2.3 to 5.0 booster swap question- and MC question


Jun 9, 2004
southern NH
A few years back I swap my 2.3 drivetrain to a 5.0, (93)
I did not change the brake system or rear end at that time, I've been planning a 5 lug rear disc and 8.8 swap for the future (next year)

Ok, so I recently had my master cylinder changed to another 4 cylinder stock unit because it was craping out on me (brake would slowly sink at a stop light after several momments) When the master cylinder was removed, you could see it was leaking internally and it was filled with crap! The brake lines were flushed 4 times and the unit replaced. Now the pedal feels weak and the first inch or two of the pedal movement especially, half way down it feels normal. Symptom is most noticable leaving a parking spot vs slowing down for a stop light.

So I have two questions:

1. Since the master cylinder is NOT adjustable, why would my pedal feel this way after replacing it with a remanufactured unit? Anyone hear of this issue with re-man units before? The guy the flushed the brakes for me claims he tried his best to resolve the issue and claims there is NOT any air in the system.

2.A. Is it possible the restricted old master cyclinder was responsible for the harder brake pedal feel that I got used to, and now the new unit is showing me OTHER issues related to my brake booster?

2.B. If my booster is suspect and should be changed out...COULD I put a v6 94 booster in my car since I'll need that for my 5 lug disc upgrade later? Is this booster compatible with my 4 cylinder set up? I CANNOT do the swap yet and I'm pissed I had to waste money on a stock master cylinder that I have to change again anyway...so I refuse to replace the 4 banger booster with another wasted purchase.

I'd like the answer to 2.B regardless of my other issue, simply because whatever parts of the conversion I can do in advance would make that project smaller for me when the time comes.
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Mr. Rustypwnz

Advanced Member
Jun 1, 2005
indianapolis/ valdosta ga
yes you can use the v6 piece, it is awesome, much better than the stock 5.0 unit, it holds more vaccum as well if im correct, which is nice... i had one in my 86 and it would stop very well... only thing you have to do is to route the one line that goes under the stock mc and tie it into the feed block below, and it will work fine..

but if you want a good v8 unitm I just pulled mine out to put in a sn95 unit in..

pm me if ya want it its leak free...


New Member
May 21, 2008
phoenix, az
I have done over 3 4cyl to v8 conver... you can use the 4cly with out any issues. What you might of done is blown out the booster seal while bleeding the brakes. On older cars when your bleeding the brakes if you go to the floor you can blow a seal. The other deal is it could be a bad master that happens from time to time.

As far as going to rear disc brakes what i have done and just did is i bought front lincoln mark vII rotors for the front and used the front spindles for the mark vII to get bigger brakes up front and makes them 5 lug. For the rear i used drivers side axles from 87-91 ford ranger they are also 5lug. I took the rear disc set up off of a mark vII as well and just used a c-clip elimantor kit for the axles. For the master cyl i just used the lincoln mark VII's. they are easy to find in the junk yard.

I paid under 200.00 for the whole setup. way better then 500.00+ new kit. You can also use the brake booster off a mark VII if you wanted to as well.
hope this answers your question


That is…until I whipped out my Bissell
Mod Dude
Feb 18, 2001
You can swap the booster now with no ill effects. The Boosters are interchangable.

I'd recommend a '93 Cobra booster over the Sn95. Smaller compact design, but just as powerful as the Sn95.

The 4-banger booster is a single diaphram. The V8's got a dual diaphram.

The master cylinder is not adjustable, but the booster is! There is a rod that pokes out of the front of the booster that is adjustable in lenght and can be used to take up the "dead zone".

Another possibility is air still trapped in the MC.