by, Jack Davis
When first viewing the four mounting studs on the bottom of the W-670 engine on which the carburetor mounts, it doesn’t look all that bad. Get the four nuts and washers ready, put a thin coat of ssealant on the gasket, and ease the carburetor up into place.
Get the two rear nuts started, then the front left, and things look pretty good. should be through and ready for lunch in a half hour.
Now you get your first good look at the right front stud. Wait just a minute!! Several things seem wrong. First the intake tube on the #4 cylinder is smack in the way, and you can hardly get a good look at where the nut has to go, let alone get a wrench on it from that side.
Also, the leather cover on the accelerator pump on the carburetor is right under that stud, with almost no room to get a nut underneath so it can be started on.
Well maybe things will look better from the back of the engine. From the back you can just see where the stud should be way up in front on the carburetor. But getting the nut with a washer started and then getting a wrench on it, looks out of the question.
It looks like there might be a chance from the side, if the #4 intake tube were removed. Good idea, except for the fact that if the intake tube was installed onto three mounting studs on the cylinder, you can’t get the tube off without pulling the cylinder.
If whoever put the engine together in the first place was thinking ahead to this time, they removed the lower outside stud and replaced it with a proper bolt that goes in from the outside of the tube. With this arrangement, the bolt, two stud nuts and the packing nut are removed an the intake tube can be maneuvered out.
That sounds a lot easier than it turns out to be, because one of the stud nuts on the intake tube is so buried that it creates it’s own frustration.
Although the engine I was working on has the “problem easing” bolt on the intake tube, I decided to skip lunch and see if there wasn’t a better way. The following is what I came up with, that allowed me to install the carb in about 20 minutes.
Before you position the carb, put a test nut on the right front stud and make sure the threads are good and they are smooth. You will want the nut to go on easily.
The first thing is to only put the three easy nuts on by a couple of threads. This leaves the carb in a position that is about 1/4 inch down from the engine.
This leaves 1/4 inch more space between the bottom of the right front stud and the accelerator pump stuff.
Now get a strip of .030 to .050 stainless that is 3/4 inch wide and about 10 inches long.
In one end, drill a hole 1/2 inch in diameter. This hole will allow a nut (castle or lock) to fit down in with the hex side up, but won’t go through. It also fits loosely enough so that it can be easily turned while it is nestled down in the hole.
Put a layer of heavy grease or fuel lube around the hole and push the nut in. Put another layer of fuel lube on top of the nut and stick the washer on.
Now you will need a long thin screw driver.
From the side, just to the rear of the intake tube, slip the SS strip with the nut and the washer stuck on so that the nut is just under the stud. (on top of the accelerator pump leather).
Gently apply some torque on the end of the strip so that the washer and nut are forced up against the bottom of the stud.
The trick here is to keep the nut and washer square with the stud. Someone holding a flashlight would be a help.
With the washer over the stud and the nut up against the bottom, reach in with the long thin screwdriver, and turn the nut by pushing on the outside edges of the hex points.
If you keep the nut square and the right amount of up-pressure on the steel strip, after a bit of trying you will sense that wonderful feeling that the threads have caught and the nut is moving upwards.
You can then remove the steel strip and it is required that you spend a few minutes celebrating that much progress. A high-five with the person holding the flashlight is recommended.
Now to get the nut screwed up into place and properly torqued.
I spent about a half hour making the following tool, and I wouldn’t change much if I had to make another one. (The answer is “NO”, make your own)
I found a length of 3/8 OD stainless tube in the junk bin. About 10 inches long.
I cut a small 1/2 inch open end wrench in two, so that the pieces were about 2 1/4 inches from the end to the center of the wrench jaws. I only needed one, but knew the odds of screwing up the first one. The wrench end that I used had the jaws at 45 degrees to the wrench axis, and I never did try the other end with the straight jaws.
I cut a 3/4 inch slot in the long tube wide enough for the end of the cut wrench to slip in.
Drill a 3/16 hole in the end of the wrench and matching holes in the end of the slotted tube, 90 degrees from the slot.
Join the two together with a 10/32 screw and nut, so that the wrench will swivel, but have some friction in doing so.
By slipping this tool in from the rear of the engine, the open end of the wrench can be positioned on the nut. Then by pushing on the tube, one can get a very satisfying turn on tightening. Then pull it off, bring it back and do another turn.
After moving the nut up a bit, it is best to tighten up the easy nuts so that you are not lifting the carb with the new tool.
When the nut started to bottom out and the final torque was being applied, I started to notice a recurring pain in the palm of my hand. Being a somewhat slow study., it took a while for me to realize that I was coring a hole in my palm when I pushed hard on the steel tube.
Looking around some more in the catch-all box, I found a black knob with a hole that would fit right over the end of the tube. (Now that was just luck).
With the knob on the end, I was able to push hard enough on the tube to turn the wrench to get exactly the right final torque.
Not counting the making of the tools and thinking about various solutions, I would guess that one could mount a carburetor using these techniques in about 20 minutes or so.
Fastening the rod end bearings to the throttle and mixture control arms on the carb, and installing the cotter pins while it is still out on the bench, will save another chunk of time.
Over torquing of these nuts on the mounting studs, especially when using a thick gasket, can warp the flange on the carburetor and cause an air leak in the wrong place. Somewhere I have seen a technical order to use a very thin gasket in this joint. I don’t remember where.