steve91tt

Nice work. Your setup is close to my car so I love seeing data to help me calibrate my butt dyno. Did you get any air to fuel ratio data (AFR) with the dyno run? As you start making changes to intake and exhaust you may change how much air the engine is sucking in (volumetric efficiency?). I'm no expert, but from what I've read, the engine may need a jetting tweak to take advantage of the extra air that you will introduce with changes to intake and exhaust. If you don't increase the gas with the air then you may see the dyno numbers drop off as the car starts to go lean (unless the car was running rich to begin with then the extra air will have a double positive effect). In other words, if you don't keep the AFR relatively constant from run to run then it will be difficult to tell what whether your changes are helping the engine breathe or messing with the carburetion.

Just a quick update on this thread in case anyone has the same problem in the future. I am still suffering with the inconsistent clutch described above but I think I might be making progress. Since I first posted I discovered that the clutch master was not consistently releasing pressure in the system when I took my foot off of the pedal. This results in the master acting like a pump. When it does not release pressure the master adds pressure and fork travel with each time I press the pedal. Thus, the inconsistent clutch pedal. I first tried removing the stops on the top and bottom of the pedal box and adjusted the push rod to get the clutch to engage very near the floor in an attempt to get as much room at the top of the pedal travel as possible. This seemed to help for a while. I next tried a smaller slave cylinder to shorten up the engage point and again give me more travel at the top of the stroke to help the master release. This did not help. Next, I took the master out of the car and found that even on the bench the plunger needed to be 100% disengaged before any pressure could be bled back to the reservoir. Even moving the push rod side to side slightly closed off the communication between the reservoir and the clutch line. I then took the master apart and found black material in the piston bore. I assumed that this was rubber from the seals and pressure release value. The master is less than 1 year old so I'm guessing that the fluid I'm using is eating the seals (ATE Original Super Blue Racing DOT 4 Brake Fluid). I cleaned it up and put it back on the car with different fluid in it (standard DOT 3). This seemed to help for a day or so but the problem came back. I pulled the master again and once again found black material in the bore. My working hypothesis is that the original brake fluid had swollen the rubber on the release valve to the point that it would not longer work consistently so I ordered a new master. While waiting for the new master to arrive I filed 1/8" off the the end of the master push rod to allow the cylinder to move back further in the bore in hopes of getting the sticky valve to release. This definitely helped but it still sticks from time to time. Still waiting for the new master to arrive from Rockauto. I'll keep this thread updated with the results. Anyone else seen similar?

That's funny as hell!

Installed a fire extinguisher last night. It's the only improvement I remember ever doing to a car that I hope I never need to use.

Have you made any changes around the rad support lately? These cars are prone to air going around the radiator rather than through it (especially with a 4 core radiator). I had a cooling issue with my 73 when I temporarily removed the plastic ducts that move air from the rad support to the fenders. The issue went away when I replaced the ducts and plugged up the other big holes on the support. If those holes are left open the air from the front of the car takes the path of least resistance and goes around the radiator. This likely isn't your problem as you are not overheating on the highway but I thought I'd throw it in as food for thought as I don't see it discussed much on the cooling related threads.

I had green gel goo in the cooling system of my 1971 when I first bought it. I picked as many of the goo balls out as I could and I flushed the rad with a garden hose but I seriously doubt if I got anywhere close to it all out. On the bright side, I have had no trouble at all with cooling. In fact, even after a hard 30 minute track session in the Texas summer heat the temperature gauge was reading somewhere close to the middle. My 1971 is a track car so I don't have a heater system hooked up. If I did I would take more care to get the system as clean as possible before filling it with coolant. Just my $0.02

Great reference! Keep them coming. Looking forward to the SU modification thread you mentioned above.

Wow, glad both you and your Z are alright. I'm ordering an extinguisher today.

If you are in the market for an electric pump you might look at the low pressure rx7 pump. I've got them on both of my 240's here in Texas and never had VL. They are very quiet and about $30 on eBay.

Wow looks like a great car. Keep us updated with the progress.

You may have dislodged the reaction disk. Here's a link that describes what to do about it... http://forums.hybridz.org/index.php/topic/69706-reaction-disk-pictures-and-walkthrough/

If you end up needing a new rear brake cylinder I recently found Autozone has the best prices on them. At least in my area. Good luck with the build.

OK, it's not a Datsun but this one made me laugh!

