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03-04-2008, 10:29 AM
The machine shop that is re-working my head called and said they cannot get the spring pressure to act right, way low.
I ran by there this morning before work and, lo and behold, there are no valve collars! They maintain, and I tend to believe them, that all parts are accounted for. There apparently were never any collars or ring pedestals installed under my springs! How it ever ran with really low spring pressure is beyond me. Or did they lose them and deny doing so. Can a valve work without this collar on the bottom?? Whatever, I have all new springs in a box at their shop, along with new Teflon seals. New (12) collars are being blue-labeled from Moss. I was really nervous when the machinist told me all this.

So, if this is what happened, and if this all goes back in without a problem then I might be good to go. The head and valves are otherwise in perfect shape.

It never ends.

Any thoughts??

03-04-2008, 10:34 AM
And so maybe all this trash talk that has come out of my mouth against some vendors was ill-conceived. Maybe, just maybe, the cam was not the problem, not the tappets. Just way low valve spring pressure. And I might have just been floating the valve springs.

God forgive me if I was wrong. :angel:

03-04-2008, 10:35 AM
And I didn't build that head. Someone else did for me. :devilgrin:

Dave Russell
03-04-2008, 11:13 AM
I assume that by collars, you mean the lower spring seats. If so, this would result in lower than intended spring pressures.

A "good" performance head rebuild involves measuring spring pressures, & setting spring lengths with shims under the springs to obtain the desired installed spring lengths & pressures.

Yes, an engine can run quite normally with low spring pressures until you reach an rpm where the springs no longer correctly seat the valves. If the spring pressures are too low, the valves will float (fail to completely seat) at higher rpm. This would normally be detected by rough running or even misfiring at higher rpm. If excessive, valve heads could collide with piston tops.

Even so, short periods of time with valve float or partial valve float, only when running at higher rpm, would not be likely to cause cam lobe damage. And then, not on one cam lobe only. I don't know how much time you may have run the engine under these conditions but not likely very much.
D

bobh
03-04-2008, 11:27 AM
Look at last weeks post "Cam shaft early demise"

https://www.britishcarforum.com/bcforum/u...mise#Post426585 (https://www.britishcarforum.com/bcforum/ubbthreads.php/topics/426585/Cam_shaft_early_demise#Post426585)

"I received a line drawing with engine parts for my engine
rebuild. I took a photo for reference. It will follow.

Note in big letters: "DO NOT USE LOWER SPRING SEAT," with
an arrow pointing to the part not to install.

Now, I did shave the head down to increase compression.
Got different springs for the head (which are larger than
were stock) to go with the upgrade.

See the line drawing now to show what not to install
when the larger upgraded springs are installed in lieu
of the OEM's:

Out of abundance of caution, I visited the machine shop to
view the head and verify that these parts were not on my
head.

Now the plot thickens as follows:

"2WRENCH Question: So what happens if these little do-dads
(spring seats) get installed with the longer springs?"

"MACHINIST Answer: Excessive pressure from the springs
causing excessive wear on the cam shaft and valve train
parts."

Okay. I aint gonna say this is it, but doesn't this sound
familiar to anybody.....say.....Bill, maybe?

So the line drawing spring seat looks different than the
originals that came off my head (poor drawing? Different design?) Don't know.

Here is a photo of my rebuilt head (no lower spring seats).
Just the new upgraded springs.

I am holding an old spring with the spring seat to show
the heights are equal from old install to new install.

Possible Conclusion?

If new upgraded (larger springs) are installed and the
old lower spring seat is reinstalled as well....could
result in too much spring pressure and undesirable/excessive
wear to cam shaft and valve train parts.

Something to consider.
_________________________
2wrench "

2wrench
03-04-2008, 11:40 AM
I hope you get her back on the road, Bill, cause
I feel your pain. Your friend,

TR3driver
03-04-2008, 01:49 PM
Possible Conclusion?

If new upgraded (larger springs) are installed and the
old lower spring seat is reinstalled as well
I'd offer a different conclusion :

When installing non-original parts, be sure you understand which parts go with what !

Some aftermarket springs need the collars, some don't. You have to understand which you have, and install them accordingly.

Brosky
03-04-2008, 05:33 PM
I'll be curious to see what my new valve springs look like when they arrive on Friday.

I now understand why the machinist INSISTED that I bring the head for a COMPLETE inspection. Not that I wouldn't have anyhow, but that was the first question that he asked. I will feel much better having him check all spring heights and pressures after he cuts the guides for seals.

DNK
03-04-2008, 11:11 PM
After all this work, I'm glad Ted built my head.