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1984 Eldo HT4100

Started by Duane Hillebrand, February 22, 2021, 06:14:12 PM

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Duane Hillebrand

Good afternoon everyone,

I am reassembling my harmonic balancer flange mount to the crank. This is the press on flange. Everything is clean, keyway is lined up fine.
I am using a general harmonic balancer installer kit, 14pc. I have metric sizes: 12x1.75, 12x1.5, 10x1.5, 14x1.5, 14x2.0, 16x1.5, 16x2.0, SAE: 7/16-20, 1/2-20, 9/16-18, 5/8-18 & 3/4-16. Nothing will thread into the crank.

What thread size is the internal crank threads?

Thanks,

Duane

79 Eldorado

Hi Duane,
I don't know the direct answer but if you can get a "rub" of the threads you may be able to measure the thread pitch. Since everything will be close if you measure a single thread pitch try to rub several threads. Measure the distance between several marks, touch points on your mark, and then divide by the number of gaps between the 2 marks you measured which will give you a better average to tell the difference between 1.5 and 1.75mm for example.

For the diameter, since you could use a pin gauge or maybe calipers, to get the ID of the threads. That won't be exactly the minor thread diameter of the correct size but it will be close. The actual should be slightly less. I searched the terms: thread minor diameter chart and a lot of charts show in google under images.

If you don't have a pin gauge or drill shank large enough to check the ID of the thread roll a piece of paper and let it unroll to the correct size while inside and then mark the overlap with a pen. Lay it flat and measure the linear distance and divide by 3.14159 and you will have the diameter.

Scott

TJ Hopland

Thats quite an assortment,  you would think it would be one of those.

Did it have a bolt in it originally?    If so can't you use the bolt to figure out what the thread is supposed to be?

How did you pull the hub?  Is it possible that the threads were damaged during the pull?
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

Duane Hillebrand

Thanks Scott, are you a machinist/tool & die maker? Sounds like an answer my pops would have said if he was still alive. I will give that a try.

TJ, no, no bolt present. In my google searches, this pops up a lot but have yet to find a solid answer. Closest was on another forum and someone mention 16x1.75 bolt three inches long. So I am waiting for Fastenal to call me back with avail of a bolt. There is no existing bolt. This is a press on flange and GM stuck a cork in the hole to keep threads clean. This is a low mileage (37k miles) car so I assume its never been previously worked on, so nothing is missing. Bought at an estate sale here in Denver, last reg was 2003.

Duane

Duane Hillebrand

Quote from: 79 Eldorado on February 22, 2021, 07:00:41 PM
Hi Duane,
I don't know the direct answer but if you can get a "rub" of the threads you may be able to measure the thread pitch. Since everything will be close if you measure a single thread pitch try to rub several threads. Measure the distance between several marks, touch points on your mark, and then divide by the number of gaps between the 2 marks you measured which will give you a better average to tell the difference between 1.5 and 1.75mm for example.

For the diameter, since you could use a pin gauge or maybe calipers, to get the ID of the threads. That won't be exactly the minor thread diameter of the correct size but it will be close. The actual should be slightly less. I searched the terms: thread minor diameter chart and a lot of charts show in google under images.

If you don't have a pin gauge or drill shank large enough to check the ID of the thread roll a piece of paper and let it unroll to the correct size while inside and then mark the overlap with a pen. Lay it flat and measure the linear distance and divide by 3.14159 and you will have the diameter.

Scott

Well, weird. The paper trick laid flat measures 43mm. Divided by 3.14159 equals 13.6. This is def larger than a 14mm bolt. My install kit has both 14x1.5 & 14x2.0 and they just fall in.

