[AG]

Originally Posted by Jimbobeast

Already mostly done. My neighbor has a racing transmission business and is himself a drag racer (and winner) for over 30 years. Taking 0.035 off the boss is easy (or so he says). He has a cutter made for just that purpose. Following that we will shim the springs to get 1.80" installed height, check the seat pressure and the pressure at full lift, then assess the valvetrain for geometrical symmetry and figure out the proper pushrod length. If all this does not work I'll put a small block chevy in. Just kidding.

I would first take every spring and measure the height to get the seat pressure you want and mark each spring. Then check the installed height of every valve and you'll know how much you have to shim each spring to get your seat pressure.

[steve25]

From the old HO racing catalog.

[Jimbobeast]

Craig and Kern, they knew what they were doing.

[Jimbobeast]

Curiously that fact was never mentioned in their "High Performance Engine Design" book or their Pontiac Performance magazine articles.

[Jimbobeast]

Heads are done, spring bosses have been machined and all Comp Cam springs are installed to exactly 1.8" with only one valve needing a 1/16" shim. New Viton seals, retainers, 1.65 roller tip rockers, new poly-locks and the stock 9.2" pushrods fit perfectly. All adjusted to 1/2 turn past contact. Sheesh. I hope I never have top adjust this beast again. Now to put everything back.
Quick question: the engine was painted at the factory with the valley cover and oil pan in place, right? So those fasteners would have been painted also.

[Jimbobeast]

For some unknown reason, my I-phone photos for January did not upload into the computer, but they are back for February???
Here is the fully machined and reassembled RTAIV motor - valve guide bosses milled, springs all set to 1.8" and checked at 112 lbs seat pressure, new valve seals, lifters, cam, pushrods. Geometry checked and double-checked and perfect. Painted with Eastwood's ceramic engine paint, supposedly good to 500 degrees.
I willl take and hopefully upload some pics today.

[steve25]

112 psi on the seat is not much boy, especially for the intake valve!

These motors left the factory with 124 on the seat and over 340 open @ .520” .

[Kenth]

Originally Posted by steve25

112 psi on the seat is not much boy, especially for the intake valve!

These motors left the factory with 124 on the seat and over 340 open @ .520” .

1969 RA III uses 124 lb on the seat, NOT RAIV. 112 lb on the seat will be just fine.

[steve25]

When the springs break in all the way and drop 10 lbs out will see how fine he is if the valves float or bounce on and off the seat.

He will stand a good chance of bending stuff again.

The RA4 valves being taller then the D port valves of the RAIII weight more, so more pressure is needed.

The 30 degree seat intake seat and valve needs more spring pressure then a 45 seat does to ward off seat bounce.

A 30 degree seat clamps to seal more then a 45 seat that both clamps and wedges to make a seal.

[Kenth]

The RAIV springs were good for at least 6100 rpm`s w/o "bouncing", how bad is that?

And, RAIV heads uses 30° intake seats, like all large inte valve heads, (except 455 S.D.). NOT 45° intake seats.

[Jimbobeast]

Don't forget, this car will probably never see 5000 RPM. It's a convertible, too heavy to race and in all likelihood a show car that will end up in some collection eventually. RELIABILITY is what I'm looking for here at the risk of losing a bit of high RPM potential.

[Formulas]

Put some RAIV valves and D'port valves on a actual scale see what the real results are, the RAIV'ex valves might be a tick heavier but RAIV intakes are are substantially lighter than stock D's.. and intakes will float first

A 1/8 longer stem does not compair to what goes away in the tulip

I have done this comparison

Aftermarket valves are typically lighter than stockers as well

[Jimbobeast]

Trans, clutch, shifter, starter, linkage, exhaust, driveshaft, etc all re-installed. What a pain. Now to finish the top parts, pre-lube and break her in.

[P@blo]

The seat pressure was not the problem in wiping your previous cam. If you used a high rate spring on a short IH, your spring pressure over the nose increased by a large factor. Unless your cam wiped the base circle?

Over the nose pressure on a HFT should be kept in check. Well, the ones you want to last anyhow...

[Jimbobeast]

Originally Posted by P@blo

The seat pressure was not the problem in wiping your previous cam. If you used a high rate spring on a short IH, your spring pressure over the nose increased by a large factor. Unless your cam wiped the base circle?