Started turning a pile of parts into a running 1973 240Z this weekend. Installed trans, diff, rear control arms, half shafts, brakes, springs/struts, intake, exhaust, fuel pump and a bunch of little stuff. Almost done, just a few odds and ends to button up but for now...Advil.

Went to the track with the 240Z this afternoon. It ran like a top. No issues at all. According to my data logger it's about 10 MPH slower on the back straight than my other car (Rebello 3.0l with SU's) but it's actually a second or so faster around the track. Overall a great day at the track and great little car to drive.

The accelerator pump is adjustable. There are three holes on the pump rod into which the cotter pin can be placed. Higher hole...richer on transition. I would try a different hole and see what happens to the the transition.

You could try pulling fuses and see if the current draw changes.

I've spent a little more time tweeking the tuning on the carbs. I now have my idle 13-14. I took the following video of the AFR readings for the first three gears to readline. Sorry about the quality My 9 year old copilot wasn't very steady but I think you can still see the readings. Yes, my clutch peddle is squeeky and my 2nd gear syncro is shot.:laugh: Overall I'm impressed with how well the car runs. I'm going to try to put a few track sessions in on Thursday afternoon to shake her out at high speed.

I'd have to agree with you that SU's with SM needles are not a great match for my engine. That's the reason I switched to Mikuni's for my track car build and I am in the process of moving my 73 daily driver back closer to stock. For clarification my idle is in the 10's in the texas heat with no heat shield extension. With the heat shield or in the winter I get closer to 11.5 at idle, 12's at WOT and 15's at cruise. I'm still fat at idle compared to your number but it runs fine idling in the mid 11's.

I'd snap a pic but the intake and exhaust are off the car right now along with the transmission, diff and rear suspension. I'm stripping all the go fast bits off and transferring to my 71 track car and returning the 73 closer to stock. I'm guessing mid august till I get it put back together.

This is outstanding. I have read and followed your writeups for many other tasks in the past. Your pictures always make things easy. I'll be rebuilding my early 4 speed soon. This will be a great resource. Thanks!

I left the stock heat shield in place and drilled three small holes along the edge of it. I then poked holes in the heat blanket and zip tied it to the stock heat shield on one side and to the brake lines etc on the inner fender on the other side. I never meant this to be a permanent installation but more of a proof of concept. It held together without moving for 8 track sessions on a NASCAR oval and several weeks of daily driving. The heat blanket I am using has a finished edge. This most likely helps it to hold a zip tie better. I will eventually get around to building a more permanent, better looking heat shield but for now this one seems to be working great.

I second the use of an RX7 pump. I'm using it with a mechanical booster pump on my 1973 3.0 liter Rebello stroker with SU's and by itself on my 1971 which has triple Mikuni's. Very quiet pump. The only time I hear it is when the engine is off.

Lots of tweaking and test driving this week. It turns out that a miss turned set of carbs can use a lot of gas. That combined with a busted fuel gauge can lead to an embarrassing call to your wife. Car refueled...sending unit fixed. updates... 1. I installed a helper spring which goes from the valve cover to the throttle linkage. Idle is back to a nice stable 1000RPM. I could probably go lower but I don't have the choke circuit hooked up at the moment so the higher idle helps with cold start. 2. I maxed out the accelerator pump adjustment so Wolfe Creek sent me a set of bigger accelerator pump jets. This helped the transition from low to high throttle. 3. Wolfe Creek also sent me a set of bigger pilot jets. I installed these and backed the pilot screw back to 1.25 turns out. This help the transition as well. 4. The WOT AFR's were getting up into the 14's sometimes so I moved the mains up to a size. This smoothed out the top end. Now I have an idle AFR of 12ish. Cruise in the 12's and WOT in the mid 12's to 13ish. The transition has gone from a severe miss to a light stutter. Much better. I'm working with Wolf Creek to see if there something else to do to get rid of the stutter. My current setup... 44mm carbs 34mm venturis 145 fuel jets 210 air 57.5 pilots 1.8 needle/seat 45 pump jets

I put a K&N filter in my stock air box hooked to a set of ZTherapy SU's and noticed no difference during track days at two separate road tracks where my top speed exceeded 100 MPH on the straights. I'm running a 3.0 liter Rebello stroker with a free flowing exhaust. I'm pretty sure I'm intake limited. I suspect the flow limit of the SU's is more important than than the flow limits of the paper filter so going to a higher flow oiled mesh style filter does little for performance until you can get the carbs to flow better. Don't get me wrong, SU's are wonderful carbs, even on the track, but I suspect they are a biger flow restriction than the paper filter that protects them.