single 45 DCOE on a Lynx mani, about to throw in the towel!

[inquisitive]

I am running a single 45 DCOE on a Lynx manifold and I am thinking this is more of a tinker toy than I want/need(?) to deal with. 

 

No one in the Bay Area wants to touch it and every shop I spoke with just tells me "it's an old school setup" and that I'm better off going with a 38/38 or dual sidedrafts for ease tuning and/or performance gain. 

 

The carb setup is attached to a fresh (5kish miles) M10 with a port n polished E12 head, 9.6:1 comp and 288 cam. It has also been bored out to 2100cc's. The car runs like absolute crap right now and I am tired of messing with it. 

 

Would a 38/38 be "enough" carb for this setup? I regularly partake in spirited drives and plan on taking this car on several vintage rallies. 

 

At this point, I'm fine sacrificing aesthetics and sound for a nice reliable setup, but not keen on killing performance. 

 

I just want to enjoy my damn car already! 

 

 

EDIT: Open to paying a savvy person to tune this thing as well. I'll be wiring up the wideband this week to get a sense of what is going on, but I've got almost no time to mess with it in the next few weeks so...

Edited June 20, 2017 by inquisitive

[kbmb02]

I believe a 38/38 is enough; for example, here's one, on a 12.5:1 C/R engine with a 304 camshaft.

(my apologies for posting this in duplication ...sometimes video demonstrates more than a signature line). -KB

 

 

[bitbckt]

I don't have a lot of experience with carb'd BMWs (only Porsches). That said, you want to start with the size of the venturi (Weber calls them "chokes") you're using in the 45, rather than the size of the throttle body. With some back of the envelope math, you probably want to be using about a 36mm venturi on a 2100cc 4 cyl. @ ~6-6.5k RPM. Maybe a 38.

 

The 38/38 doesn't have interchangable venturis - one less thing to think about, but also one less thing to fine tune. It's probably plenty of carb (kbmb02's cars all seemed to run fine on them at Sonoma ), but you've already got a 45 in-hand.

[Tommy]

I agree with Ken but it should also work with the Lynx and your 45. The single DCOE setup should be less tinkering than duals because you don't need to worry about sync. You just should get the basic tune right. I can't remember any values but I remember my dynoguy say that the emulsion tubes were somewhat special and after they were right it worked really well.

[Tommy]

Yes 36mm choke should be right for street tune.

[2002Scoob]

Do you have a wide-band? It might just be you're running rich (or lean). Getting my Jetting right (or having a guru get it right) made all the difference in my DCOE setup. So smooth.

[zinz]

3 hours ago, kbmb02 said:

my apologies for posting this in duplication ...sometimes video demonstrates more than a signature line). -KB

 

I'm glad you reposted this, Ken. It always brings a stupid grin to my face 

 

The single 45DCOE and Lynx should not be so difficult to tune! It's already on the car, so all it needs is to be jetted properly...and get the ignition timing correct. 

 

You say it runs like crap...what is not satisfactory about it? Do you know what jets the carb currently has? This is a simple, 5 minute exercise to remove and inspect them. Is the carb new/freshly rebuilt?

 

Post a picture of your setup and what air filter you are running. You don't need to pay someone to tune this, that's what FAQ is for!

 

Ed Z

[Stevenc22]

38/38 is more than capable of making the power you want without alot of tuning problems.

 

However i agree. You have the single 45, might as well try and fix it.

 

Start with your distributor. Which distributor do you have? You likely have no vacuum pickup and if you still have a vacuum distributor, the car will run like crap since there is no real advance curve. This just happened to me. Got my car back with a fresh motor, dual side draft 40's and the shop left my old vacuum distributor in there. Car ran pretty bad until i changed distributor to a 123.

 

Then wire up that air fuel gauge and see how where you are A/F wise. 

 

 

 

[pompei426]

I'd agree with others, a single 45 should be just fine with some tuning. But, if you decide to go a different route, a 38/38 is more than capable of handling a slightly modified m10.

[airborne85]

Joey at Performance Options can dial your carb in

 

Performance Options
1009 7th Street
Oakland, CA 94607

Telephone Number:
510.272.9869

 

ira

[inquisitive]

Thanks for all the replies. 

 

Here's where I'm at : 

 

When I picked the car up a month ago, this is what I knew was in the carb: 

 

36mm Venturis

155 main jets

65 F8 idle jets

 

Unsure of emulsion tubes and air correction jets

 

The car ran "OK" albeit smelled super rich and lacked power up top, where I expected it to "open up." There was also a stutter right at 4k and 5k. Ran very nice at partial throttle and would go "flat" at WOT. 

 

I took the car to the only local shop who was willing to work on it and although the head mechanic is very 02 savvy, he has limited experience with modified 02's and had never worked on a sidedraft/lynx setup. He adjusted the valves to .007" per TEP's recommendation and set the timing to 34 deg at 3000 rpm. 

 

The car barely ran any better. The stutter up top was gone, but the gas fumes seemed to have gotten even worse. 

 

Here's what he put in the carb: 

 

32mm venturis

140 main jets 

70 F8 idle jet 

1.70 air correction jets

32 F15 emulsion tubes 

 

I think it's time to order up an array of jets and go to town with this thing for a day with the wideband wired up. The crappy thing is, that day is eluding me. I'm extra busy these days and I am at the point where I would rather just pay someone who knows what they are doing to get it right for me. 

 

Also, Performance Options is no longer in business. Perhaps there is a way to contact Joe directly?

 

 

 

[airborne85]

wow...that's news...they were tops

 

i sent you a pm with joey's #

[bitbckt]

That 36 seemed right for your engine - sounds like others around here feel the same. 32 is very small for a 45 DCOE.

[eurotrash]

Some suggestions:

Stick with the side draft set up you have.. 

Get in touch with Jeff Chang.  He bought Todd21's blue car that had a screaming single side draft motor.  you may be able to get the jetting info from Jeff.

Or.. Try Le Tran, he's in Ontario, CA.  He may have experience with that kit. 

Get your wide band in, it tells you volumes..Not having it is like having paper and no pen.  A smoke and no lighter..  

or try this one  (CLICK HERE).. its great when installed into the dash pod.  Very discrete.    

and any motor worth its build $ is worthy of a 123 ignition distributor.  Consider it.  

[TobyB]

A question- does the Lynx split 1&4, 2&3, or is it common plenum?

I can't tell from search/pix.

 

t