trouble shooting brakes (3)

grumpyvette

Administrator
Staff member
these links hit most of the common tips and areas of info
keep in mind having a SHOP MANUAL HANDY to refer too HELPS


before you assume the (brakes) are defective on any car,be aware the (BRAKES) are really a series of sub systems , that work together,and each component is individually likely to fail over time, carefully inspect the vacuum line and vacuum line valve, on the brake booster,for leaks, cracks, etc, inspect the master cylinder for loose connections and check the fluid color and fluid levels, then carefully inspect the brake pads or shoes and individual wheel cylinders , or disk brake calipers for leaks the as they are far more likely to fail and inspect the rotors and wheel bearings.

its also a good idea to check your brake fluid levels monthly and bleed your brake lines,at least every 18 months and inspect the calipers and pads at least every few months
http://www.aa1car.com/library/2005/ic80560.htm
brakelu.png

brake_lubricant.jpg

I learned DECADES ago that if you read instructions that specifically indicate a certain grease or type of lubricant should be used in an application, theres usually a reason, in this case its to ease the movement of brake components,prevent brake chatter, so the brake pads tend to wear more evenly side too side, vs one pad rapidly wearing while the other did not quite as fast,and too prevent corrosion and prevent heat from allowing the grease to tin and run off, like most axle grease products tend to do when brake calipers exceed 30-0F which they do regularly, and yeah! I ignored the advice and used moly axle grease a few times without any catastrophes but I also noticed that when I used the correct material grease it lasted longer and the brakes were less noisy.
yeah! just like damn near everyone else I either ignored or used the wrong grease for a few years until it became all too obvious there WAS A REASON!

ID also point out a bit of research into the brake pad material you select, for any brake job, might be very helpful, and CERAMIC BRAKE PADS have improved a GREAT DEAL IN THE LAST FEW YEARS, metallic brakes tend too a leave a bunch of fine powder residue and carbon brakes are rarely ideal on the street as they are designed for extreme high temp use in racing.
yeah Ive bought and installed the wrong brake pads at times but I tend to remember ,take notes and try not to repeat mistakes, and learn from my screw-ups and yeah! LONG LIST!


mistake.jpg

viewtopic.php?f=34&t=380

http://www.corvsport.com/Corvette/C4/19 ... aking.html

viewtopic.php?f=71&t=1848&p=16080&hilit=brake+fluid#p16080

http://corvette.wikia.com/wiki/C4_Brakes_Tech_Paper

viewtopic.php?f=50&t=10345

http://www.ecklers.com/catalogsearch/result/?search_year=1994&q=brake+booster&x=28&y=10

http://www.ecklers.com/corvette-brake-m ... -1996.html

http://www.howstuffworks.com/brake.htm

http://www.popularmechanics.com/automot ... 13448.html

http://www.classicperform.com/TechBook/BrakeTroubleshoot.htm

http://www.lbfun.com/warehouse/tech_inf ... _Paper.pdf

viewtopic.php?f=71&t=1848&p=16080#p16080

http://www.vbandp.com/SearchResult.aspx?CategoryID=331

http://www.procarcare.com/includes/content/resourcecenter/encyclopedia/ch26/26TS.html

http://www.digitalcorvettes.com/forums/showthread.php?t=81993&highlight=c5+brakes

http://www.digitalcorvettes.com/forums/showthread.php?t=77136&highlight=c5+brakes

http://www.digitalcorvettes.com/forums/showthread.php?t=48855

http://www.corvettemagazine.com/2002/january/bigbrakes/bb-1.asp

http://www.corvettemagazine.com/2001/august/brake-upgrade/brake1.asp

http://www.corvettemagazine.com/content/view/85
 

grumpyvette

Administrator
Staff member
Re: trouble shooting brakes
brakes3a.gif

brakes3c.gif

http://www.stoptech.com/tech_info/wp_wa ... disk.shtml

http://www.classicperform.com/TechBook/ ... eshoot.htm

http://autorepair.about.com/od/troubles ... brakes.htm

http://www.afcoracing.com/tech_pages/shoot.shtml

http://home.att.net/~m.prendergast-alli ... AKCHRT.htm

http://www.clarks-garage.com/shop-manual/ts-07.htm

http://www.holley.com/types/Solo Bleeds.asp
Solo%20bleed%20chart.jpg

theres a return spring in the booster that may be defective or busted,and on the c4 corvette the boosters frequently made from PLASTIC, not metal, and subject to cracking and leaking, so verify theres no leaks in the vacuum booster , hoses etc. and the return spring works

