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Steve's AWESOME Brat


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196 replies to this topic

#1 Splinter

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Posted 10 March 2010 - 11:01 PM

Thought I'd start a little log of what we're doing with our Brat, beginning with the carb swap.

Holley 2bbl 2210 carb off a Dodge 318, currently working on making an adapter plate, I've got the bolt holes all set up, going to start on blending the edges into the intake manifold (on both the plate and the manifold)

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#2 GeneralDisorder

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Posted 10 March 2010 - 11:34 PM

That's a LOT of carb for a 1.8. It's designed to fuel a 5.1 - can you even jet it small enough for the EA81? I would think the flow charactaristics of the massive venturi's would require more CFM to operate properly. I should think it will have problem with progression from idle to mains.

It will be interesting to see if that works - do you have much experience with that model carb? What made you choose it over something more appropriately sized like the 5200 series Holley (Weber DFV copy)?.

GD

#3 Splinter

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Posted 10 March 2010 - 11:55 PM

A customer of ours who builds ea81 powered planes says I probably won't even have to rejet it. I don't understand why this is myself, as I don't have a ton of experience with carbs, but according to him it's the one to use if you're on a budget.

Picked up a rebuilt one for 30 bucks, if worse comes to worse, I can resell it and try something else :)

#4 dragonfire

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Posted 11 March 2010 - 12:50 AM

i as well am instrested to see if this works. i agree with GD. i have alot of exsperience with holley and edelbrock set ups. but old cars and truck 50's - 70's stuff. i had the simular carb on a FE block 390 ford F-100. you jet it higher alot easier. than going smaller. between metering blocks and jets just might be able to pull it off.

but i have seen stranger set ups on modified vw bugs and squre backs and rx 7 rotary engines as well. so look forward to hearing what happens. good luck always nice to know if there is another way doing things.

Edited by dragonfire, 11 March 2010 - 10:48 PM.


#5 VaporTrail

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Posted 11 March 2010 - 09:20 AM

it depends on how you plan on driving it...

at WCSS7, I had my Brat there with a built EA81.
I used a weber adapter plate with 2 half inch spacers, then a slightly modified 2->4 bbl adapter plate.
I was running a vac secondary Holley 600 CFM carb. (don't recall the exact model). I had to adjsut the idle circuit down, and learn to drive a bit differently off idle, but it was a freaking blast in the gravel/water pit.

2nd gear, low range. it was happiest above 2000 rpms...

I eventually went back to the weber because for slow trail running, it was less than ideal, but did work....

#6 GeneralDisorder

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Posted 11 March 2010 - 11:06 AM

Airplane engines run at mostly a constant speed so the acceleration characteristics of the carb are not as important. If you can jet it small enough it will idle - and you may be able to jet it for constant speed on both the mains. I just have a feeling it won't progress from idle to main very easily as the vacuum signal required by a large carb is generally expected to be similarly large. It relates to airflow across the venturi's - until enough airflow is present the main venturi's simply will not pull fuel. This causes you to have to open the primary throttle plate farther with a smaller engine and you now have a problem - the idle jet that you downsized to get a decent idle now can't cover up the dead spot just off idle and the primary can't pull fuel - what you get is a huge bog when you floor it from an idle - something airplane's never do since they just slowely increase the throttle speed via a lever.

If I were going to try a very large carb I would probably try something like the Quadrajet - since the mains are very small it would progress easily. Don't know if you could get the manholes to run right, but maybe..... :confused:

GD

#7 VaporTrail

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Posted 11 March 2010 - 01:33 PM

Airplane engines run at mostly a constant speed so the acceleration characteristics of the carb are not as important. If you can jet it small enough it will idle - and you may be able to jet it for constant speed on both the mains. I just have a feeling it won't progress from idle to main very easily as the vacuum signal required by a large carb is generally expected to be similarly large. It relates to airflow across the venturi's - until enough airflow is present the main venturi's simply will not pull fuel. This causes you to have to open the primary throttle plate farther with a smaller engine and you now have a problem - the idle jet that you downsized to get a decent idle now can't cover up the dead spot just off idle and the primary can't pull fuel - what you get is a huge bog when you floor it from an idle - something airplane's never do since they just slowely increase the throttle speed via a lever.

If I were going to try a very large carb I would probably try something like the Quadrajet - since the mains are very small it would progress easily. Don't know if you could get the manholes to run right, but maybe..... :confused:

GD


exactly what happened with mine... but it was easy enough to drive around it... it will work, but drivability i decreased.... why I went back to weber.... I eventually got to the pont, where because of all the mods I had done to make it a bette offroader (whichit was), it was not as much fun to daily drive it in town traffic....

