Newly rebuild engine with bent valve (?)........

[boyt911sc]

What would be a good way (procedure) to test a newly rebuilt engine suspected of having a bent valve/s? The exhaust rocker for cylinder #6 broke while cranking the engine with the starter and all fuel injectors disconnected? The crankshaft is encountering rotational resistance when you manually turn the crankshaft pulley. Short of an engine tear down, what test could I perform to evaluate the condition of the valves? Thanks.

Tony

[bpu699]

Leak down test would do it...

You can also take the cam covers off... A bent valve can be seen...

[boyt911sc]

Originally Posted by bpu699

Leak down test would do it...

You can also take the cam covers off... A bent valve can be seen...

The intake valve is stuck open. Is there any advantage in removing the complete bank (4-5-6) with cam tower, cylinder heads, and P & C as a unit in comparison to piece by piece tear down? Due to the massive weight of the combined parts, it would be physically strenuous for me to remove them as a unit. Thanks.

Tony

[mreid]

Here are the options I can think of:

Measure the closed valve stem height on each valve looking for one or more that are significantly shorter.

Loosen all of the rocker adjusters. Back them off as far as possible. Rotate the engine by hand until resistance is felt and inspect each valve, rocker, and cam lobe for interference.

Pull the distributor and try rotating the engine.

Remove the rockers, blow compressed air through each spark plug hole and listen for escaping air (intake, exhaust, case?) (assumes you don't have leak down testing equipments).

If the clutch is installed, make sure the pp bolts aren't too long and are hitting the case.

That's all I got!

[bpu699]

Not sure what you meanby the valve being stuck open.

Again, from what I recall, if you take the cam cover off you can somewhat see how the valve seals. If it clearly bent, your motor is coming out...

[boyt911sc]

Originally Posted by bpu699

Not sure what you meanby the valve being stuck open.

Again, from what I recall, if you take the cam cover off you can somewhat see how the valve seals. If it clearly bent, your motor is coming out...

bpu699,

First, the 3.0 liter SC engine was already out and has been installed in an engine test stand for start up. The previous problem I had was non-delivery of fuel to any of the six (6) injectors which I have been troubleshooting since summer of this year with no luck. Then on X'mas day, something came to my attention what could possibly be causing the very minimal movement of the sensor plate. Anyway, the fuel delivery problem has been fixed.

Right now, the clearance between the #6 intake valve stem and the elephant foot (rockers) has changed from 0.1 mm to atleast 10 mm gap. So the intake valve has not fully returned back and OPEN. And from TDC Z1 (cylinder #1), the obstruction occurs to the next firing order (cyl. #6), this is the cylinder with a broken exhaust rocker and stuck open intake valve.

Tony

[boyt911sc]

Originally Posted by mreid

Here are the options I can think of:
...................

Pull the distributor and try rotating the engine.
....................

MReid,

Thanks for the other suggestions. But why do I need to pull the ignition distributor? Thanks.

Tony

[mreid]

Hey, Tony, I was typing my thought when you posted the diagnosis. I was responding to your initial post that "when manually rotating the engine it hits an obstruction". I was eliminating things driven by the crank that might cause the obstruction. Sounds like you found it though.

[boyt911sc]

Originally Posted by mreid

Hey, Tony, I was typing my thought when you posted the diagnosis. I was responding to your initial post that "when manually rotating the engine it hits an obstruction". I was eliminating things driven by the crank that might cause the obstruction. Sounds like you found it though.

mreid,

A couple of hours ago, I began the engine tear down to get the #6 cylinder to the machine shop. The following have been removed:
CIS unit (intake runners, air box, FD, vacuum hoses, etc.).
Fiberglas shroud
Alternator
4-5-6 chain housing cover
Locking bolt for the cam shaft
Carrera hydraulic oil lines and tensioner

To be done next (tomorrow).
Chain housing
SSI header
Cam tower
Cylinder heads
Etc.

Thanks, Tony

[SoyRacer]

I had an engine dropped off that had "just been rebuilt" at another shop. Was asked to diagnose the "stuck valve". Took it apart (cam timing was way off left to right) and found two intake valves were stuck in the guides. Took all of the heads apart and found burrs on all of the valve stems. This has been more common recently. I micro-polish valve stems anyway though. The other valves were so bad that when disassembling they gouged the guides on their way out. There's no way that they didn't feel this on reassembly. Just another thing to consider.