c4booster.png




vacbrk1.jpg

keep in mind the brake vacuum to the brake booster is generally connected to the intake manifolds plenum vacuum, if you don,t have a proper PVC valve on the valve cover on at least one valve cover and a breather on the other valve cover you may have engine crank case back pressure reduce the intake plenum vacuum, reaching the brake booster reduced
vacbrk2.jpg

boosterl1.gif

boosterl2.gif

boosterl5.GIF

boosterl3.jpg

boosterl4.jpg

power-brake3.jpg

c4booster1.png

http://www.oreillyauto.com/site/c/searc ... vi=1041219

http://www.ecklerscorvette.com/corvette ... -1996.html

http://www.rockauto.com/catalog/moreinf ... cc=1041398
http://www.summitracing.com/search/?key ... leed&dds=1

http://www.summitracing.com/parts/RUS-639590/?rtype=10

http://garage.grumpysperformance.com/index.php?threads/better-brake-pads-and-drum-wear.13975/

There are a few different systems for bleeding the brake system (2-person, 1-person vacuum, pressure, etc.). Which one of them would you consider the best and why? Do you have a preference?[/QUOTE]

mastercylinder122.jpg



http://www.mityvac.com/pages/products_hvp.asp

vacpump1a.jpg

http://www.aaawholesalecompany.com/bem-484410-pk.html
NOTICE THEY COME singly for about $8-$9 each or 12 to a carton and cost about $60 a dozen so get two to 6 buddies to split the cost
medical supplys can be useful bleeding brakes
vacbra.jpg


read this
http://www.popularmechanics.com/automot ... 13448.html
http://www.popularmechanics.com/automot ... 13448.html

brake-bleed-a-0407.jpg

brake-bleed-b-0407.jpg

brake-bleed-c-0407.jpg

brake-bleed-d-0407.jpg


"Ive only found one semi-fool proof way, and thats with two guys, doing the old...
check the fluid level, pump the brake pedal,several times,....., hold it,firmly to the pressure point f,...release the bleeder valve, on the wheel, let the pedal hit the floor,...close the bleeder valve, only then, let the pedal up, repeat, about 4 times than refill the master cylinder,repeat until you get clear new fluid and no air in the clear tubing, routine, on each wheel with a 1/4 diam. section of 3 ft long clear plastic tube routing the old brake fluid into a large plastic container, all the time getting feed back on feel from the guy pumping the brakes whose also making sure the brake fluid reservoir never gets low

So Grumpy, are you of the opinion that a single person bleeder is NOT the way to go? I like to work on my ride at 0-dark thirty in the middle of the night and my buddies hate it when I call and try to drag them out of bed at that hour.
(although I could probably call you... you don't seem like you would mind at all :D )


no, I probably would not mind at all, (I enjoy working on cars) but the wife might!
yes the brake bleed , suction tools can be used successfully, but its still not as good as having someone help and give constant verbal feed back as to pedal feel and master cylinder fluid levels in my opinion.

http://djvmerchandise.com/pro1124764.html

http://djvmerchandise.com/pro1133025.html

http://www.scooterhelp.com/genmaintain/brake.bleed.html

http://www.summitracing.com/parts/WMR-W89727/?rtype=10
WMR-W89727_XQ.jpg

I know as we get older many of us need glasses to see details in dim light or up close and wearing safety goggles becomes a BIG P.I.T.A. as they either don,t fit or you can,t wear two sets of glasses or goggles fog up.
clear face shields work fairly well, screen shield also have uses and don,t fog up, both are much cheaper than doctor care

lighted safety glasses and head band head lamps help at times

http://www.harborfreight.com/five-led-m ... 93549.html
http://www.jegs.com/i/JEGS/551/LSG279760JEG/10002/-1
http://www.harborfreight.com/adjustable ... 46526.html
faceshield2.jpg

faceshield1.jpg

http://www.harborfreight.com/mesh-face- ... 97010.html
http://www.harborfreight.com/brake-blee ... 92474.html
 
