Turning up a 260Z - What is sensible?

Ron Earp

Ron Earp

Administrator
I'm curious as to what Z pilots feel like is a reasonable redline for the 240/260/280 motors - I know they are all slightly different. Reason I ask is this 260Z that we are returning to race trim does like to rev and seems to make power in the upper RPM range.

The PO had a 6100 RPM chip in the MSD. However, the car is pulling really strongly at 6100 and I don't see any reason to not try and let it go up around 6600 or so. I would guess the 240z is a little better at revving, but this one seems to like it quite a bit. Any thoughts on this?

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
 
Ron, My stuff revs to 7000 Rpm and fom time to time 7200 on the L26 because of the longetr stroke 6800 maybe a good limit. The big issue is changing Valve springs on a semi regular basis.
 
Thanks Joe, that makes some sense. I do not know this car though and I don't know if it has good springs or not - so, maybe I should back off to around 6500 or so until I get a feel for it. If I detect valve float obviously I'll have to stop, but sort of inch up a bit at a time.

At CMP once we fixed the carb problems, and before it caught on fire, it pulled strongly to 6200 with nary a miss - but we only had about 2 laps like that before the accident so we just don't have much of a feel for the Z yet. Hope to run it at VIR next week and slowly break it in - the car and me as a new driver, should be fun!

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:
Thanks Joe, that makes some sense. I do not know this car though and I don't know if it has good springs or not -
Click to expand...

Ron,
Pull out one spring and measure spring height to determine if extremely fatigued. I still have a set of pistons with eyebrows on the top from weak valve springs. Along with bent valves. Cheap check to avoid more damage.
david
 
David,

I'll check the manual since I bet it has the specss, but is the free length the same on all of the z cars? 240/260/280 all the same springs? If so I bet they are cheap and it'd be some cheap insurance to put some in. I have not taken the cover off and looked at the head design but I would imagine I could hold the vavles up with compressed air and pull them out two at a time for replacement.

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
 
Ron, Stock springs are pretty cheap. If you do them on the car Nissan sells a nice spring compressor that hooks under the cam. Do not mix up your rockers or lash pads when doing this job and you'll be just fine. I change the springs for most of my customers every 6 races if they are bouncing above 7000 to much. The smiley's in the pistons often come from getting a little quick with the clutch on the downshift.

[This message has been edited by Joe Harlan (edited March 13, 2005).]
 
Thanks Joe, if I have time this week I'll check it before VIR, if not I'll check it before the next race.

So it sounds like the top end limits the RPM and I am assuming we have no problems with rods, crank, piston speed, or anything like that? I do remember something about some small con rod bolts/nuts that sort of put a damper on RPM, but I was thinking it was for early Zs and not for later 240s or 260/280s.

I've got a 7100 or 7200 RPM chip I can put in to stop the party before things get too out of hand.

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 Joe Harlan:
Ron, The smiley's in the pistons often come from getting a little quick with the clutch on the downshift.

[This message has been edited by Joe Harlan (edited March 13, 2005).]
Click to expand...

Ron,
I admit a time or 2 or 3 maybe a little quick on clutch release....specially at Road Atlanta after brakes have signed out...
 
Your engine will have 9mm bolts with no option on the rods. The crank is good to 7500 so it should not be an issue. you will run out of stock cam before you can get to 7500. Rods are good above that rev pretty easy even stock.



[This message has been edited by Joe Harlan (edited March 13, 2005).]
 
Originally posted by Joe Harlan:
Your engine will have 9mm bolts with no option on the rods. The crank is good to 7500 so it should not be an issue. you will run out of stock cam before you can get to 7500. Rods are good above that rev pretty easy even stock.[This message has been edited by Joe Harlan (edited March 13, 2005).]
Click to expand...
If you can check whether your engine has good aftermarket rod bolts, such as ARP, then I would feel better about revving higher. If the bolts are stock, that may be your weak link.
 
Ron... I set my rev limiter at 7400, although I try not to EVER hit it. That being said, I'm changing my motor before VIR because of a piece of vavle spring that I found on my oil plug magnet. I was having some clutch/trannie/downshift problems that caused me to be a little too anxious letting the clutch out at Kershaw. I zinged her pretty good more than once. Well above the rev limit.
The moral of the story is "Don't do it, and if you do, change the valve springs".

Steve
ITS 57
Hoping to see ya'll at VIR
 
Don't the bolts have to be stock???

