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Single sidedraft info only

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So hopefully this doesn't spawn into something more than intended... I am hoping this can be a thread just for jetting and tuning info of a single sidedraft carb only... I see the debates about single vs dual and downdraft but none of that matters here. This is for someone who is running or trying to run a single sidedraft only...

Whats your Engine setup

Intake choice

And internals of the carb your running...

And whatever else can be thought of to help....

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Single side draft 48mm mikuni on an L20b, only gets 17mpg buuuuuut, she's fun to drive, swapped to a larger air filter few weeks ago and she gained noticable response on the pedal, can't recall the jetting...I know I had to order bigger jets after initial tunning....

 

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Seriously though, a heat shield and some soft mounts (between the carb and manifold) will help, not just for HP, but for around town driving too.

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Seriously though, a heat shield and some soft mounts (between the carb and manifold) will help, not just for HP, but for around town driving too.

Yes, very important, I made my own heat shield, $30

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Have you tried using the search function? I did and there are multiple post on this. True you have to dig out what you want. This is pinned in the ENGINE forum....  http://community.ratsun.net/topic/27094-weber-dcoe-stock-jetting-information/  ... the links posted do not work now but Radim ( http://community.ratsun.net/user/5068-radim/ ) is still active maybe he could find and re-post the info.

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I have tried searching Mike but to me the info seems more about dual setups... I was just hoping to get real info about single carb setups that people are actually running..

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Seriously though, a heat shield and some soft mounts (between the carb and manifold) will help, not just for HP, but for around town driving too.

  

Yes, very important, I made my own heat shield, $30

x3. Makes all the difference in the world, especially with the short Mikuni manifold I have which puts the carbs right over the exhaust. I made one with stuff I had laying around. Just sheet metal and aluminum band for rigidity. No extra heat barrier stuff necessary. I can touch the bottom of the carbs and they are barely warm. The mechanical fan also helps push hot air away too.
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Yes heat shields are good and worth mentioning but please keep this focused on tuning info specific to the carb setup. Because As Mike said there are multiple posts about sidedrafts and things like heat shields, timing, vacuum hook ups, the pcv system, etc have been debated about in other posts.

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So here's my setup for example

l16 1mm over bored with dome pistons

W53 peanut head, 10.7 to 1 cr,

260-70f Schneider cam,

Header with 2" exhaust

lynx intake, weber 40 dcoe.

4" air filter

32mm chokes

155 main

50 pump jet

55f9 idle jet

180 air jet

F11 emulsion tube

With this setup and while breaking in my motor idle was a little rich but not bad.. really rich in the midrange, and better after 4000rpm....

I also modified my gas tank with a 3/8 pickup tube and put 3/8 fuel lines in with an electric carter p4070 rotary pump.

I plan on ordering the factory weber tuning guide, and some jet to lean the midrange out by around 20% and see how that runs....

This is kind of what I am hoping to see... videos of them running definitely welcome..

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It's very difficult to drive when the fuel is percolating in the accelerator pump chamber and float bowls, not to mention embarrassing. Someone may think they're running too lean if the car is bucking and not responding to throttle, but it's possible the problem is heat soak. I had issues with that, and a heat shield solved it. Lack of air flow can also be an issue.

 

Going off topic again, sorry, but it's something worth mentioning. Could save someone reading this in the future a lot of grief.

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I forgot that I work today, otherwise I would have been able to get some numbers off my jets today

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Shacks510 it's definitely worth mentioning so someone's not miss diagnosing there tuning... if we are gonna mention it let's at least posts some pics and maybe how did you mount it?

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I have dual Mikunis with a Mikuni manifold. I'll save the details for an appropriate thread.

 

F32DD4A5-DA37-4C86-A600-329DAAC5DDA0_zps

 

Manifold has two threaded bosses on the underside.

 

9D6794AC-F11D-44A7-8660-FB76873703C1_zps

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Ahhh now I am getting off topic....

So other than the fact this looks like it cost 5cents to make... how similar is your heat shield....

Screenshot_20170302-092134_zpstlxldvvl.p

 

And has anyone thought of or tried using header wrap on the intake runners.... I know people don't like it on headers but with the intakes being aluminium they shouldn't rot like a header would being wrapped....

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Well thats handy... easy enough setup... I'll have to be a little more creative with my lynx intake....

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I laugh at those Weber heat shields. The big flaw is that they screw onto the carburetor using the screws for the accelerator pump chamber... durr what do you think causes fuel percolation? Heat soak! Carburetors being over the exhaust doesn't help. You need to have an air gap for a heat shield to be effective. Exhaust wrap is more to keep heat in, not block it. People have used that gold foil stuff to block heat.

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Yes heat shields are good and worth mentioning but please keep this focused on tuning info specific to the carb setup. Because As Mike said there are multiple posts about sidedrafts and things like heat shields, timing, vacuum hook ups, the pcv system, etc have been debated about in other posts.

I don't think it's off topic at all to discuss these things, as they are all related. The combination of all these items will change along with a change of induction.

 

I mentioned the heat shield because if heat soak is an issue, it can really confuse the carb jetting.

 

Heat coating on the intake might help too. Jet Hot ceramic coating.

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Good point shacks510... and stroffregen I know it's related and I think the heat shield info is a bit more relevant to this thread but all the other points have been overly discuss in other posts... this post was intended for those who are paying attention and doing the necessary upgrades to make a side draft work already but still need to get the jetting right... a baseline for comparison.... I just didn't want this to become a check you timing post

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Both the heat shield and air filter size will change your tuning, very relevant as it's part of the equation, I found that the thinner air filter was causing a restriction in air flow, since I got the larger filter it runs much better under a load, pedal reaction upgraded dramatically with the larger air filter, spark plugs are a factor too, I run NGK BP5ES during winter/Spring then switch to BP7ES for Summer/Fall since it's hot.

 

20170205_123552.jpg

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I just didn't want this to become a check you timing post

I hear ya.

 

Re - the air cleaner. KoHearts makes an excellent point. If the filter lid is too close to the inlet of the velocity stack, the air flow gets seriously disrupted. It's probably a good idea to do the initial tuning without an air cleaner (but with the velocity stacks) and then make adjustments once the air cleaner has been installed.

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Well this post didn't go to far.... I guess not to many with the single side draft out there.... any how I have a question....

I was wondering willz and KoHeartsGPA do you guys know what your running for timing?.... I think I need to bump up my timing.... I've read in a few articles that the weber dcoe like a little extra timing... i started the motor with the timing on the low side just to get it broken in...

I think right now I am around 12 initial and full around 34...

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Oh ya and also what about fuel preassure... from things I read it ran a carter p4070 with no regulator... seems to be putting out about 6psi.... I think it needs to be around 3.... is anyone running for a regulator?... I was looking at a 1 to 4 psi holley regulator 12-804...

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Timing.....Used 12 as a base and tuned it from there....Shit.... Didn't even check where it landed, no far from 12 though, has been 3 years since and never moved it again, as for fuel pressure, I'm running an Japanese screw-top late (bigger) fuel pump and working perfectly fine, I can get you the name and numbers off of it when I get back home this weekend if you like....

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No I am good with the carter it's brand new but thanks.. i know I to get the pressure down a little I've just heard mixed things about fuel pressure regulators... I've seen a few people reference the holly one I mentioned with Webers and they were happy with it.... I know I am running a bit rich and just wanted to sort a couple things out before I start rejetting....

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