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voodovette

Member
Re: trouble shooting brakes

Have not driven the 523 CID ZR-2 in weeks due to previous summer travel/guest
commitments, so when I had the chance to fire up the old beast for a short regional trip
was happy to do so for the ongoing trial and error process of sorting out the cooling
system as documented elsewhere in these forums.

http://www.johnstuartpowerbrake.com/Auto-Vacuum-Pumps.page

Anyway.... things were going quite nicely with engine temps holding 184 190 in
a very humid 88 degrees F ...

... and then, unexpectedly, a brake system malfunction....

...coming down a hill to "T" intersection with a 20 foot drop off to a lake
on the other side of the "T".

Basically, the pedal built usual quick pressure, but just as quickly
the pedal seemed to blow past/through that and went all the way to the floor
and there was very little remaining force, despite immediate, but unproductive
rapid "pump-up" attempts, hence the quick downshifts.

Thank goodness for:
A) Low speed to begin with, in a 30 zone, no traffic around.
B) The massive compression braking of a fresh, tight 523 with
two quick double clutched gear reductions from third to second,
then second to first.
C) Remaining, diminished braking force.

If possible, it would be good to advance the brake troubleshooting thread,
to include diagnostic probabilities possible in this case.

Having followed the guide lines provided in this topic, I have inspected the
booster valve, the vacuum lines from carb to valve, the fluid, reservoirs, lines
and all related fittings. All appear normal, no fluid leaks. After sitting overnight
when I popped out the booster valve, there was still some vacuum in the booster
as you could hear by a little "woosh" of air.

Are there seals in the master cyl. that can fail or allow partial malfunction?

Twice when I shut it off and re-started it, the pedal seemed to come back
after the shut-off for one or two pumps, but then down to the mat it goes,
slight initial pressure that is quickly pushed through, same again as when running.

As mentioned, there is still some braking force, just not much.

The system is the stock '85 Z51 and has been absolutely trouble free until now.
 

grumpyvette

Administrator
Staff member
Re: trouble shooting brakes

I wish you were local because it would obviously make things far easier to diagnose,\
theres a ton of valid info in the links on the site,
If it was my car ID carefully inspect all four wheel cylinders and brake lines, and replace any that looked old or leaking, Id bleed all four wheel cylinders and flush out all current brake fluid as a first step, because any moisture in the fluid can turn to steam once the brakes get used and heat up or cause corrosion if left sitting for days, or cause rust either of which can and does cause problems.
Id find some safe place to test the car where youve got zero traffic and a large parking lot and a place to stand on the brakes and lock them up repeatedly from 30-40mph, several times but still have lots of room to coast to a stop, and I strongly suggest having rapid easy access to a car transport trailer and a tow truck for the trailer if the brakes prove defective.
your problem might be vacuum related but Id seriously doubt that from your description of the symptoms, because usually when its a vacuum problem the brake petal still works it just takes a HUGE increase in petal pressure to get the cat to stop and an increased distance, it sounds more like air in the lines or a defective wheel or master cylinder problem.


related info

http://www.classicperform.com/TechBook/ ... eshoot.htm

http://autorepair.about.com/od/troubles ... brakes.htm

http://www.procarcare.com/includes/cont ... /26TS.html

http://mysite.verizon.net/vzep121w/rons ... /id17.html

http://www.freeautomechanic.com/brakes.html



viewtopic.php?f=27&t=845&p=12264&hilit=trailers#p12264
 

voodovette

Member
Re: trouble shooting brakes

grumpyvette said:
I wish you were local because it would obviously make things far easier to diagnose,\
theres a ton of valid info in the links on the site,
If it was my car ID carefully inspect all four wheel cylinders and brake lines, and replace any that looked old or leaking,"


All 4 corners are dry, tight and were working correctly up until one instant.

