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Hardway's Red Rocket 1972 240z Build Thread


Hardway

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The replacement accelerator pump rod assembly arrived from the UK and it is better than I expected.  I cut the excess threaded rod off but was happy to finally make some progress.

AcclPumpRod2.jpg

Since carb #2 was already clean it went back together very quickly.  Getting the float set went quicker too!  It looks so good next to carb #1.

CarbDone05.jpg

With carb #2 done I disassembled carb #3 and as I did my heart sank when I saw this.

ThrottlePlate01.jpg

I finished the disassembly and pulled the throttle plate out.  I don't exactly know how this happened but I have a theory.  I think this throttle plate was on the other bore and as a previous owner attempted drill out the progression holes and they drilled too far and went in to the soft brass of the throttle plate.  Recognizing their mistake they swapped the throttle plates.  When taking a long look at it, the hole may not present much of an issue but this project is a full refresh of these carbs and that will include addressing and repairing all issues.  With that, another order was placed to Italy and the part along with a few more idle jets are on their way.  

ThrottlePlate02.jpg

With carb #3 fully torn down the large body parts went in to the pale of cleaner.  As you can see, I am putting some mileage on this stuff but it is still working great.

CarbWash02.jpg

After an overnight soak of the body parts and another overnight soak of all the small parts, now its just a matter of waiting.  With any luck I will get everything and reassembly the carb over the Thanksgiving holiday weekend.

FreshCarb03.jpg

FreshCarb04.jpg

FreshCarb05.jpg

Edited by Hardway
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Oy. Nice throttle plate. At least you have a plausible explanation. When I saw the first pic, my thought was "improved throttle response off idle" or something stupid like that. Then I read your theory about drilling the progression holes, and that makes much more sense.

Out of curiosity, what's a replacement run cost wise?

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11 minutes ago, Captain Obvious said:

Oy. Nice throttle plate. At least you have a plausible explanation. When I saw the first pic, my thought was "improved throttle response off idle" or something stupid like that. Then I read your theory about drilling the progression holes, and that makes much more sense.

Out of curiosity, what's a replacement run cost wise?

Thank you Captain!  The cost was very reasonable, $11.80 plus a few bucks shipping.  I had thought about trying to solder up the hole and shape it back using some fine sand paper but decided a new one is the better way to go.

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Wow. Cheap! I was looking at that damage thinking about ways to fix it, but at that price, there's no way. Cool!

Make sure you get the tapered edges facing the right way on the new one! You won't have tarnish marks to use as a guide like you probably had on the old one.

Bet you can't wait to get those things back on the car and see how much better things work!    :)

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  • 2 weeks later...

I hope everyone had a great Thanksgiving holiday.  With a 4 day weekend I was able to get Saturday all to myself to get some work done on the Z.  I was thrilled to have the replacement throttle plate and other parts arrive on black Friday.  The tracking through the shipping company provided no delivery date so I was quite surprised to find them there.  A quick comparison of the old throttle plate to the new one provided a small shock.  The part number on the old one is 7481.1 and the new one is stamped with 7841.1.  I doubled checked my communication with the seller and I requested the correct part number.  I some more comparisons and they appear to be very close but not exact copies of another.  Before I started to panic I tried to see if any Dellorto carb had a part with the number 7841.1.  Thankfully I could not find one so I believe the numbers are just transposed so in to the carb it went.

ThrottlePlate03.jpg

ThrottlePlate04.jpg

ThrottlePlate05.jpg

The third carb went together like clock work and finally completed a major phase of the project.  They are so pretty!

CarbDone07.jpg

CarbDone06.jpg

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Before I set about reinstalling the carbs I took some time to clean up the intake and valve cover.  Since the carbs looked so good there was no way they were going on the filthy engine.  Some Castrol Super Clean and elbow grease helped clean things up.  Eventually I will clean up the entire engine bay but for now it already looks a lot better!

EngBay01.jpg

EngBay02.jpg

EngBay03.jpg

Next went the carbs along with some new stainless fasteners.  They were originally held on with lock-nuts but since it is hard to get a wrench on them I opted for stainless split-lock washers and nuts.  Another change I made was the fuel line routing.  Dellorto and Weber carbs cannot share their fuel fittings so I bought an adapter for carb #3 that allowed the fuel to enter at carb #1 instead of carb #3.  It should provide several benefits in addition to looking better than the previous setup.

EngBay05.jpg 

With a turn of the key to let the fuel bowls fill up and the system pressurize I checked everything for leaks.  All looked good so I turned the engine over and after a several revolutions it fired up!  With some small adjustments it settled in to an idle around 1100 rpm.  I still need to get them sync'd and make some more adjustments but I was thrilled to hear it run again.   

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Great thread!  I've been off line for the past two weeks so I've been quiet :)

From recent reading, the Dellorto's are reported to work better than Webers and have better castings.  The Aux Venturi Nozzle in particular has been tested by David Vizard and it atomizes fuel much better. In fact some modify the 40mm Dellorto Aux Venturis to fit in 40DCO's.

The error in plate stamping is most likely another example of Chinese quality control.  Parts made there are now flooding the market place.  (FYI Weber tested and matched jets on flow benches before stamping, I doubt the new jets are tested and matched)

For  your drilled throttle plate, I first thought it may have been drilled to balance air but like you point out, the vertical drill angle seems like it was from the roof of the throat. Please check all progression holes in the 6 throats and ensure they are all the same (diameters, quantity, and location).  They need to exactly match to ensure even progression. 

The other important dimension to check on the replacement plate is the angle cut into the edge. It determines where it stops and seals.  A quick check for sealing is to release the throttle plate stop screw so that the plates stop in the throat. Once fully closed, hold up to a light source and see if any leaks between the plate and the throat.  You can also place the carb vertically on a plate and pour alcohol into the throat and see if any leaks between the throat and plate.

 

Edited by 240260280
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Wait... That shiny throttle plate on the right side is the NEW one???  Color me not impressed in the workmanship! Make sure you get those brass burrs off the edges before they chew up your carb bores when they dig into the aluminum.

And 240260280 mentioned the edge angle above, Is there even an angle cut on the edge, or is it straight cut?

And what's with the scraping marks? It probably doesn't affect operation, but there's no reason a brand new part should be marked up like that! And then there's the oversized tri-lobular holes. Like they drilled them at the wrong speed with the wrong drill bit and didn't ream the final hole to size. Again doesn't affect operation, but it's just poor workmanship.

Sorry to poo-poo your brand new part. I know it was cheap, but what the heck??   :facepalm:

Maybe I should go into the carb business...

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Yes, the shiny one is the new one and I agree, it could be better.  At the moment it runs good and a short test drive proved all my hard work and waiting was worth it as the car pulls very well.  If I feel there is something to be gained by soldering the hole and installing the original throttle plate I will.  No worries CO on your feelings on the quality of the part.  If you do decide to venture in to the carb parts business please let me know!

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