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Old 07-26-2020, 12:20 AM
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Okay, here it goes. I started out replacing the leaking valve cover gaskets on my '72 Lemans sport 400. That lead to a leaky exhaust flange. I tried to tighten the flange bolts and they broke off, necessitating the removal of the exhaust manifolds. That lead to the removal of the heads as three bolts broke off in them as well. Okay, since the heads had to come off, might as well send them to the machine shop and have them reconditioned since they are over twenty years since last freshening up.

So, after three weeks, I finally re-install the heads and bolt everything back together with new hardware. Upon installing the rockers I notice that they are all the same height when torqued to 20 ft lbs and I thought that was unusual.

So I start the engine and it acts as if the valves are too tight. So, my question is, could the lifters have hydrolocked during those three weeks? How do I solve this? Is this familiar to anyone?

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Old 07-26-2020, 01:10 AM
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More likely they were collapsed, but they still should and have to be opening and closing or you would have no air in, out and therefore no compression....and no run.
Verify some basic other stuff first... firing order and ignition timing, no vacuum leaks, etc.
Post a video of how it runs after verifying. With bolt down rockers you should be able to lay a straight edge across the tips of the valves, and they all be even.

"So I start the engine and it acts as if the valves are too tight."
Describe more. low speed misfire, misfire at any RPM, won't idle, etc.

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Old 07-26-2020, 03:46 AM
Goatracer1 Goatracer1 is offline
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If you do determine the valves are the problem with the engine running back off on the rocker nuts one at a time until the engine smooths out and then SLOWLY turn the nuts back down. The lifters should then let the valves seat. By the time you get around to trying this they may have bled down by themselves.

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Old 07-26-2020, 05:29 AM
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The first rule of thumb that I have lived by for 50 years when assembling a Hydro Cam motor especially with used lifters is to first confirm that the lifter plunger is fully up on its retainer clip, this is naturally done with the valley pan and Intake off.

Then install and adjust each push rod when the valve next to the one jour adjusting in that same cylinder is open or you can clearly view that the one your adjusting is in the middle of its base circle.

The lifters plunger must be up on its clip so you may need to yank some or all the lifters out at first, sit them in a can of very light oil and pump them up with a push rod, as you do this you will likely see air coming out of the lifters fill hole on its side. This is a clear indication that they needed to be pumped up!

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Old 07-26-2020, 09:25 PM
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If you're not adjusting the rockers while the cam is on the base circle, you are in all likelihood not adjusting/torqueing them to spec and your 20# of torque is merely depressing the valve spring.

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Old 07-26-2020, 09:47 PM
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Okay, thanks for the responses. I did not remove any of the lifters as they were all quiet and seemed fine before I tore the engine down. I did visually verify that all the lifters were up to the retainers as I inserted each push rod. I tried to compress a few of the lifters by hand with the pushrod and could not do so.

So update today, I didn't do any thing but tomorrow I will back off the adjustment of the rockers and see if that helps. The engine acts as if it's straining to rotate and it will not rev up.

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Old 07-26-2020, 09:52 PM
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Quote:
Originally Posted by NeighborsComplaint View Post
If you're not adjusting the rockers while the cam is on the base circle, you are in all likelihood not adjusting/torqueing them to spec and your 20# of torque is merely depressing the valve spring.
This is what I was thinking but I re-read the manual and it didn't mention putting the base circle. The way I understood it was that was applicable to adjustable valve trains. In the past, I always adjusted them while the engine was running, but hoped to bypass the mess from oil squirting everywhere.

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Old 07-26-2020, 11:08 PM
mgarblik mgarblik is offline
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Before you pull the covers, you may want to start the engine and see how it sounds after sitting with pressure on the lifter plungers for a few days. That being said, if it still runs lousy, it's possible the machine shop was not aware Pontiac engines came from the factory with non-adjustable valvetrains. Pontiac engines have been out of production for many decades now and unless the shop has some crusty old machinists and is familiar with Pontiacs, it's possible they thought they were adjustable like a Chevy. If that's the case, they may have the stem heights all jacked-up from the valve job. The easiest fix for that is changing the studs to Chevy adjustable style. Otherwise, off with the heads again. If the studs are press-in style, things get more complicated. Hopefully, it will be just a matter of the lifter plungers adjusting themselves in the lifter body. Good luck with it.