" Id bleed all four wheel cylinders and flush out all current brake fluid as a first step, because any moisture in the fluid can turn to steam once the brakes get used and heat up or cause corrosion if left sitting for days, or cause rust either of which can and does cause problems.
Id find some safe place to test the car where youve got zero traffic and a large parking lot and a place to stand on the brakes and lock them up repeatedly from 30-40mph, several times but still have lots of room to coast to a stop, and I strongly suggest having rapid easy access to a car transport trailer and a tow truck for the trailer if the brakes prove defective.


Duly Noted


your problem might be vacuum related but Id seriously doubt that from your description of the symptoms, because usually when its a vacuum problem the brake petal still works it just takes a HUGE increase in petal pressure to get the cat to stop and an increased distance, it sounds more like air in the lines or a defective wheel or master cylinder problem.

I'm hugely inclined to agree with this above assessment, particularly
"defective wheel or master cylinder problem"

As previously mentioned, fluid levels are perfect. There is slight discolouration of the fluid,
however thinking that is not reason enough for the brakes to work perfectly up to that very
second of malfunction, then act up in an instant.


Based on useful samples from links provided, such as:

freeautomechanic.com

"Brake pedal goes to floor when pressed and will not pump up

Check the brake hydraulic fluid level and inspect the fluid lines and seals for leakage.
Repair or replace leaking components, then bleed and flush the brake system using
fresh brake fluid that meets the manufacturer's recommended standards.

Check the brake fluid level."


"Inspect the brake fluid level and brake hydraulic seals. If the fluid level is ok,
and the brake hydraulic system is free of hydraulic leaks, replace the brake master cylinder,
then bleed and flush the brake system using fresh brake fluid that meets the manufacturer's
recommended standards."


and from: your second from bottom link,"Ron's Pit Stop"

"Brake Pedal Goes To The Floor When It Is Depressed :
When the brakes are applied the pedal goes almost completely to the floor.
The vehicle may not stop or needs a lot of distance to come to a stop.

Possible causes:

Brake fluid is very low: Check the master cylinder fluid level and fill to the marked level.
The Master Cylinder is bad: Replace master cylinder."



The next question(s) could be go stock replacement? or...
Wilwood or some other aftermarket option. I should mention that I've
got a set of C5 ZO6 callipers and adapters that need to go on, so
wondering if an aftermarket unit would be any advantage, if affordable.



related info

http://www.classicperform.com/TechBook/ ... eshoot.htm

http://autorepair.about.com/od/troubles ... brakes.htm

http://www.procarcare.com/includes/cont ... /26TS.html

http://mysite.verizon.net/vzep121w/rons ... /id17.html

http://www.freeautomechanic.com/brakes.html



viewtopic.php?f=27&t=845&p=12264&hilit=trailers#p12264
 

grumpyvette

Administrator
Staff member

http://www.aaawholesalecompany.com/bem-484410-pk.html


http://www.harborfreight.com/mityvac-va ... 39522.html



http://www.mityvac.com/pages/products_hvpo.asp#

http://www.mityvac.com/pages/products_hvp.asp

vacpump1a.jpg


http://www.aaawholesalecompany.com/bem-484410-pk.html
NOTICE THEY COME singly for about $8-$9 each or 12 to a carton and cost about $60 a dozen so get two to 6 buddies to split the cost
medical supplys can be useful bleeding brakes
vacbra.jpg

vacpump.jpg


http://www.harborfreight.com/cpi/ctaf/d ... mber=93547

http://www.harborfreight.com/cpi/ctaf/d ... mber=92474

https://www.homedepot.com/p/Powerbuilt-Vacuum-Pump-Kit-648744/203120693
powerbuilt-testers-install-kits-648744-c3_1000.jpg

with a few cheap components you can manually bleed the brake fluid
read thru this thread, but its usually best to match the master cylinder to the calipers when doing a brake upgrade
Id suggest careful dis-assembly and careful detailed inspection ,
then if the problem is not easily resolved,by replacing defective parts,
replace the calipers, its a whole lot less expensive,
than having an accident due too defective brakes!
check local salvage yards and price out replacement calipers they are generally not very expensive
http://www.rockauto.com/en/catalog/...897,brake+&+wheel+hub,caliper+repair+kit,1720

http://www.rockauto.com/en/catalog/...1496897,brake+&+wheel+hub,caliper+piston,1724


https://www.google.com/webhp?source...ke+calipers&tbm=shop&spd=10404121658339813768