#8 Ricearu

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Posted 11 March 2010 - 01:56 PM

old 2bbl motorcrafts work well on ea81's :lol: seen it myself, the guy made the adapter plate from 1/2" aluminum with a drill and a rat tail file. Worked DAMN good :banana:

that thing will suck, both figuratively (and literally "gas")

#9 Splinter

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Posted 11 March 2010 - 02:20 PM

exactly what happened with mine... but it was easy enough to drive around it... it will work, but drivability i decreased.... why I went back to weber.... I eventually got to the pont, where because of all the mods I had done to make it a bette offroader (whichit was), it was not as much fun to daily drive it in town traffic....


see ours isnt a dd, its for camping and mild offroading, etc

we both have other cars

#10 GeneralDisorder

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Posted 11 March 2010 - 02:41 PM

see ours isnt a dd, its for camping and mild offroading, etc

we both have other cars


The problem is that with "mild off-roading" and camping, etc - you want to go SLOW. A carb that doesn't progress from idle to main properly will be a huge pain in the butt to drive like that. If you are getting rowdy in the mud-pit at 3,000 to 5,000 RPM it will be fine. But slow crawling in 1st and 2nd..... not a chance.

Personally - I've done a LOT of carb work and read a ton on theory of operation. I've also fitted more Weber's to EA81's/EA82's than most other members on this board. I've even jetted them using a wide-band O2, blown through them with turbo-chargers, etc. From my experience, that 318 Holley is just too big for the EA81. It can neither use the flow that such a carb is capable of, nor will it be easy to setup as all it's vacuum signal passages and such are designed to work around the airflow capabilities of a much larger (over 2x) engine.

For the budget minded, the carb to use is the Holley/Weber 5200 series. It was a factory carb on Ford Pinto's among other things. It's a licensed copy of the Weber DFV which is a very similar carb to the DGV that is commonly used. As such it uses the same adaptor plate's that the DGV uses and can be bought from any Redline dealer for less than $40. They are cheap used, cheap to rebuild, use the same Weber jets as the DGV, and the same adaptor plate. Typically one can be bought, rebuilt, rejetted, and installed for around $150 to $200 if you are careful.

GD

#11 Qman

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Posted 11 March 2010 - 02:56 PM

Damn, quit beating him up unless it doesn't work. No one has tried this carb before so it may just work.

#12 GeneralDisorder

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Posted 11 March 2010 - 03:13 PM

Point taken - not trying to beat the guy up. I just don't want to see him throw money and especially his time to adapt it away on a bill of goods that won't do what he wants or needs.

GD

#13 Qman

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Posted 11 March 2010 - 03:14 PM

Point taken - not trying to beat the guy up. I just don't want to see him throw money and especially his time to adapt it away on a bill of goods that won't do what he wants or needs.

GD


Have you seen Steve's other endevours? He is not afraid to try different things!

#14 GeneralDisorder

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Posted 11 March 2010 - 03:28 PM

Have you seen Steve's other endevours? He is not afraid to try different things!


I don't beleive I have had the pleasure - I don't recognize the user name but then I'm terrible with names in general :rolleyes:.

Different is good - maybe it will work. Ultimately it depends on the venturi size/design and how sensitive it is on that carb. It could indeed turn out to work better than I expect. I mentioned the Quadrajet (and probably the Dualjet as well) for example as it's tiny mains and double-venturi's make it very sensitive to progression vacuum signals and thus it rarely has a problem with off-idle bog like other design's.

I will say that if you don't have much experience tuning carbs - especially since this is likely going to require jetting changes that can get expensive if you don't know which way to go with your changes and all you have is your butt and your ear to tune with....... get or borrow a wide-band O2 sensor. It will make tuning ANY carb easier.

GD

#15 Splinter

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Posted 11 March 2010 - 04:18 PM

I currently have a 6 speed SVX and a 98 RS with 05 STI running gear down to the hubs, both put together in my back yard :P

I'm not afraid to dive in and experiment

Ultimately, I'm done spending money on the carb; I have access to enough parts to get it running, now it's all just time. And as far as I'm concerned, when you're playing with building custom car parts, there's no such thing as wasting time. As long as you've learned something from the experience, it's time well spent.

If this carb doesn't work out, when I replace it I'll have learned a ton about setting up carbs.

#16 GeneralDisorder

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Posted 11 March 2010 - 05:57 PM

Excelent - you should do fine then.