Duane

79 Eldorado

Hi Duane,
To me it seems like it's M16 based on the 13.6mm you measured because you are roughly measuring the minor diameter. Take a look at the information in this link below. It was the best I could find as it gives a pretty clear chart plus a diagram for both internal and external threads. Your 13.6mm measurement falls between the minor diameters expected for internal vs external for M16 so I would bet it's M16.
https://eicac.co.uk/Metric-Threads

Were you able to count/measure peaks to see if you could estimate the thread pitch? If it's M16 it seems it should be a 2mm pitch. I do see from your original post you have 16mm in both 1.5 and 2mm pitch. As TJ mentioned it might be some slight damage to a thread causing the issue. If you have a tap/die set with a thread gauge you may be able to check the pitch as the thread gauge is thin metal so you can try to measure in various places. If you can sort whether or not it's 2mm or 1.5mm you may want to try threading a tap in but by hand very carefully.

Scott

Duane Hillebrand

Yeah, I have a 2.0 tap coming tomorrow. Fingers crossed its just boogered threads.

Thanks again for all your help.

Duane

TJ Hopland

While waiting for confirmation how about telling us what the project is?   I'm sure knowing the thread size will be useful info for others but maybe the overall project would be too.   Not many people trying to keep a 4100 going so not a lot of info around on them for those that are trying to keep going.   

I'm wondering if maybe stripped water pump bolts?  Were these like previous Cads and Olds where some bolts only threaded into the 'tin' timing cover?   

StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

Duane Hillebrand

Quote from: TJ Hopland on February 23, 2021, 05:59:56 PM
While waiting for confirmation how about telling us what the project is?   I'm sure knowing the thread size will be useful info for others but maybe the overall project would be too.   Not many people trying to keep a 4100 going so not a lot of info around on them for those that are trying to keep going.   

I'm wondering if maybe stripped water pump bolts?  Were these like previous Cads and Olds where some bolts only threaded into the 'tin' timing cover?   

84 Eldo found at an estate sale. 37k miles, red/red velour interior. Dings and scratches but no rust and interior is just dirty. Replaced a fuel hose on the in-tank pump and fired her up. New plugs, runs nice. Leaked at water pump, so replaced. But I didn't see one of the 10mm bolts that, yes, bolts into cover under grease so when I pulled the pump the timing cover separated from the block, so decided to do its gasket and crank seal too. And here I am!

Duane

Duane Hillebrand

Success! Thanks Scott and TJ.

So, my thread was just the tiniest boogered up. I couldn't see because of the angle. Got a 16x2.0 tap today, carefully started it and it went in. Cleaned, blew it out, installed my adapter for the balancer installer and viola!

Now fingers crossed that the triple O-ring therm housing doesn't leak!

Duane

TJ Hopland

Hopefully it will run for a while so you can enjoy it.   Don't forget things like the flexible brake lines.    Also at this age a throttle body refresh kit may also be worth doing sooner than later.  The refresh kit has new orings that hold the injectors in as well as the soft parts for the fuel pressure regulator which is also part of the throttle body.   Back in the day this stuff never failed but like that hose in the tank age and likely some ethanol got to it.
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

79 Eldorado

Duane,
That's great!

This site is pretty photo friendly once you've figured it out. I know sometimes I want to simply get the job done and I don't take photos but like TJ mentioned there is a lack of repair info on the HT4100 here because a fair number of people start running in the opposite direction as soon as they see the HT4100. Anyway the photos won't appear in the preview, only after you post, but under the section where you type your reply there's an option for "Attachments and other options". This site even supports uploading a pdf which I didn't expect. I bring it up because I've never seen the triple o-ring thermostat housing you described and that must be quite a piece of hardware. Pretty crazy to have 3 o-rings... well it is a Cadillac :)

Yours is already back together but... if the front cover is similar to Oldsmobile I've added a welded nut on the back of the front cover using a bolt from the front side to properly locate the nut. On Olds the size for those few which go only into the cover is smaller and torque is lower. If you ever strip one you're toast. If that happens you need to remove the front cover and the bottom of the front cover has a seal shared with the front of the oil pan which is no easy task to replace. A friend recently told me the trick he's used which was place the replacement seal in your tool box, clean the seal you removed, install the old seal with the proper sealant. The advantage is the seal you remove is already perfectly compressed. I haven't tried it yet but it sounded like a great idea.

Scott