 
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DorianL

solid fixture here in the forum
Staff member
Re: trouble shooting brakes

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1f2870c4.jpg


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6967b98e.jpg


8724c505.jpg


c5806d0a.jpg


Replaced the 1-inch master cylinder with a 15/16

It is quite wet outside so I can't get a good feel... but I'll tell you this, it seems to be a VAST improvement. The front tires seem to lock on emergency.

More testing she dry...

D
 

grumpyvette

Administrator
Staff member
Re: trouble shooting brakes

yes please post results after more testing, after your sure of the results your getting under varied conditions

What is the difference between brake fluids?
Help Center

Search by Keyword
DOT 3 vs. DOT 4 vs. DOT 5 vs. DOT 5.1
Obviously, the braking system on any vehicle is a critical safety system. It becomes even more critical in race and performance applications. Bringing your car to a stop generates a lot of heat. The heavier the vehicle and the faster it is going, the more heat is created. Brake fluid must be able to stand up to all this heat and still do its job: transfer force from the brake pedal to the caliper or wheel cylinder.

To ensure everyone's safety, brake fluid must meet certain standards. The standards are set by organizations like the SAE and the Department of Transportation (DOT). The standards are what designates the fluid as DOT 3, DOT 4, DOT 5, and DOT 5.1.

The important factors involved when comparing brake fluids are:

  • Boiling Point
  • Viscosity
  • Corrosion Prevention
  • Compressibility
What is it made from?
Before we get into the specific standards, it is important to know what the different fluids are made from. DOT 3, DOT 4, and DOT 5.1 are all glycol-ether based. DOT 5 brake fluid is silicone based.

Glycol based fluids are hygroscopic, meaning they gradually absorb moisture from the atmosphere and disperse it throughout the system. As the water content of the fluid increases, its boiling point decreases. The additional moisture in the fluid will also start to corrode the metal components of the system.

The silicone based fluid is hydrophobic, meaning it will not absorb moisture. If any moisture is introduced into the system, it can collect in pockets that can either freeze or boil off. This can lead to damage to the brake system and/or brake failure. Silicone is also more compressible than glycol, which can lead to a "spongy" feeling brake pedal.

Because of the way they deal with water, glycol and silicone based fluids are NOT compatible with each other. Never mix the 2 types of fluid. Only add DOT 5 silicone brake fluid to a completely dry system or a vehicle that already has DOT 5 in it. Do not add anything other than DOT 5 to a system that calls for DOT 5 brake fluid.

Boiling Point
When it comes to performance applications, boiling point is probably the most critical. Brake fluid must withstand very high temperatures without vaporizing in the lines. Vapor is highly compressible, compared to fluid. So, if the fluid is vaporized, it fails to transfer the force from the pedal to the caliper or wheel cylinder and the car will not stop.

Don't forget to consider the water content of the fluid. Remember that the glycol based fluids will absorb moisture over time. Brake fluid must meet standards for both a wet and dry boiling point. The wet boiling point is defined as 3.7% water by volume.



Dry Boiling Point

Wet Boiling Point

DOT 3

401° F

284° F

DOT 4

446° F

311° F

DOT 5

500° F

356° F

DOT 5.1

500° F

356° F

**Some manufacturers sell brake fluid with much higher boiling points. These fluids are intended for use in race vehicles only and should not be used in daily drivers or street vehicles.**

Viscosity
Viscosity is basically the thickness of the fluid. For example, oil has a higher viscosity than water. Brake fluid must maintain its viscosity through both extreme heat and cold to provide reliable, safe braking. DOT 3 has the highest viscosity. As the DOT number increases, the viscosity goes down.

