40 replies to this topic

[EA HOMIE]

Hahaha mine actually says 12. Didn't open it up yet. Ill make sure to count and see how many it has.

Wait, something was just came to my attention...



Did you guys here read that it has 12 valves or did you actually count?

[othrpinkthng]

On models sold in the US w/carbs they came with either 2 intake valves/ 1 exhaust valve or the more conventional single intake and exhaust valve layout, according to model and year of manufacture.

AKAIK the standard or DX model had the 12 valve setup, and the HF model had the single intake/exhaust.

[GeezRX]

Well, my '86 USDM DX definitely "SAYS" 12 valve on the valve cover but in the numerous times that the valve cover has been off in the last 4 months worth of work it has always had 2 intake valves, 1 exhaust valve and 1 auxiliary CVCC valve PER cylinder which to my math equals 16 valves total...but hey if Honda chooses to call it 12 valves...By the way it is bone factory stock.

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[EA HOMIE]

question: if my head is a 16 valves, can i just get a si head and it will bolt on no problem?

Wait, something was just came to my attention...



Did you guys here read that it has 12 valves or did you actually count?

[EuphoricBlue]

question: if my head is a 16 valves, can i just get a si head and it will bolt on no problem?

Yes, the head will bolt on.

You will need to either swap over the cam from the carbed head for the mechanical fuel pump lobe, or you will need an electrical fuel pump (I would use an electric pump instead of swapping cams).
You will also need to change carbs/intake manifolds since you would be eliminating the CVCC.

[EA HOMIE]

soo i just finished taking off the valve cover and sure enough i have 16 valves.
wat kind of manifold do i need to get? can i use the one of the si?

Yes, the head will bolt on.

You will need to either swap over the cam from the carbed head for the mechanical fuel pump lobe, or you will need an electrical fuel pump (I would use an electric pump instead of swapping cams).
You will also need to change carbs/intake manifolds since you would be eliminating the CVCC.

[EuphoricBlue]

soo i just finished taking off the valve cover and sure enough i have 16 valves.
wat kind of manifold do i need to get? can i use the one of the si?

You would need to get what ever manifold works with the carb you're gonna get. "Easiest" is a CDM manifold and CDM carb. But you are probably looking at about 100 for parts and 50 for shipping. And there is no guarantee the parts are working unless the person pulls them from a running car.

Another, fairly complex, option would be to go with bike carbs, but you'd need to jet those to match the engine. But, with bike carbs you won't ever need to worry about them not flowing enough air.

[EA HOMIE]

Soo I'm going to go with the weber carb. Do u know of any manifold that would work with the si head and the weber carb? If not, I would have to make a custom one, right?

You would need to get what ever manifold works with the carb you're gonna get. "Easiest" is a CDM manifold and CDM carb. But you are probably looking at about 100 for parts and 50 for shipping. And there is no guarantee the parts are working unless the person pulls them from a running car.

Another, fairly complex, option would be to go with bike carbs, but you'd need to jet those to match the engine. But, with bike carbs you won't ever need to worry about them not flowing enough air.

[EuphoricBlue]

I think originally Webber made adapter plates to mount their carbs on our cars.

I've never worked with Webbers so I don't know what is involved with getting them to work on our cars.

[EA HOMIE]

does the si head and dx head have the same manifold housing? cause weber does have the adapter for are cars and i have no clue where i can get a manifold. soo is it possible to use the dx one on the si?

by the way i wanna say thanks too all of u for the help.

I think originally Webber made adapter plates to mount their carbs on our cars.

I've never worked with Webbers so I don't know what is involved with getting them to work on our cars.

[EuphoricBlue]

No, the DX DCM VS USDM VS Si are all different.

But if you are lucky the addapter plate works with the USDM DX manifold and blocks the SVCC port. I just don't know anything about the Webber carbs/addapters to be able to say anything for sure


The only thing I CAN say for sure is that you can not run a webber on an SI manifold. The SI manifold has that horisontal tube that all 4 cylinder runners connect to that the throttle body mounts to.
If you take a look at a typical FI engine you'll see the "pipe"/tube I am talking about, it usually runs parallel with the engine.

[EA HOMIE]

soo wat i can do is make a custom manifold right?

quote name='EuphoricBlue' date='Jul 11 2009, 03:24 AM' post='451940']
No, the DX DCM VS USDM VS Si are all different.

But if you are lucky the addapter plate works with the USDM DX manifold and blocks the SVCC port. I just don't know anything about the Webber carbs/addapters to be able to say anything for sure


The only thing I CAN say for sure is that you can not run a webber on an SI manifold. The SI manifold has that horisontal tube that all 4 cylinder runners connect to that the throttle body mounts to.
If you take a look at a typical FI engine you'll see the "pipe"/tube I am talking about, it usually runs parallel with the engine.
[/quote]

[86rustbox]

soo wat i can do is make a custom manifold right?

quote name='EuphoricBlue' date='Jul 11 2009, 03:24 AM' post='451940']
No, the DX DCM VS USDM VS Si are all different.

