Daytona Parts Carburetor - CHV or UN2 ???

[lostarkitekt]

So, I moved to Denver two years ago, and I'm finally getting the 1961 Series IIA running. Long story, but the "new" (to me) LR had a seized engine after two days of driving. Anyway, I found a used engine (2.25L Petrol), but the problem is that the carburetor on this vehicle is for Sea Level, and I live at 5,000 ft ASL. It is a Weber 34 ICH, and even though I could change out the jets, I'll be frequently driving up to 12,000 ft ASL, so the idea of jets that I can adjust on the fly sound great to me.

These Daytona Parts Carburetors have a very good reputation, and the CHV is based on the Holley 1904 and the UN2 is based on the Rochester B. All parts are ethanol resistant, which is also a positive. Wondering if anyone has experience with these carbs and/or if they would recommend one model over the other?

Thank,
Paul

[jimrr]

i have a quarter million miles on my rottenchester. my 2a has something looks like a zenith but a nice lean/clean looking one. I'm not familiar with the carb you've mentioned but predator had something like that i heard had problems, if you're running high octane you might just jet it for 8,00 or something. if you don't mind a rich mix it isn't going to hurt the engine i don't think. (they'll take anything!!)
I bought this 2a with a ''frozen'' engine which i eventually drove a bit till it started knocking, you might lever the flywheel and see if you can get it to turn over........ it may not be a write off?

[vlad_d]

@LostArkitekt: You came on the forum for a question, but you end up providing an answer instead ;P

The question I have, as a sea level LR owner, is why would you have to change the jets? Let me know if I'm mistaken, but my understanding of carburators is they have 2 places to adjust air/Fuel ratio:

1) The first is the idle Air/Fuel ratio screw on the bottom of the carb. You set this one when the car is nice and hot(regular running temp) and keep turning until you get the highest idle RPM. Turn too far either way, and it will start to run rougher(lose RPM). Then turn back 1/4 turn. So, highest RPM means the engine loves the mix and you've got the right ratio. This one is for baseline idle.

2) The next one is your choke. That's usually basically an air/Fuel adjustment for warming up. You make it really lean(lots of air) which burns better on a cold engine. Then push the choke in once you're at operating temp. The choke linkage just adjusts that flap at the top opening of the carb...lets in more/less air for the given throttle position.

Is your problem idle? Or that it doesn't have proper combustion at operating temperature and at throttle? Is that why you're messing with jets? I never heard of people changing out their jets for altitude (but I could be wrong).

I used to go Snowboarding alot. It was a 3 hour drive, up the mountain. I'd go from sea level to 6,000 feet in the morning, and back down at night. I can't imagine they'd expect you to field strip your carbeurator and change out jets twice in one day for something like that!? Isn't it just working your choke? Isn't that how you're supposed to deal with that type of thing?

I could be wrong. Let me know. But my instict would be to adjust my choke to the range I'm expecting to operate in. Same kind of methodology: go to 6,000 feet and try to get the highest RPM. Mark that spot on your choke cable. Go to 12,000 feet and do the same.. That's your range. Hopefully your choke cable is long enough for both positions? Let me know what you think. Maybe I've missunderstood.

If not, ask a sherpa!(Dang that's high. Do you have trouble breathing?);P

[roverp480]

Rover list alternative jetting in the parts book for extended running at altitudes above 5000 feet. This is from the 2a parts book for the Zenith Cab. I am no expert but surely using the choke ( which cuts the air flow and enriches the mixture) is the opposite to what is needed for altitude. Fixed jet carbs run rich at altitude and need weakening off not enriching. The Rover list is showing smaller jets for greater altitude.

[wrongway]

2) The next one is your choke. That's usually basically an air/Fuel adjustment for warming up. You make it really lean(lots of air) which burns better on a cold engine. Then push the choke in once you're at operating temp. The choke linkage just adjusts that flap at the top opening of the carb...lets in more/less air for the given throttle position.

Vlad I think you meant to say pulling the choke makes for a rich mixture.

[vlad_d]

Thanks for correcting me, folks!

I guess I come from the Hot Rod world in Socal. Whenever anyone talked about changing out jets, they were doing it for more gas flow/horsepower, etc. I didn't have much experience with jetting for practicalities like altitude. I stand corrected.

I knew the choke adjusted air. It's kind of like a see-saw, though...you take away one is the same as saying you raise the other, right? It's relative.

I guess changing jets is the ultimate "non-relative" edit, because then you're actually increasing volume of gas. Okay. I think I get it. Thanks for the clarification, folks.

Tell us how it turns out.

Was just looking at something like this:
(What do you think?)
https://www.holley.com/blog/post/upg...uel_injection/

[lostarkitekt]

I need to change my settings as I never got an email update on replies. Thanks for all the messages. The reason I want to change the jetting is for fuel economy (cough, cough)! I know these beasts don't get great economy, but dumping fuel into the carb at altitude severely cuts down on MPGs. Running rich isn't a problem, but the other way, could be. Also, I'm living at 5,000, and would probably adjust for 6,000, and then not worry about it unless I'm spending extended time at 10,000+.

I wanted to hold out until Robert Davis and crew get the adapter made for the Holley Sniper Autolite 1100 EFI, but I want to get this thing on the road, so I'll see about that at another date.

Thanks again for all the info!