Corrosion Prevention
In addition to withstanding heat, brake fluid must also not corrode the metal brake system components. Additives are added to the fluid to accomplish this. The added chemicals protect the metal parts from corrosion, but they will damage painted surfaces.

The glycol based fluids are very harmful to paint. If the fluid is spilled, or leaks onto a painted surface of your vehicle, the paint will be damaged. DOT 5 silicone based fluid is much less harmful to paint.

Compressibility
Brake fluid is intended to transfer force. If the fluid compresses, even a little bit, the force is reduced. Brake fluid must maintain a low level of compressibility to maintain the feel of the brake pedal and provide consistent performance.

 
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DorianL

solid fixture here in the forum
Staff member
Re: trouble shooting brakes

So....

Took it for a morning drive. The road was not super dry, but enough to gauge the improvement of the 15/16 MC over the 1-inch MC.

The pedal feels more spongy and seems to sink down easier. I lost a bit of brake feel... when cold! As the pads warm up, it is easier to modulate the braking; you can better feel the pads grabbing the rotors. They are more grippy when hot.

New: I can now lock the front tires at any time. With the 1-inch MC and cold pads, I could stand on the brake and could not get the front to lock. If the pads were hot, I could manage. But that doesn't do you no good if yer pads are cold and a 16-ton didn't see the stop light was red... Ahem - let's not get into that one. Can we say puckered seat vinyl?

The pedal will go further down but will not sink to the firewall and certainly not before locking the front brakes.
 

grumpyvette

Administrator
Staff member
Re: trouble shooting brakes

"The pedal feels more spongy and seems to sink down easier. I lost a bit of brake feel... when cold! As the pads warm up, it is easier to modulate the braking; you can better feel the pads grabbing the rotors. They are more grippy when hot."


symptoms sounds like theres still a bit of air or water in the brake lines to me!
 

Indycars

Administrator
Staff member
Re: trouble shooting brakes

When changing from a 1" to 15/16" master cylinder, the pressure goes up for the same pedal force, but the volume goes down. The pedal will have to travel a little further to move the brake pads the same distance.
 

grumpyvette

Administrator
Staff member
Re: trouble shooting brakes

VERY TRUE! but its the "SPONGY" in his reply ,describing the symptoms that sounds like theres still a bit of air or water in the brake lines to me!
 

DorianL

solid fixture here in the forum
Staff member
Re: trouble shooting brakes

Very possible. I am certainly going to bleed it again.
 

DorianL

solid fixture here in the forum
Staff member
Hm, this one needs an update. I pulled off the brake calipers some time ago (to put stock ones back on) in order to pass annual tech inspection and never swapped back again. However, I no longer have to pass tech anymore - I may try out the new calipers again...
 

DorianL

solid fixture here in the forum
Staff member
A change in automotive legislation - as of this year once you pass tech with a car that is 25+ years old, that's it you are done! So no more yanking off the super, taping the boost gauge, pulling the water injection... o_O Now I can also put the after market calipers back on there. It used to be a lot of work each year to sneak through tech...
 

grumpyvette

Administrator
Staff member
that sounds like A HUGE PLUS! I'm glad to hear the regs were changed to make life a whole lot easier... and adding the improved brake components sounds like a total no- brainer , Id be doing that if it was my car for sure!
 

DorianL

solid fixture here in the forum
Staff member
Yesssssss - here if it's not stock... "take it off!" Likely, I will not resist putting those calipers back on this weekend. :D
 

Grumpy

The Grumpy Grease Monkey mechanical engineer.
Staff member
gtr1999 said:
As the others said you don't need to go for the expensive bling items for a street vette. Correctly setup stock brakes work great.

I deal with Muskegon Brake so might want to call them as well since they all get the parts from the same source.

Do you need "o" ring calipers, not if you dial in your bearings correctly and rotor runout under 003" and drive the car. If you store it for months then you might experience leaks. I haven't needed them in close to 40 years of driving vettes.

NAPA premium rotors are fine to use. Some of the fancy rotors with slots and holes crack at those points so buyer beware.

There are plenty of pads out there, I still like organics unless you plan on road racing and standing on the brakes a lot.

