Restore threads for spark plugs on old Mack truck

[oliver35]

Restoring 1918 chain drive model AC 5-1/2 ton Mack Truck. The
spark plugs holes in the cast iron heads are damaged and need to be chased. A new 7/8" 18 tpi tap cost is about
$ 180.00 with a long delivery. As it will be used only once I prefer not to buy a new one. The original plugs that Mack installed were Splitsdorf/Edison. The plugs in the truck when
I got it were Champion W-18. I think that Champion Stock No.
429 part number 3X will work. I hope to be able to either rent or buy a used tap and am seeking information on restoring these threads. Comments and ideas will be appreciated.
Charley M.

[Eric M.]

I have seen a couple of sparkplug thread chasing tap sets go on ebay. They are double-ended taps, one side is 18 mm, the other 7/8-18. They're typically part of a set that also has a 10mm/14mm tap.

EDIT:

I checked McMaster-Carr. www.mcmaster.com

Part number 2595A425
(Same as 2595A828)
Special Thread High-Speed Steel Hand Tap 7/8"-18, H3 Pitch Diameter, 4 Flute, Bottoming
In stock at $58.84 Each

And their delivery is lightning-quick.

[Pat Barrett]

Check at the local Napa store. Jawco makes a double ended thread chaser for spark plugs, has a hex in the middle. Run about $20.00. If you don't find one, PM me and I've also got a tap you can use.

[LeRoy IHC]

Hello

Travers Tool Co. 1-800-722-0703 Part # 14-056-183
7/8-18 Tap $28.07 each

I'd say who ever told you $180.00 was making a wee bit of
profit.

Good Luck
LeRoy

[DaveWachter]

We have shaired all of the tap secrets with you now whair the pictures of the truck thanks dave wachter

[oliver35]

Eric - Thanks for heads up on Mc-Carr. My copy is #94 and doesn't have the numbers you called out in your reply. I will call them tomorrow.
Charley M.

[oliver35]

Dave - I will post some pictures of my A/C Mack very soon. Charley M

[paulbrook]

Good luck with the restoration - I am doing a 1929 AC - pictures at www.rustytrucks.com. I would love to keep in touch and exchange experiences and tips - two heads are better than one!

I would be particularly interested in any leads you get for parts, particularly pistons, valves springs and so on as well as a water pump and a magneto.

But in the meantime, all the best,

Paul