I am trying to find a good location for the line lock solenoid on my car. I am building an “A” body with a big block and Pro Parts headers. The line lock is either a Biondo or Moroso (they look the same).

There are two problems finding a location.

1. The #7 tube loops over the steering column and then drops down inside the torsion bar.
2. The line lock solenoid is supposed to be located after the distribution block (with the safety switch).

The most logical place is to mount it on the firewall, next to the master cylinder. But to do this and make the connections, I need to run a line from the M/C, along the firewall (to miss the header tube) to the top of the distribution block, and then a line from one of the front outlet ports back up along the firewall to the line lock solenoid (probably the top). Then a line from the bottom of the solenoid down along the firewall, to a tee, and then split out to the right and left front wheels.

Does anyone have pictures of a better plan?

Beside that, I am still debating using a rear wheel line lock, which will also complicate the “batch of spaghetti” brake lines.

Thank you, John

mines a bit different...if you look close you will see it located on the drivers side frame rail just ahead of the engine plate(ears)

I mounted mine between the master cylinder and the distribution block, right beside the master cylinder on the inner fenderwell. That makes the brake warninng light come on when I use the line lok That doesn't bother me in any way

Mine's also mounted on the firewall low just outside the frame. I also put mine before the dist block and it works just fine. As I was informed a few days ago on some of the A bodies the block is just a distribution block so it doesn't matter that it's mounted before.

If it is mounted before the distribution block it is not NHRA legal. Sorry to "brake" the news to you.

Of course you may get away with it for years if not for ever.

dragrcr97, that sounds like one of those rule book "myths". Give me the page and para number, ole dumb me can't find it.

Well mine may not be legal either it is mounted on the framerail in the rear line. But it won't leak on my paint anymore either. Jim

Jim, if it is in the rear line going to the rear brakes and it is installed AFTER the distribution block, it is legal. I am not 100% sure, because I am not with my rule book at the moment, but if it is installed on the rear brakes/line it may even be legal if it is installed before the dist block.
Ron.

I have NO distribution block on my system. The front side comes out of the MC. T's to both front calipers. The rear goes from the MC to rear brakes. It does have an adjustable prop. valve in that line. Jim

Blucuda413 , I don't believe in "myths"....

2009 NHRA Rule book, Page 258, Near the end of the 3rd paragraph (3:1 BRAKES).

That is where I found the NHRA rule issue also. All of the installation instructions I checked outshowed the line lock solenoid after the distribution block. Other than making the warning light come on, it may be a functional reason to have the solenoid after the distribution block.

When you pump up the brakes and then energize the solenoid, the front brake fluid is locked. 700 to 800 PSI, depending on how hard you lean on the pedal. When you take your foot off the pedal, the pressure in the rear brake circuit drops to zero. This allows the spring biased piston to get moved (and the light comes on), because the pressure in the front circuit is more. I am going to pull my distribution block apart, and measure the bore and how much the piston strokes.

It is possible that there is enough piston movement to change the volume in the front brake circuit to reduce the pressure locked in, and allow the front brakes to slip.

But I still have the question, has anyone installed their solenoid after the distribution block?


Thanks, John

drqagrcr, I beg to disagree. It does not say after the "distribution block". What it says is "If brake system includes a differential pressure switch, line-loc on front brakes must have solenoid installed after the differential switch". My distribution block DOES NOT have a differential switch. I could replace the whole distribution block with a "T" for the front brakes and a pass-thru adapter for the rear and still have the same functionality.

Blucuda413, In most cases the distribution blocks on Mopars is a differential pressure switch. If it has a wire going to it, it is a differential pressure switch. If you plumb it like you say with a "T", then the solenoid can go wherever it fits.

I planned on leaving a differential pressure switch in my car, because it will see 10% street duty, so the warning light might be handy.

I disassembled the differential pressure switch in my car to try and figure out how much volume shifts when the line lock is used, and the rear circuit pressure goes to zero. But, amazingly, after forty one years, the piston is froze in the bore, so I cannot get it apart to figure it out.

Thanks again, John

There may certainly be differences between the year model Mopars. The early Barracudas do not have a differential switch (mine has no wire going to it). The distribution block is basically a hunk of brass. The comment that started this discussion was that a lineloc plumbed prior to the "Distribution Block" was not legal. That is just not true. The rule is explicit in that it talks about a "differential switch". If I remember correctly the 69 and later A bodies are a different story.

