Temperature at intake nipples/manifold

Hi all-

Somewhere had been posted a picture showing the temps in and around a 45 cylinder but I can't seem to find it. Would anyone have a link to that post or posssibly repost it?

Don't know if this was in the pic or not but what I'm trying to find out is this- does anyone know what temp is present at the intake nipple/manifold area? Or maybe I should ask what temp is the manifold seal subject to with a fully warmed and running engine?

[Pa]

Is this what you were looking for G ? Pa

Thanks Pa!

That's the one I was looking for.

[Pa]

My pleasure G. My question about this drawing is .....which cylinder does it represent ? Pa

Pa!

It shows the forked rod, so we can assume it is the rear cylinder (1943).

That's the cooler one, right?

....Cotten

One would think the intake nipple seal is cooler when running as the out side air is pulled in and the feul is evaporated just before it thus cooling some too. I would think the intake get warmest about 2 to 3 minutes after shut down.Paint the intake flat black and shoot it with an IR gun to see.

44dwarf

[Pa]

I should have seen that. I still argue that point Cotten. Front cylinder receives fresh flowing air. Rear gets it's air off of the hot front. NOS fronts are pretty easy to find. NOS rears are not. I know....fires at warehouses where rears were stored. I don't buy that. As I recall, someone here on the forum was going to take temp specs of both cylinders and heads ? I don't remember if they did or not though. Pa

I have been using an dual laser, infared temp gun to check motor temps for a while.

I think that chart is bunk.......it shows temps WAY over anything I've ever seen, especially heads. I've found that rear cylinders run cooler, but the heads run hotter. Front cylinders run hotter, but the heads are cooler.....(on both flatheads and ohv). The spark plugs "area" always measure the exact same temp while the bike is running, and soon after it's shut off. Typical cylinder and head temps run from 250-375, depending on different circumstances.

Greybeard.........the intake nuts on a well tuned flathead run around 200 degees.

Tom,

Do you think the head temp is directly related to today's fuels?

There's a heck of a lot more additives in today's fuel to prevent knock, increase power, prevent wear than back in the day when that drawing was made.

Kurt

on our racing kr's we found the rear cylinder to run cooler than front also.. we also played with staggering plug heat ranges to even them out.. needing a hotter plug on the rear cylinder. i do not remember the temps anymore tho.. we also found that pump gas was evaperating in the intake manifold making jetting hard to get correct.. which was corrected by running racing gasoline. we were able to go down about 10 sizes in mains(mikuni carb) with racing gas.

[Pa]

Tom....on what part of the cylinders are you getting your readings ? The reason I ask....is.... I assume the lower end of each cylinder will remain cooler than the top area since the upper portion of the cylinders are next to the heads. Better lube at the rear may account for cooler temps, heh ? I should have took taper dimensions on all the old rears I unloaded. Maybe the data might have helped a bit, especially if the fronts were measured for the same wear patterns. Ideally, a pair from the same engine would have been best for data documentations. Pa

Has the emistivaty of the heat gun been checked for the color of the surface your looking at? silver will measure difrent then a flat black.
But you numbers seem close to what my hand reads on a cold ride i'll put a hand on a cyl while going down the road.

44

44dwarf....agreed, you wouldn't be able to keep your hand on 500 degrees going down the road. You remind me of my mom putting her hand on my forehead when I was a kid, to check my temp (she always seemed to be right? ??). Incidentally, skin surface temp is only about 86 degrees, (not 98.6) I guess that's why they check "inside". Pa, the temps check different everywhere you check. The equipment is so good, it can drive you absolutely nuts, with all the info you can collect. Flathead heads when the bike is parked a couple minutes after a ride are only about 250. Kurt, I don't know why the chart is the way that it is, maybe, it is a "worst case condition". They certainly had simple technology to check temps back then.....even welder's "temp sticks" have been around for quite a while.

I think it is safe to assume the chart was meant to illustrate internal temperatures, where the heat is being made.

Surface temperatures will always be subject to conduction, airflow, etc.

....Cotten

I'd agree Cotten, but one arrow is pointing directly at the fin on the head towards the end and the another is pointing directly at the combustion chamber.

Guys !
don't forget this fact :
i know a man . he REALLY races ...on modern bikes .
about the spark plugs :
he order them by full boxes .
and check them all one by one , with a special tooling ...to complicated to explain .

on a 50 units box :
ONLY 4/5 are really FINE for racing .
all the others : to the bin .

i just wanted to say
"" before measuring the front or rear cylinder temp : how can you be SURE the spark plugs are THE SAME ? ""

Geez, Kurt, its a drawing.
So call the fins 400F and the core 500,.. (I can remember a Wisconsin haybaler motor that matched that easily: igniting dried timothy.)

On to sparkplugs, when did they start controlling combustion temperatures?

.....Cotten

Don't you think sparkplugs can interfere in the temp of the head ????

No.

Fran-6 asked: "Don't you think sparkplugs can interfere in the temp of the head ????"

Only when they foul out.

A hotter plug does not increase combustion temperatures,... unless it melts down and causes pre-ignition!


....Cotten