Does anyone have the experience and time to briefly describe any needed tricks to delete the brake compensator on an early car / This, so as to make way for a 6 engine mount?

Things like / Is more brake line needed in addition to the "tee" fitting? And is the tee a hardware store item or another "porsche-priced" item that would be metric, brass, and overpriced by 3x?...

Sounds like a good time to change out all brake fluid as well.

I have heard the warnings if one is running 914-4 brake calipers / I am not and have nice beefy 911 calipers which will do the job up front verses in back.

Thanks in advance.

Relocate. And delete this thread before Eric Shea sees it and calls in an air strike!

My experience is limited to the theory as I.ve kept my car mostly in stock form and went through my suspension with the weight ratios in mind.

In stock form the car was almost perfectly balanced. The valve as I understand it is like a antilock device or prevents brake bias....meaning if the car is balanced for the midpoint it will spin at that center of inertia.

Since you are converting you car to a heavier motor...its a tough question since you will be altering this balance. Have you considered this in the suspension on tje car? Probably need more info on tires...brakes...suspension mods if any to get opinions.

So this are some things to think about before you go to Home Depot.


Like your Moniker....there is some inherent risks in your Traunches.

Rob gave you the short answer.

I figure the engineers's at Porsche added it for a reason and Eric Shea agrees. So I kept it on all my cars.

I relocated by moving it further left,I had to replace both rear brake pipes anyway but you could get away with replacing only the right hand side pipe only.
Its an easy enough job,never for a minute thought of removing it.

I had mine removed when I put boxster brakes on the front with stocks on the rear. Should I re-install my stock proportioning valve when I put my car back together again?

Chances are the rear brakes aren't really going to be doing much against the fronts but I'm all for following a system. When we put boxter fronts in a 911 we usually had SC's or Carrara''s on the back.

Interesting and sage advice / thanks to all for input.

Just got off the wires with Rich Johnson who has a 3.0SC motor in his conversion of many years back and has had no issue with brake performance in the snow,rain, and icy condition of Texas w/o the compensator. That said, I will retain this piece of Porsche engineering after removal and test the brakes under several conditions without it to see if there is appreciable difference in performance.

The correct Tee is a VW part, the VW aircooled shops sell same part for a 1/3 of the price of most porsche shops.
Often a VW shop will have a good used one for dirt cheap.

I'm keeping the compensation valve in my car for the same reasons stated above. Plus, I don't want Eric getting mad. One could install a racing/adjustable type valve, but with most engine mounts such as the Patrick Motorsports mount that I'm welding in, it isn't in the way. It's close, but a non-issue. I'd keep it, Forrest.

It would be interesting to see if some of these big engined conversions (running 915 transmissions) would lock up the stock back brakes with the additional weight in back. A 911 uses the T fitting, I assume because of the heavy rear end bias in the car.

As a safety feature, no reason not to keep it.

just a point of reference and it only partially applies to the Original posters question:

back when I had a 4cylinder race car I installed a T fitting and had a terrible experience.

the car was a 4cylinder (so did not have the extra 150lbs of weight changing the overall balance)

but the car also was running 911S calipers front and stock 914 rear calipers

Further I varied the pad compounds for more brake balance to the rear with much softer compound pads on the rear compared to the front

I had run an adjustable proportioning valve and felt that I need test the next step of increasing rear bias by trying out the T fitting, once my adjustable valve was fully open to the rear brakes.

Well I went down the back straight away at our now defunct 2nd creek track.

hit aboult 105/110mph going into the braking zone for a 90degree rt hand turn.

the rears locked up (while in the braking zone and going perfectly straight) and within a flash the car did a 180 spin and continued on into the corner at 100mph going back wards.

it happened so fast there was nothing I could do
I went off the corner backwards at an excessive rate of speed


So my opinion on the stock valve, is that you will rarely ever need it
but when you do need it, there will be no warning and no time to correct. This will likely only occur at a high rate of speed where traction is imperative. and you will have very little control in the extreme situation where you do need it.

