Valve in new engine not seating

I have never had an issue with valves not seating fresh from the shop.

I did have issue with one shop when I discovered that they were only doing one cut on the valves and seats and I was paying them for a three angle.

After that I bought my own equipment, and do my own. I even do the valve guides as well.

None of it is difficult, but it is time consuming.

I have done leak down tests on fresh rebuild straight from the shop. There I let the shop do all the machining and I do the assembly.

Fresh short blocks always show leakages. That is to be expected.

Your cylinders look good.

I have heard the term, "warped valves" before but I still don't know what that means on fresh seats?

It is a good idea to hand lap the valves as Marlin suggested but I have never had an issue with Sioux equipment.

This isn't necessarily very complicated. I could have high school kids doing "valves" in not much time.

The issue is being conscientious. It helps to be "nerdy". The work is not for "hot dogs" at all.

While the head is out, why don't you "cc" the combustion chambers?

@panteradoug posted:

I have never had an issue with valves not seating fresh from the shop.

I did have issue with one shop when I discovered that they were only doing one cut on the valves and seats and I was paying them for a three angle.

After that I bought my own equipment, and do my own. I even do the valve guides as well.

None of it is difficult, but it is time consuming.

I have done leak down tests on fresh rebuild straight from the shop. There I let the shop do all the machining and I do the assembly.

Fresh short blocks always show leakages. That is to be expected.

Your cylinders look good.

I have heard the term, "warped valves" before but I still don't know what that means on fresh seats?

It is a good idea to hand lap the valves as Marlin suggested but I have never had an issue with Sioux equipment.

This isn't necessarily very complicated. I could have high school kids doing "valves" in not much time.

The issue is being conscientious. It helps to be "nerdy". The work is not for "hot dogs" at all.

Just doing one angle would likely not provide you with the correct seat width…  the other 2 angles are needed to set the correct height and width to have a proper seat…
a warped valve (anything not true like valve stem or head ) would easily identified by the lapping picture on the valve.. only the high spot of the valve is getting lapping marks…

Great information all.  I will lap the two valves and test with gasoline.  After assembly I will do a leak down test with compressed air since it is already setup.

On the other head (driver side) there is a faint compressed air leak on one exhaust valve.  It is unlikely that gasoline would leak through that valve since the 85 PSI air leak is only barely detectable.

Before assembly I will measure the volume of the combustion chamber.

Thank you all.

@stevebuchanan posted:

Great information all.  I will lap the two valves and test with gasoline.  After assembly I will do a leak down test with compressed air since it is already setup.

On the other head (driver side) there is a faint compressed air leak on one exhaust valve.  It is unlikely that gasoline would leak through that valve since the 85 PSI air leak is only barely detectable.

Before assembly I will measure the volume of the combustion chamber.

Thank you all.

You can give the leaking valve a “gentle “ tap with a hammer while air applied..

hopefully cleaning the seat …

if it’s a dirt issue…

@panteradoug posted:

The issue is being conscientious. It helps to be "nerdy". The work is not for "hot dogs" at all.

Well, I'm no nerd.  Just because I walk around in the garage with the 351C firing order taped onto my sleeve does not mean that I'm a nerd.  My wife saw something taped onto my sleeve and was somewhat amused.

You wish Steve…

but we are still not as nerdy as the guys who have pet dung beetles and share pics of their daily endeavors on their forum and don’t let people join who can’t prove they have one.. makes me so mad!!

...Lapping does Not widen the Seats. It Only deals with the 'One' Angle where the Valve MEETS the Head (Seat). 'That' Single angle is cut on the Valves at 44 Degrees, on the SEAT at 45 Degrees. You can see the two angles meet at a Taper. Lapping Insures the 'Contact Area' is a 100% Custom FIT!

The Bores are Perfectly Round, there should be Hash Marks at 30 Degrees in Both Directions. These Hold 'Oil' from the Oiling Ring to Lubricate the Cylinder Walls, Piston and Compression Rings. Ofcourse the Oiling Ring.

The Pistons are Cut as a OVAL, this is so there is 'Room' for the Piston the Expand when HOT. When Cold these Leak in a 'Leak Down Test'. The Ring Gaps. although 'Staggered' will Leak when COLD. These Gaps are Calculated to come nearly Closed when Hot.

When COLD any Engine will show leaks in a L.D. Test, even though the Valve seats are PERFECT! It would be just about Impossible to Do a L.D. Test on a HOT Engine. But more than likely...Very Successful.

I agree with Doug and All Others who Lap their own Valves. Shops are in a Hurry to be done and get paid. And some just don't Have the Disciplines!

...Some racers will Have Just One ROUNDED Seat Cut, in the Head, with the Valve cut 'Normally'. With an even THINNER Contact Area! and No other angles in the way of the Fuel/Air Flow, within the Head. These Must be 'Drag-Racers'.

Doug Makes Sure of His Valve Seats!! You Dig!! I Applaud You!

