Custom, Performance Carb Intake Manifolds ( 2bbl / 4bbl )

[HondaBoy]

yes, but it should be. many of the things from carbs still apply to fuel injection. as way of routing your intake to its best ability i guess. anyway, i dont think carbs will ever die out. not soon anyway. ah, you have your good and bad points on either carb or fi. so its all prefurence i guess. i dunno, its fun to tinker with carbs. you can only go so far with fi. fi doesnt take as much skill now days, but then i does, ya know. dont know what i'll do if i do the B20 swap, then i'll have to do the fi thing. that's kinda what i'm getting my money together to do instead of fixing up the A20. ah, i dont know, probley not too soon though.

[A20A1]

I was so worried the shaft wasn't going to be drilled straight... I used the base of the keihin and clamped it to the adapter... then drilled thru a smaller hole in the keihin to act as a pilot and drilled straight on thru the base and the adapter...

Starting the next hole will be tricky since it's lower then the one I drilled so there will be less surface for the gasket to seal with.

[Mike's89AccordLX]

Mike when you you put it all together get a tube of this sealant called Hylamar. It's a blue colored sealant and I used that on every gasket surface when I put my custom intake manifold on with the car and to the head. It will make sure there won't be any leaks and the stuff is an anarobic sealant so it never drys or gets solid so it will keep it sealed up.

-Mike

[A20A1]

Right now it seems like I'll have to fill in the bolt holes after I get the manifold peiced together... there just isn't enough meat left around the edges.

I was thinking I could put down some quick steel to act as a mold then lay over alumaloy. This will cover the big gaps on the left and right side of the manifold as well as help form a new plenum that will help direct fuel around the sharp bend... as it is right now the primaries are placed closer to the valve cover... which means fuel will have to travel back towards the firewall then make the turn towards the cylinders. I want to fill in some areas so that fuel will ramp down from the primary barrel because of a taper I will add in the plenum... and the fuel will end up colser to where the secondary barrel is... this will mean the fuel will have to make less of a turn. I need my special engraving bit to help roughen up the smooth surface of the alumaloy some... then run over a some sand paper to get rid of the sharp burrs.

[Civvy]

Nice work mike! Wonder if i should try that RX7 carb on my B20 afterall! Anybody know if the ignition is controlled by PGM-Fi?? I want to try disconnecting the injectors and installing the carb and mani. but, will the ignition still work??

[A20A1]

can you use a B18 distributor and ECU? or just Distributor... the accord DOHC carbed B18... I think...

[Oldblueaccord]

If you get something you can use I can make you up a better spacer. Aluminium is easy machinng. I think I have one of those spacers in the shop it looks fimiliar.

Not to push but if your making 8 -10" of vacuum you want a very adjustable carb like a Holley. I really think that model 2300 is a great carb plus it takes all the special Holley stuff they make and 2 barrels are simpler carbs then 4 barrels.

You might want to modify the mechanical advance in your distributor. Most of the time you want more advance sooner just off idle. Domestic cars you can fool with the springs and weld up the slots on the plate inside the distrbutor to get the advance in sooner with out having to bump up the static timing so far it wont start hot. It really helps give you alot more vacuum which means a better carb signal which means a better running carb.

wp

[A20A1]

I have a stock cam so if it runs like poop I'll swap out my race cam.

[A20A1]

Look at the first post, I added more pics.

[doug]

i'm using 40DCOE 136's... i've got the DCOE flange, CNC in aluminum... and it's not a big deal for me to finish cutting down a head side flange... i am having trouble finding the proper piping, though... i don't plan on supporting it with anything from the bottom, so it needs to be pretty hefty...

i think the cabs they are wanting to use are in the upper range of being good matches... some of the carbs that have been brought up are way too much for a 2 litre motor, unless they go with forced induction... that's why my choice is in the DCOE carb... tunability... too much fuel? whoopdee doo... change the jets, chokes, and/or venturies and you have a carb that behaves totally different...

that's my $.02

vanilla, don't know if you have heard of these guys but check out the wbsite, andy mentioned them I think for one of his projects, if not andy then another member that was planning to do a manifold, I think they used 2" tube with 3/8
thickness but not sure. the site gives you alot of good choices. good luck. doug\\

http://www.onlinemetals.com/

[A20A1]

I think I'll stick with that vacuum secondary Quadrajet... I was reading up on manifolds and carbs and what not and although they didn't specify progressive vs synchonous, it was said that having a vacuum secondary overcomes some issure when having one cylinder fed by 2 barrels... I assume thats why they convert DGV carbs to vacuum secondary when preping them for turbo.
Now 1 cylinder per 2 barrels isn't completely true in my case cause there are 2 cylinders paired with 2 barrels... but still... I have my doubts at how effective the lower rpms will be.

