260z How Does it Do? And, how does one do it?

I'm new at this, but CMP seems like it is pretty hard on brakes. There are a few heavy braking zones there - turn 1 at end of front straight, turn 8 (9) before turning on the back straight (not too bad since you carry a lot of speed), and the big turn right after the kink turning into the technical section.

Then, in the technical section I feel if you do it right you've got a lot of sprints and hard braking there too, four right after one another before turn 14 and you're back on the front straight again. If you are aggressive through here you can pick up a little time on your opponents I think.

But, I don't know how Road Atlanta is so maybe it is a lot worse with the stopping and going.

Ron


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Ron Earp
NC Region
Ford Lightning Tow Beast
RF GT40 Replica
Jensen-Healey ITS
1/2 a 260Z ITS - Zero
 
Imagine the speed before braking for turn 1 at CMP, then point it down a hill and enter a much slower turn and you have turn 10a at Road Atlanta. If you're hard on the brakes anywhere else at CMP you're slowing down too much. Our Charlotte setup lasted exactly 6-3/4 laps at the current Road Atlanta configuration before completely vaporizing the pads and welding the caliper pistons to the pad backing plates. That was several years ago, we've learned much since. That was with a 240Z, a 260Z will be worse. Let me know if you ever make it to RA and I'll try to meet up and pass on some tips.

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katman
 
Katman, we will let you know when we make it down to RA. Will try the ARRC this year I think.

One question though (since I have a brake challenged car as well). CMP is hard on the brakes for me, for this reason. From Turn 11 through the "autocross" section, I'm not using the brakes all that hard, but I'm using them 4 times in a row. No time for them to cool.

This causes me problems, far more than VIR where I believe the braking for Turn 1 is a lot like 10a. About 130 mph down to 50 or so. At VIR I'm off of the brakes a lot, no real time to cook them.

So, what I'm getting is literally a melting of the piston seals in the caliper. I've got the brakes ducted to the rotors, but have not yet added caliper ducts.

At CMP when I use the brakes that many times in a row in that succession, I get too much heat in the caliper and the piston seal starts to go away.

Any thoughts/ideas/solutions? I've tried some things, including one thing that I ripped out because I decided it was illegal (a fluid recirculating valve), but no luck yet. Cooked the right front seal at CMP before I broke the transmission a few weeks back.

The only thing I haven't tried, other than caliper ducts, is hard metal pads that Kirk recommended. He thinks they will transfer less heat to the pistons. I will try this next if the problem continues, but again wanted the advice of (a) someone who obviously knows what he is talking about and (B) someone who has worked with brake challenged cars.

Thanks.

Jeff
 
Joe, when the problem started I was using PFC 90s. That compound has been discontinued , and I'm using Porterfield's recommended replacement, the ridiculously expensive Raybestos ST-42 (or 43, I can't remember).

I change the pads usually well before they have a 1/4 of their thickness left.

Thanks for thinking about this.

Jeff
 
Fellows, anything you can suggest on the Z brakes would be helpful as well as the TR8 - both are about the same in specifications. The only difference in the cars right now is that the Z has full ducting - hat duct on the rotor and duct to the caliper, while the TR8 only has a hat duct on the rotor.

R



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Ron Earp
NC Region
Ford Lightning Tow Beast
RF GT40 Replica
Jensen-Healey ITS
1/2 a 260Z ITS - Zero
 
Originally posted by JeffYoung:
Katman, we will let you know when we make it down to RA. Will try the ARRC this year I think.

One question though (since I have a brake challenged car as well). CMP is hard on the brakes for me, for this reason. From Turn 11 through the "autocross" section, I'm not using the brakes all that hard, but I'm using them 4 times in a row. No time for them to cool.

This causes me problems, far more than VIR where I believe the braking for Turn 1 is a lot like 10a. About 130 mph down to 50 or so. At VIR I'm off of the brakes a lot, no real time to cook them.

So, what I'm getting is literally a melting of the piston seals in the caliper. I've got the brakes ducted to the rotors, but have not yet added caliper ducts.

At CMP when I use the brakes that many times in a row in that succession, I get too much heat in the caliper and the piston seal starts to go away.

Any thoughts/ideas/solutions? I've tried some things, including one thing that I ripped out because I decided it was illegal (a fluid recirculating valve), but no luck yet. Cooked the right front seal at CMP before I broke the transmission a few weeks back.