All the Best,

Marlin I may not have the terminology that you do because I have not been formally trained.

I do learn proportionally more from my mistakes then anything else and just hope that they weren't expensive mistakes on irreplaceable items.

I have learned much of this through necessity and the failure of others that I relied on and am the better for it as a result.

I ultimately have to fix their mistakes.

Doing my own valves also lets me get the width of the seats where I want them. I find that the thin "drag race" seats offer the most improvement. For me that doesn't matter so much since I don't put many miles on them anyway and can always redo them if necessary.

I was pleasantly surprised how detailing the seats gives so noticeably increased pep to the engine. It adds crispness to the throttle amazingly.

Only cutting the 45 degree angle will widen the seat! Obviously!

@panteradoug wrote:

“I did have issue with one shop when I discovered that they were only doing one cut on the valves and seats and I was paying them for a three angle.”

...ALL of That is Eliminated when I Polished the Sharps and the Valve Bowls!!

This Increases Horsepower.

I was complimenting Doug on his Great Work! Improving and Making the Valves/Seats More Accurate. Don't take it Wrong.

Most Seats are already 'Cut', we are Just Re-Dressing It. Some work is Not even finished.

The Diagram Shows a 'Common' '3 Angle' Valve Job! Some Engine Builders have Modified Those angles.

My Mentor, is Responsible for the Building of No Less than 12 Nascar Championship Winning Engines! Yes, Hard to Believe, Right??

He's the Expert, I'm Going to Listen to and Follow!! I just take the time to Try and Pass his wisdom on this Forum, to Those who will Listen. Seems, some need an Interpreter.

MJ

The one set of heads I was refering to, when I popped some valves to look at the seats, the seats must have been .120" wide! Just a single cut.

It was a "high performance shop" frequented by the local drag racers.

I can tell you that in experimenting on some scrap heads with the 60° bottom cut and "port cutter" that it is pretty easy to hole through. I definitely learned that.

I had come to the conclusion that the casting thicknesses varied from head to head. I would not want to do heads for a living at all.

...All Exhaust Valves and Seats are cut to the .120" For Improved Heat Transfer to the Head. The Intakes are, I believe at .090"? (.070" for the Boss 302)

The Top 30 Degree should Have been Cut. I would think they didn't do the 60 Degree cut, to Be Taken Out during 'Bowl Polishing', anyway. For Improved 'Deep Breathing'. 'Volumetric Efficiency', Race Engines are 85% and More.

Good Job!

MJ

...This is an Example of polishing the Sharp Edge and Turning Radius of the Valve Bowl. I couldn't find a FORD Head this a Chevy. But, the Principle is the Same. Bowl Polishing is always done Before the 'Valve Job', if the Seat should be Marred by the Burr, it may be fixed during the 2 angle job. See in the Before and after pictures, the 60 Degree Angle, and Sharp Edge are Removed and inner Radiused. Intake and Exhaust both done is good for a Increase of 20-40 Horsepower. That helps a 351 Cleveland approach 500 HP with 4V Iron Heads. When Ran with Dual Quads and Higher Compression.

MJ   

...This Bowl Has just Been 'Roughed-Out', it has yet to be finely Polished., and the Guide Boss, also.

The Cleveland iron head has a cast in "restrictor ring". It is intended to increase the velocity through the pockets.

When "performance" prepping the heads, that is commonly cut out with the 60° pocket cut and sometimes the iron valve guide is also and replaced with a pressed in bronze guide like the aluminum heads use.

There is easily 25-30hp to pick up with those modifications but are intended for manual transmissions and performance driving. Not automatic transmission cars used for everyday transportation.

There is a reason a Boss 351 is only 330hp. It was detuned in many ways to make it a dependable street car. The valve pockets is one area.

You also need to narrow the seats by about half from stock but remember that is for racing and those engines get torn down al ot so cleaning the seats isn't that much of a big deal.

If you wanted to put 100,000 miles on the car before you do the valves again, you should stay stock.

The only thing that I would add to that is likely the stock iron valve guides only last about 30,000 miles.

Update:

I hand lapped the two leaking valves and tested them with gas.  They both sealed.  One of them (the exhaust valve) needed a lot more lapping than the other (intake valve).  I reassembled everything and did a compressed air leak down test on the two valves.  The intake valve was completely sealed while the exhaust valve had a very slight leak.  It should seal during break-in.

The valve that prompted this posting was the intake valve and it probably would have sealed during break-in without doing anything.

While doing leak down tests early on, I came across the leaky exhaust valve.  I don't think it would have sealed during break-in.  While everything in this posting has been a bunch of work, it likely eliminated a big hassle later on when the engine is in the car.

Nice job Steve

Perfectly done!!

I know, it was a lot of additional work, especially after you were already so close to the finish line…  But definitely worth it!

” while I’m there, I should… - Opening a can of worms” @stevebuchanan I’m sure you know where that came from…

https://pantera.infopop.cc/top...uld-the-can-of-worms