----------

I went to borders and almost bought the three books I listed in the Turbo FAQ.
Maximum boost was the best of the three but a bit biased concersing carb/turbo althought it made some good points.
What I got from it was that the major problem concerning draw thru was heat... heat is needed to keep from icing and heat isn't taken away bacause there is no intercooler. Pull thru the problem is with Fuel and pressure, how to enrich the mixture and how to pressurise the carb and fuel and keep a safe relation between the two.
the end performance result with the pull thru is how well you manage heat without detonation
the end performance result with the blow thru is how wll you manage fuel without detonation
Both fall short to EFI in that they have restrictions in the form of the carb venturies and may have gaps in the fuel curve that lose power. Also added problems like fuel slosh. Still carb turbo is nastalgic and seemingly worth the effort... but I'm going N/A at the moment.

BOOKS ON TURBOCHARGING
Supercharging, Turbocharging and Nitrous Oxide Performance
By: Earl Davis, Diane Davis


Maximum Boost: Designing, Testing, and Installing Turbocharger Systems
By: Corky Bell


Turbochargers
By: Hugh MacInnes

I was also looking into TBI 4BBL injection for turbo apps. I don't think I'd go port injection cause I might as well do a B-series DCOE injection manifold swap. :P

[carotman]

Civvy, the Euro B20A Has a vacuum advance ignition even if it is EFI (which is pure crap I think)

You can use a carb setup with that kind of distributor. However since it already has the EFI setup, I wouls stick with that.

[rjudgey]

Nice work and research!! thumbs up!!

Just a thought but i presume you are doing all this just to be different from all of us who have DCOE's?
If so fully understand i'm working on a new project that uses a DCOE manifold but has seperate adapters that fit DCOE flange that actually pairs up two bike carbs then i can fit 4 bike carbs onto any twin DCOE inlet manifold, this has one of a few advantages that are better than DCOE's, angle is not as critical, bike carbs are also bigger 38-42mm maybe bigger on something really nasty, internals of bike carbs are a lot less complicated then DCOE's or other carbs so they flow more fuel and air and apparantly they produce much smoother low end power. Found a company in the U.K that had been making up manifolds and using Bike carbs on race cars for the last ten years!! Also may be easier to Turbo as well but not sure on that 100%
What do you think!! P.S if anyone copies me i'll send my ninjas round to sort you out ;0)
check out my cardomain site last page has pics of my new head and custom made inlet manifold,made it extra short as every other manifold i've seen has really long runners thought it would be interesting to see what effect it would have, normally most engine people would say i would loose torque and gain more Bhp be interesting to see if this rule of thumb is correct, my other manifold is really long and i also have long trumpets on as well!! so short manifold and short trumpets next!! Also it's a EURO ET1 2G accord head which i think is one of the best Honda designed early heads almost as nice as the D15 heads just wish we had the same exhaust port layout looks so much neater having them paired up not too mention being better for thermal heat retention and for making manifolds up!!
http://www.cardomain.com/memberpage/281725/8
In the process of building this one up at the mo!! It's based on a ET block thats been recently re-bored to 82.75mm, rods are stress relieved and polished, oil holes moddified, lighter piston pins, sealed power pistons, hastings oversize rings to fill up the extra 0.5mm gap in bore size, crank balanced, polished and oil holes chamfered, flywheel will be CM ally integra job, with AP pressure plate and ACT 6 puck disk, ACL bearings all round by far the best engine bearings in the world!! But still need to get my arse into gear and get my car to a new exhaust specialist i found other side of London who makes exhausts for Touring cars he can make me up a 4-2-1 with extra long primaries as well as big bore size, running straight into 2.5" system my current system which has 2.25" bore size but the cast manifold is still be using although heavily flowed and ported, but the custom downpipe i had made the numb nut cheaped out on me and only used 2" main pipe and joint then it goes 2.25" so i'm 100% sure it's bottlenecking as before it used to put so much back pressure on the older system that it would break off the silencers of the main pipes, and it's just done the same to the new stainless steel system on at the moment!! So i think it's time for a bigger setup again!! I'll put the 2"-2.25" system on my B20 and see if that makes it run any better!!

