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Thread: Vapor lock year two, the good fight is back on.

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    Registered User 5thhorsemann's Avatar
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    Default Vapor lock year two, the good fight is back on.

    It's 100+ deg again today, the car is running really bad at higher RPM. I didn't want to thread jack the octain thread, so here we go.

    I just ordered a Holley blue pump with a regulator to replace the pogo pump. This is about the last thing I haven't tried among the common remidies like insulation and heat shields. I thought about cutting the hood, but I have never seen a hood scoop that looks as good as the solid 240 unvented hood. My hood has a dent, but my body man says his father's a TV repairman and he has the ultimate set of tools and he can fix it. (thats for the old guys out there) So I figure that if I must cut the hood, now is the time as paint is coming soon. Any of you guys done a hood scoop (other than the Nissan part, not too keen on them) that looks like something? If so pics please. I was thinking that a Mustang cobra scoop might be a candidate, but it looks like alot of fitting work. That would look sort of like the old big block Vette hood, sort of. (no Klingon pics please)

    So, back to the holly pump, I'm a little afraid that the pump might blow by the SU floats and spill raw fuel in the engine compartment. Has anyone put a catch can on your SU bowl vents? If so what did you buy or make and where did you install it?

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    Registered User grantf's Avatar
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    Quote Originally Posted by 5thhorsemann View Post
    but my body man says his father's a TV repairman and he has the ultimate set of tools and he can fix it. (thats for the old guys out there)
    Who are you calling old Spicoli?
    1977 280z
    1974 260z long gone

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    Registered User 5thhorsemann's Avatar
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    Quote Originally Posted by grantf View Post
    Who are you calling old Spicoli?
    US, you know who you are.

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    Registered User Walter Moore's Avatar
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    The Holley pump that I used has a red label on it (For what that is worth.) I mounted it back by the fuel tank, and have never had a problem with fuel spillage from the carbs. I assume that the return line must be working...

    I have electric fans that run off of a thermostat I installed in the carb heater line. I generally don't have any issues with vapor lock. I haven't driven the car much in 100+ degree F temperatures, but just because I don't like sitting in a pool of my own sweat.
    '71 240Z, Because any fool can drive fast in a straight line.

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    Nova Scotia,Canada,Earth Blue's Avatar
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    If you have enough pressure and flow from the pump then enlarge the orifice in the tip of the return line on the fuel rail to get more "cooling effect" (heat extraction) from the fuel that only passes through the rail and back to the tank.
    There is scarcely anything in the world that some man cannot make a little worse, and sell a little more cheaply.
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    No more body roll! SteveJ's Avatar
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    Funny, I just fixed the vapor locking problems on my 260Z. It was missing the insulation on the fuel line going to the front carburetor. I bought some Vulcan Fire Sleeve and slipped it over the fuel line. I drove it around in 90++ degree weather with no signs of vapor lock, despite the issues it had when the weather was 20 degrees cooler. What type insulation did you use on the fuel line?
    73 240Z
    74 260Z

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    Registered User Scarab155's Avatar
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    Click image for larger version. 

Name:	Scarab #155 hood louvers.jpeg 
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ID:	54631I would punch some louvers in the hood (and inspection lids as well). I have this on my Scarab Z and they really do a greatv job of venting the heat from the engine bay. They also do not spoil the lines of the 240Z hood. Just my opinion.

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    Registered User 5thhorsemann's Avatar
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    Walter, I have considered the fan idea, but haven't yet found a fan setup that looked like it would be both ellegant and trustworthy.

    Blue, great idea, as usual, I will be sure to add that modification when the pump goes in.

    Steve, I used a ceramic wool, wrapped in FG mesh (header wrap) held in place using aluminum tape with the reflective side out. The fuel rail is isolated from the head and mounting hardware using pheonalic washers. I can't see how I could better protect the rail from heat.

    Scarab, I haven't looked into the louvers, but it is a good looking alternative.

    Thanks men!

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    Registered User MotoManMike's Avatar
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    Sounds like a mixture issue to me, popping at high rpm tends to be a lean condition. What oil do you have in the dash pots?

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    IF I get a vote, I think the scarab idea is brilliant. If you have to modify a 240Z hood, why not go something the old school datsun guys did.

    Popping at high RPM is an issue that is near and dear to my heart. Lets just say that it could be a GREAT many things.

