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Ecklers AutoMotive
Username Post: Dual M/C fit up problem        (Topic#354743)
Beltfed 
Poster
Posts: 32

Reg: 10-04-18
01-06-19 04:48 PM - Post#2756730    

Fitting up dual m/c to firewall. My problem is the mounting studs are too short for the thicker shoulder on the two bolt m/c. What ‘cure’ is used to get longer studs. 1. Cut old stud flush with firewall and drill out? 2. Grind head off inside and drive old stud out? 3. Some trick I don’t know of?
Thanks



 
Ecklers AutoMotive
Rick_L 
Honored Member
Posts: 27575
Rick_L
Loc: Katy, Tx, USA
Reg: 07-06-00
01-06-19 06:57 PM - Post#2756739    
    In response to Beltfed

The studs are spot welded to the brace that mounts the brake pedal. Seems like about half of them can be removed with a decent hammer blow. The rest have to be drilled out. The methods you mention or a combination of them will work.

Even if you remove the brake pedal brace from the car, the half hammer out/half drill out still holds.

Your next dilemma is how do you keep the new longer studs/bolts from turning. I wouldn't tack weld them unless they were in place and with nuts on them. Can't do that with an assembled car.

Some people use half thickness nuts (jam nuts) with the new master cylinder and call it a day. I think that's ok if you can torque the nut to 30-35 ft lb.



 
Bad56Sedan 
"12th Year" Gold Supporting Member
Posts: 1041
Bad56Sedan
Loc: Pasadena, Texas
Reg: 04-29-04
01-06-19 10:20 PM - Post#2756753    
    In response to Beltfed

The replacement bolt is grade 8, 3/8" fine thread x 2".
Shoulder bolt is best, mine were 3/4" shoulder.
Yes you can try the hammer method to drive/ pop the TOO short bolts out.
The original bolts are pressed into the main brake pedal bracket, may even be hot pressed. They are mechanically hit so the shoulder expands, the dimple in the head, I guess.
I put liquid wrench, wd 40, the other stuff and then that stuff on the bolts for a few days.
No way, I had hit the bolt so hard it did not budge, it bent the crap out of the main brace under the dash, messed the bolt end up.
Used small cutting disc to true end of bolt, center punched and drilled out.
Push the new bolts through under the dash, carefully put MC on the bolts hand start nuts.
Then under the dash position 1/2" wrench over the head of one bolt, one side you can brace the wrench on the main bracket, other side i actually tied the wrench to the main brace.
It worked .


VC56S 2 door Sedan, 39 Years

[image]http://www.chevytalk.org/fusionbb/fbbavatars/a v-3564-1354211547.jpg[/image]


 
acardon 
Ultra Senior Member
Posts: 11149
acardon
Loc: DFW TEXAS
Reg: 03-25-05
01-07-19 07:50 AM - Post#2756772    
    In response to Bad56Sedan


  • Quote:
Then under the dash position 1/2" wrench over the head of one bolt,



OR, get a helper.
Drilling is the easy way. Cut off flush with firewall, center punch, and drill, as mentioned.

Don
66 Corvair (driving)
57 2dr HT (driving)
56 2dr HT (waiting to be restored)


 
4dr 57 
Valued Contributor
Posts: 4572
4dr 57
Loc: Texas Hill Country
Reg: 11-10-04
01-07-19 09:30 PM - Post#2756832    
    In response to acardon

I don't see why a lock washer under the bolt head wouldn't work. You don't kneed to crank down on the nuts on the master cyl. side, just snug should be fine.

That's what CPP) told me about my m/c to booster when I noticed their pre assembled units seemed "not very tightly connected at all!" They said no they weren't. Cool!



It's all good. mostly




 
Beltfed 
Poster
Posts: 32

Reg: 10-04-18
01-08-19 08:12 AM - Post#2756865    
    In response to 4dr 57

Thanks again guys. Being lazy and with old bones, I tried the easy way first. I double nutted the stud, whacked them about five times with a 12oz. hammer and they broke loose. Each one had three very small spot welds under the flat head.



 
Bad56Sedan 
"12th Year" Gold Supporting Member
Posts: 1041
Bad56Sedan
Loc: Pasadena, Texas
Reg: 04-29-04
01-12-19 05:38 PM - Post#2757221    
    In response to Beltfed

I'm glad they popped loose for you,
Naturally there is more to what I posted, I had to chisel the heads off, use a long "drift" to knock the main bracket back into place.
But then like ALL conversions on a 5-6-7 Chevy NOTHING ever fits correctly.

VC56S 2 door Sedan, 39 Years

[image]http://www.chevytalk.org/fusionbb/fbbavatars/a v-3564-1354211547.jpg[/image]


 
Beltfed 
Poster
Posts: 32

Reg: 10-04-18
01-12-19 06:11 PM - Post#2757224    
    In response to Bad56Sedan

If I had to stay under the dash long enough to chisel those heads off, I would be crippled for life.



 
Ecklers AutoMotive
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