57 Airbox column mounted tach question.

[Bruce B.]

Can someone describe the 2 screws used to fasten the bracket for the 8000 rpm column mounted tach bracket together on the steering column?
They appear to be clutch head machine screws, what is the thread size and length and were flat and split lock washers used?
Thanks.

[Richard M.]

Re: 57 Airbox column mounted tach question.

Bruce, I see that the 57 AIM RPO 579 Sheet 4.01 shows the following part numbers:

134551 NUT
120380 WASHER
450997 SCREW

I looked them up my 29-59 Parts Book. I found no reference for the Screw and Nut, but I did find 120380 washer. It's a split lock, 1/4" diameter.
When I magnify my digital copy of the picture of the screw in the AIM, it appears to be a cross recess thread (i.e. Phillips). I string searched my digital copy of the AIM for the 450997 screw and it appeared nowhere else.

When I searched for the 134551 NUT, it shows up used on the following items:

Sec B Sheet 8.00 (mirror base)
Sec B Sheet 10.00 (reinforcement brackets)
Sec 6 Sheet 7.00 (clutch bushing bolt)
etc, etc

Based on this info I believe the 450997 SCREW is a 1/4" course thread(1/4-20), likely Phillips, likely Round Head as shown below, and maybe 1" to 1 1/4" long. Surely a guess...

Rich

[Bruce B.]

Re: 57 Airbox column mounted tach question.

Rich,
Thanks for the great information.
If you have a copy of Kayers FI book there are a few pictures of the tach and bracket with the screws on page 412. There is not a difinative picture but some that look like either phillips or ?.
Thanks again.
Bruce B

[Richard M.]

Re: 57 Airbox column mounted tach question.

Bruce,

I just called a friend who had a airbox car in the past and he says they're Phillips screws, 1/4-20. Because the lower clamp is close to the upper bracket and about 1" screws were used as he recalls.

He also said Phillips were typical finish trim types for interior stuff and that makes sense to me too. Clutch head usually for more torque but likely not needed there.

Rich
p.s. email sent too with a RPO 579 experts phone #

[Steven B.]

Re: 57 Airbox column mounted tach question.

Bruce, Rich's description match up with my fasteners, assuming they are original to the tachs.

Is the Hilborn car running?

Steve

[Bruce B.]

Re: 57 Airbox column mounted tach question.

Steve,
The Hilborn is ready to start.
I have gone through 3 computers which would not work properly and I recently got a different ECU and realy box setup from the builder which should take care of the previous problems. I had to rewire the whole system which was no big deal and hope to start the car next week. It has been making me crazy but I will get it running.
I hope to drive the car to the Hot Rod Reunion in Bowling Green, KY in June. I know a lot of guys from OK will be there.
I have attached some pictures, notice no fuel rails, hidden TPS and sort of inconspictuous injectors.
By the way, thanks for asking.
Bruce B

[Tom B.]

Re: 57 Airbox column mounted tach question.

GM had a separate catalog for what they called standard parts. Bolts clips, clamps and hundreds of other hardware parts that were used across all car and truck lines were listed in that book.

My 1982 catalog lists the nut, PN 134551 in the drawing, as 1/4-20, grade 286M, thickness 3/16", cad or zinc plated.

The washer PN 120380, was replaced in March 1970 with PN 9421423, 1/4" hole size, 31/64 O.D., zinc plated.

The bolt was discontinued too long ago to be in my Standard Parts catalog or the Parts History manual. The few remaining bolts that were still available in 1982 that were in the PN 450 sequence are Fillister head cross recess bolts. They are Phillips with a taller cylindrical head. This would be my guess as I don't find any standard pan head Phillips with part numbers that start with 450. I think that a Fillister head had a smaller diameter than a pan head for use in tighter places.

Hope this helps.

Tom

P.S. Bruce, How wide are your wheels? They look wider that 6".

[Bruce B.]

Re: 57 Airbox column mounted tach question.

Tom,

Thanks for the hardware info.

The wheels on my 62 are American Racing Torq-Thrust D which I bought in 2000, made in USA. They are PN 105-5761 which are 7" with a 3 3/4" backspaceing.
The tires are 205 75 15 Michliens. I like the way the tire-wheel setup fills the wheelwells and the car drives very nicely. The tires are the same hight as 670-15 but obviously wider.
I have tried them on my 57 and like how they look. I will probably get a set of PS Engineering wheels for the 57 since I don't care to buy the current Chinese made American Racing wheels.

Bruce

[Steven B.]

Re: 57 Airbox column mounted tach question.

Bruce, nice looking setup! Thanks for the pix! What other engine mods did you make? Rear gears? That is going to be fun!

Tom, you need to head due south and go see Bruce's '62! I hope to make it back this year and see you. Thanks for the fastener info. Have you seen Roger's '62 lately?

Steve

[Bruce B.]

Re: 57 Airbox column mounted tach question.

Steve,

Thanks for the feedback.
At this time there have been no other changes to the 62.
It currently has a 3.55 gear although I have a few others I might change to. I have an old set of Traction Masters which I will probably install.

The engine is stock 340 HP and I need to get the Hilborn tuned to see if any other modifications will be made.

Bruce B

[Tom P.]

Re: 57 Airbox column mounted tach question.

MANY years ago when I installed the column tach on the 56, it was my understanding that the screws were supposed to be clutch head. So, I use a couple of 1/4-20 clutch head screws that I had acquired from somewhere and so far no one has commented either way.

[Bruce B.]

Re: 57 Airbox column mounted tach question.

Tom,

The info Rich M. and Tom B. provided is no doubt accurate based on part numbers but there was no PN or defination of the part number for the screws.
In Kaysers book on page 412 are pictures of the bracket and the screws on car #4387. They look like clutch heads but not positive.

If you get a chance can you see if there is anything marked or stamped on the tach bracket? Do you know if it is original? I know you have had it for a while.

Time to get back to the garage and finish wiring up the ECU for the Hilborn.

[Tom P.]

Re: 57 Airbox column mounted tach question.

My tach bracket is "home made". I made it from stainless steel then polished it. I borrowed an original bracket from a friend (John Neas) MANY years ago, then laid it on a piece of paper and drew around it, cut out the patern on the paper and made a flat pattern on stainless steel sheetmetal (approximately .050 thick).

[Bruce B.]

Re: 57 Airbox column mounted tach question.

Tom,

Nice bracket.

Bruce

[Philip C.]

Re: 57 Airbox column mounted tach question.

If anyone needs these tac brackets, I have a couple of sets left. I get 150.00 for them plus shipping. Phil 8063