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SteveJ

Can't maintain fuel pressure

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By the time I finished my test drive, it was too late. Maybe tomorrow. Maybe later. Besides, I'll be doing some stop-n-go driving this weekend when I take the car to The Mitty. I want to give it the acid test.

 

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 That degree:( of improvement is very impressive. What insulation did you use? I'd like to see a few pics of the finished shield.

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Improvement?? Im still stucked and trying to tackle this heat soak hesitation or whatever it is during traffic jams even after installing an aluminum heat shield extensión as in the picture attached and swapping the spark plugs with NGK BP5ES (hotter) to keep them from fouling during short stops and traffic lights. As the cam i have is a Schneider 274F and has an RPM range from 1800 to 6000, he recommeded to raise my idle to 1100 instead of the 1000 i have it set at.  

We checked the PSI pushed by the Airtex 8012S electric fuel pump yesterday and it showed 2.5 to 3 psi.

Still clueless on how to solve this!! Will test the car again at 1100 RPM idle tonight.

 

 

heat shield 1.jpg

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I left the fuel lines as is. When I was testing today, I could see they were being subjected to a fair amount of heat, and I could feel it on acceleration. It makes me wonder if it would be better to make a new fuel line that would go closer to the carburetors.

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such  nice Steel fuel rail to be dumped in the trash and replaced with cheap fuel hoses? still testing with idle at 1100 rpm which goes down to 900 when ac is activated!

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Try putting fuel pressure regulators between the metal fuel rail and each carb (2 regulators) and run. Stronger psi through the main fuel line (bigger pump). I would not for for a fuel injector pump as 60-90psi will blow out the fuel lines, but a steady 10psi should prevent percolation


Sent from my iPhone using Classic Zcar Club mobile

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21 hours ago, gwri8 said:

Can't you just slip one of these in the fuel tank?

Unknown.jpeg

 

6 hours ago, jalexquijano said:

why the offense? trying to solve fuel percolation at idle during traffic jams and you come up with this?

No offense intended, it's a joke about Viagras ability to make an older man (or car in your case) preform like a young man (or car).  

If you try this beware that any effects lasting longer than 4 hours you should see your mechanic, FYI.

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Here are a couple of photos of the heat shield. Maybe I'll take some later without the air cleaner in place.

Heat Shield 1.jpg

Heat Shield 2.jpg

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 Good looking heat shield. Do I see a future garage business in the works? A bolt on answer to the heat soak problem would be a valuable addition to the owners who haven'r solved it yet..

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On ‎04‎/‎21‎/‎2017 at 10:57 AM, Jarvo2 said:

I'm hoping you've referenced the attached fuel system modification guide, right?  Just one of the many bits of documentation that I've collected over the years.

Fuel-1973 240z 1974 260z fuel system modifications.pdf

Jarvo,

I had downloaded it a year ago and once read, i decided to look for a stainless Steel heat shield extensión  that covers both floats bowls of the 3 screws carburetors on my 72. Anyway today i swapped the complete exhaust of the car with the MSA PREMIUM EXHAUST which has a 2.5 diameter pipe and xlerator turbo  muffler. Once finished i drove out of the shop and got into a 10 minute traffic with lot of heat fron the road.. idle became lumpy until the car died 2 times. I decided to order a Malpassi glass filter and regulator  (85mm versión) to regulate any excess of fuel:

http://www.ebay.com/itm/Malpassi-Filter-King-Fuel-Pressure-Regulator-and-Gauge-clear-glass-bowl-/110622432307

 

If pressure is too high, this will be the symptom? I still dont want to remove the Steel fuel rail!! WHo else had this problem and solve it? I already wrapped the Steel fuel rail and installed a heat shield extensión. What else????

Edited by jalexquijano

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I'm still of the opinion that its your hot cam from California Datsun.  Get a stock head that's rebuilt to factory specs.

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 Jarvo2, Yeah, that cam has always been kind of lurking in the back ground.  It can't be helping the situation, that's for sure.

 jalex, Do you know anyone else in Panama that has a Z. I'm curious if anyone else there is fighting or has solved the problem? 

 

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19 minutes ago, Jarvo2 said:

I'm still of the opinion that its your hot cam from California Datsun.  Get a stock head that's rebuilt to factory specs.

California Datsun LLC?  :cry:

Edited by siteunseen

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Fuel lines!!! Come on, how hard can it be to cobble together a set of test lines????????

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Yes! Rubber hoses! This is a process of elimination. Try some rubber hoses and bypass the metal fuel rail. If it helps come up with a more elegant permanent solution later! Solve the problem first, then make it pretty...

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trying to find a picture of somebody who has replaced the stock metal fuel rail with rubber hoses to determine the exact lenght, material, and routing.

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10 hours ago, Mark Maras said:

 Good looking heat shield. Do I see a future garage business in the works? A bolt on answer to the heat soak problem would be a valuable addition to the owners who haven'r solved it yet..

Ironically I was showing the heat shield to an acquaintance today while we were enjoying the vintage car races at Road Atlanta, and he asked if I could make one for him. Since I don't have/want a milling machine or band saw, I know this won't be happening in my garage. LOL

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This is pretty basic. Not rocket science, I don't normally get involved with your posts any more because you don't take the advise given. 5' of fuel hose and one tee and 6 hose clamps. Cut it up to fit, pretty basic....

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