Steve I'll we'll set the MSD to 6900 this time and try to avoid it while we work up to that RPM. Our biggest problem, as you know, are the damn carbs and until that is sorted it is probably a mote point. We'll get it right, but I imagine that VIR won't be it.

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
 
I'm with Joe on ARP fastners, especially rod bolts on an L-series race motor.

A fresh, properly built, IT-legal engine can rev to 7500 RPM, but if you are going to do that every lap, you had better plan on replacing your valve springs every four or five races. Peak power is below 7000 RPM, so except in circumstances where gearing constraints require terminal straightaway RPM to exceed 7000 RPM, you are better off saving your engine.

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Wayne Burstein
WDC Region, ITS #10, Datsun 240Z
www.mountainmotorsports.net
 
Ron,

You can buy several sets of valve springs and test them to get a closely matched set as far as spring rate. (ie balance/blueprint) I don't know if this has much of an effect but its worth a shot. The local Nissan dealer doesn't have much trouble with me buying several sets and then returning all but 1. (so far)

Tom
1970 ITS 240z
 
Well, we'll probably be in for some valve springs soon. At CMP, a short track, we topped out in 4th at 6100 RPM, but of course that was with the old limiter.

Now if we're safe to at least say 6600 we can get some more RPM out of it, but I would guess at VIR it'll run to 7000 or so, but I am not sure. Probably find out tomorrow!

I can see tearing this motor down in the near future and making sure it is right. We didn't build it but it is a simple engine to work on and remove, so it'd be worth it to pull caps, inspect bearings, and replace hardware with some good fasteners. Make sure the compression is right and at the limit, as well as cam timing, clearances, and get the springs right.

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Ron Earp
NC Region
Ford Lightning Tow Beast
RF GT40 Replica
Jensen-Healey ITS
1/2 a 260Z ITS - Zero
 
Jeff and I were able to get a lot of data on the Z last weekend at VIR. The car actually runs very well with the flat tops - no kidding.

The first owner back in 93 spent a lot of time with the carbs to make them run well for racing. Basically we just needed to rebuild them and get out on the track to excercise them a little since it has been many years since the car has run.

The car will idle, although slightly to heavily rich. But, it will idle. It runs VERY well from about 4800 to 7000 and I think that this is where the needle/engine combination is setup properly. It might be a tiny bit lean on top at around 6900-7200, but overall it is fine.

And even better, the engine really pulls well in the 5k-7k range. You can feel a little power roll off somewhere in the 6400 range but it is still worthwhile to be there because there is no 5th, and it is making more power there than at 4500 if you happened to be in 2nd or 3rd. Plus the way it is setup if you shift too early you'll be in a range that it doesn't like for carburation.

The car braked well and ran well, the only complaint, and it is a big one, was that we had the chassis setup incorrectly. We basically had no camber in the front and the front end just wanted to wash out in turns 1-5 that really cost us a few seconds per lap. I'm a novice (but got my two races in so no rookie X for me) and ran a best of 2:27:xx with it. Jeff ran it a few seconds faster but felt it had a lot more in it if the pushing problem was fixed.

Seems the PO, not the first owner, re-assembled the car after teardown and I think the plates are installed incorrectly as they show just about max camber but there is none. Something is fishy there. Not sure what, but this Z looks nothing else like the others racing out there as far as camber goes.

But, it is a fun car - maybe not as fast as the 240s that are well prepped but we think that it'll be in range for decent finishes once it is completely sorted. Another oddball lives!

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

[This message has been edited by rlearp (edited March 27, 2005).]

[This message has been edited by rlearp (edited March 27, 2005).]
 
Glad to see it survived the weekend. I was too busy dealing with electical problems to come take a closer look. If the car doesn't have the oblong bushing on the a-arm plan on getting a set. These cars are too camber challenged to go without.


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Rick Harbaugh
#72 240Z
[email protected]
www.htmracing.com
 
Ron,
as Rick mentioned..Exccentric bushings are what many use.... Katman shared with list a way without bushings, that involved partially cutting the strut tube, bending ever so slightly, then rewelding to acheive camber.


David
Originally posted by rlearp:
.

We basically had no camber in the front and the front end just wanted to wash out in turns 1-5 Ron
Click to expand...
 
Who might have these bushings, Z Thearapy or some place like that? Or are they not specific for a car?

Rick thanks for the help with Jeff's problems. We fought electrical problems with his car too and finally solved them only to get beat back down by an engine failure. Such is life! We've already got the engine out and we'll be ready for Roebling in April.

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

[This message has been edited by rlearp (edited March 27, 2005).]
 
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