I have another 68 Cuda that is 100% stock, I haven't started restoring it yet. I'll check tomorrow to see about the block on it also.

Well my 68 has a block with a safety switch wired to it

You are talking symantics.

What you have to realise is why NHRA has each rule. Basically in this case they do not want to car to move when the driver thinks it will not (during the burnout), and they want to brakes to return to normal operation and work like they should when the driver needs and expects them to.

It really is about safety of the driver and track personel.

I personally want to be safe and I would never want to be responsible for hurting anyone else.

I'm sorry, I did not mean to get anyone twisted up by using the wrong term. Differntial Pressure Switch is what I meant.

I assume NHRA, and vendors for line-locks want the solenoid mounted after a differntial pressure switch to eliminate the possibility of an unsafe condition if trhere was a pressure drop within the differntial pressure switch when the brake pedal is released.

Functionally, if you want to use the line-lock to hold the car in position at the line against the rev-limiter, than any pressure drop is possibly going to let the car creep forward.

So that is why I was asking for examples of line-locks mounted down stream of the differntial pressure switch. Has anyone actually mounted a line-lock like this?

Thanks, John

Guys, I must eat some CROW!!!! First let me say that I did some research on the differential pressure switches. The total function of the switch is to turn a light on on the dash to alert the driver that there is a difference in pressure between the front and rear brake circuits. There is no other purpose. These switches were Federally mandated to be in all automobiles by 1970. Therefore it is extremely possible that until that time some vehicles did not have them.

However, that is not the case for the 68 Barracuda. Today I checked my totally stock 68 and there is definitely a wire running to a location on the distribution block. I then compared that to my race car block and there is definitely a place that at one time I'm sure there was a wire connection. I bought my racecar about 1987 and there has never been a wire connected to that block. I therefore now agree that my 68 cuda has a switch in the distribution block even though it is not hooked up.

Now the question of legality arises. The stock dash from my racecar has been gone for many, many years as has the light which would have been activated by the differential pressure switch. The switch in my car can therefore serve NO function. Is my installation legal?? There certainly could be some question since the switch is still there in the block. However in the current configuration it makes no difference where my lineloc is plumbed. It could definitely be a discussion item with a tough inspector.

I don't understand why the rule is there. If plumbed in front of the differential switch when you locked the front brakes and released the pedal the light should come on telling you that the lineloc is working. If the light didn't come on something is wrong.

Also I for the life of me cannot figure out how to plumb a one line line-loc with 2 lines. Maybe there are units out there that can do the job but I have never seen them. There would have to be 2 inlets and 2 outlets. Most are not like that. I know my 2 TCIs aren't.

Anyway, I stand corrected about the distribution block on my car, I was wrong. However I won't change the config which has been in use for 15 yrs, but I will delete the distribution block when I plumb in my new line-loc in a couple weeks, I just need a few more connectors.

And just a sidenote I am very aware of why the NHRA has developed the rules they have. I started racing altereds in 1955 and have seen the rulebook grow from the original few pages to the almost 300 it is today. And, I agree with 99.9% of them and even implement those I don't agree with so my car will be correct.

Gearhead01, when you release the pedal there is definitely a pressure drop. The front brake system has pressure but the rear brake system pressure drops to zero. That's exactly what is supposed to happen. However if the line-loc in pre switch the warning light would come on. That doesn't mean there's an unsafe condition. It means there is a pressure differential. I assume NHRA wants the light functionality to be as designed and that would be a problem if it comes on.

In my opinion, NHRA could care less about the light in your dash. That is a moot point. What happens is if you push the pedal and then set the line lock and then release the pedal the rear system goes to zero pressure and then the spool will slide over grounding out the connection to the light turning on the light. But when the spool activates or slides it will drop the front line pressure a bit and this may cause the car to roll when the driver expected it to stay put. OR, the rubber "O"-rings on that little spool could leak or fail dropping the front line pressure to or near ZERO and then the car could lurch forward hitting a track worker or one of your crew. So at that point you are relying on a 40 year old "O" ring to hold front line pressure and it is not the best idea. I took one of these apart and it was NASTY inside.

To plumb it properly you would keep your stock front line from the master to the dist block and then plug one of the front outlets from the dist block and then take the second one to the line lock and then out of the line lock to a "T" and then to the front brakes. They do make plugs for the unused port on your dist block.

I like to use the hurst line lock or the summit one scourced by hurst because it has several ports and actually takes the place of the dist block.

Here are some pics but it is hard to see.

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