Poly 318 flywheel id

[Drew M.]

I bought a 360/hydr bell/NP435 years ago. The seller said he "thought" the engine was balanced to the flywheel. The truck was supposedly a post 1968 W500.

The flywheel has 3 small holes (~0.5") nearly drilled through it near the outer edge facing the engine. Normally, the 360 balance holes are over 1" o.d. and closer to the center of the flywheel.

I am hoping that a regular poly flywheel lacks these holes - which supports the idea that it is balanced for a 360.

It has no part number.

Thanks.

[JimmieD]

Hi Drew, not sure if I can give info so it makes sense. From the Mopar performance Chassis book:

'71-'80 360 is externally balanced. 318 is internally balanced.

The '70-'74 Mopar V8's all used same ring gear and geared [10 tooth] starter, 10 1/2" clutch flywheel should be 130 tooth ring gear. '69 11" clutches, except Hemi, used 143 tooth flywheel gear. The '66-'69 11" street Hemi flywheel used 172 tooth flywheel ring gear.

"The 1974, 360 used a special flywheel [see Figure 5-24]."

This picture then shows a flywheel which has 3 holes for unbalance added, 1 13/64 diameter at 3.88 radius from center, 2.5" apart. Apparently that's the 360 drawing as it says '360 Cast Crank' below pic.

"The '74-'78 318 and '74 400 [forged crank] used the same flywheel."

"The 360 flywheel is the same as the 318 except for three large balance holes [1/2" diameter] drilled in the engine side. [See figure 5-25]"

Mopar Performance Chassis Book is very confusing and poorly written on this subject, as above! The drawing of figure 5-24 on page 246 shows the 360 cast crank flywheel having 3 balance holes drilled at a 3.88" radius from center, 1-13/64 diameter, 2.5" apart.

The drawing of figure 5-25, 383-440, 400 cast crank flywheel diagram shows 3 holes at 3.88" radius from center at 31/32" drill bit, 2.5" apart.

Trying to decipher the wording is a nightmare: "The 360 flywheel was the same as the 318 except for three large unbalance holes [1/2" diameter] drilled in the engine side. [See Figure 5-25.]"

Okay, which one had the 1/2" holes?!!!? From the 360, 383, 400 & 440 drawings and the dribbling text it appears that the 318 flywheel is the one with 3 holes at 1/2" diameter.

[Drew M.]

And to muddy this up more . . .

I have a 318 flywheel (internal bal) for comparision - it has holes on the engine side of the flywheel in totally different places than my poly style flywheel. That is why the 3 small holes (well under the Mopar 360 drilled hole size) have me wondering. They are located near the outer rim like a cast crank 340, which only uses 1 hole that is 33/64". I do not want to go through the hassle of using the hydraulic bellhousing setup only to later find that the flywheel is misbalanced.

All the Mopar info I find relate to the smaller flywheels - the 10.5" and 11". The old Direct Connection manual does not even reference the larger clutch size. I think I have a 12" course splined clutch plate as determined by measuring the od of the clutch plate.

My fear is that it is an internally balanced poly 318 flywheel. It is not common as the flywheel is for a 12" clutch setup and most of the stuff on the web is for the 10.5" and 11" flywheels. Yes, I could buy a new 360 flywheel and get a spacer - but I think it will be too small o.d. to use the proper 172 tooth ring gear for the hydr old style starter (1961-68) required and my plate and clutch. (I did not measure the 318 flywheel for comparision and am pretty certain it was much lighter). I also want the bigger clutch for snow plowing and the annual central PA MV Rally (Steelsoldiers.com). I wonder if a decent machine shop could check the balance on the hydr flywheel and determine the balance - and correct it if not correct.
See: http://www.moparaction.com/tech/quest/internally.html

The 360-3 engine from the combo did not show any odd wear (vibrations) when I disassembled it. Sadly, it was ruined by being improperly stored to allow water to get inside for many years.

I will take a few photos tonight - maybe MoparNorman will be able to id this thing.

[JimmieD]

Sorry I couldn't help more. Mopar Norm may well have the answer. Also, didn't Will put a poly in his truck? He might know? If I find out anything I'll holler...

[MoparNorm]

I bought a 360/hydr bell/NP435 years ago. The seller said he "thought" the engine was balanced to the flywheel. The truck was supposedly a post 1968 W500.

The flywheel has 3 small holes (~0.5") nearly drilled through it near the outer edge facing the engine. Normally, the 360 balance holes are over 1" o.d. and closer to the center of the flywheel.

I am hoping that a regular poly flywheel lacks these holes - which supports the idea that it is balanced for a 360.

It has no part number.

Thanks.

I'm not quite sure I understand what you're trying to do, but let me give it a shot.
You are correct, the Poly/Hydraulic/ flywheel will have 172 teeth, to work with the original 3 bolt starter.
Are you using the old Poly type starter and bell ?
What engine are you using, to what trans/bell/starter combo?
Here is what may be possible depending upon which way you are going.
I just installed a Poly into a LA powered truck. I kept the existing mechanical bell and clutch set-up AND the flywheel from that combo since later Poly cranks share the LA crank bolt pattern. It went together like it was made to order.
Assuming that you have a 360 flywheel and are concerned that it might mess up the rotating assembly of your Poly, you could have your local machine shop balance the entire assembly with flywheel or just balance the flywheel only, as the Poly is already internally balanced. Adding a balanced flywheel will not affect that assembly unless the flywheel is OUT of balance. So, if the flywheel is perfect, it will not affect the motor. Also the Poly has a harmonic damper that greatly helps with minor imperfections.
Talk to your machine shop about that flywheel.