Check the bearings, front and rear, make sure the endplay is under 002". Repack or replace the fronts with Timkens. Rear require machine work to really dial in.

With the bearings set, install the rotors and check them. Runout under 005 is ok but I set all mine under 002". I bolt them on as well to be sure they stay where I set them. You can read all about this in the tech page.

With the rotors set, install your calipers. Use new rubber hose at all 4 corners, these will close up over time just like our veins do! They will lock the caliper up and over heat the rotors. I have seen a fire started in a 69 vette from this happening. The front calipers use a copper washer between the hose and caliper be sure you have new ones. The rears just use a steel line and these should be replaced with new SS lines since most times they are bent.

With the system assembled bleed the new MC on the bench if you are replacing it. The way I do it is to go to NAPA and pick the metric lines that fit into the MC. These are short universal ones. Cut off one end and bend them into a curl that goes back into the MC chamber. Then you can see the air bubbles when you bench bleed it. Install and bleed the system. The best way is to use a Motive pressure bleeder. Really works great and I have use all the other methods over the years.

When you're done the brake will be firm and not pull- if you did everything correctly.:thumbsup:

PS- I only use DOT 3 fluid. If you drive the car often not a problem, if you store it more then 4-5 months then all you need to do is bleed it again.
 

Grumpy

The Grumpy Grease Monkey mechanical engineer.
Staff member
Tall order here, I have a complete 1965 l78 (air cleaner to exhaust manifold oil pan) and plan on boring it out to 427 specs. In effect making roughly l72 specs. (Yes it is a 962 block and will be sonic tested.) Got a smoking deal on what is probably the only rolling l78 IE code chassis/drivetrain radiator and shroud that someone stored for years.

It is going in a 1965 Impala, M21, 3.73 posi rear.

I am am at a crossroads, I want a hydraulic roller cam in it. I want to run power disc brakes.

Option 1 - 11:1 factory type pistons (good for the rectangle ports, more rpm with more duration,) Is this possible with power brakes?

Option 2 - 10:1 pistons (less duration, less than optimal for the rectangle ports, better for power brakes)

Option 3 - Sell the 962 block, Buy a Dart big M block, build a 509 with the 208 heads at 9.6:1 and slap the zz502 cam in it. Dress with l78 parts, enjoy the cubes, the power brakes and live with the choked down l78 exhaust manifolds.

Option 4 - Solid lifter factory cam and enjoy the engine for what it is.

What cams would you all recommend for option 1 and 2?
How many would go option 3 and 4?
I am concerned about gas quality and detonation.

Thanks in advance for your input.

ok any original factory solid lifter 11:1 compression big block engine,
matched to a reasonably radical cam that will come close to maximizing performance ,and reducing that 11:1 compression engines tendency to get into detonation issues on crappy gas,
will have a cam thats got enough duration to allow that engine to breath efficiently in the 4000 rpm-6500 rpm power band.
that L78 375 hp 396, had this cam.
PN#3904362. The valve springs are PN# 3916164

242/242 duration @ .05, .520/.520 intake and exhaust lift at valve, .024/.028 lash, 114 Lobe Center-line.
http://www.hotrod.com/articles/chev...g-block-makes-50-hp-more-than-factory-rating/

theres several ways to provide the brake booster with a dependable vacuum source while running a cam,
that will have enough duration and a fairly wide LSA to allow the engine too run with a fuel with less than the ideal octane.
the most effect and cost effective in the long run is too install a small electric vacuum pump and not use intake plenum vacuum to power the brake booster, on your power brakes.
yes you could install a more modern roller cam, to boost performance, but the truth here is simply that any 11:1 compression big block engine especially with an old school flat tappet cam will best be matched with a brake booster that gets its vacuum supplied by an auxiliary vacuum pump.

http://www.superchevy.com/how-to/brakes/sucp-0210-vacuum-pumps/

https://www.summitracing.com/parts/...MIwPuNvZaj2QIVSp7ACh1NiAw5EAQYASABEgLn0_D_BwE

http://www.mbmbrakeboosters.com/ind...-booster-faq&catid=2:brake-boosters&Itemid=10


https://www.summitracing.com/parts/sum-760152
 
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