I still run an adjustable proportioning valve on the track, now in a different car. I change my brake bias on a nearly daily basis for nearly each different track I go to. I have a pretty good feel for the balance and make very very small adjustments.

but the one time a person is on the street and over their head... it will be a hard lesson to learn in an emergency situation

The proportioning valve is there to keep the back brakes from locking up when you need them most. When you slam the brakes, the car's weight moves forward and the rear end gets light. The proportioning valve reduces braking power to the rear as the weight transfers forward. Without the valve, the rears can lock and disaster can follow. I was having trouble bleeding the lines with the valve and considered removing it as a quick solution. Sage advice on this forum kept me from removing and, whenever I read something like Brant wrote above, I'm thankful.

FWIW, this is the best explanation so far, with one clarification . . the proportioning valve does NOT reduce braking. . it LIMITS the max psi to the rear calipers. .until the proportioning valve operates, brake line psi is relatively equal front and rear. {Any difference is due to the twin valve master cylinder's design}. when the rear fluid psi reaches a factory preset level, the internal valve plunger in the proportioning valve moves and covers the fluid outlet port to the rear calipers. . Therefore no matter how hard you press the pedal, no more pressure goes to the rear calipers. . there is an external adjustment to preload the internal valve spring which regulates the valve psi cut-in pressure. .

Apparently 911's didn't need such a valve, because the motor was rearward and weight transfer / lift was less noticeable. . with the mid engine 914, the tendency in hard braking for a stock suspension car is to lift the rear end weight off the rear wheels. Therefore the brakes will then tend to lockup. The non rotating wheels render the rear end to become squirrelly and tends to slid the car around sideways. Remember, brakes are most effective at the point just before lockup. . a sliding tire has no traction relative to a still spinning-braking front wheel causing an unstable skid rather than straight line braking

I also did this.

If you read Brant.s post about what happened and you believe in one of Newtons law of physics.....you may not notice the affect when braking in a straight line. The moment of inertia will shift when going into a corner fast and braking hard.

Just sayin.

YUp, I feel the missiles coming in from Eric........I put the T" in about 1980, Stock brakes, high performance pads, race fluid. Engine was a big bore four, Webers and cam. Very fast in the day, lots of auto-crosses (Scca, Pax, PCA) and three plus years of Road America....high speed, wet, dry...Went home with a few/lot of Chicago PCA trophies....and never a braking issue. My 914-6 GT Tribute will still have the original T. And NO, original lines do not need modification.....Eric's stand is on the mark, he is selling top shelf products to keep you safe if you have not done the testing or have the understanding. Best, Mark

Not to hijack, but in addition to Forrest's question about the brake compensation valve, what do most here think about keeping the stock 914 sway bar in place on a /6 conversion?

My opinion is that depends on tires and spring rates....but for sure I believe more needed on a 6 conversion then on a -4 that is in stock config. Also depends on how you drive the car...as you can tell by some of the racers that responded.

I.m a civl engineer and not a mechanical engineer so I know enough to get into trouble and know I.m in trouble.

The PO of my car or PO,PO,PO of my car removed the bias valve and replaced with a T when he switched to 930 brakes. It was a dedicated race car at that time.

I can tell you my brakes work fine and the car stops on a dime. I have no intention of putting it back.

So far it seems that the valve is designed for lighter stock type engines and trans combinations. Are there any experiences for the heavier drivetrains? The weight transfer issue is still there but would the heavier mid weight setup keep the car more stable or exacerbate the tendency to spin at the limit? I'm thinking that the car would tend to stay planted. If the brakes had been upgraded all around, they'd respond as designed with the additional weight being controlled with the valve if it was still installed. What are the racers doing with the additional power and weight on the track?

...not a "racer" but I do have a hot-rod with more mass (mike) - I obviously do no run a "T" in my car. Also, the hydraulic (plunger) style proportioning valve does not provide enough adjustment for my application. My "large" changes are made with the balance bar - the plunger style valve mounted on the console is for the fine-tuned, on track adjustments. The only "914" I have ever spun (on a track) was a stock-ish car, with all OE installed.

