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hucklburry

Carby Help - Autolite 2100 or Weber 38 discussion

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I live near St. Louis, Missouri, and have a 76da block with an 82 alloy head, I am installing extractors, and it has a torquey crow cam that doesn't look like it will not rev real high.  It is going into a 66 Bronco that had a 170cu six, low end torque is better for spinning 33" tires etc.

 

It came to me with a 34 ADM, and its just flat not supported in the US.  In addition, I would have to wire in the choke and the sensors on the carb, and deal with the fuel return.  I'd prefer to keep a manual choke like it had originally.

 

I plan on driving it mostly street, to ball games and the hardware store, but am planning a trip here soon to Colorado and the rockies, with trail rides to 10,000ft and more.  And inclines.

 

My research says a 38 DGMS would be good, I think.  At least its supported over here, and bolts right in.  I guess a lot of jeepers run it, and they either do some mods to the float bowl, or turn the carb around with the float bowl near the firewall, to avoid stalling out on inclines. Both my throttle and choke are cable actuated, so linkage isn't a big concern.

 

The Autolite 2100 is very similar to the holley 500 - and I can get the adapter over here in the states.  But it looks like the 2100 could have some clearance issues with the valve cover? I am not sure.  I was wondering if someone could share a pic of their holey near the valve cover, as the 2 are very similar.

 

Or even better, has someone installed the 2100 and can give me some advice on installation?  I have both the older valve cover in place, and the newer aluminum one on the shelf.

 

The 2100 handles inclines very well, I know the carb very well, I'd like to run one on this engine.  I actually already ordered the adapter, but not sure if it will fit, or I should just go with the Weber 38 DGMS (manual choke).

 

I appreciate your help!  At some point when its running, I will share pics.

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the 34ADM doesn't need much to work, you can block the return pipe, choke is just a certain voltage added to it(can't remember which, i thought 5volts?) and the fuel cut solenoid on the side 12v when ign is on. (some of the vacuum ports stay vented. there are diagrams on this site if interested) 

that said, unless it's been used recently or rebuilt it would likely need diaphragms at min for accelerator and power valve etc. 

 

the 38/38 (38DGAS OR DGMS) has both barrels opening at once, i was told they are a good upgrade but will use more fuel. 

 

same goes for a 350 holley(often fitted here in oz, but mostly with aftermarket manifold) 500 probably overkill, but same applies

 

not sure what a 2100 is, not common here. 

 

the alloy rocker cover needs some clearance grinding to fit the 34ADM even. but if you have plenty of height available you can just go higher with spacers for any carb you choose.

the alloy rocker cover with silastic to seal it will never leak unlike a cork gasket/tin cover.  

 

you may even find a weber 32/36 might work well if it's not going to see big revs, has a smaller primary than the 34ADM and bigger secondary, may help with economy and low end torque you'd need to sort jetting out.  not sure what issues you'd have on inclines with any carb though.  

 

nothing stopping you from sticking a single barrel on either, as the 76DA engine had originally. 

there are also 4 barrel manifolds available for the alloy head if you thought there was a need for it. 

 

weber performance in Melbourne Australia probably would be able to advise on whatever you might need to know https://www.weberperformance.com.au/product_info.php?cPath=1_103&products_id=249&osCsid=jaqh47nsftqeteml4a3ihi42p4

 

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Welcome, and interesting combo t have in the States... long live the crossy!

Dean is right about the 34ADM being reliable, once dialled in. They just need to be understood if you want to overhaul them for whatever reason (as a precaution, etc). Up to you if that's something you'd like to take on. Once done right, they should be another set-and-forget carby.

Jetting for altitude shouldn't be too difficult, I'm sure your Aussie friends could help with parts if you're in a pinch. Jet drills might need to be used in any case (we don't normally need to play around with jets as we're not a mountainous country by world standards).

Personally I think the 2100 is a great old-school carby that should give years of faultless service. The CFM rating will depend on what model you have, determined by the throttle bore diameter.

I understand that these Autolites were OEM on 70s Jeeps, am I right? This would tell you that they are well-suited to off-road work. Many folks consider these a set-and-forget carby. I don't think they are in the same category as a 500 Holley, I think they are more like a 350 for flow. If comparing to 4-barrel flow (different test criteria), the 500 is more like 390 and the 350 is around 280.

One issue I see is that turning the carb around with the throttles 90 degrees to where the ADM was will have the flow restricted by the tight turn it has to make into the manifold. Not really ideal for performance. There are various manifolds available here that you can mount a 2- or 4-barrel Holley straight onto, which you would adapt the Autolite to. They aren't cheap though.

I think it will be tight up against the manifold going by the mount position you described. Most folks here either adapt it with the bowl facing forward or just mount it on a performance manifold. If you really have to mount it sideways, could you have the bowl facing outwards?

Sent from my CPH1920 using Tapatalk

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Dean, I emailed weber redline here in the states asking about the 38 choice given the engine spec's.  We shall see what they say.

 

Gerg, here are some pics.  The 500 has one vacuum port on one side and thats it.  The 2100 has a port and some stuff and a choke linkage - I ordered the adapter and took the ADM off, so I can maybe mock something up and check clearance.

 

I have very little room to the hood.

 

I don't mind up grading the intake at some point, but I'd like to have this engine running first.  It might be perfect for this little bronco, the torque should be there already.  So I guess I'd just like a simple carb that fits easily??

 

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6 hours ago, hucklburry said:

like what is the tallest point in Australia? OK, so I just googled it, 7310ft, taller than I would have thought! 

Mount Kosciuszko, 

be less than half of 1% of Australians going to that mountain. but you can drive there.  i wouldn't use that as a guide. 