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Old 07-26-2020, 11:44 PM
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Quote:
Originally Posted by mgarblik View Post
Before you pull the covers, you may want to start the engine and see how it sounds after sitting with pressure on the lifter plungers for a few days. That being said, if it still runs lousy, it's possible the machine shop was not aware Pontiac engines came from the factory with non-adjustable valvetrains. Pontiac engines have been out of production for many decades now and unless the shop has some crusty old machinists and is familiar with Pontiacs, it's possible they thought they were adjustable like a Chevy. If that's the case, they may have the stem heights all jacked-up from the valve job. The easiest fix for that is changing the studs to Chevy adjustable style. Otherwise, off with the heads again. If the studs are press-in style, things get more complicated. Hopefully, it will be just a matter of the lifter plungers adjusting themselves in the lifter body. Good luck with it.
The machine shop that refurbished my heads is the same shop (and guy} who built my engine back in the nineties. That's been a while but I was confident that he knew what he was doing. For now, I'm not going to blame it on the head job as I will adjust the valves as I have in the past, and see where that takes me. The heads are 96 and they have screw in studs. The machine shop owner is in his late sixties and does most of the work himself.

Actually, the engine ran pretty well before I got into this, but there were signs that the valve seals were failing. If it weren't for the broken exhaust bolts in the heads, I would have left it alone. When I removed the heads, I found some sunken exhaust valves so that's what sent them to the machine shop. The engine ran great, but the exhaust smell indicated that oil was getting into the combustion chambers, so while I had it torn down, I just thought I might as well fix the other issues.

Tomorrow, I will back off the adjustment on the rockers and see if that cures the problem.

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Old 07-27-2020, 02:45 AM
Joe's Garage Joe's Garage is offline
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Default Just a thought: I don't see where you said what cam was in your engine....

Presuming it is a STOCK camshaft (or a duplicate of a stock camshaft), installed in an engine that still retains the 3/8" stock bottleneck-style studs and factory NON-LOCKING nuts, you have to remember that the 20 ft/lb torque figure is measured AFTER the nut is COMPLETELY threaded down on the stud, against the tapered shoulder.

You do NOT just torque the nut down until it measures 20 ft/lbs of resistance/torque while tightening and the nut is still up on the threads and not against the tapered shoulder at the bottom of the threads. There is a taper built into the nuts that matches that taper on the stud and they have to be tightened against each other to correctly orient the rocker arms.

At that point, all the rocker nuts will be in a row, at pretty much the same height from front to back. If your adjusting nuts are currently NOT all in a row, adjusted to basically the same height, they're probably NOT adjusted correctly.

That would cause hard cranking because you will be cranking against cylinder pressure / compression when it shouldn't have any (ie: when one of the valves is supposed to be open but isn't).

Actually, calling it an 'adjustment' is a misnomer. It's really an assembly spec because there really isn't any adjustment on a stock non-Ram Air setup. Just tighten the nuts until it's at the bottom or the threads and then torqued to 20 ft/lbs. The hydraulic lifters take up the slop on their own.

Good luck!

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Old 07-27-2020, 10:10 PM
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Quote:
Originally Posted by Joe's Garage View Post
Presuming it is a STOCK camshaft (or a duplicate of a stock camshaft), installed in an engine that still retains the 3/8" stock bottleneck-style studs and factory NON-LOCKING nuts, you have to remember that the 20 ft/lb torque figure is measured AFTER the nut is COMPLETELY threaded down on the stud, against the tapered shoulder.

You do NOT just torque the nut down until it measures 20 ft/lbs of resistance/torque while tightening and the nut is still up on the threads and not against the tapered shoulder at the bottom of the threads. There is a taper built into the nuts that matches that taper on the stud and they have to be tightened against each other to correctly orient the rocker arms.

At that point, all the rocker nuts will be in a row, at pretty much the same height from front to back. If your adjusting nuts are currently NOT all in a row, adjusted to basically the same height, they're probably NOT adjusted correctly.

That would cause hard cranking because you will be cranking against cylinder pressure / compression when it shouldn't have any (ie: when one of the valves is supposed to be open but isn't).

Actually, calling it an 'adjustment' is a misnomer. It's really an assembly spec because there really isn't any adjustment on a stock non-Ram Air setup. Just tighten the nuts until it's at the bottom or the threads and then torqued to 20 ft/lbs. The hydraulic lifters take up the slop on their own.

Good luck!
Thank you so much for that contribution as the manual is vague with vehicles equipped with chevy engines and you really have to be careful which procedures apply to a Pontiac engine. I was pretty on-par back in the nineties but I guess my old age is affecting me now.

