SOHC Posted April 20, 2012 Share Posted April 20, 2012 Hello I am doing the brakes in a car I have been building for a wile, I have a Jag IRS diff with inboard disk brakes and 1954 Customline Drum brakes on the front, don't laugh. I have a Holden HQ master tandem cylinder, one port on the master cylinder has a residual pressure valve and the other dosn't My question is can I run the line witch was originally for the HQ rear to my now front drum brakes? Quote Link to comment Share on other sites More sharing options...
KKtrips Posted April 20, 2012 Share Posted April 20, 2012 Normally the rearmost port (closest to the firewall) is normally the front brakes.. Quote Link to comment Share on other sites More sharing options...
SOHC Posted April 20, 2012 Author Share Posted April 20, 2012 Normally the rearmost port (closest to the firewall) is normally the front brakes.. I was wondering could I run it the other way round? as one port has a residual pressure valve, I want that line to go to my drum brakes Quote Link to comment Share on other sites More sharing options...
Valiant Posted April 20, 2012 Share Posted April 20, 2012 I can't think of a reason why not. Or The residual pressure valve should be easy enough to remove, you could swap which port it is in. Quote Link to comment Share on other sites More sharing options...
KKtrips Posted April 20, 2012 Share Posted April 20, 2012 you can put an inline residual valve into the front circuit.. And you may have to do some calcs with the piston size - generally the front brake sleeve size is bigger for disc brakes.. Quote Link to comment Share on other sites More sharing options...
eke_zetec_RWD Posted April 20, 2012 Share Posted April 20, 2012 is this going to be a road car? if so check with your certifier. Quote Link to comment Share on other sites More sharing options...
SOHC Posted April 20, 2012 Author Share Posted April 20, 2012 is this going to be a road car? if so check with your certifier. Its fine, alot of hotrods have Jag diffs and Ford Juce brakes still on the front Quote Link to comment Share on other sites More sharing options...
KKtrips Posted April 20, 2012 Share Posted April 20, 2012 So you have a jag diff with disc brakes and deuce front drum brakes... Hmmmmm Quote Link to comment Share on other sites More sharing options...
SOHC Posted April 21, 2012 Author Share Posted April 21, 2012 So you have a jag diff with disc brakes and deuce front drum brakes... Hmmmmm I mean Juice as in hydraulic, Couldn't afford proper Ford Deuce Coup style brakes, but yer drums on the front and disks on the back, hope i can run the master cylinder with the lines going in revere. The car originally had mechanical brakes, now they run on juice Quote Link to comment Share on other sites More sharing options...
SOHC Posted April 21, 2012 Author Share Posted April 21, 2012 Here are my front brakes, 54 customline, there pritty big By rudolphtec at 2012-04-20 Quote Link to comment Share on other sites More sharing options...
KKtrips Posted April 21, 2012 Share Posted April 21, 2012 Are you running a booster? I think you may end up with brake balance issues here. Quote Link to comment Share on other sites More sharing options...
SOHC Posted April 21, 2012 Author Share Posted April 21, 2012 Are you running a booster? I think you may end up with brake balance issues here. Nar the front drum brakes are self self energizing, don't need a booster. An adjustable proportioning valve fitted in the rear brake line will fix the balance issues Quote Link to comment Share on other sites More sharing options...
KKtrips Posted April 21, 2012 Share Posted April 21, 2012 I've owned hot rods and worked on cars for a good 20 years now and can't say I have ever come across a drum front, disc rear setup. It MAY work, but something in my head just screams WAIT! - I think the only way you will get a decent brake pedal out of this is if you do some calcs and get the master cylinder bore suited to the brakes. Just chucking an HQ master cylinder on there seems like a bit of a stab in the dark to me.. It may work by fluke but the chances of it being right and getting a good brake balance is low.. But hey - I've been wrong before and will be wrong plenty more times before I die.. Would love to see how this works out. Quote Link to comment Share on other sites More sharing options...
SOHC Posted April 21, 2012 Author Share Posted April 21, 2012 I've owned hot rods and worked on cars for a good 20 years now and can't say I have ever come across a drum front, disc rear setup. It MAY work, but something in my head just screams WAIT! - I think the only way you will get a decent brake pedal out of this is if you do some calcs and get the master cylinder bore suited to the brakes. Just chucking an HQ master cylinder on there seems like a bit of a stab in the dark to me.. It may work by fluke but the chances of it being right and getting a good brake balance is low.. But hey - I've been wrong before and will be wrong plenty more times before I die.. Would love to see how this works out. Most people recommended me to use the HQ master cylinder as it is a good size for the old ford brakes, but yes disks on the back is a bit strange, but no one can tell me should i cross over the brake lines? I could tell you how it works out soon, but I broke my tube flaring tool Quote Link to comment Share on other sites More sharing options...
SOHC Posted April 21, 2012 Author Share Posted April 21, 2012 I can't think of a reason why not. Or The residual pressure valve should be easy enough to remove, you could swap which port it is in. That is an option but I would have to destroy the valve I think Quote Link to comment Share on other sites More sharing options...
eke_zetec_RWD Posted April 21, 2012 Share Posted April 21, 2012 Are you running a booster? I think you may end up with brake balance issues here. Nar the front drum brakes are self self energizing, don't need a booster. An adjustable proportioning valve fitted in the rear brake line will fix the balance issues self self energizing?? Quote Link to comment Share on other sites More sharing options...
Rookie Posted April 21, 2012 Share Posted April 21, 2012 generally the front brake sleeve size is bigger for disc brakes.. Did you miss this bit mate? Even though the rear port may have a residual pressure valve , chances are that the bore of the master cylinder is stepped, so you will run into issues. Quote Link to comment Share on other sites More sharing options...
SOHC Posted April 22, 2012 Author Share Posted April 22, 2012 generally the front brake sleeve size is bigger for disc brakes.. Did you miss this bit mate? Even though the rear port may have a residual pressure valve , chances are that the bore of the master cylinder is stepped, so you will run into issues. same size bore right down, Quote Link to comment Share on other sites More sharing options...
Yammies Posted April 23, 2012 Share Posted April 23, 2012 I'm gonna go with no... don't reverse the lines... front brakes generally deliver more fluid, and just because the rear is disc doesn't mean that you should necessarily deliver more fluid to that area. Wilwood make inline residual pressure valves - 2 PSI for Disc, and 10PSI for drum brakes.... Quote Link to comment Share on other sites More sharing options...
SOHC Posted April 24, 2012 Author Share Posted April 24, 2012 I'm gonna go with no... don't reverse the lines... front brakes generally deliver more fluid, and just because the rear is disc doesn't mean that you should necessarily deliver more fluid to that area. Wilwood make inline residual pressure valves - 2 PSI for Disc, and 10PSI for drum brakes.... Spoke with someone today and he sed the same as what you have,the master cylinder delivers pressure to the rear brakes before the front so don't want to mess that up witch is another reason not to revers the lines. Going to dig the R/P valve out of the M/C and fit inline ones and hope it works Quote Link to comment Share on other sites More sharing options...
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