Stock carb ITC Prepped, Emissions? Mileage?

D

Davidov

New member
I have done some research on getting my stock 3 BBL carb from my '86 Civic Sedan (1.5 liter)prepped by OPM or Rivergate.

All the reviews I have seen about these two companies say the prepped carb adds a good amount of power and retains driveability.

I just have a few questions for those experienced with these prepped carbs.
First off, I w have no immediate plans to race my car in ITC, just autocross for now.
So it will be a daily driver for most of the time.

Will I still pass American emissions tests? I live in Texas is that helps.

Also, what will happen to my gas mileage, I kind of like getting 28 MPG city, with rather "spirited" driving.

Finally, what kind of power does this carb give me? Good upper RPM horsepower? (4k and up?) Or how much horsepower?

Thanks
 
The simple answer is no, you will NOT pass emissions. They install richer jets and this will cause it to go way to high on HC's and CO. The stock carb works in factory trim by providing a rich prechamber mixture and a very, very lean primary/secondary mixture. This causes good swirl action to give you very good gas mileage at very low emissions (early CVCC Honda's didn't require CAT's because they burned so cleanly until the standards were raised) While this is great for the environment, it sucks for making power. Richer jets & an K&N filter help a lot. The other trick to making good power is to remove all of the emissions controls, choke linkages, etc.

For Solo, I would suspect that there wouldn't be enough of an improvement to make a difference. The carb mods help mostly with the top end (4500-6500rpm) with a slight sacrifice in bottom end performance (anything below 2000rpm). I would leave it stock.
 
I have had both. DO NOT waste your time or money. Put a Weber 34/34 on.

EDP
 
Damn, that's what I was afraid of.

The only reason I considered this instead of a Weber is cost, and stories of people saying they are a bitch to get running properly.
Plus I have a spare stock 3 BBL carb in my garage.

What kind of power will either the 32/36 or 34/34 get me?

I have only found the Weber 32/36 and it's about $400, is the 34/34 about the same?
Does the Weber bolt right up fairly easily?
How much knowledge of carbs do I need to get it tuned right?
And how do Weber carbs do for emission standards?

[This message has been edited by Davidov (edited October 08, 2002).]

[This message has been edited by Davidov (edited October 08, 2002).]
 
THE STOCK CARB WORKS FINE!

The Weber will have the same problem with emissions as the modified stock carb. I have heard of instances in which people bolt on the Weber to their car with the cat still installed, and had the cat get super hot!

You either need to be born with olive oil in your blood or pay somebody who does in order to get the Weber working properly.

You will probably get 50/50 split on this site from people who say stay with the stock vs go with the Weber. Among the people who run the Webers, you will get a 50/50 split as to which Weber to run.

In my opinion, for someone running solo or just starting out, stay with the stock unit.

If you don't have the Weber set up properly, it will give you fits. Especially for the stop and go action of solo. You want good throttle response with the car turning left and right.

If you want to experiment (and save some money) use your spare carb as a guinea pig.

Have the carb cleaned, install new gaskets, put in a new power valve and floats, perform the legal mod's yourself. If you want advice on what to do, post another thread. Shouldn't cost you more than $100 for the parts.

Some people DO know how to make the Weber work. A properly set up Weber WILL make more peak power. I still have my Weber that I got from King (34DMTR, for sale, make offer!). I struggled with it for over two years before I gave up and went back to stock. Didn't like the drivability. Unless you are a front running ARRC car, it's not worth it IMO.

The only problem you can run into with a stock unit is age. I did have a boneyard carb that had a weird problem that acted like a float problem, but I finally proved it wasn't the float by taking the top section w/float and bolting it onto a different bottom section and my problem went away. I suspect that there was corrosion or wear or a microscopic piece of crap in one of those itty bitty orifices, or something. Never knew exactly what the problem was, but i knew what the problem wasn't!

Final note: Does the $400 for the weber include the adapter plate and air filter? You'll need to buy or make one. You will also need to cut the round lead thingy off the end of the throttle cable (buy a spare so you can switch back and forth) since the weber uses a screw clamp w/washer.

BTW if all you are doing is swapping the carb (Weber or stock) and aren't changing anything else i.e. pollution control, stock manifold, etc, you won't see that much improvement in power.

The single biggest improvement in horsepower on these engines comes from adding the header! The best header IMO was the original Mugen Tri-Y especially for Solo (very good low end and midrange power). You probably can't find one unless you check e-bay and fine a good used one.

Otherwise the DC Sports unit is a quality unit. You will need to switch to an Si oil pan in order to make it fit (the pan is a direct bolt on replacement). There are other headers out there (4-1 as well as tri-Y). A 4-1 will make more peak power but at a narrower power band. The tri-Y is better for Solo.