 

Cabramurra was the third-highest permanently inhabited town on the Australian continent, situated at 1,488 metres (4,882 ft) in the western Snowy Mountains of the Great Dividing Range, in the state of New South Wales.
...
Cabramurra, New South Wales.
Cabramurra New South Wales

 

even then, that's probably not a big town? (i haven't heard of it) here's a list i just googled of top 50 towns by elevation http://www.bonzle.com/c/a?a=f&sc=h&st=0&mo=91772837&cmd=sp 

ORANGE (town in NSW) at 869Meters (2851 ft) is still a small town,

 

People also ask How high above sea level is Sydney?  35.6 m (116ft)

Sydney's the most populated city of Australia, due to water/sea access 

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We do have alpine regions and decent mountain ranges, but nothing like the Rockies or Switzerland.

Our skiing experience involves a lot of gum trees

The Great Dividing Range runs up the east coast and probably averages around 500m (1600ft) in height, with peaks in the Blue Mountains up around 1400m (5000ft) and 1600 in Barrington tops.

Dean I thought Mt Hotham was higher (around 1800m or 6000ft), or is that just a resort (not a town)?

Australia is old and worn down. There are no active fault lines or volcanoes within our continent so no new mountains have been made since forever.

I would love to see the Rockies and the Oregon Coast one day.

Sent from my CPH1920 using Tapatalk

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So I pulled the ADM, and yes I think with some work I can get the 2100 to fit, but its not right, and its too tall for my hood space.  So I am ordering a 38 today and see how it does off road I guess.  Mounted sideways?  I'll post pics of the Bronco in Colorado I hope, wish me luck. Thank you

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The 38 DGMS showed up today, I will be installing over the weekend - it will orient with the bowl towards the firewall, meaning the only real obstruction is one of the idle jets is hard to get too.  It matches real well to my choke cable, and I installed a lokar shift cable, making that easy as well.  The other way the linkages are close to the valve cover and one vacuum port is really blocked - the jeepers say bowl to the firewall is better for inclines off road so this may be best for me.

 

I will plug one fuel inlet and use the other as is, not worried about that location, it would be nice if I could have it enter from the fender side, but that port is not open.  I have seen where someone drilled and tapped it to work, I am not ready to start on that right now.

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9 hours ago, hucklburry said:

I will plug one fuel inlet and use the other as is

 

i think the top one will be a return line, especially if it's smaller.. that's how the ADM is from memory. might pay to confirm this with the mob who sold it or a technical diagram. 

 

interesting the reverse facing set up, hopefully doesn't cause any issues

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On 8/10/2021 at 1:40 PM, gerg said:

We do have alpine regions and decent mountain ranges, but nothing like the Rockies or Switzerland.

Our skiing experience involves a lot of gum trees emoji23.png

The Great Dividing Range runs up the east coast and probably averages around 500m (1600ft) in height, with peaks in the Blue Mountains up around 1400m (5000ft) and 1600 in Barrington tops.

Dean I thought Mt Hotham was higher (around 1800m or 6000ft), or is that just a resort (not a town)?

Australia is old and worn down. There are no active fault lines or volcanoes within our continent so no new mountains have been made since forever.

I would love to see the Rockies and the Oregon Coast one day.

Sent from my CPH1920 using Tapatalk
 

There's some bloody big mountains around here, just ask my poor old trucks.

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Hey hucklburry, how'd that 38 dgms go..? Interested in how it performs on the crossflow.. I see Weber in the US talk them up for use on the 258 AMC.. but one thing they stress a lot, is watch for vacuum leaks..  although that's probably more a problem with adaptor plates/spacers..

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59 minutes ago, vanJack said:

but one thing they stress a lot, is watch for vacuum leaks

something My dyno tuner told me people do the nuts up TOO TIGHT and that causes vacuum leaks *At the base gasket. 

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Well I had stuck a US fuel pump from a 170ci, from a Bronco, it has a vacuum pump built in to help the vacuum wipers.  I didn't get the engine with a fuel pump in it I don't recall.

 

That didn't work.  I spent a day on it I suppose.  I had gotten a motorcraft fuel filter with 2 in, 1 out - and had the overflow on the carb come down to that filter, with the other coming from the tank, and one out to the pump.  I played with all that thinking I created a pressure point or caused it to not get prime.

 

Nope, swapped out to a regular fuel pump from like a 69 mustang with a 250 and she fired off nicely!  The arm on the stock Bronco one was angled higher, i think it was missing the lobe or barely engaging, not enough to pump.

 

I'm in the middle of installing the header and getting clearance.  Also I have a fan issue - since I raised the water pump like 2" going from the 170 to the 250, the stock 14" fan wont work, a derale aluminum 13" race fan will just barely hit the top radiator hose/inlet.

 

Once I get the header clearanced, I may raise the radiator 1/2". 

 

Also, in the US I can't find a Bosch starter BFX456 or 129.  At ALL.  The stock starter had issues hitting the flywheel. I picked up a powermaster 9603, ministarter that you can adjust where the solenoid is (clocking).  The stock ford mini starters over here are all the same, and the solenoid portion hits the block before I can start the top bolt.  The powermaster is working very well.

 

So she starts, then I pulled off the manifold for the header.  I may have a vacuum leak, I threw a gauge on it, and its erractic, but it has a cam - I wanted to dive into that after I got the header on and maybe adjusted the Weber some - or even after getting a fan on it so I can let it idle and not get hot??  I'm going in many directions at once right now, but she did has 40psi oil pressure at idle and sounds great.  I will post pics soon.  Overall, she sounds very healthy with the 38 on it.

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