second with lots of pressure, it will etch the seat no matter how much lube you use. I've had trouble before with the serdi leaving waves in the seats, but it was because the seats were hardened, and needed to be replaced with new softer seats. You shouldn't Ever have to lap a valve in to get it to seal. Lapping should Only be used to check the consistancy of the contact patch for any imperfections in each face. If you have to lap in a valve to get it to seal, then you've done something wrong and it needs to be machined again. The compound does nothing as far as changing the surface contour of the valve and seat.

I have been using a serdi for 12 yrs myself and I was talking about hardened seats. Back when I did my head, I didnt have any problems with the intake seats but the ex seats chattered really bad. I even switched to a new cutter, faced the cutter, and had no luck. After they were cut for the 1mm os valves, I kissed the seats with stones just for peace of mind. I have also had bad experiences with bowtie aluminum heads. Ive done the seats and after a couple of runs on the dyno, it would show about 10-15% leakdown. After pulling the heads, kissing the seats with stones, and then 5-8% afterwards.

 

[RoasT BeeF]

According to ffwdconnection 1mm oversize will pick up flow about 12cfm on an unported head with stock cams.

 

[Suparata]

What kind of concentricity numbers did you guys get and which one of the Serdi’s you used?

 

[SlowSpyder]

What do you guys use to see if the seats seal if you dont mind me asking. Also what kind of #s for valve face runout and valve seat runout did you guys have when you machined the seats and valves?

 

[Defiant]

I've Never had to lap in one valve out of the thousands i've cut.

But... that's the fun part. It's even better if you have the TV set up and run a copy of LeMans in the background.

 

[defrag010]

I have been using a serdi for 12 yrs myself and I was talking about hardened seats. Back when I did my head, I didnt have any problems with the intake seats but the ex seats chattered really bad. I even switched to a new cutter, faced the cutter, and had no luck. After they were cut for the 1mm os valves, I kissed the seats with stones just for peace of mind. I have also had bad experiences with bowtie aluminum heads. Ive done the seats and after a couple of runs on the dyno, it would show about 10-15% leakdown. After pulling the heads, kissing the seats with stones, and then 5-8% afterwards.

Ain't that the truth... about every chevy head I've cut has those damn hardened exhaust seats. The shop I worked at didn't maintain their equipment very well, and when we made the transition from wet stones to serdi, nobody kept up the maintenance in the wet cabinet. The thing that sucked the Most is using the wet stone on alum. heads with soft seats like 173 aluminums. All of the stones we had were worn out, so you had to be extra careful when running it over those damn 173's or the stone would contact off balance and rattle aroud the seat. Then it was either start over or put new seats in.

someone asked, the serdi I used is the 60 series I think, but I'm not 100% sure. All I know is that it was a piece of CRAP, and was always breaking something. We used to go through pilots like nobody's business. There was talk for a while of buying a new sunnen machine, but We never were so lucky. The thing I don't like about the serdi is that you have to know how to work it to achieve good results. Whenever I would call in sick, some dumbass would always cut the seats for that day, except he didn't know how to use the serdi the right way.
Someone else asked what was used to check the seal: the serdi machine I used had a vacuum checker built in to it so you could check seal before even dismounting the head from the platform.
Whenever I do a seat, I don't allow more than .0015" runout. and .0018" concentricity. I know the concentricity should be a little more tight, but it's not too far off from the allowable .001" for every 1". I don't really have a good way to measure the valve face, though. As I said earlier, our shop wasn't the most "maintained", and the valve grinders we had were older than dirt. They had air chucks, but the alignment was off, and the valves were always wobbly. The guys who worked the grinders when I was cutting seats never cleaned the slag traps, so the grinding machines were always down getting fixed.

Defiant, lapping might be fun, but when you produce around 100 rebuilt heads daily in a 9 hour working day, the thought of lapping in each one raises the hair on your back.

 

[Nautica985]

When I first bought my car it was stock accept for a ported head and 1mm OS valves. I raced my friend that has a stock wrx which has 220hp?. I beat him by a 1/2 of a car length. The ported head and valves do make a substantial increase.

 

[DsMWookie]

How much more beneficial is this than a good port and polish with 3angle cut valves? I was going to just port and 3angle but I wouldnt mind doing bronze guides and 1mm oversized valves..... Also how do you tell if your machine shop knows what they're doing? I live in Augusta GA so I question most everyone here.