Rochester Monojet Question...

[Oregoon]

Hey everyone!

It's been a while since I posted, though I lurk around pretty often...

My bone-stock '74 is running like a champ, though my Rochester 1bbl carb features that atrocious thermal-choke, and it causes me a lot of headaches. It stays on for waaaay to long, and doesn't seem to like my HEI very much, either. I would swap that carb out, but it's original, in excellent shape, and once that choke opens, it performs well and my 250 delivers a consistent 18 mpg.

I'd prefer a manual choke, though I'm not sure if our squares came with such a thing? My interior is near-perfect and totally original, and I'd like to keep it as close to that as I can. Anybody have interior or under-hood pictures of the choke (if indeed squares were so equipped)?

I'm heading to Old Car Parts at lunch today, but figured I'd ask here, too!

Thanks in advance!

[geezer#99]

Thermal choke!!
Got pics?
Likely easy to adapt a manual choke kit to it.

[Oregoon]

Originally Posted by geezer#99

Thermal choke!!
Got pics?
Likely easy to adapt a manual choke kit to it.

I'll snap a pic later today. It's essentially a heat activated spring that lives in a little housing on the intake manifold. As it heats up, the spring lengthens and actuates a rod that opens the choke.

I think they had a baffle from the factory, to block some of the airflow from the fan, so the thermo-springy-good-deal would heat up faster. This baffle is said to have also caused fuel boiling issues... That's all hearsay to me, since I've never seen one, and there's no baffle on my intake, though there does appear to be a place where one may have been. At the moment, it takes a good 15 minutes for the choke to fully close, and if I turn the truck off before that happens, it wants to diesel. Also, the intake cools off pretty fast, so when I'm out running errands, the choke closes in about five minutes, and causes hard starting, because the motor is already warm.

The truck is 99% stock, and the mother of all base models. 250-cid, 3 OTT, manual brakes, manual steering. Non-folding seat, white bumpers and wheels, lap-belts, etc. That choke is about the only automatic thing on the truck, and I'm surprised the OO didn't order a manual choke, too. I put an HEI in it after I bought it (boy did that make a big difference!, and rebuilt the carb.

At any rate, it needs to be addressed since it's my daily.

[Dead Parrot]

If it is what I think it is, it is called a 'divorced choke'. My 75 came with one of those. Did pretty much the same thing. Theoretically, you can adjust it by either straightening(open quicker) or adding more bend(open slower) to the little bent rod. Never had much luck with adjusting. Switched to a manual choke. Don't think the EPA allowed OEM manual chokes on most road vehicles by 74.

They eventually switched to a round housing mounted on the side of the carb. Early ones used a pipe in the manifold for heat, later ones used an electrical heater.

One idea would be to see if they made a 1 barrel carb with the later style electric choke.

[dh81k30]

you might consider using an electric choke conversion

similar to:

http://www.carburetor-parts.com/Mono...it_p_4128.html


I've no experience with this but it's a possibility.

[Oregoon]

Thanks for the suggestions, everyone!

I grabbed a manual-choke kit, and I'm planning in putting the pull-knob somewhere unobtrusive (under the dash).

Aside from the fact I don't want to drill holes in my stock dash, putting it somewhere out-of-sight will serve as one more anti-theft measure.

I was sorely tempted by an electric-choke Carter YF over the weekend, which I have a lot of experience with, but I like the Rochester. It works fine for now.

And I'm hoping to convert everything to a 390 cfm 4bbl and matching manifold/header after the Swap Meet this spring. Strongly considering a lump-port head, too.

I love sixes, and they wake up pretty good with that combo.