But if you are lucky the addapter plate works with the USDM DX manifold and blocks the SVCC port. I just don't know anything about the Webber carbs/addapters to be able to say anything for sure


The only thing I CAN say for sure is that you can not run a webber on an SI manifold. The SI manifold has that horisontal tube that all 4 cylinder runners connect to that the throttle body mounts to.
If you take a look at a typical FI engine you'll see the "pipe"/tube I am talking about, it usually runs parallel with the engine.

i don't believe a custom manifold needs to be made. from talking to zakats and a couple other members i've learned you can run a stock USDM carb and manifold on an SI head. this sounds like it won't work since the 3rd barrel on the USDM carb/mani will lead to...nothing. the mani will bolt up just fine and the main ports will line up, but the CVCC ports will be blocked off. BUT...the 3rd barrel does not have a power valve (the thing that shoots the gas into the other barrels when you rev the engine), the fuel is simply drawn into there by the engines vacuum pull. so if there's no vac, there's no fuel to the 3rd and the other two barrels will run the SI head similar to how the CDM carb runs the CDM head.

naturally if you can run the stock DX manifold on the SI head you should be able to throw a weber on there with no problems. same concept: it shouldn't draw into the 3rd barrel if there's no draw.

check out zak's postings in this thread about carbs/manifolds:
http://www.redpepper...e...=44754&st=0

i'm planning on as SI head when i get some dough, but i have to run the stock throttle body for my rallyx class.

[zakats]

thanks for chiming in for me. on your e85 thread, it kinda seems like we're just talking to each other!

let me summarize some info in here to get things organized just in case there is any confusion or whatever...
*ALL SOHC EW'S ARE CALLED 12 VALVES UNLESS NOTED AS 8VALVE (IIRC only hf models)
*ALL non Si USDM cars had CVCC, even the 8 valve engines which were, so to speak, actually 12 valve engines in that they had the 4 cvcc prechamber valves
*Si heads do not have "quench pads" but rather, an uninterrupted, sort of, hemispherical (dodge isn't the only one that can make hemi's) resulting in a much lower compression ratio. This head with the stock DX pistons (cdm and usdm are the same) results in a major drop in compression and isn't recommended.
*USDM DX intake manifolds and carburetors can be used on non cvcc heads successfully as stated above. it is also possible to drill openings holes between the main intake runners and the cvcc ports in order to use the cvcc function of the carburetor and effectively raise the cfm output of the carburetor (slightly but significantly for such a small engine) a gasoline safe epoxy then can help aid the smooth flow by blocking off the opening on the manifold base if so desired though probably not absolutely necessary.


I am currently building an Si engine with brown top integra pistons and, unless I manage to find a cdm carb/manifold, I will rebuild and reuse my usdm set as per the aforementioned plans. OT, I also have a theory about using a small, long bead hone, like used for honing and rebuilding master cylinders, to open up and smooth over the stock intake manifold runners and casting.

[kaymo]

STOP!!!!!


ok guy, before you go running off and buying all these parts they are telling you to get and start mix and matching things together, it is important that you share your GOALS with us.

from your original post i understand you engine was ticking an knocking, and you were rebuilding to fix that. in this case, you will not be really ADDING much performance. you are more bringing the engine back closer to its original condition. you DID however say you were shaving your head, which will increase compression and give a slight increase, but unless you are shaving alot off, this is not enough to really make a huge difference in power or necessity for further air/fuel induction beyond stock.

as euphoricblue pointed out:

There isn't really any power to be made at the carb unless it's restricting flow. In stock configuration they do, which is why you get a noticeable difference when you disable the fuel economy and "automated" devices. After that is done your gains from tweaking the carb become minimal, it's time to open up the head. After the head is opened up then you go back to the carb (Enlarge ports/replace with bigger carb) This is mostly why there isn't a huge difference to be seen between a Webber and a stock carb, on a stock head.

read that, and then go back and read it again. you will not see any noticable gains over a stock carb with a stock head and stock compression ratio.

many of the people here have told you to go get a Canadian carb and intake manifold. their hearts are in the right place, but this not the only way to skin this cat. yes the CDM carb and IM will help eliminate CVCC... but do you really want to eliminate CVCC? do you even know what CVCC is?

the only thing anyone has told you is that CVCC is better for economy, and no CVCC is better for power. but, are you opposed to gas mileage? i dont think anyone here is. how much power do you gain from losing the CVCC? this is something i have yet to hear anyone really tell me.

as a matter of fact i am gonna have to challenge the idea that CVCC is "BAD" for making power. my argument being the EW5. the EW5 motor is a JDM variant of the fuel injected SI motor that had 16 valves, 4 of which were cvcc! IIRC the HP rating of the EW5 was 108... which is the same as the 91 SI engine. thats 17 HP over the american EW engines without CVCC. where does this extra 17 hp come from?

back to what you are trying to do with your car. im going to hazard a guess that this is meant to be a daily driver, and not a track machine. you are rebuilding the engine with factory internals, and slightly shaving the head. in this case, you will gain almost nothing by changing carbs. (CDM or weber) with either you lose CVCC and fuel economy, and change the way your engine runs. if you want an explanation of the CVCC let me know and ill find one for you.

another issue that no one really touches on when doing a CDM carb swap is, what if you have to rebuild it? now you must source a CDM carb gasket set! now you are adding more hassle to your car! and talk about hassle, get a webber! now you have a carb that did not come tuned for your engine! i have not heard of a single webber swapped car that didnt have a DRAMATIC decrease in fuel economy. its hard to go fast when you're out of gas!


im not sayin DONT do it, im just saying KNOW waht you're getting into! a webber is GREAT carb! but without engine mods, and the knowhow to tune it.. you are gonna be in a world of regret.


as captain regular said, your stock carb can be easily modified to be as simple AND as powerful as the CDM carb. there are many writeups on the subject. combined with the darkhand manual secondaries mod, this will really change your carb into a new animal (unless your carb was running REALLY good in factory form, which i have NEVER seen)

the rebuild kit for your factory carb is cheap and easy to do, so if you are unsure of its condition at all i recommend it. this was the first carb i ever rebuilt and it was pretty damn easy.


anyway, before you go purchasing all this stuff, PLEASE put your engine back together and devac your stock carb and try it. it will not cost you anything to try the your old one, and if you feel you need more after that by all means. but just try it before you go spend money on carbs that will gain you almost nothing but more hassle