    Fix the easy ones first. Then after you go freaking nuts, buy webers. HAHAHA
    1971 240Z HLS30-38691
    93.9% done and getting better every day
    Now with 100% more DATSUN SPIRIT L28 Power
    1968 Datsun 2000 SRL311-03416

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    Torch Wielding Villager gogriz91's Avatar
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    If you can get ahold of an original fuel rail for originalities sake I had my fuel rail "modified" and moved so it flows from the transmission tunnel along the firewall then to the carbs and had it wrapped with fire sleeve.
    '73 HLS30 129806 ; L-28, street cam, SUs, 5-speed, Koni's, Suspension techniques springs, swaybars, 3.90 R200 LSD

    Heavily medicated for your protection

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    I got my pump today, it will go on this evening. I know the carbs are set up right because when the temp hits 97 to 100 degrees is when the problem starts. If I pop the hood at speed it goes away. I'll see what the pump does, It's not supposed to get hot enough this week to be an issue, so time will tell.

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    Registered User 5thhorsemann's Avatar
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    Okay, so I had to waite till today to do the install as I had to order the gauge for the regulator.

    The pump is a little bigger than it looks, the only nice place to mount it, and have room for a high quality filter, was on the bracket that the jackpot mounts to. I was having a hard time manipulating the mounting hardware on the back side of the bracket around the moushtash bar and such, so instead of drilling and bolting I used two beam clamps to mount the pump, it works really well.
    Click image for larger version. 

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    I put the regulator up in the front corner on the inner fender which makes all the hoses as short as possible.
    Click image for larger version. 

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    So I presurized the system and checked for leaks, it's all good, started the car and adjusted the pre mechanical pump regulator to 3 to 4 PSI and let her run for a while to make sure the bowls on the SU's were not overflowing, again, all good.

    So now I wanted to see if Blue's idea of inlarging the return restriction was necessary. I removed the returne line from the fuel rail and put a quart glass jug on it, I turned the pump on with stopwatch in hand, the electric pump alone pumps a quart in 8 seconds thru the return pipe. So thats almost 2 GPM and I think that should be plenty of bypass to combat the vaporlock, so I'm gonna reserve the drilling of the rail as a last resort.

    I'll report back on the next hot day.

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    Registered User epsark's Avatar
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    I have a very similar set up on my 240Z, only I have the Holley red pump. 4 year old pump died, so I bought a replacement. That one was dead out of the box. Took me a while to figure that one as I never expected that to be the issue. Next one now has "locked up" twice on me. By that I mean that the pump sounded like it was on, the humming noise (loud) that it usually makes, but no pressure. Took everything apart and thought vapor lock since the issue, no pressure, finally went away. The second time no pressure again, but pump was a little quieter. Checked a few things before deciding to knock on the pump. Once I did that, the pump jumped in volume and pressure was flowing.
    Just not sure about Holley quality any more is what I am trying to say. Hopefully you have better luck. I am going to try a pump from Airtex, I think that is their name, who makes most OEM pumps for the major manufactures. It is said to be much quieter and more reliable. Time will tell. Good luck with your set up and I hope it takes care of your vapor lock issues!

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    Amazingly, 721 never had a vapor lock issue with either the SUs or Mikunis. I had removed the mechanical pump and installed a Stewart Warner "thumper" pump years ago (40). I had the fuel lines routed adjacent to the original lines, up the firewall, over to the center of the car, then forward to a fuel block mounted with the intake/exhaust studs then to the carbs. Pressure was regulated at the pump at just below 6psi. No return line was used.

    Vapor lock is a varying mystery, isn't it?
    First & Third owner of HLS30-00721
    B. 01/70 D. 03/12

    New owner of HLS30-15653
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    Frank in Houston, Texas

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    I've used the Holley pumps in the past, never had a problem with them. Since I'm using the returne circuit, the pump should run stress free, as long as there is pressure at the suction side of the mechanical pump, it should be fine.
    I will be watching everything closely for a while to make sure I don't overfeed the bowls and wash the motor down. Like you said, time will tell.

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    Registered User 5thhorsemann's Avatar
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    Update, looks like this did the trick, it's been in the high 90's for the past two days and no sign of the problem. I do still have to get used to the buzz of the new pump, it's loud compared to the old thumper.

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    Try running a rubber insulator between the pump and bracket.

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    Registered User 5thhorsemann's Avatar
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    Quote Originally Posted by rcb280z View Post
    Try running a rubber insulator between the pump and bracket.
    The pump bracket has a rubber isolator built in, I dont see how to further isolate the noise and still have a secure mount, I just have to learn to live with it.

    Is that a FG hood or just a 3" scoop mounted to the stock hood? I like it, and just ordered a FG cowl scoop for mine. http://www.ebay.com/itm/150852819409...84.m1497.l2649

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