Performance carb vs stock

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JDNightFox
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Performance carb vs stock

Post by JDNightFox »

So my first tank of gas with the new distributor is averaging me 25+ miles per gallon with the 3.73 gearing and 195/75R14 beefy tires

I have a new Weber redline 32/36 kit here that I was thinking of installing, but how much performance gain will I be looking at if I do that? My carb seems to be running good now I guess

I don’t want to put an extra $300 product on if I don’t need to but I would like better performance also if it will give me any
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Petros
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Re: Performance carb vs stock

Post by Petros »

some claim increased performance, others not so much. I have owned and driven both stock carb and webber equipped T4wd. It is difficult to tell if there is much difference, I was not able to do a before and after comparison on the same vehicle. I have driven powerful and economical Tercels with stock engines, and some not so much due to wear and age. the one I drove cross country with the webber did not deliver good economy, it needed to have the jets adjusted. I was able to do that after I returned home, but I soon after sold it so I do not know how much re-jetting helped. there was not a lot of difference noticeable in the power output with the smaller jetts.

I suspect that with a properly working stock carb/fuel system you will get good economy, and also drive better at very cold and very hot driving conditions. much of the systems on the stock fuel system improve drivability in extreme temperatures. The webber has a good reputation for drivablity, and in really cold conditions it will improve after the intial start and warm up. so it is not a large benefit to have those complex systems in the car. (when I first started driving in 1974, all of my cars had manual chokes, you used it to start, but had to wait a few min before you can drive off on really cold mornings, or it would have a bad flat spot or stall out). So you can get used to it and learn to live with a few stumbles on cold mornings.

One advantage with the webber is you have to remove all of the complex fuel system devices, since they can not be used with the webber. It will greatly simplify trouble shooting and car maintenance, no more chasing around the system to find vac leaks.

I actually like the stock system, it is remarkably reliable despite how complex it is. but than keeping it running good can often take a lot of frustration time sorting out problems.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)
JDNightFox
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Re: Performance carb vs stock

Post by JDNightFox »

Yeah I can't tell if mine is running good or not, it is pretty worn and has some oily spots on it from seals starting to leak. On cold starts it has a misfire and I have to rev the engine a few times to correct it.

Is the stock carb also a 32/36? I couldn't find any info on it
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NWMO
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Re: Performance carb vs stock

Post by NWMO »

On cold starts it has a misfire and I have to rev the engine a few times to correct it.
I assume most of us are doing just that when we start it. Mine likes to sputter around the first block or so and after the first run up to 3k or 4k rpm, it runs much better. I am curious to see how much warm up it needs this winter (first winter after the rebuild).

What does the 32/36 stand for? I've always assumed that was a Weber thing and the Aisan carbs may or may not have comparable designation??

While poking around, I did come across this site which looks like it might be useful for the Weber folks:

https://www.racetep.com/manufacturer/ca ... carbs.html

Please let me know if this would be a worthwhile addition to one of the "link" libraries as a reference.

Chris
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JDNightFox
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Re: Performance carb vs stock

Post by JDNightFox »

32/36 simply means it's a 32mm primary venture and 36mm secondary

Usually it correlates with how much air it can flow through it, so I was just wondering if the stock one has similar diameters in which case you wouldn't see much performance gain theoretically (since they would pull the same amount of air)
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Petros
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Re: Performance carb vs stock

Post by Petros »

as I recall, forum member Tercel4wdrules had looked into it, the stock carb has smaller venturis. he was considering using the old truck carb, which is almost identical but has the larger venturi similar to the weber, but it would need to be rejetted. that could be done, but it would be a bit of a chore since, unlike the webber, you have to take the Hitachi carb apart to get to the jets. his motivation was that it would perhaps pass the california emissions inspections, since all of the right vac lines would be connected, and it would look the same, but be larger. it would likely cost less to do, presuming you can get a good working carb from a wrecking yard. you would not have the advanage simplfying the fuel system as with the webber, however in some states you are still required to keep all of the emission systems.

For what it is worth, it is against federal law to remove or tamper with federally mandated emissions systems, no matter how old the car. As a practical matter, there is no way to enforce that since there are no federal car inspectors, and most states do not require inspections after the car is 25 years or older, California is the exception.