Carbs are a whole different world though - lots of black magic and voodoo. It's not anything like bolting a bunch of parts together. Things don't play well with each other unlike the digital world of fuel injection, and you can't simply test something with a multi-meter or an o-scope. Sometimes you have to slaughter a chicken and read the entrails.

GD

#17 Twitch de la Brat

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Posted 11 March 2010 - 10:41 PM

Excelent - you should do fine then.

Carbs are a whole different world though - lots of black magic and voodoo. It's not anything like bolting a bunch of parts together. Things don't play well with each other unlike the digital world of fuel injection, and you can't simply test something with a multi-meter or an o-scope. Sometimes you have to slaughter a chicken and read the entrails.

GD


That's a good way to put it. :rolleyes:

Carbs need lots of attention and you need to have a ton of patience, with a
long fuse.
Just keep in mind, that with that big of a carb, you'll be seriously fighting
flooding the engine and, as was mentioned, transition from idle to throttle may
be touchy and difficult to get right.

Twitch

#18 Splinter

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Posted 22 April 2010 - 11:06 PM

After a lot of screwing around trying to make a good adapter plate for the big carb... I said screw it. My buddy had a spare 32/36 (actually the carter version, mirror image, but no big deal)

Bought an adapter, hooked it up, fire it up today. Runs... not properly, but just needs some fiddling at this point.

Unfortunately... the effing gas tank still leaks. Apparently I didnt quite cover all the holes. So it's either pull it and slap some more fiberglass on it, or try to mount a fuel cell, which I'd really rather not do. Bah.

For now I might see if I can just use some Seal-All to patch the two small pinholes left to get it through inspection so that's finally taken care of.

#19 Splinter

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Posted 23 April 2010 - 03:22 PM

Got it to idle fairly decently :D

It's got the mechanical throttle linkage on it, anyone know if I can pull that off and put the cable... pulley thing off the hitachi on?

#20 GeneralDisorder

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Posted 23 April 2010 - 05:04 PM

The throttle wheel off the Hitachi works well on the Weber. That's all I ever use.

GD

#21 swampbrat

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Posted 23 April 2010 - 05:17 PM

If the gas tank off a 91 4wd wagon will work - you are welcome to it. Just be some shipping costs unless you can swing by page arizona sometime.:rolleyes:

#22 Splinter

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Posted 23 April 2010 - 05:46 PM

If the gas tank off a 91 4wd wagon will work - you are welcome to it. Just be some shipping costs unless you can swing by page arizona sometime.:rolleyes:


I don't think it would work, those are fuel injected aren't they?

I appreciate the offer, but shipping would be prohibitively expensive :(

#23 GeneralDisorder

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Posted 23 April 2010 - 05:53 PM

It has to be an EA81 tank. EA82 tanks will not fit.

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#24 Splinter

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Posted 08 June 2010 - 03:29 PM

So we have it running pretty well with the weber now, but no gas tank. Just running out of a jerry can atm. (not driving it like that, of course.)

I tried to fiberglass the tank, and it still leaked. I guess when the fiberglass sets it gets hot and metal and fiberglass expand at different rates so it sets with a gap, which fills with gas and then it slowly eats away at the resin. Yargh.

Can't get a good tank anywhere around here, the holes are too big to plug with tank sealer, so it came down to cutting out the bottom of the tank and welding new metal in. Shops want way too much money to do this, so I'm doing it myself. This can be VERY, VERY, VERY dangerous. I've been as safe about it as I can be.

First I pulled the tank and drained it, then submerged it in water (built a pool out of cinderblocks and a tarp). I put in some strong cleaner, and used an air regulator and compressed air to slowly bubble air through the tank while it was underwater to agitate it. Took it out after a day, dried it, then left it out in the sun with a shop vac blowing through it for several hours.

Then I took it to a tank specialty shop, he stuck a torch in it, told me it was perfectly safe to weld. Still didn't believe him.

So, I plugged up all the lines, filled it to the brim with water until it was leaking out the rust holes, and used a hole saw to cut holes all over the area I wanted to remove. Used these to get some tinsnips in and cut out the whole section.

Now I've got it back out in the sun, wide open, to evaporate any more gas. Tomorrow I'll put a torch in it, heat up all the seams to make sure anything left is gone. I might be being totally over cautious, but I like not blowing myself up.

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#25 bheinen74

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Posted 08 June 2010 - 03:39 PM

wow, never seen a gas tank in the manner like that....:)
thats a lot of work. hats off to your determination.
i've come across new replacement tanks on ebay...pretty cheap, never used one of them -they could be junk for all i know

Edited by bheinen74, 08 June 2010 - 03:41 PM.





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