If...you are doing just the opposite and installing a 360 to the older bell and starter, you'll have to find a 172 tooth flywheel and have it balanced to, and with, the 360 rotating assembly.

[Drew M.]

Norm ,

Maybe I better explained things here: http://www.dodgepowerwagon.com/wwwbo...s/2840688.html

-Drew M.

[MoparNorm]

I must be dense as a brick, as I'm still not getting it.
Please explain from the beggining what you are trying to do.
Is the motor in your truck a 360?
Are you having flywheel problems?
Is the current flywheel a Poly flywheel, but bolted to your 360?

[Drew M.]

It was a 360/hydraulic bell/NP435 with driver's side PTO opening. The seller alleged it ran ok when parked. All he had was the truck frame - no body.

The engine was shot from water damage. I picked up another 360 to rebuild. After following W_A_WatsonII's swap, I am thinking of going the same route, abet with the engine mounted closer to the firewall.

I am looking to confirm the flywheel is balanced for the 360 based on the 3 unusual holes - maybe balance holes or standard for all poly flywheels?

So in other words, got a decent photo of the engine facing side of a poly flywheel? That will tell me what I want to know. Thanks :)

Update: A local machine shop said they could spin the flywheel next week to determined its balance specs:)
I took photos of the 318LA vs my flywheel - but can't post them. I did manage to get the link working:


Flywheel on left is 1978 318 from a W200. Flywheel on right is unknown poly type - that I hope is balanced for a 360. Notice balance holes don't match even though the crank bolt holes are in the same alignment.

[MoparNorm]

Ah Ha, "I see", said the blind man.
Yep, you are doing exactly what needs to be done, have a machinist confirm the balance and he can make it right if the balance is not perfect.
To recap, yes you need that flywheel to work with the bell and it would appear that someone went through the process to balance that flywheel to the past 360.

That being said, every motor is different and that flywheel would have to be re-balanced to the replacement 360, so you are going about it correctly, IF the new 360 is already rebuilt, otherwise you are jumping the gun because you are most likely changing pistons etc.? When the new 360 is completed, THEN take it and the flywheel to the balancer.
Hope that helped.

[Drew M.]

Thanks MoparNorm. This was meant to be a simple swap and is turning into anything but.

The replacement 360 is just a re-ring job as the bores were ok. It is unassembled. The frustrating thing is not knowing if it will all work while committing the little $$ and time I have to it. W_A_Watson did the same swap with many complications - largely caused by placing the engine so far forward IMHO.

A 318 or 360 setup with a mech bell and NP435 with dr PTO opening from a 2wd or 4x4 with divorced t/c is looking pretty good right now. It is a tried and proven swap. The problem is finding the right NP435 locally. My NP435 uses the ball bearings on the frt input shaft - so as I understand it, I can't just swap in the mech bell 23 spline shorter shaft version that uses the tapered bearings.

First I will check the flywheel balance. If neural - I will use a junk 318 and see how the hydr setup fits in the M37. If ok, then install it and check out engine to see if needs rebuild. If not, the do a mech setup with the 318.

If the flywheel is balanced to the 360 (ext bal), I will assemble the 360 - under the assumption that it and previous 360 were sufficiently close in balance as neither was rebuilt, and run w/o major balancing issues. Then test fit it.

[MoparNorm]

Thanks MoparNorm.
...If the flywheel is balanced to the 360 (ext bal), I will assemble the 360 - under the assumption that it and previous 360 were sufficiently close in balance as neither was rebuilt, and run w/o major balancing issues. Then test fit it.

Generally speaking, with aftermarket parts, yes, because they are weight matched more closely than production parts, which may have pistons and connecting rods varying by a few grams each and therefore prompting the required balancing.
Here's hoping that it all works out OK.

[Drew M.]

The answer is (bad) . . .

Per the machinist, the flywheel off my 360/NP435 combo is neutrally balanced!! So, although the seller said the parts were off a running engine - I doubt it ran very well while vibrating to death.

BTW: the cost to have a custom balance on a disassembled 360 engine & flywheel is ~ the same ($300 in Central PA) as buying a new less acurately balanced factory 360 flywheel.

[MoparNorm]

Bummer!
That hydraulic/ bell flywheel was just a stock 318 flywheel then....
I'm wondering if a trick harmonic balancer would compensate enough for you to get by? Worth a chance?

[Linked Dakota]

Does anybody have a picture of a hyd bellhousing? My friend bought a 1987 NP435 with bellhousing, but it was a manual clutch. I posted this topic in a different thread but nobody responded. He wants to have a hydraulic clutch. The motor is a 1980 318.

[Drew M.]

Datoka,

Your buddy does not want the 1961-68 hydraulic clutch setup. It will not fit his stock trans input shaft as it is too short.

Just call a decent performance store (Summit/Jegs ect) and order a hydraulic throughout bearing for the machanical type throughout bearing, add a clutch master clyinder with hoses to the clutch pedal and your friend is done.


Some misc info on this setup I saved (posted somewhere in the PWA with photos - do a search):
The clutch linkage I used was a Wilwood slave cylinder to a Howe release bearing. This setup works very smoothly.Wilwood web site it is under combination "remote” master cylinder.3/4'' combination master cylinder kit 1.1 stroke #260-3374.

Garbee - It’s the same remote mount MC that Tilton supplies under their name... I used a 3/4" bore when I was using the Howe hydraulic TO bearing with the Ranger OD setup behind my Cummins (Chevy clutch setup with Ranger setup to mimic a SM465). Currently, I am running the 1-1/8" remote master with a Ford slave on a ZF S5-42... (turn out to be the same as the slave used with a NV4500)