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Old 07-27-2020, 10:23 PM
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Okay, here's what happened today. I removed the valve covers and the oil deflectors and backed off the rockers. Made NO difference. So I re-torqued them to 20 lbs ft and put the valve covers back on. Then I pulled the intake off for a second time and realized a boneheaded mistake. The Fel-Pro gasket set comes with two sets of intake gaskets, and I chose the wrong one on the passenger side cylinder head. I replaced that one it solved one issue. But the engine was still struggling to run and would not rev. At that point, I took a break and got away from it altogether. Then, suddenly, it donned on me that the engine was acting as if the timing was off, and sure enough. I realized another boneheaded mistake. I had forgotten that I had loosened the distributor hold down and didn't remember to check it upon reassembly.

So now, the engine runs great again and all is well. Thanks to all for all the tips and possibilities.

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Old 07-27-2020, 11:10 PM
mgarblik mgarblik is offline
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Glad you got it all straightened out without having to go into the heads again. I didn't mean to imply in my above post that your machinist didn't know what he was doing. He obviously was familiar with Pontiac engines. But mistakes can happen. Another Strato-Streak back on the road!

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Old 07-28-2020, 06:00 AM
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Yup it's a common mistake I think we have all made with leaving the Dizzy loose when you have so many other things going on during a full or partial rebuild and restart.

Great to hear you stuck it out and got it all good again!

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Two pairs of brown leather flip flops, never seen more then 2 mph.

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Old 07-28-2020, 09:36 AM
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Pilots go thru Checklists every time they fly an airplane, they may have flow that plane 1000 times in their lifetime. I always use a check list to make sure I did not forget something. There always seems to be a big hurry to get the engine running vs a logical
process for making the event happen.

There are several Pontiac style Engine Build documentation sheets.
With today's computers and printers/ Word or Excel files it is very easy to keep on the right path and not miss things.

Every Experimental Engine we build had a documented Engine Build Sheet with all of the steps followed. Bob Armstrong and Chris Piper (two Pontiac guys) were involved in many of these Research Engine Builds.

It you did not write it down, it never happened, (when you try to remember later).

Tom V.

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Old 07-28-2020, 09:50 AM
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Quote:
Originally Posted by Tom Vaught View Post
It you did not write it down, it never happened, (when you try to remember later).
THIS SO MUCH! I write down the specs of every engine I build and the things I have forgotten about them all is amazing. But my notes are still there detailing every piece. I also give the info to the new owner when\if I sell the car too.

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Old 07-28-2020, 10:18 AM
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You are a good Engine Builder and you really help the "next guy" who owns the car/engine with the documentation on a given car/engine (if you are willing to pass along that information). Every engine I ever built/had built for work was a learning experience. I still know little about Modular Engines though vs Pontiac Engines.

Tom V.

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Old 07-28-2020, 10:42 AM
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I'm the worlds worst at getting into things and low and behold the guys on here have always bailed me out. Good luck!

I gotta ask......how in the world did pulling the valve covers to R&R a leak lead to a leaky exhaust flange?

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Old 07-28-2020, 11:45 PM
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Quote:
Originally Posted by Tom Vaught View Post
Pilots go thru Checklists every time they fly an airplane, they may have flow that plane 1000 times in their lifetime. I always use a check list to make sure I did not forget something. There always seems to be a big hurry to get the engine running vs a logical
process for making the event happen.

There are several Pontiac style Engine Build documentation sheets.
With today's computers and printers/ Word or Excel files it is very easy to keep on the right path and not miss things.

Every Experimental Engine we build had a documented Engine Build Sheet with all of the steps followed. Bob Armstrong and Chris Piper (two Pontiac guys) were involved in many of these Research Engine Builds.

It you did not write it down, it never happened, (when you try to remember later).

Tom V.
That is an excellent idea!

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Old 07-28-2020, 11:58 PM
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Quote:
Originally Posted by David Jones View Post
I'm the worlds worst at getting into things and low and behold the guys on here have always bailed me out. Good luck!

I gotta ask......how in the world did pulling the valve covers to R&R a leak lead to a leaky exhaust flange?
Well, after I replaced the valve cover gaskets I had the engine running and was looking closely for leaks. That's when I noticed the exhaust leak between the the pipe and manifold. So I jacked up the car, tried to tighten the flange, and the stud twisted off. So I tried to remove the exhaust manifold and a couple of the manifold bolts broke off as well. That, in turn, necessitated the head removal.

So I could have attempted to remove the broken studs myself, but I have not had good luck in that area. So since I had to remove the heads, which haven't been touched since '99, I figured I'd just let the machine shop recondition them and have the broken studs removed at the same time.

It's funny but I couldn't believe that it's been over twenty years since I last did any thing major to that engine, and this car has been driven a LOT. Time flies!

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