T

With a -6 and the in creased weight, I run an adjustable valve. Not a T

I quess Tony with consideration of the OP and what Brant said is that these things or answers may of may only partially apply. There are so many considerations when setting up a car. Braking and suspension are but a few. When I say "racer" it involves a lot of seat time and experience dinking around with what works. So seat time is important to know what these things "feel" like and what they do. I know how the math works and I have enough track time...twice..to be scared.

I asked the late Ron Mier (Slits) one time...many years ago now.. how it feels going into a corner and how to brake. He said at the old Riverside track that he knew it was time to brake when his asshole would start to quiver.

You have an awesome car BTW.

One thing to keep in mind: The stock prop valve will actuate ONLY when you stomp on the brakes in a (mostly) panic situation. That is because the prop valve acts like a tee until the brake pressure exceeds something like 650-750 PSI.
If you are driving normally you will never know it is there.

And the people who race will likely not ever "stomp" on the brake as racers are more skilled and would rarely ever depress the brakes so abruptly.

And this statement is incorrect:


The pressure to the rear brakes WILL continue to increase as you apply more brake pressure only at a reduced rate compared to the fronts.

This graph shows that the rear pressure does not go "flat" at the transition point, it still has a slope, just less slope than before the transition:

Interesting stuff, maybe that's why only in the emergency braking drill at an HPDC i had one rear wheel locking. We thought it was the vent spacing on that wheel (rear passenger-side), but maybe it was since I removed the T.

I'll have to look at my car and see how easy it'd be to add the stock prop valve back in, since I kept all my old parts

In summary, I am going to move the damned thang once I get my motor mount in the car and I know where it will fit without interferring with oil lines, thermostat, wiring, fuel lines, brake lines thereto, and a host of other simple things to deal with.......

Thanks for the input.

Sidebar: My attorney recommended deleting it...... after carefully documenting which engine mount supplier directed me to delete the valve, then,.. right after I kill myself in a hideous fiery accident, allow him to help my lovely wife sue the supplier so they can live happily ever after. With friends like that,

Forrest, your motor mount should not get in the way of the brake valve, Relax.

Put the mount in, and then re-attach the valve.

Have a bottle of wine, and forget what you did until the next day.

You'll be fine.

I had mine refurbished by pmb and it looks brand new. Since a team of engineers put it in the braking system I kept everything original.

I've been running a "T" for over 20 years on my car. Many auto crosses and trips to willow springs including "big willow". Now that my car is a street car again. I might look into the factory valve again. Can it be modified for a six conversion with boxster brakes?

I converted my car to a six with parts from an 84 3.2l donor car. I also put the 84 disk brakes on all around. My proportioning valve was pretty grungy. The 911 donor car had what's called a brake "regulator" that is inline in the rear brake line just beyond the master cylinder. So far seems to work fine and I have had a few "hard stops". The pressure calibration isn't identical to the 914 prop. valve but it's darn close.

It's part number: 930 355 305 00

The "bar" is set at 33 with a reduction factor of .46

I have the "T" but 255/50/16's and 225/50/16's have increased the contact patch and the rolling inertia which requires more clamping force on stock solid rotors. Oh and I am running a 19mm master and BMW 2002 4 piston calipers on the front. It woes the car down in a straight line. Considering my engine weighs as much as a big block Chevrolet I guess I'm satisfied.

I know there are early and late brake valves. The line routing on one causes some interference. Anyone know what that is ?

The late often has to be adjusted/moved on 6 conversions.

I'm doing my engine compartment right now with the Patrick mount. Everything fits fine, and I will be re-using it.

This is mine, stock lines on a 74. Best, MarkClick to view attachment

I hope that all of you worrying about relocating the stock valve know: You CAN make your own brake lines for a couple of dollars.

OR you can order some premade from belmetric.com

https://www.belmetric.com/475mm-brake-line-...59lcfa53lhceir1