It is one of perhaps 300,000 stupid federal laws that we are subject too. I just learned the other day you break federal law if you make and sell swiss cheese without enough holes in it.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)
JDNightFox
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Re: Performance carb vs stock

Post by JDNightFox »

So as far as the weber goes, the company says the carb is tuned for my application but how exactly do I know when it's running correctly
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Petros
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Re: Performance carb vs stock

Post by Petros »

I very seriously doubt they put a 3ac engine on a dyno and tuned it for your engine. what they send you will start and run okay, but to get the best ecnomy and performance, you will need to get a jet kit and fine tune it yourself.

there used to be shops around that specialized in tuning the webber, they would use either a CO meter or a dynomometer to optimize the jets to your particular engine build. I had a friend in 1977 who bought a Subaru 1600, and was tweaking it to get more power out of it, installed a webber (the subaru was relatively new to the US market, and there were no performance parts availble for it, so he had to trail and error his own performance up grades). One such shop in Long Beach Ca changed him like $350 to reset the jets. That was a lot of money for a collage student back than, but he said it was worth it. Unfortunately I doubt there are many such shops like that around anymore. BTW, he eventually put a DIY turbo charger on it, but it was so troublesome, and after a blown engine, gave up on it, sold it, and bought a toyota 4wd truck, that he still drives.

There is a webber thread on this forum where various members list what jets they are using, that would be a good place to start. Than you can fine tune them by trail and error, checking your fuel economy and drivablity with each change. it is not so complicated once you get a feel for how changing them out affects the performance. you can buy a jet kit for the webber on line, it will give you a selection of different sizes, they are not costly.

You also have a big advantage we did not have back in 1975 (when the weber was very popular to put on import cars), with the internet you can find a lot of good information on how to DIY, and fine tune it. with instructions on how each jet affects the engine behavior, and procedures on how to optimize economy and performance.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)
xirdneh
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Re: Performance carb vs stock

Post by xirdneh »

in my limited weber experience the 32/36 comes with 140 jet on primary
i got 25 mpg with it
i jetted down in increments of 5
i stopped at 125
it ran better every time i jetted down but MPG did not go up
so i went back to stock carb and got 30 mpg in summertime
if i ever try it again i will keep going down until it runs crappy then go up 5
i now have a set of tiny drill bits and soldered over the left over jets so i can drill to whatever size i want
i also missed having a carb that keeps rpms up when shifting
the stock carb is less likely to allow slight grinding of gears when shifting
Love those Tercell 4x4 wagons but they sure suffer from road noise.
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dlb
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Re: Performance carb vs stock

Post by dlb »

I found the weber made a substantial difference in performance, but that doesn't mean it's going to win any races with the Weber. It's still nowhere near as zippy as my wife's 2003 Hyundai Accent, for example.

I also had problems with icing in my Weber during the winter. Wasn't a big deal but was definitely annoying.

I found the fuel economy was about the same.

I ultimately decided that I preferred the stock carb due to the icing issue but if I had a stock carb that I couldn't get to run well and I had a weber kicking around, I wouldn't hesitate to throw it on. Both have their advantages and disadvantages.
xirdneh
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Re: Performance carb vs stock

Post by xirdneh »

you should be able to rig up an anti icing vent off the exhaust manifold for winter time
Love those Tercell 4x4 wagons but they sure suffer from road noise.
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Petros
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Re: Performance carb vs stock

Post by Petros »

the title is performance carb vs. stock. I am not aware of any other carb that will work in the tercel besides the webber. but in the archives have been several variants: a throttle body injector adapted from a Geo metro/Suzuki swift (nice simple set up), a set of four Yamaha motor cycle min carbs (one per cylinder, awesome looking set up, cheap too). As I recall, someone adapted an old Datsun Mikuni 2 barrel carb as well.

I think the weber would be less troublesome, because it is well documented what needs to be done, but there are other alternatives out there. with much fiddling and parts/adapter making you can also likely get a mulitport injection system to work.

But also consider, the deign of the head (eight small int/exh valves) are ultimately what will limit the amount of performance you will get out of the 3ac. Swapping the engine with a 4age or 4afe would be a big improvement in terms of performance, even using a completely stock set up.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)
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