Switching 72 carb setup to 73/74 style.

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grandfatherjim
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Switching 72 carb setup to 73/74 style.

Post by grandfatherjim » Fri May 09, 2014 5:00 am

I am gathering parts to convert my '72 from the original oil bath air filter to the paper type. So far I have the different central idling tube, the air filter housing and its standoffs, and the taller manifolds. I also possess a crusty set of carbs mounted on said taller manifolds (they would need to be refurbished) and a guy I know is offering me a "newly rebuilt and never used set" - I need to find out what that means of course. We're talking PDSITs here.
I see ports on the taller manifolds that must be for the EGR system that appeared in later years, which initially, I assumed I should just block off.
However: I have an acquaintance who has been telling me for several years about how he made some pipe a much larger diameter, with great improvement to performance. I had been thinking he meant the vacuum pipe for the brake booster but now realize it must be this EGR pipe.
Since I am at this juncture and need to do something with those ports, what is recommended?
I need to talk in general terms now, as my new engine is a bit of a Frankenstein - 1800, with Q heads, and with the carbs lifted from the previous stock 1700 and dropped right on with no adjustments having been made. (It performs better than the previous engine ever did but gas mileage is poor.)

Thanks,
Jim

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Amskeptic
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Re: Switching 72 carb setup to 73/74 style.

Post by Amskeptic » Fri May 09, 2014 6:57 am

grandfatherjim wrote: I have an acquaintance who has been telling me for several years about how he made some pipe a much larger diameter, with great improvement to performance. I had been thinking he meant the vacuum pipe for the brake booster but now realize it must be this EGR pipe.
It is called a "balance pipe" and evens out the pulsing that occurs through dual carbs. Do NOT get all big about it, max 10mm diameter. Just find a factory EGR pipe (illustrated with green in the below) and pinmch off the EGR inlet, this pipe will have the two intake manifold flanges with pre-drilled holes all ready to go, just slap on some 10mm nuts to install.

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BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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Re: Switching 72 carb setup to 73/74 style.

Post by zeta » Tue May 04, 2021 9:53 pm

Well not sure if this post will get any viewing but thought of trying...why would you want to change from ‘72 to ‘73/74 setup?

I ask because my bus (‘74) came with a Weber single progressive and I received a ‘72 setup with air cleaner and linkage. I am about to invest (time/$) to get it ready but wondered if I should gather the original Solex setup (‘74) it was originally designed with.

Thus what is the advantage of a ’74 setup over the ‘72, if I don’t need the EGR?

Thanks
Z

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grandfatherjim
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Re: Switching 72 carb setup to 73/74 style.

Post by grandfatherjim » Wed May 05, 2021 6:21 am

The primary reason for me, was to switch from the oil bath air filter to the paper air filter. But when VW made that switch in 1973, they also switched to longer intake manifolds, and so the top of the carbs was higher up, meaning if you just tried to put the housing for the paper filter on the 72 carbs, it would sit too high for them. I have also been told that there were several iterations of the carbs themselves (5?) from 72 through 74 as VW made various improvements, such that later carbs are "better". For me it came down to what I could get my hands on to rebuild, or have rebuilt. I see I started this thread seven years ago but haven't quite got to this yet...been busy building a house. That's done and now I'm on to the garage which has a tall bay so that I will finally, for the first time, be able to bring my hightop indoors to work on it. Luxury! I won't have to lie on my back on gravel to drop my engine!

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Re: Switching 72 carb setup to 73/74 style.

Post by zeta » Wed May 05, 2021 6:22 pm

I have never used these filters (oil nor paper) due to the weber progressive. what were your experiences with the oil type ('72) that made you want to switch? I do have all components for the '72 setup, so then changing them were not a performance improvement decision?

Seven years! I have been dormant since 2011 and just now woke up as well. Congrats on the awakening and on the luxury garage! Thank you for responding. It sure helps me.
Z

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grandfatherjim
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Re: Switching 72 carb setup to 73/74 style.

Post by grandfatherjim » Thu May 06, 2021 5:06 am

The oil type air filter filters air very well, but I have had to remove it plenty of times and while it can be done, it requires some dexterity to get it out of there without spilling oil out of it i.e. it's messy.
As far as a performance improvement, I only guess that there would be some, due to the longer intake runners and whatever other tweaks VW incorporated as they saw fit, over time. My assumption is that since they changed them several times in just a few short years, they thought it worth doing. I do not know how many of these changes may have been due to the pollution control requirements that were starting to happen around then.
Now, I have a 75 1800 in the bus. It was originally fuel injected but I have got my dual PDSIT setup from the 72 on it, and it runs very well.
However the caveat here is that I really don't have much experience driving other buses so it's hard to compare. I can say, now I've have three versions of a 1700 and this one 1800 since I wrote the original post, and this is the best running configuration I've had - but it's most likely due to the 1800 having been rebuilt by VWoC very shortly (in miles) before I installed it.

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Re: Switching 72 carb setup to 73/74 style.

Post by asiab3 » Thu May 06, 2021 5:53 am

I would like to bid on the ‘72 setup!

As the years went on VW was stuck conforming to emissions laws and rising costs of the early ‘70s oil fiasco. So is the later setup really better? Or does it just have more “features?”

The ‘72 linkage is the best linkage on any multi-carb setup I have ever worked with, full stop.

Robbie
1969 bus, "Buddy."
145k miles with me.
322k miles on Earth.

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Re: Switching 72 carb setup to 73/74 style.

Post by zeta » Thu May 06, 2021 7:31 am

Music to my ears!!! Thank you both.

I have no knowledge nor experience so I was somewhat apprehensive on the investment part since these carbs ('72) were not original to the '74 bus. BUT, it seems I should worry not and continue with the setup. I have gotten the correct distributor from Bill already (such a beauty). I checked with Tim regarding the carbs, and he confirmed they are a pair and capable of being built/loved again. I do have the short bases, linkages, etc., for the '72.

Two items I must confirm are in working order: (1) the choke on the carbs and (2) the flap (thermostat???) on the oil filter horn (?) assembly where the vacuum hoses attach. Don't know how to test these on the bench, but are on the list of things to research (ever so long and growing). Once I figure those items, if working, then send carbs to Tim.

Truly appreciate both responses.

Grandfatherjim, your experiences with the setups as well as sharing your knowledge level helps me gauge my status and provides me a level of comfort.

Robbie, glad to know about the linkages as I was worried they were inferior than the straight/fatter bar of later models. I am only missing the dashpot and I think something mentioned on Goose's thread (https://www.itinerant-air-cooled.com/vi ... hp?t=13619) by Colin regarding "...Check for the white plastic ball socket and spring inside throttle crossbar tube on the right side. It preloads the crossbar towards the left. Let me know if you have it/them." Maybe that applies only to '73 and later models(?). If not, a new item to the research list.

I have so much ahead, know so little, but determined. Thank you.
Z

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