Over the nose pressure on a HFT should be kept in check. Well, the ones you want to last anyhow...

I beg to differ. The aftermarket springs were installed without machining the valve stem "boss". The inner spring sat 1/4" above the seat (and the outer spring), giving an effective seat pressure of 160. The springs were OK for the application but were installed incorrectly (and assembled by a previously very competent Pontiac loving machine shop).
The boss is now machined and the inner springs are flat on the seat along with the outers. All is in harmony.

[P@blo]

Originally Posted by Jimbobeast

I beg to differ. The aftermarket springs were installed without machining the valve stem "boss". The inner spring sat 1/4" above the seat (and the outer spring), giving an effective seat pressure of 160. The springs were OK for the application but were installed incorrectly (and assembled by a previously very competent Pontiac loving machine shop).
The boss is now machined and the inner springs are flat on the seat along with the outers. All is in harmony.

A 322psi rate spring with a 110psi seat pressure will put you at 271psi open pressure at 0.50" which is perfect. I had a set of 670s done and used the 995 402psi spring and have 292psi open which is perfect. Not sure the focus on closed pressure but I would keep open pressure to 300psi or less.

Also, I would not trust anyone, Pontiac friendly or not, who did not verify a spring fits before installing. Not by a country mile. The issue should have been caught when checking the spring pressures before sending the heads out the door too. Two strikes right there. The third would be them willing to fix it for free. I'd run the other way with the heads you have. Scary really.

[PAUL K]

Originally Posted by P@blo

A 322psi rate spring with a 110psi seat pressure will put you at 271psi open pressure at 0.50" which is perfect. I had a set of 670s done and used the 995 402psi spring and have 292psi open which is perfect. Not sure the focus on closed pressure but I would keep open pressure to 300psi or less.

Also, I would not trust anyone, Pontiac friendly or not, who did not verify a spring fits before installing. Not by a country mile. The issue should have been caught when checking the spring pressures before sending the heads out the door too. Two strikes right there. The third would be them willing to fix it for free. I'd run the other way with the heads you have. Scary really.

How do you take into account the pressures lost during the first couple heat cycles?

[P@blo]

My 995 springs were broken in prior (used) but to answer your question, I would say the pressures would drop after break in as expected. Just like the factory spring would and specs Kenth posted. The factory probably understood the initial pressure loss and springs are spec't accordingly.

I have a question for you too Paul. After initial break-in and loss of pressure, is it assumed that valve springs are stable and will last forever? Or will they wear based on cycles that decline over time with use? My thinking here is the decline after breakin might be slow but still there and wanted to get your thoghts.

[Jimbobeast]

Originally Posted by P@blo

A 322psi rate spring with a 110psi seat pressure will put you at 271psi open pressure at 0.50" which is perfect. I had a set of 670s done and used the 995 402psi spring and have 292psi open which is perfect. Not sure the focus on closed pressure but I would keep open pressure to 300psi or less.

Also, I would not trust anyone, Pontiac friendly or not, who did not verify a spring fits before installing. Not by a country mile. The issue should have been caught when checking the spring pressures before sending the heads out the door too. Two strikes right there. The third would be them willing to fix it for free. I'd run the other way with the heads you have. Scary really.

Unfortunately Yow's Machine shop closed their doors 12 years ago and Roy, Johnny and Dave Yow have long since "shuffled off this mortal coil". That's from Hamlet. It's a play. By Shakespeare. It means they're dead. In their defense they did the machine work on 5 other GTO engines for me, including a RAIV, without problems.
I do love the looks of an Orbit Orange/Black Top '70 Judge convertible, even in the garage. Always have.

[PAUL K]

Originally Posted by P@blo

My 995 springs were broken in prior (used) but to answer your question, I would say the pressures would drop after break in as expected. Just like the factory spring would and specs Kenth posted. The factory probably understood the initial pressure loss and springs are spec't accordingly.

I have a question for you too Paul. After initial break-in and loss of pressure, is it assumed that valve springs are stable and will last forever? Or will they wear based on cycles that decline over time with use? My thinking here is the decline after breakin might be slow but still there and wanted to get your thoghts.

After the initial break-in the pressures stabilize and stay like that for a long time. Sometimes we'll shim up expensive roller springs depending on the application. But for the most part once the springs start to loose pressure after the initial break-in they're replaced.