Dauntless V6 valves not seating

Guys,
I have encountered a problem I have never seen before on my 225 V6, the valves won't seat when I tighten the rocker shaft stands down all the way.

A little background here:
I bought this Jeep about 2 1/2 years back, and within weeks had torn it down to do a rust repair and repaint on the body. The PO told me the engine had been rebuilt by a shop for him and had low mileage since then. It seemed to run fairly well, although the carb had no working choke on and it would occasionally backfire back through the carb. As far as I could tell it ran on all 6 cylinders. I never did do a compression check on it when it was still in a complete Jeep.

So for the last 2 years or better it has been sitting mostly inside the garage. I cleaned up the engine and repainted it, and it has been idle until recently, when I began putting all the accesory items back on it with the intent to restart it.

I cranked it with the plugs out to pre-oil the bearings before trying to start it, and it was probably a good thing. I could not get any oil to come out the pump until I opened up the oil pump and stuffed vaseline in the oil pump gears. This worked to get the oil pump to pull prime. I cranked a little more until the new oil filter filled up and I started getting oil at the rocker shafts. I figured I could put in the plugs and wires, and before I put fuel in it I cranked it again just to hear the compression.

Here is where I noticed a problem: the engine was obviously not making compression on all the cylinders. I did a compression check with the finger in the plug holes because I couldn't find the 14 mm adapter for my compression tester, and found that only 4 of 6 cylinders had compression. #4 and #6 were completely dead.

After checking the rocker arms for those cylinders with the cylinder on TDC, I noticed that there was no clearance between valve tip and rocker arm. I loosened the rocker shaft stand bolts a couple of turn and cranked it again, and those cylinders now had good compression.

So I started doing some research. I searched here on the forums for any similar problem, and only found an old thread from 2008 by DaveFL that sounded like he had something similar to mine but never posted a resolution.

The FSM showed the spec for the valve installed height, but I have no way of accurately measuring this. I looked at the pushrod length, but again have no way to accurately measure these. The rocker arm shaft assemblies are obviously fresh replacements, the hardened tip inserts on the rocker arms have no perceptible wear, nor do the ball ends of the pushrods show any wear yet. I looked at the hydraulic lifters, and they look practically new.

So my best guess now is that the rebuild shop may not have set the installed height on the valves correctly. I have pulled the heads back off the engine, and pistons and cylinders also look like very low mileage wear.

Does anyone have a suggestion for a knowledgeable machine shop around Sacramento CA? I need to find one that knows these Buick V6 engines, and get to the bottom of this.

Don

 

Check the length on the valve push rods to make sure they are all the same length.

 

Lamar,
Good idea, I thought so as well. I checked and the push rods are all the same length, and look like new.

Don

 

Use a straight edge to check the valve stem height. It won't tell you if it's within spec but if they are all close the problem is probably elsewhere.

 

valve stem height, machine shop should have set this, it also can be set with shorter push rods, heads could have been milled prior to the last valve job, or just one head, and had shorter push rods on only that head, and may have gotten mixed up. you have done pulled the heads correct? if the shorter ones were in the wrong posistion they may not have shown a problem in that location, but longer will show up. lifters could have been pumped up as well if you primed the engine with a drill, and the problem may have went away after running it for a few minutes. think you doid the right thing though, take it to a good machine shop and have it inspected

 

I don't know yet about whether the heads were milled, or the valve seats may have been cut deeper than what would work with standard length push rods and rocker shaft stand height.

I did check the push rods, they are all new looking, same length, with Sealed Power part #RP3173. Napa lists the same push rod for the V6.

If the heads check out OK for installed height, I may try one of the 3 different length push rod sets from TA Performance, after I get an accurate measurement of the RP3173 push rods.

You mentioned priming the oil system with a drill, I didn't do that but something similar, I cranked the engine without the spark plugs in it. This would pump up the lifters I think. Do the lifters run at something less than full extension of the internal plunger when the engine is running at normal RPM and temperature?

Don

 

the way you primed it should be ok, sometimes they do run just shy of full extension, this is to my knowledge where "floating the valves" term comes from. at higher rpms the oil pressure can overide the valve spring and hold the valve open. if it were running at full extension this would not be possible.

 

Well I dropped these heads off at Del's machine shop in Sacramento on Friday, and when the owner inspected these heads visually on the counter he right away saw the valve tips were not all the same height. All the intake valves appeared higher than the exhaust valves, and both the exhaust valves and intake valves appeared to be sunk too deeply in the valve seats. The valve seats do not appear to be hardened steel inserts, just cut from the cast iron as they were from the factory.

So, I am probably looking at all new seat inserts, new valves, and we don't know yet about guides and springs. This is going to be expensive, but at least I will have a set of heads done properly. Hopefully neither casting is cracked, that will be a whole other issue.

Don

 

Man that's the s&^#s. Why can't they do it right since it was rebuilt prior. Sorry to hear.

 

Correctly adjusted hyd lifters run in the middle of their chamber height. That allows quiet operation and enough additional room to compensate for wear. Priming the engine with the rocker shaft installed would have allowed them to fully fill but the lifters should have leaked down within a few seconds after rocker installation.

 

OK, the heads are back, $706 later.
All new valves, new springs, new hardened seats and new guides. No cracks, and the heads are lightly resurfaced.

The machinist did point out that I should take the rest of the engine out and have it inspected (at no charge), because of the way the heads were done in such a crappy shortcut manner the rest of the engine may be not much better.

What the hell, in for a penny in for a pound. The motor is coming back out of the chassis and getting a complete teardown this weekend. I sold back some vacation time at work to help pay for this. Wish me luck

Any suggestions at this time will be appreciated regarding parts selection for a good trail engine. This isn't my first engine rebuild but is has been a while ago.

Don

 

I don't know...
my engine is completely stock.
does everything I need it to.
goes everywhere I want to go.
no need to reinvent the wheel, oops, I mean engine.