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TxGoat

Re: Valves & seats

#51

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Excessively weak or over-extended springs can allow valves to "float" and perhaps bounce on the seat, usually at higher RPM. Weak springs might also contribute to carbon or other debris sticking to a valve face or seat, or to a valve stem, or to a valve sticking in the guide.

Posted on: Yesterday 12:23

53 Cavalier

Re: Valves & seats

#52

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Quote:

Packard Don wrote:
I’m not really sure that these heads need to be machined as the studs will easily pull them down flat. The only real reason to machine one is if it has some sort of localized damage. I always use a coat or two of well-shaken CopperCoat on both sides, let it tack up, then tighten it down!

On the studs, you said you didn’t removed them but perhaps someone before you did as some do not appear to be threaded in all the way. Put in properly, no threads should be showing.

I did spray this gasket down with a few coats of copper coat, didn't do that the first time.

I agree that the heads will pull down, but if you're head is warped then it will not pull down even. Torque values will be the same, but pressure on the head gasket will not. Machining the head, or not, wasn't even a question for my machinist.

It is possible that the studs were removed, in fact I think it's likely because the inside of my engine was coated at some time in the past.

Posted on: Yesterday 12:44

53 Cavalier

Re: Valves & seats

#53

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Quote:

kevinpackard wrote:
We had briefly considered using spacers on the spring seats but in the end decided not to. I'm really not sure how necessary they are on engines like ours. So far it seems to be working quite well without the spacers.

For copper spray, our engine builder friend told us to use 6 coats on both sides. We did not have the head machined. He may have been giving us an extra bit of security in case there were small defects in the sealing surface of the engine. '

Don - on both 327's I've had open (Rusty's and brother in law's '52) the head studs have all had at least 2 threads showing above the block. I know the '52 had the head off before, but almost 100% positive the studs were never removed. Rusty's engine has for sure never been opened before.

I think you're right about the spacers, after all we are talking about engines running at a few thousand rpm, not 10,000 rpm. Having said that..........I could geek out a bit on this. I'm not sure what the factory length and strength of the springs was, but I suspect after 72 years they are not what they used to be. Along with what TXgoat mentioned, how much might weaker springs affect performance, efficiency and/or valve longevity? I think the answer for us is, not enough to worry about it, but makes me curious.

Posted on: Yesterday 13:07

Pgh Ultramatic

Re: Valves & seats

#54

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Weak springs will give you valve float at a lower RPM and therefore your engine will have a lower effective redline. You will also have marginally worse heat conduction, which slightly increases your chances of burning a valve. I say marginal as the valves are positively sealed by the cylinder pressure during operation by a greater figure than the spring pressure.

I’m almost certain in the engine manual. It actually tells you the spring constant for the springs for this exact reason, so that you can check them with a valve spring tester.

The springs usually also have a right side up.

Posted on: Yesterday 14:08

53 Cavalier

Re: Valves & seats

#55

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Quote:

Pgh Ultramatic wrote:
Weak springs will give you valve float at a lower RPM and therefore your engine will have a lower effective redline. You will also have marginally worse heat conduction, which slightly increases your chances of burning a valve. I see marginal as the valves are positively sealed by the cylinder pressure during operation by a greater figure than the spring pressure.

I’m almost certain in the engine manual. It actually tells you the spring constant for the springs for this exact reason, so that you can check them with a valve spring tester.

The springs usually also have a right side up.

Don't you get valve float at higher rpm?

Heat conduction is also a good point, although minimal, all these little things add up.

You're right, valve spring specs are under specifications!

Click to see original Image in a new window

When I tested my valves, I just made up a tester to see if they were all the same, which they were. But that doesn't mean that they're all good either. "Next time" I'll check them properly.

I know some valve springs are directional, but I don't think the ones for my 327 are. If they are, the service manual doesn't make mention of it anywhere that I could find. Visually they appear symmetrical.

Posted on: Yesterday 15:01

Jack Vines

Re: Valves & seats

#56

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It might be theoretically possible to float the valves in a Packard I8, but practically, a rod would come through the block long before that happened.

Posted on: Yesterday 15:23

TxGoat

Re: Valves & seats

#57

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Some valve springs have closer spaced coils at one end. If that's the case, the closer spaced coils go away from the cam, against the head or block casting.

Posted on: Yesterday 18:24

kevinpackard

Re: Valves & seats

#58

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Quote:

TxGoat wrote:
Some valve springs have closer spaced coils at one end. If that's the case, the closer spaced coils go away from the cam, against the head or block casting.

I just put the springs back in the way they came out. The star washer on top leaves marks on the spring that makes it easy to tell what direction to install it. Not sure about other engines, but pretty easy to tell on the straight 8's.

Posted on: Yesterday 21:46

Pgh Ultramatic

Re: Valves & seats

#59

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Quote:

53 Cavalier wrote:
Quote:

Pgh Ultramatic wrote:
Weak springs will give you valve float at a lower RPM

Don't you get valve float at higher rpm?

I meant a lower RPM then they would otherwise…

That being said, based on Jack Vines’ comment, it would only be a concern on the V8’s.

For your spring tester, the only other thing you need is a dial indicator resting on the wood. Substitute a steel plate for the top board and you will be all set.

Posted on: Yesterday 22:38

todd landis

Re: Valves & seats

#60

Home away from home

I see mini valve spring pressure testers on ebay for al little as 65.00, might just purchase one for? What is the pressure range for prewar super eight springs? Thanks

Posted on: Yesterday 23:58

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