drum to disc swap
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Joined: Jul 1999
Posts: 12,212
Likes: 13
From: Bertram (outside Austin), TX
Car: 87 GTA
Engine: L98
Transmission: 700R4
Axle/Gears: Dana M78 3.27 posi
Re: drum to disc swap
You COULD grab the prop valve, but most people just swap the rear ends & the brakes are PERFECTLY fine without doing that.
Joined: Aug 1999
Posts: 19,282
Likes: 103
From: Lawrence, KS
Car: Met. Silver 85 IROC/Sold
Engine: 350 HO Deluxe (350ci/330hp)
Transmission: T-5 (Non-WC)
Axle/Gears: Limited Slip 3.23's
Re: drum to disc swap
If they parking brake cables are in good condition, grab them and the S-hook guides as well (should you be missing them).
JamesC
JamesC
Joined: Feb 2008
Posts: 213
Likes: 1
From: Woodstock, GA
Car: 1989 IROC
Engine: 305 TPI
Transmission: T-5
Axle/Gears: 3.23
Re: drum to disc swap
JamesC helped me and was great with all the info I needed.
If you are going from drum to disk get the prop valve you will need it. Disk wont work properly with drum valve. I tried it and they have no power it wont push enough fluid.
Joined: Jun 2002
Posts: 1,296
Likes: 6
From: Vancouver, WA
Car: 87 IROC-Z28
Engine: 305 TPI-New 355 on the engine stand
Transmission: T56
Axle/Gears: 3.73 Eaton posi-Soon a 9" Ford!
Re: drum to disc swap
My experience was the same as yours FUNIROC. They didn't work perfectly, nor did they hardly work at all with the drum prop valve. With the car on stands the rear brakes wouldn't even lug the motor down with has hard as I could push on the brake pedal. Changed to the disk/disk valve and problem solved immediately.
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Member
Joined: Nov 2008
Posts: 124
Likes: 0
From: springfield OR
Car: 85 Z28 scca C Prepared
Engine: 5.7 348 RWHP
Transmission: t5
Axle/Gears: dana 44 3.41
Re: drum to disc swap
my dad questioned re using essential brake parts when i swapped my dana44 disc rearend out of a turbo ta so i just ordered the ssbc brake proportioning valve from summit SSB-A0707E. this also allows me to set it exactly how i want it. all it took was a little cutting the tubes and re flaring them with new fittings
Member
Joined: Nov 2008
Posts: 124
Likes: 0
From: springfield OR
Car: 85 Z28 scca C Prepared
Engine: 5.7 348 RWHP
Transmission: t5
Axle/Gears: dana 44 3.41
Re: drum to disc swap
Oh and almost forgot the master cyliders are different too although with the right proportioning valve i don't know if it would make a difference
Joined: Aug 1999
Posts: 19,282
Likes: 103
From: Lawrence, KS
Car: Met. Silver 85 IROC/Sold
Engine: 350 HO Deluxe (350ci/330hp)
Transmission: T-5 (Non-WC)
Axle/Gears: Limited Slip 3.23's
Re: drum to disc swap
https://www.thirdgen.org/forums/susp...fferences.html
JamesC
Senior Member

Joined: Jan 2006
Posts: 726
Likes: 1
From: League City, TX
Car: 90 Formula -- tot resto in progress
Engine: 350
Transmission: 700R4 w/ 2500 stall, by Owen @ ARD
Axle/Gears: 3.23 posi disc
Re: drum to disc swap
Question for cprepared125:
It may sound trivial, but how do you adust the valve to get the best braking?
These valves can only reduce the line pressure: so is the effect of having
to much, that rear wheels lock-up w/ insufficient braking by the front? to
little that there is now insufficient rear brake effect?
Maybe the question is better phrased by asking what should the car feel like
when the optimum proportion is reached?
thanks,
kk
It may sound trivial, but how do you adust the valve to get the best braking?
These valves can only reduce the line pressure: so is the effect of having
to much, that rear wheels lock-up w/ insufficient braking by the front? to
little that there is now insufficient rear brake effect?
Maybe the question is better phrased by asking what should the car feel like
when the optimum proportion is reached?
thanks,
kk
Member
Joined: Nov 2008
Posts: 124
Likes: 0
From: springfield OR
Car: 85 Z28 scca C Prepared
Engine: 5.7 348 RWHP
Transmission: t5
Axle/Gears: dana 44 3.41
Re: drum to disc swap
with my system the front brakes run full pressure and we adjust the rear and from what i've been told it is optimal to reduce rear brake pressure to where the fronts lock up just before the rears. this allows you to find your braking limits without upsetting the car and putting it sideways when they lock up. well thats my theory anyway
Senior Member

Joined: Jan 2006
Posts: 726
Likes: 1
From: League City, TX
Car: 90 Formula -- tot resto in progress
Engine: 350
Transmission: 700R4 w/ 2500 stall, by Owen @ ARD
Axle/Gears: 3.23 posi disc
Re: drum to disc swap
Thanks for the input.
Is that the way you set-up for SCCA activity?
I would have assumed setting rear wheel lock-up just before
front, would allow for steering control. Or is this an idea
better in theory than practice?
thanks again,
kk
Is that the way you set-up for SCCA activity?
I would have assumed setting rear wheel lock-up just before
front, would allow for steering control. Or is this an idea
better in theory than practice?
thanks again,
kk
Member
Joined: Nov 2008
Posts: 124
Likes: 0
From: springfield OR
Car: 85 Z28 scca C Prepared
Engine: 5.7 348 RWHP
Transmission: t5
Axle/Gears: dana 44 3.41
Re: drum to disc swap
yes it is a dedicated scca car. I'n not pro by any means but just from my few years of driving experience for me anyway it is easier and quicker to recover when the fronts lock up (just let off the brake) than when the rears lock up.(let off, counter stear and continue the corner sideways)
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