74" Cylinder growth verse Intake manifold gap

[dukekleman]

Does anyone have any experience with the Engine growth values on early 74" Panheads. I'm adjusting the length on the Intake manifold and Wondering if anyone has information they'd be willing to share in regards to intake manifold length verse clearance between the intake nipple fittings.
Harley Davidson states a intake manifold length of 3.375"@ 74", however an acceptable gap isn't listed that I've seen.
As we know the intake nipple to nipple dimensions vary for many reasons...
Any chance anyone has measured the ambient air temperature distance verse engine operating temperature distance?

[T. Cotten]

Does anyone have any experience with the Engine growth values on early 74" Panheads. I'm adjusting the length on the Intake manifold and Wondering if anyone has information they'd be willing to share in regards to intake manifold length verse clearance between the intake nipple fittings.
Harley Davidson states a intake manifold length of 3.375"@ 74", however an acceptable gap isn't listed that I've seen.
As we know the intake nipple to nipple dimensions vary for many reasons...
Any chance anyone has measured the ambient air temperature distance verse engine operating temperature distance?

I stopped worrying about it, Duke!

After I successfully reconditioned a few EL manifolds for FLs.

(I challenge anyone to show me an OEM '48-'49 manifold of anything but EL width; They are absent from the fossil record.)

How would you measure the distance between nipples at operating temperature?

....Cotten

[dukekleman]

Well,
My thought would be to remove the Intake manifold nuts, Base nut at the fuel bowl and fuel supply line fitting at the fuel tank valve, tilt the assembly forward and measure nipple to nipple.
A measurement from manifold nut to manifold nut would also be telling as well as head casting to head casting beyond the intake manifold nuts. However nipple fittings to nipple fittings would be required in my opinion to tell the entire story with the dissimilar materials that are all involved.
Very similar to Intake manifold leak testing when @ operating temperature hot verse ambient temperature cold .

[T. Cotten]

Its gotta be operating, Duke,

To be at operating temperature. You can't remove the carb and manifold quick enough.

Maybe you could just spin off the nuts and quickly caliper between the nipples with the manifold and seals in place. Let us know.

Bubble-testing a manifold hot is masochism; Fifteen psi is already over-kill..

....Cotten

[dukekleman]

Operating temperature is not a given but a range based on many factors. It would be possible to capture a measurement within 30 degrees F with disassembly, say 250 F and capture a measurement by 220 F . Just wanted to ask the question in case someone had the information and was willing to share it. Save me sometime ... Never hurts to ask as they say...
Thank you for the replies.
Duke

[Steve Swan]

fwiw, i was told by a man far more knowledgeable than myself that a JD engine at full operating temp expands in length 0.090"

[T. Cotten]

fwiw, i was told by a man far more knowledgeable than myself that a JD engine at full operating temp expands in length 0.090"

I'm clueless about JDs, Steve!

(The best I can do is study the carbs 'n stuff...) Do they have a top motor mount?

Another question is what happens to the compression ratio?

No doubt the rods get longer too, but what about those exposed inlet pushrods? What holds them in?

...Cotten

[duffeycycles]

I might believe .009" not .090

[dukekleman]

I apologize for budding in on the questions ,
I personally do not know how much a JD motor grows...how ever, I know all HD motors grow and I know some more than .090". Growth takes place radially on all engine components regardless, the only Bias involved is the material type and it's location within the Engine.
Cylinder pressure is variable in the engine based mainly on RPM, Ignition timing, AFR and Heat. Pressure transducers are used to monitor this during engine development. There are two common designs used. Integrated and non integrated meaning one is built into a special spark plug while the other is independent and threaded into a machined hole in the cylinder head itself close to TDC of the the piston.
Duke Kleman

[T. Cotten]

,,, I know all HD motors grow and I know some more than .090". Growth takes place radially on all engine components...

'Radially' confuses me, Duke!

You mean how the hole in a donut gets bigger if the whole donut gets bigger?

And its a good thing frames are springy, huh.

....Cotten
PS: If there is any way to monitor the change of inlet geometry with temperature, I'd be excited. It is certainly one of the historical banes of American v-twin motors.

[dukekleman]

Yeah, so basically from center out in all directions. However the shape of a component isn't always symmetrical, so growth varies throughout the component itself. Infrared 3D imagery shows this when viewing the component, different temperatures, similar to stress analysis of a component.
I'm always interested in attempting to make the older vehicles run better, longer, smoother, etc. and it's fun conversing about them.
Manifolds and carburetors have been a challenge from day 1 at HD as well as other manufacturers.
The older designs coupled with the materials used back then present issues many see today trying to make things better as well as run consistently throughout the operating temperature. The manifold area definitely calls for attention...

[Jerry Wieland]

I think that .090' growth due to heat is about a factor of 10 more than reality. Jerry

[Steve Swan]

I'm clueless about JDs, Steve!

(The best I can do is study the carbs 'n stuff...) Do they have a top motor mount?

Another question is what happens to the compression ratio?

No doubt the rods get longer too, but what about those exposed inlet pushrods? What holds them in?

...Cotten

it's what i'm told, i have no clue... interesting link to H-D engine growth >>> https://harleytechtalk.com/htt/index...,117113.0.html

Front and rear cyls both have motor mounts to frame, made of spring steel. the the upper and lower "ball and socket" of inlet pushrods are deep.

[dukekleman]

Ok, I had a little extra time this evening to do a quick test on one of my personal bikes, a 71' shovelhead .
I put it in my test cell and ran it up to 238F. Could have gone farther in temperature I know but just wanted to try this quick on that type of engine.
I set up the tooling and it grew exactly 0.023" from 68F to 238F as a range being test. This was overall summative growth on a 1971 74" FLH in that temperature range for what that's worth...
Duke

[Steve Slocombe]

Dear All, the earlier Harley shop manuals say leave the cylinder base stud nuts a little loose, fit the inlet manifold, then pull everything up tight. Are we worrying unnecessarily because we have modern tools available? Those remote temperature guns now let us worry about cylinder temperatures, which we never could before.