The only thing I haven't tried, other than caliper ducts, is hard metal pads that Kirk recommended. He thinks they will transfer less heat to the pistons. I will try this next if the problem continues, but again wanted the advice of (a) someone who obviously knows what he is talking about and (B) someone who has worked with brake challenged cars.

Thanks.

Jeff
Click to expand...

Email me at [email protected] and I'll send you some info.

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katman
 
Jeff/Ron,
We have dound it best not to run the pads below 50% if you want to avoid seal melting, I have in the past made up a spacer block to put between the pad and the piston when the pad gets worn to try to use up the last bits of the pad. (not worth the effort)

ON the Z keeping the front brakes alive requires constant adjustment of the rears to keep the balance and the pedal up. Ducting to the rotor shoud be a can the splits the air inside and out. Do not duct air to the caliper. Heat will travel to the coolest surface. If the caliper body is chilled the heat from the pad will travel toward the fluid instead of transfering into the rotor. You want the rotor to take the heat and transfer it to the air. I have never run the raybestos stuff so I am not sure what to offer there. I use the Hawk 9012 and HT10 compound for those cars and that is what all of my customers run.

[This message has been edited by Joe Harlan (edited March 02, 2005).]
 
Originally posted by Joe Harlan:
Jeff/Ron,
ON the Z keeping the front brakes alive requires constant adjustment of the rears to keep the balance and the pedal up. Ducting to the rotor shoud be a can the splits the air inside and out. Do not duct air to the caliper. Heat will travel to the coolest surface. If the caliper body is chilled the heat from the pad will travel toward the fluid instead of transfering into the rotor. You want the rotor to take the heat and transfer it to the air.I use the Hawk 9012 and HT10 compound for those cars and that is what all of my customers run.

[This message has been edited by Joe Harlan (edited March 02, 2005).]
Click to expand...

I agree with all that except for the suggestion not to run a duct to the caliper. The difference in temp between the source and the sink affects the rate of heat transfer, but you'll still get heat in the caliper regardless. I think airflow over the caliper outweighs the potentiol increase in transfer rate. That would make an interesting test, eh?

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katman
 
Katman, I have actually done the test same day realife with heat paint and measuring fluid temp at the end of each session. The fluid temp went up when ducting the caliper. I did all of these tests about 5 years ago so the result could be different today with different fluids ect.
 
Joe, that is great stuff! I understand the temp paint for swowing max surface temps, such as on the caliper, but, how did you get the actual fluid temp? Drill a caliper and insert a probe?

Cool stuff.

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Jake Gulick
CarriageHouse Motorsports
ITA 57 RX-7
New England Region
[email protected]
 
No we just measured the difference in the Master cylinder the test was head to head using fresh fluid each time and enough time for all parts to cool back to a similar a starting point. I had a couple of Z car guys melting seals and we just wanted to figure out why. The ideal way would be to make a small temp sender to thread into the bleeder hole to get exact data but that would be Kirk type anal....
smile.gif
I would have to dig deep to find all of my notes but the end result was a set of cans the covered the largest amount of the lead edge of the rotor and forcing air over the top to the outside of the rotor.
No kidding we even tried different compounds inside and outside to try to equalize the surface temps....(waste of time)
 
Originally posted by JeffYoung:
We brought it to CMP to shake it down -- it was of course claimed to be "race ready." HA HA HA.

It was cutting out in right handers on Friday's test day...
Click to expand...
I'm sorry to hear you guys had bad luck. I wish you the best with your 260. I, too have had carb problems and finally gave up on the flat tops. Since I wasn't competitive anyway, I got some round tops just to see what it would do, and it was like night and day. I'm building a 240 now. Someone else suggested having Eddie Radatz work on the carbs, and I'd second that. You need someone experienced with them and who might have some different needles he can try to get you leaned out some. Get Eddie to play around with them and try different things on the dyno.
Another thing you might want to check is your fuel pressure. The round tops seem to want 5-6 pounds at high rpms/speed, and the flats may be the same way. Of course your valves will have to be able to handle the extra pressure.
If you need any parts, I have some flat top carbs on my retired car. I had ripped out the stock wiring harness and built my own, so I can't help you out with any wiring.