[This message has been edited by Greg Gauper (edited October 08, 2002).]
 
Wow, thanks for all the info.

I already have the Si headers with the bigger downpipe, along with the Si oil pan.
A cheap alternative to true headers, and helped my top end out.

I have removed all my vacuum/emission control devices, so I don't think I'll pass emissions tests with my stock unmodded carb.

Now will rebuilding the stock carb, experimenting with floats and power valves, give me better power or response?
 
Yes.

You don't have to change the float settings from stock. I suggested changing the floats since they tend to stick and act up when they get old. Ditto on the power valve. After changing, just follow the shop manual and set the level to stock settings i.e. fuel level centered between the lines of the float bowl

The basic mods are to remove all of the choke plates and linkages etc. This provides less restriction. (it will also make the carb very difficult to start in cold weather! This isn't a problem when racing in the summer). Take the guts out of the fuel evaporation chamber and make a blanking plate. Note - Once you do this you may have to crank the car over for several seconds if it sits for a long period in order to refill the float bowl. Remove the anti-run on solenoid and snip the head of the pin off and replace, or remove the solenoid and plug the hole with a screw and some JB weld. Plug all the vacuum lines to the carb. Seal them with silicone. Check them every season since they can get brittle and develope cracks. Get (make) some slightly richer jets for the primaries. If you don't know how, contact Rivergate/OPM and see if they will sell you just the jets. This will give you more top end power and won't hurt the drivability at all. You may get some loud 'pops' i.e. real race car noises
smile.gif
from the exhaust when you close the throttle at high RPM (since you have removed the pollution controls) but this won't hurt anything. The drivability of the stock carb is great! Especially in the rain! Throttle response is excellent!

Change to a K&N filter. There is one element that fits the stock housing, and there supposedly a different (slightly taller) element from earlier (83??) Civics that will fit the stock housing if you remove the large rubber seal from the bottom of the housing. The part number is different by one digit.

Get rid of the screen mesh cover over the carb. Knock the guts out of the bimetalic valve that is built in to the air cleaner assembly for the incoming air (pollution control) and block off the duct for hot air. Keep the stock cold air intake since it draws air from the front of the car (near the headlights).

Route the vent line from the valve cover and PCV valves into a catch tank. You must block off the opening created in the filter housing.

Don't ever, ever, ever futz with that small painted screw on the third (prechamber) barrel!!!! There is nothing in the manual to describe what it does, but if you mess with it, the car will run like crap!

Helpful tip...Your car has two fuel filters. One located after the fuel pump (easy to get at) and one that's a royal pain to get at near the fuel tank. Remove the fuel tank filter and replace with a piece of hose. Relocate that filter to the engine compartment. I just cut the rubber line where it exits the firewall and put the filter in-line there where it is easy to service. It just hangs from the rubber hose but you can tilt the filter to inspect/change. Some people might suggest just leaving the filter out completely, but filters are cheap insurance. Just change them at the beginning of each season.

[This message has been edited by Greg Gauper (edited October 08, 2002).]
 
Cool, I learn something new about my car every day, seriously.

Unless I can find someone experienced with carbs, and has some free time to assist me, I will prolly leave the prep work to someone else.

I already have most of my pollution control devices removed, so my car rumbles and pops like crazy when I drop the throttle above 3500 RPMs.

Right now I have all my vacuum ports plugged by rubber caps. Do you suggest silicone over the vacuum caps? And is that silicone, like you can buy from the caulk sections at Home Depot or so?

I live in Texas, so it's like summer about 300 days out of the year! So cold start problems won't get too bad.
I know what all the other components of the carb are, but what is the power valve and what does it do?
Where are the choke plates located, just to be sure.

Finally, what about gas mileage? I'd imagine a decrease with richer jets? I'm impressed with my current 28 MPG city with no emission controls.

That's alot of valuable info you gave me, I saved both of your last posts, lol!
 
Use high temperature RTV to 'glue' the vacuum caps on. The main reason is to prevent the caps from blowing off if the car backfires. If you loose a cap, you'll have a vacuum leak. The RTV is precautionary.

The choke mechanism are the first set of plates you see when you stare down the barrels. They are controlled by a bimetallic thingy on the side. Its black, about an 1.5 inches in diameter, held on by three rivets or tamperproof screws. Just drill out the rivets and take the guts out. Take the choke plates & linkages off. When you are done, the only thing remaining are the three barrel throttle plates and the accelerator pump. When you operate the throttle linkage, you'll see all three plates open and closed.

The power valve is the small brass thingy located in the bottom of the float bowl with the small pin sticking out. There is a corresponding spring loaded pin on the upper half of the carb that pushes down on the pin. Use a small (8mm??) thin wall socket to remove the valve. It has a small o-ring at the base. Clean this passage out with carb cleaner and shop air before installing the new valve.

