different carb

Upgrades, downgrades, modernizations, alterations or just being creative.

Postby RiverPatrol » Mon Jul 09, 2018 12:49 pm

L60Boerne wrote:Thank you RiverPatrol. I can't wait to discover the difference!


Me too!
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Postby richw » Tue Oct 15, 2019 9:12 pm

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A while ago I decided, having read this thread, to go for a Motorcraft carb from Michael at Gronk Performance.
My original Hitatchi carb was showing its age and I had an intermittent big flat spot under acceleration that could only be overcome by flooring the throttle when normal service would be resumed. Not great driving like that! All the basics checked out, clean main jet, accelerator pump squirting a good stream of fuel and it idles perfectly.
This is on a low mileage engine with valve clearances adjusted, good compression and new points set correctly with the timing bang on and the vacuum advance working normally.
The intermittent nature of the problem stumped me, carbs are not normally like that!
About the same time as the carb arrived so did a workshop manual that covered my Hitatchi carb.
I read about the 'power valve'. There's something I had not come across before, if this was working one moment and not the next that would cause my problem...see description from the manual here.

With the carb off of course I had to try the new one.
The package had arrived damaged but a broken vent stalk and throttle arm didn't seem a big deal.
The carb comes with an adapter collar for the P series motor with the standard single bore intake manifold.
Initially I had the carb fitted 'back to front' so the throttle butterflies fouled this adapter.
An easy mistake as it looked the correct way around.
Once full throttle action was acheived I connected the fuel line and started up.
It sounded great and idled nicely...but there's not much to learn about performance revving up in neutral!
The next issue was throttle linkage.
Not so easy!
The 2.5" action from the standard set up gives you upwards travel.
This carb needs outward travel from a point in space towards the master cylinder!
I rigged up some spectra line and various 'fairleads' and achieved a 'working' throttle.
Off for a drive I go.
To be fair it wasn't a proper trial. The throttle action kind of pumped this carb from mid throttle to 3/4 in a rush.
The engine ran smooth with fixed throttle but when that 'gush' of throttle came on it did not like it and actually stalled out.
At that point I decided that discretion was the better part of valour and headed home.
I could have ploughed on and made a more permanent throttle set up, most likely using a cable driven by the original arm(?) BUT instead a good friend of mine helped me look into this power valve thing. His history is porsches, he has mini syringes on wire clips to measure output from accelerator pumps!
We remove the power valve diaphragm and the 46yr old rubber looks OK. We find that the valve stem is very slightly rough and it feels 'sticky'.
Some '00' grade steel wool and a bit of a polish and it feels much smoother.
In short order it's fitted with all the vacuum lines checked.
Problem solved, normal acceleration and she runs like a dream.

So, sorry not to have a firm opinion on the Motorcraft.
The carb is well priced but some 'home assembly' is required.
Michael threw in an air cleaner but at 2" it was too tall and the bonnet would not close.
For now I'm happy with the original set up and I'm fortunate that my carb does not have high mileage problems like worn shafts and perished diaphragms.

Has anyone out there worked out a throttle linkage for this carb?
I'd like to see that.
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Postby richw » Tue Oct 15, 2019 9:17 pm

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Here's the low down on that troublesome 'power valve'.
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Postby RiverPatrol » Wed Oct 16, 2019 10:04 am

Nice that you were able to get the original one performing well for you.
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Postby Mr. Zero » Fri Jan 10, 2020 12:31 pm

I just received a PM regarding some aspects of the Motocraft installation in my previous post. Since the install images had gone MIA I went ahead and re-posted the images along with a couple of vids of the truck running with he carb installed and adjusted. I hope this might be of use to some other forum members. :)
Jason @battlebornpinzgauer
[1975 Pinzgauer 710K 2.7L EFI]
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Postby Slackd » Sun Dec 26, 2021 4:02 pm

RiverPatrol wrote:I think you are thinking of the Rochester carb. You are absolutely correct about the insulator. I had forgotten about this but I actually took pictures to depict this. In the picture below, you can see the vacuum passage on the bottom of the carb, circled. The insulator on the left is the original one that has the cutout for the vacuum passage. The insulator on the right is a new one, that doesn't have the cutout for the vacuum passage. I had to cut it myself. This is very important, your Patrol will run too rich without this. Where have I heard that before? :think:

IMG_4891-1.jpg


River, my ‘69 is running a rebuilt Rochester B. I’m intrigued by the post above regarding insulator and cut out for vacuum. I have a simple gasket between carb and intake manifold so I’m not using any type of insulator. Patrol runs ok but I believe the fuel mixture is too rich. Super bad gas mileage, stutter at low RPM (especially when engine is cold) and I can smell gas.

Any help appreciated.
Thanks
Dave
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Postby RiverPatrol » Sun Dec 26, 2021 9:33 pm

You definitely need the insulator, no gasket between the insulator and carb. I think I have NOS insulators.
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Postby Slackd » Mon Dec 27, 2021 7:34 am

Terrific. Any chance I can purchase insulator from you? Glad to pay a premium for S&H! :D

Thanks
Dave Slack
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St George Island, Fl
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