Rochester Carb Vs. Stock Aisan for 2F

[BLKDOG40]

Hello all-
I got a 1975 fj40 with a 2F, sm420, Rochester Carb, & headers several months back. It starts up GREAT but stutters and hesitates when I get up to about 15-20 mph (in third gear). It does take a bit to warm up (again, has headers) and idles nice. I don't know if the thermostat is stuck open or missing, I will get around to checking & fixing- along with the death wobble, lol. I think the carb is running rich. I've changed the oil and it had a heavy smell of gas & seemed thin. The spark plugs were black & sooty. I haven't checked the functionality of the choke (just thought of it as I'm typing this). I haven't tried adjusting anything on the carb but did clean the outside and under the air cleaner. I do not have a repair manual for the Rochester carb.

I recently bought a stock Aisian 2F carb, which looks like its in good condition but might need to be rebuilt. I will need the hard fuel lines from the fuel pump and probably a new accelerator cable- no biggies. I do have a 2F FSM.

This rig is going to be a DD (I don't work too far from the house)/wheeler. So what I am looking for is thoughts/comments/pros & cons/suggestions on whether I should keep the Rochester or go back to the stock carb. From what I have read about stock carbs, I am leaning toward rebuilding the stock Aisan carb but wanted to get some input on the Rochester too. Trollhole's 'cool Rochester' comment from this post got me wondering, thats why Im asking

other notes
- I have not messed with or checked the timing, distributor, ect
- I have changed the fuel filter

Thanks in advance & happy FRIDAY!

Rochester carb

Aisan carb

 

[40's rock]

My 76 came with a rochester....I changed to a weber. Based on my experience, dump the rochester and get a quality rebuild on the Aisan.

 

[FF LC FREAK]

Rebuild the stock Aisin carb. Mark A (aka 65swb45 on mud) who is one of the carb gurus around here likens the Rochester to flushing a toilet. He much prefers the stock Aisin carb. I tend to agree. You can't really beat the stock carb in most situations.

 

[Sputnik40]

The Rochestor has some good qualities - namely super easy to rebuild, parts are dirt cheap, and if I recollect correctly - with the jets I ran you could get a fair amount of fuel into it - oftentimes too much - but it was good for accelleration.

Bad - too much fuel at times, not as smooth a system as the Aisin and as such I think your fuel economy would suffer. Usable for the street - but terrible on very very steep climbs, regardless of how low you set the fuel bowl.

If you intend it to be a DD - go with the Aisin; however, kinda ironic that you'll be driving an SM420 as a DD - not the easiest to shift, but if you have small tires you can just run 2 - 4.

Good luck.

 

[Downey]

I recall the Rochester carbs being vented directly to the atmosphere (which means they absolutely should not be sold for off road use because mud, sand, or any other kind of garbage does not have to go through the air cleaner to get inside the float bowl), however the Rochester shown here and on Tollhouses post don't seem to have the rubber vent boot in the top of the float bowl area, unless it's under that little steel plate at the side of the float bowl????

 

[Sputnik40]

I recall the Rochester carbs being vented directly to the atmosphere (which means they absolutely should not be sold for off road use because mud, sand, or any other kind of garbage does not have to go through the air cleaner to get inside the float bowl), however the Rochester shown here and on Tollhouses post don't seem to have the rubber vent boot in the top of the float bowl area, unless it's under that little steel plate at the side of the float bowl????

Interesting - I haven't run Rochestors since 1998 - but after rebuilding two I don't recollect ever seeing any external venting on the fuel bowl.

 

[inkpot]

Howdy! Is the dizzy vac adv or retard? Is the vacuum supply set up right? Looks like the ported vac on the base of the Rochester is blocked off. John

 

[DSRTRDR]

we could have an Aisan rebuilding party

I need to rebuild a spare carb that I recently acquired; earlier year, though

 

[BLKDOG40]

Thanks for all the input!

Howdy! Is the dizzy vac adv or retard? Is the vacuum supply set up right? Looks like the ported vac on the base of the Rochester is blocked off. John

hmm, I will have to check into it.

we could have an Aisan rebuilding party

I need to rebuild a spare carb that I recently acquired; earlier year, though

Sounds cool! I also have an F engine FSM if you need it. I'm going to order my kit from Mark next week after surf n turf.

 

[inkpot]

Thanks for all the input!



hmm, I will have to check into it.




Sounds cool! I also have an F engine FSM if you need it. I'm going to order my kit from Mark next week after surf n turf.

Howdy! After looking at the pix again, I would guess that the dizzy vacuum supply is hooked up to the manifold vacuum on the nub with the 3 nose nipples. It's right in front of the carb. Is your rig desogged? John

 

[tacoma73]

BIZARRE


I was going to post the same question.