Dawg
 
Hey Dawg,

we need a set of flat tops, are you selling yours, how much do you want?

It is funny how people have had trouble with them - they are horrible carbs. But that being said I am determined to get them to work since I have to for the car to be ITS legal. Ain't nothing but a big motorcycle carb and I'm certain I can work something out - once I find a original set to learn on. Ours have been bastardized to the point where not much is left and they don't work well, so, I can't really tell which way is up. Reason I'd like to get an original set.

Our 260Z originally raced at 240Z weight and you can tell because that is crossed out in the log book. I think that someone was cheating with the car and passing it off as a 240Z. It also has on the VIN plate, convienently rubbed off, the section that tells what the car is....hmmmmmm, that and the weight in the log book being crossed our and re-written as a 260z seems to indicate to me something fishy was going on.

Ron

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Ron Earp
NC Region
Ford Lightning Tow Beast
RF GT40 Replica
Jensen-Healey ITS
1/2 a 260Z ITS - Zero
 
Originally posted by rlearp:
Hey Dawg,

we need a set of flat tops, are you selling yours, how much do you want?

Reason I'd like to get an original set.

Our 260Z originally raced at 240Z weight
Ron
Click to expand...

Ron,
I have a couple of 260s in the yard, If interested, I'll be glad to send you a set of carbs. See if they can be used, buy me a beer..... I'm cleaning out around the barn presently, so let me know, before the scrap yard gets em...
david
 
Hey David,

We could use a set and we'll buy you some beers, that is for sure. If they are available and you can send them to us that'd be fantastic!

Ron Earp
132 Loch Pointe Drive
Cary NC 27511

Or if you are coming to VIR and could bring a set that'd be even better and probably easier. We'll have beer for you! If one of your 260s has that crazy plastic linkage ball we could use on of those too, getting hard to find these days. Thanks much,

Ron

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Ron Earp
NC Region
Ford Lightning Tow Beast
RF GT40 Replica
Jensen-Healey ITS
1/2 a 260Z ITS - Zero
 
Soon as the rain quits, I'll get you the carbs to the firewall...
BTW I drove a friends 260 at VIR couple years back into the 2:19s..I hope to be back in business by the MARRS/SARRC in May.
Good Luck
David

Originally posted by rlearp:
Hey David,

We could use a set and we'll buy you some beers, that is for sure. If they are available and you can send them to us that'd be fantastic!

Ron Earp
132 Loch Pointe Drive
Cary NC 27511

Or if you are coming to VIR Ron
Click to expand...
 
I mentioned Eddie Radatz in a previous post as a resource on the flat top carbs because he says he has made them work and work well. It's just a lot more work and more money for parts to get them functioning like the round tops.

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Bob Pinkowski
Atlanta Region SCCA
ITS Honda Prelude
 
Originally posted by rlearp:
Hey David,

We could use a set and we'll buy you some beers, that is for sure. If they are available and you can send them to us that'd be fantastic!
Click to expand...

Problem is the carbs are at my mom's house in the back of parts car and it may be several weeks before I can get up there and box them up.
You can have them for the cost of shipping. Or if I can drop them off at Road Atlanta later this spring, that would be easier for me. But then if you need them to get ready for your next race, that wouldn't work for you.
 
We're in no hurry and we'll take both sets you guys have, we'll cover the shipping and give you beers for the hassle.

Bob, we'll call Eddie too and see what can be done.

The funny thing is just about everyone that looked at the 260 at CMP said the same thing - never seen a 260 with those on it, everyone runs the round tops. "Just run the round tops" Well, there is that little problem of legality and we've got to have the car legal. Apparently a lot of people turn a blind eye to this issue but I'm sure it'd get protested sooner or later.

We'll talk to the folks in the know and take a look at the original carbs when we get them. They really are simple carbs and there has to be a way to get them to do something decent. It is a shame though the 260z carries with it a weight burden that is is excess of the small displacement increase it has. The weight coupled with the horrible carbs sort of makes it a non-competitive car but I'm hoping we can at least get around the carbs. 190 lbs additional weight for 185ccs displacement is a little steep!

R

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Ron Earp
NC Region
Ford Lightning Tow Beast
RF GT40 Replica
Jensen-Healey ITS
1/2 a 260Z ITS - Zero
 
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