Your gas mileage won't suffer too bad. You might loose 1 or 2 MPG, but that will probably be from having too much fun with the new set up
smile.gif


The car will be very rough when it is warming up. Mine doesn't smooth out until the water temp reaches about 160.

Cold starting is a bit of a pain without the choke. I usually give the gas pedal one pump to squirt some gas and then crankover. When it catches it usually dies right away. Give the pedal one more pump and crank again. When it catches a second time, give the gas pedal some very fast 'taps' i.e. 1/4 pedal travel pumps as fast as you can. This causes the accelerator pump to continue to add a slight amount of fuel to 'richen' the mixture. If you try and hold constant throttle, it will die cuz the mixture isn't rich enough for cold conditions. After about 10-15 seconds, you should be able to stop tapping and hold the throttle to maintain about 2000rpm to let the engine warm up. Let it idle for about 30 seconds and then drive away, taking it easy until the engine is warm.
 
Ok, great.

And how is the reliability on those prepped carbs?
Do they work everytime
and do they last long enough to be worthwhile?
 
When you say 'work every time'...what do you mean?

If you mean do they start everytime, then my answer is "mine has for the last 5 years" but I don't drive the racecar all year round. My biggest problem is when the car sits for long periods between race week-ends and the gas in the float bowl evaporates. I have to crank for about 20 seconds to get gas in the carb before I try and actually start the car with the 'pump' method described above. I was able to start the car early in the season when we had very cold, wet weather (high 30's/low 40's). It IS a bit rough until the engine warms up, but like all Honda's this doesn't take much time. Mine has an even harder time since I run very cold range sparkplugs for sustained (30min) high speeed runs. The stock NGK's work much better for cold starting, and should work fine for Solo/Autocross. I have occasionally fouled a plug, resulting in a 3-cylinder beast, but again, once the car warmed up, the plug cleared and everything was fine.

The only problem I ever had with a stock carb was with a boneyard unit as described in an earlier post. It would start fine, run great on the straights and right hand corners, but would stumble on high-g left handers. I thought it was the floats but was able to prove it wasn't.

I would suspect that if you change your fuel filters on a regular basis, the carb should run trouble free. The fact that you have a spare carb means it doesn't really cost you much to try it.
 
Originally posted by Greg Gauper:
Don't ever, ever, ever futz with that small painted screw on the third (prechamber) barrel!!!!
Click to expand...


Dang - I gotta start reading this forum again! You never know WHAT you might learn around here!
biggrin.gif


I missed racing with you this year Greg.. Being out of work the whole summer sort of put the kabosh on a lot of things..

Folks - what Greg has said here about the stock carb is right on the money. You will save a lot of money and lose precious little in performance by sticking with the stock 3-bbl carb with the mods Greg has outlined here. I chose to stick it out with the Weber DMTR and finally found the problem I was having with it (dirt in the emulsion tubes). The reason I like the DMTR is the ability to change jets to match the atmospheric conditions (Temps/Humidity) and to fine tune the mixture to the optimum EGT reading (the only way to properly tune a CVCC engine).. Do I have an advantage over Greg's car because I have a Weber? Doubtful.

((Shameless Plug))

If anyone is looking for a well sorted ITC Honda - Mine is for sale here..

asp005002.jpg


If interested, please email me at:
[email protected]


Regards - Randy Van de Loo


[This message has been edited by Thumper (edited October 21, 2002).]
 
Thanks Randy. Wish I could have raced against you this year as it was pretty thin in Area 5 this year. Had to go over to Area 4 to find somebody to race with...although that last race at Blackhawk had a pretty good ITC field. I had to start at the back of the field since I missed the 'dry' session because of a wedding and had to qualify in the 2nd session in the rain. I managed to claw my way up to third and was on the bumper of the other two cars on the third lap and as I updshifted into 4th gear and cranked the wheel for turn 2...the car just went straight off. Turned out to be a fluke thing in that the 50 cent circlip that retains the camber plate bearing broke, and the top of the RF shock pulled out from the camber plate and sorta flopped around. Probably broke from using the curbs at turn 1 with the RF wheel in the air and didn't know it till I got to turn 2. While it did happen at probably the scariest part of the track, I was also fortunate that it didn't happen at 4 or 5 or I would have been into the wall hard. As it was, absolutely no damage, but man was I bummed!!! We were having a great race. Oh well, that's racing.

I will definitly vouch for you that your car is fast & well sorted and reasonably priced.

It's a good deal
 
Sold!

Devon, I hope you are able to give my old CRX parts a good home. (sniff) I really miss that old car (sniff). That was my first new car, my first SS car, and my first IT car. (sniff).
 
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