i can`t see that being a problem because a cold engine might hit those oil pressure #`s and shouldn`t lockup the lifters. if you are sure that the lifters are not bleeding off and eveything else looks good , you must have weak valve springs or the springs were set at to high an install height and there is not enough pressure to seat the valve against the pressure in the lifter

I agree. The math says that it would take something like 700 psi of oil pressure to "pump up" a lifter and lift a valve:

Assume a valve spring seat pressure of 150 lb (very generous, seat pressure should be more like 200 lb).

A 1.5:1 rocker ratio means that the pushrod sees 225 pounds when it just starts to lift a valve off the seat. Assume that the ratio is really more like 1.3 (factory rockers are often over-rated in ratio) ad you still get 195 pounds of force exerted on the pushrod to start the valve lifting off the seat.

Now the plunger in a lifter is about 5/8" diameter, so it has an area of 0.307 square inches. To get that area, about 1/3 of a square inch, to lift a pushrod against 195 pounds of force means that is a pressure of 635.6 PSI!! Somehow, I think that's not going to happen. Even if I screwed up and I'm off by a factor of 2, its still not going to happen!

_________________

Update: July 10th

Last week I pulled the rocker shaft off and replaced the front six rocker arms with know good rocker arms. Put it back on, and the only way I could get the engine to run was to back off all seven rocker shaft bolts three full turns.

On Friday the 4th, I ordered a set of lifters from Comp Cams. They arrived yesterday and I installed them this afternoon. I switched out the pushrods and rocker shaft/arms from my van to the truck. The truck fired right up and has been running perfect for the past 30 minutes.

Tomorrow I'm going to swap pushrods and rockershaft assembly (one at a time) to see what was causing the problem. I'm still leaning torward the lifters pumping up and locking, since I pulled two bent pushrods from the truck today when I removed the rocker shaft assembly.

All in all, I just couldn't understand why a simple valve grind would cause all this frustration, and worse, all the money I've spent on parts and gaskets since the engine ran fine previously with only a tap caused by a worn valve guide not allowing the exhaust valve to seat properly.

FWIW, the first set of lifters I put in were Hi-Tech brand, the second set Speed-Pro.

Troy

Sounds like a probable Chinese-made "pretend brand" to me.
A well-known name, but even those are turning Chinese.

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

Well, more bad news. Even though the engine ran fine at idle for more than an hour on the weekend of the 4th, a drive to work that following Monday was crappy. The engine ran fine/so-so for the first six miles ( I figured that the carb needed to be adjusted since the rebuild ) the remaining 25 miles were white knuckled. At any of the 15 red-lights that I would have to stop at, the engine would stall out. She would start back up after 30 to 45 seconds. Made it to work, shut her down. The return trip to home was just as bad. Go a few miles, then she started backfiring at random, missing, and making the both of us look bad.

During the last ten days, I've tinkered with her. Here is what I know:

By loosening the front four rocker shaft bolts, she idles fine. Tweaking them up or down, I can get up to 15 Hg on the vac meter. Once I raise the RPM up to 2000 for a minute or so and release the throttle, she stalls out again telling me that the lifters are 'pumped up' again.

As of this point, I figure I have three options.

One: change out the old springs with new 225 springs.
Two: change out the old springs with 340 springs.
Three: Install new seats and valves and springs that lower the installed spring heigth to specs.

Troy

Well, I did some more tinkering today. First thing I did was to change out the oil from the 10w-40 to a straight 30w, due to the implied fact that the lifters are not bleeding down faster than the oil pressure is delivering oil to them.

She started up and seemed to run ok, and after a few minutes I noticed that some of the rocker arms were not bleeding oil onto the tops of the valve. I put together a different rockershaft/arm assembly and installed that. After tightening it down, I had zippo compression, the engine spum freely while trying to start her.

Put the old rockershaft/arm assembly back on, but left the front six bolt tight enough oly to keep the push rods from falling free. Started her up and slowly, slowly, slowly tightened the rockershaft bolts down until they were all tight.

Over the past four hours, she's run at idle and 2000 RPM for no less than 30 a pop, shutting her off and restarting her with no problems after each shut down. I"ll start her up again tomorrow when she's cold and take her for a test drive to see how she acts.

My conclusions as of today is that the oil was too thick and not letting the lifter to bleed down causing them to hold the valves open at TDC. By slowly tightening the rocker shaft bolts down, the hydraulic lifters "learned" how much they were to give and allow the engine to run.

We'll see what the results are tomorrow after a serious road test.

Troy