Set valves with hot engine???

[Pescatore]

Stumbled upon this method while reading about lapping.
Seems like it would help with noisy valves, but not reliable.
What say you?

[guzzisteve]

Do you put your feeler gauges in the freezer !st?

[Frenchfrog]

Nope...never seen anyone doing it this way on a guzzi.
Perhaps if they had accurate valve clearance gapping data but then define hot which is likely why Guzzi say do it cold.
And not much problem with valve noise really ! Noisy valves are generally happy valves and camshafts

[Kev m]

Nope...never seen anyone doing it this way on a guzzi.

<*snip*>

but then define hot which is likely why Guzzi say do it cold.

Just quoting to add that, though there may be an odd exception of which in unaware, after decades in the service industry (with the last one exclusively for motorcycles) I've literally never seen an OEM recommendation that wasn't for overnight cold/ambient room temperature valve checks/adjustments.

[Pescatore]

Yeah, it's crazy talk.  The main point of setting a gap is to allow for stretching from heat.  So they would have to be set to a  different gap.

As far as the guages, I should put them in the freezer so I can easily find them.

[bmc5733946]

Absolutely no application for a Guzzi but these little clips were handy when adjusting valve clearances on solid lifter Chevy engines in the past.

 https://www.amazon.com/Mr-Gasket-Rocker-Clips-Deflecting/dp/B0DJJZ7GKJ?th=1

So yes some engines were specifically adjusted not just hot but while running as well!!
Aah, memories of my youth, the smell, the smoke, the burning sensation,  etc.. I well know how old I am, now, get off my lawn!!

Brian

[wirespokes]

There was a discussion about this with the airheads. So we checked the clearance hot to see if it changed. It didn't.

Evidently the parts expanded with the heat proportionately and clearance stayed the same.

We concluded instructions to set them cold prevented us burning ourselves. :-)

[guzzisteve]

I had a long 1/4 piece of cover for doing the hydraulic lifters while running so oil didn't get all over the 289 in my 67 Mustang fastback. That car cost me 4yrs w/o license.

[Tom H]

BMC, never heard of that for solids, hydraulics yes.

Maybe BMW's are different. With my Guzzies, if you check them hot, they will have a much smaller gap than when cold. Set cold, 4 and 6, you might have 1 and 2 when hot. Check them a few times while cooling, you will see the gap increase.

Tom

[Alfetta]

As a base value. steel has a thermal exp of .000001" per degree. assuming that the valve stem runs at 250F from 65F that would be a 190F them. rise, thus 190 x .000001 = .00019" length gain.

note that the actual expansion rate of hardened specific material is likely less, and i'm flat out guessing at the thermal rise. But it's kinda clear that the change in gap would be very hard to detect, let alone set unless one has very precise "feel" when adjusting....

so go cold, and per spec, unless you are just that kind of rebel...

[Perazzimx14]

What temperature is "hot"

[Huzo]

I tend to think that the pushrods are the main contributor to fluctuating clearance with temperature changes.
Anecdotal evidence suggests that .004 and .006 cold is the way to go.

[Tom H]

Hot: IMO is at normal operating temperature.

Valve gap: I will start with this....One persons 6 in anthers 5 or 7. The key IMO is that YOU set them the same way every time. Some prefer to have to pull the feeler out fairly hard and some prefer a smooth slide. It's up to you, smooth would likely be the more accurate setting.

Tom

[wirespokes]

Agreed - cold is the best way to go.

[SIR REAL ED]

What temperature is "hot"

Generally speaking, I define "hot" as that temperature that raises blisters and makes you spout profanity.

The truly Stoic mechanics use the blister only method of measuring temperature.

[Frenchfrog]

Just quoting to add that, though there may be an odd exception of which in unaware, after decades in the service industry (with the last one exclusively for motorcycles) I've literally never seen an OEM recommendation that wasn't for overnight cold/ambient room temperature valve checks/adjustments.

Ahh well I have  Kev and that's with Panther heavy weights .Valve clearances are set on those at "Nil when hot " .Easy peasy and no need to bugger about with feeler guages.
Rather oddly with the smaller 250 and 350 upright engines from the same firm you set them at Nil when cold !!!!!!!!

[Kev m]

Ahh well I have  Kev and that's with Panther heavy weights .Valve clearances are set on those at "Nil when hot " .Easy peasy and no need to bugger about with feeler guages.
Rather oddly with the smaller 250 and 350 upright engines from the same firm you set them at Nil when cold !!!!!!!!

And there's an odd exception ... 

[Walton]

Ahh well I have  Kev and that's with Panther heavy weights .Valve clearances are set on those at "Nil when hot " .Easy peasy and no need to bugger about with feeler guages.
Rather oddly with the smaller 250 and 350 upright engines from the same firm you set them at Nil when cold !!!!!!!!

My f100 straight 6 calls for adjusting them while the engine is idling, makes the job easy and quick. Same with some old Chrysler 6s.

[Kev m]

My f100 straight 6 calls for adjusting them while the engine is idling, makes the job easy and quick. Same with some old Chrysler 6s.

Those were hydraulic right? I respectfully submit that's a different thing no?

[Walton]

Pushrods

[Pescatore]

Setting the gap with hot engine sounded weird, but never imagined doing it with the engine running.
I learn something new.

[Walton]

Setting the gap with hot engine sounded weird, but never imagined doing it with the engine running.
I learn something new.

It's actually really fun.  Just did it last week.

[Moparnut72]

The early Slant Sixes had solid lifters. I don't remember for sure but believe the later ones had hydraulics. The flat heads were solids which were used through 1959. The first small block V8, 273, had solids and the hypo would rev to 7,000 rpm. My dad had both a flat head and a Slant Six which both burnt an exhaust valve. He had never had the valves adjusted even so they had 90,000 miles plus before failure.
kk

[n3303j]

On cars ('50 Cadillac & "55 Chevy) rocker clearance was specified hot with engine running. On hydraulic lifters you would close the adjustment until the cylinder just started dropping out then back out a specified number of turns. On solid lifters you would grab the appropriate feeler gauge and slip it over the moving valve stem. If it couldn't be inserted you'd loosen the rocker at the stud then slip ithe feeler in and slide it back and forth while slowly closing the gap. At some point the gauge wouldn't move. You were at gauge clearance minus a hair. Just back the nut off until you can withdraw the gauge and clearance was set. It was all a lot quicker than trying to find TDC for each piston.