[al lkosmal]

Tony,
From the sounds of it....that valve is bent bad and/or stuck in the guide. The rocker is designed to break if there is an interference between valve/piston etc.......but that is a result of a failure, probably not the root cause. Can you take pix, once you have it apart, so that we can see what you are dealing with?

regards,
al

PS: I feel for you....this engine is kicking your ass......I've been there.

[boyt911sc]

Originally Posted by al lkosmal

Tony,
From the sounds of it....that valve is bent bad and/or stuck in the guide. The rocker is designed to break if there is an interference between valve/piston etc.......but that is a result of a failure, probably not the root cause. Can you take pix, once you have it apart, so that we can see what you are dealing with?

regards,
al

PS: I feel for you....this engine is kicking your ass......I've been there.

Al,

There were a couple of professional engine rebuilders like you that I consulted and learned from them that in spite of their vast experience in engine rebuilding they had encounterd a few set backs too. I am not alone and very motivated to continue and survive from such setback/s. BTW, I located and identified the cause of the problem for non-fuel delivery to the injectors in my other thread. Will share that experience with others. Thanks.

Tony

[boyt911sc]

Cylinder head #6 was pulled out due to vent valves. Brought the head to Bob Hirst's Anchor Atlantic for repair yesterday. Got a call today (Saturday PM) from Bob that the head was ready for pick up. He's a remarkable person and even offered to meet me half way tomorrow Sunday morning. Do you know anyone who would go out of their way on a Sunday morning to help a customer in trouble? I surely know one.

When you have the support of people like Bruce, Al, and Bob, you know you could overcome any setback in engine rebuilding with these guys and others behind you. Thanks.

Tony

[timmy2]

Sounds like you are getting awesome service Tony.
Now you can finally get that motor up and running after this latest setback.
I never read what you found for the metering plate not lifting?
I know I learned something with the harness I provided. Brown/Red on the right from 1980 on!
(Darn metal fuel lines...)

Good luck and happy building.

[boyt911sc]

Dennis,

As soon as I get this motor running, I will post and document all the problems I encountered in this project. I am not anticipating any problem but who knows. It is isn't over until the motor is delivered to the owner this winter. Just got back from New Jersey to pick up the cylinder head from Anchor Atlantic. The proprietor of the machine shop got a call from me at 7:30 AM (Sunday morning) to remind him that I was on my way. An hour later, I was on my way home. What an awesome service and the nicest guy to work with. If you ever need a cylinder head job in the future, search for Anchor Atlantic (Pitman, NJ). Ask for Bob H. Just a fully satisfied customer.

Tony

[boyt911sc]

No work was done from February to April 2016 due to my travel plans to NZ and AUS. Got back home in late April and started right away in May to continue the saga. The first first week of May was a very disappointing moment because the engine would start and die. After days of investigation, the culprit was discovered. The supposedly good FD is leaking fuel when the FP starts to run. Since I had a spare and newly rebuilt FD, I decided to switch the fuel distributors.

Immediately after the switch of the FD a dramatic change in engine behavior was observed. It did start and idle roughly with a quite loud tapping sound from the valve covers. Further adjustment made the starting easier and smoothly. After a couple of valve adjustments, the taping noise has diminished with acceptable noise level.

The engine starts and run very good except for the initial start after a long stop. The loud tapping or knocking sound is quite noticeable. Stop the motor and restart it, the noise seems to get lesser. And after a second start, the noise is quite quitter, and a third re- start it is back to normal (no loud tapping/knocking sound). I could reproduce this abnormal sound after a 30 mins. or longer engine rest.

Another discovery was that several of the elephant foot of the adjusters were loose and wobbly. Could they contribute to this annoying sound? What else could contribute to this problem (abnormally loud tapping noise) during initial starts. Thanks.

Tony

[al lkosmal]

tony,
how does the oil pressure look during start ups and running?
regards,
al

[boyt911sc]

Originally Posted by al lkosmal

tony,
how does the oil pressure look during start ups and running?
regards,
al

Al,

The engine test stand I am using has no oil pressure gauge connected at the moment. And I have a mechanical pressure gauge that I could install in place of the oil pressure sender or use the OEM dash pressure gauge to monitor the oil pressure. This a critical information we need to determine ASAP. When I had the mechanical gauge (0-10 bar) hooked up before, I was not getting any pressure reading at all (?).

If I am not delivering any sufficient oil pressure, where do I go to check for the culprit? Oil pump? Pressure relieve valve? Flow restriction in the galley? What would you recommend where to start the investigation. Thanks.

Tony