[Civvy]

They're different, i had to ditch my EX exhaust and it was new.
Cant remember if the centre pipe didnt reach the downpipe or visa vrsa, the manifold and downpipe are impessive for stock spec.

[my86dx4dr]

ok we have 2 differnt mike's that talk about a carburator like a nerd with a pentium 5 computer...


its all good

[rjudgey]

well someones got to!! If only i could get my Pentium 4 2.4 ghz running at 4ghz with a FSB of 1066mhz with dual DDR 4500 ram then i'd be a happier bunny ;0) but i suppose 3.2ghz aint bad using a big heatsink and fan!!

[A20A1]

Say what?

[Cant Stop]

i sent a pm today, however have you finished this project?, has anyone else continued on?

i am currently working on a mod to use the kei hin dual carb setup should be done end of june.

[lostforawhile]

if you want a dual webber try pierce manifolds 18008743728 last time i checked thay made a dual webber set up and manifold for our cars it was like 1500 bucks but they make one

[A20A1]

I though it was for the A18, which had different ports then the A20.

Also there are B16 B18C5 manifolds but they don't take into account the 15* tilt that our motor sits at, so if we used their manifold we'd have carbs pointing up into the hood and they wont run right.

[Cant Stop]

i guess i just need to wack a intake like the pic at the beginning of this post and weld the lude mounting plate to it(carb side that is)

[accord upset]

cfm recommendation & cid to liter translator
http://www.carburetion.com/calc.asp
check this out guys is does it seem like they calculate the cfm a lil bit low for our engines or is it just me. i mean how many of us have a 10000 rpm full race motors that would give us the sugessted cfm for the 32/36 webber(rated at 300cfm??) or worse the cfm for the 38/38 weber. i dono im just asking what u guys think. i found this stuff while looking for an adapter plate for my new 38/38 :-( uh oh still dono if it'll work i hopes so

[MessyHonda]

yeah i have an automatic so my redline is according to my trany...it always shifts at 5800RPM so i need 169CFM....all i have is the K&N filter that should supply that already

[87AccordLXsdn]

My car is still running like shit and I need some help. Does anyone have some specs of what all the vacuum lines should be pullin in?

[A20A1]

The 38 will work.
I would say you could run twice the CFM that that calculator puts out on a single plenum manifold, so about 400 CFM

It's not just CFM but how much vacuum the carburetor sees at Wide Open Throttle.
As long as there is enough restriction in the carburetor to create a pressure drop, the carburetor will work, and you'll get the added bonus of the extra air flow.

You divide the cylinders and remove the plenum and the vacuum to the carb is even stronger which is why I think 45 DCOE's are able to work. Each barrel is about 220 CFM. That’s like having a single 880 CFM carb feeding all 4 cylinders. But when you have a single 880 CFM carb feeding all 4 cylinders not all cylinders fire at once... so the lower the rpm you have the less demand there is and the less pressure drop is going to be created.

A single 45 DCOE or even a single 50 DCOE will work on our car flowing 400 + CFM, greater then a 38 weber, but the performance from something like that will be determined by how and if you divide the cylinders into pairs.

When I was considering 4bbls

390 CFM 4bbl converted to 2bbl flow rating is 551.5 CFM

500 CFM 4bbl converted to 2bbl flow rating is 707.0 CFM
...go back to what I said about the 880 CFM...
The 500 CFM 4bbl is still below 880 CFM so it should still work at WOT in the higher RPMs. But below that you might have some trouble.

The 390 CFM 4bbl @ 551.5 CFM is closer to 400 CFM and would run better in the low range then the 500 4bbl and once you reach WOT the carb can still put out.

Also consider that 4bbls are not flowing the full CFM all at once. They use primaries and secondaries... so that the primaries see most of the engine demand when the demand is low and as the demand increases the secondaries open up.

As a side note small primaries are good for gas milage but not that good for performance... really you want a primary that is large and the secondaries to be the same size or larger.

That’s why SU variable venturies are nice. They maintain a pressure drop but open to increase air flow when the demand is there.