Help a newbie learn to adjust his carb?
Is there a guide/book/document to help a newbie learn how to adjust his carb? I had a track day today, and managed to get *1* lap of the 1st session in.
I was unable to get over 2k RPMs, I could give it more throttle, but that just caused the RPMs to drop.
Distinction, it wasn't cutting out, just being a slug.
Thoughts?
-Chris
Since no one has responded yet, maybe I can help get the ball rolling. First the caveats, my only carb experience is small engines, dirtbikes and a triumph spitfire.
The conditions you are experiencing sound like fuel starvation or like the choke is stuck on. I don't even know if you have a choke, but I would start there. If the choke is stuck on, the carb can't breath well enough to suck enough air/fuel in since the choke forces the main air passage closed to draw increased fuel in. Too much fuel won't combust well when the engine is warm. Sometimes when you back off the engine will stumble back to life and puff out some a little black smoke since you were way overly rich.
The opposite possibility is a float not letting enough fuel in, so that when you stomp on it or ask for a high volume of fuel the carb isn't allowing enough in. That would act more like a rev limiter.
I'll sit back and see if I am way off base here.Good luck.
Webber Carb
Chris,
If you are sure it is the carb. soak it in some carb cleaner to make sure all the passages are open. Check the floats and needle and seat. if you don't feel like you know enough to do that or to get a carb rebuild kit from Moses and rebuild the carb, you are only about 150 miles from Darrell Drummond. I will bet if you called him, you could set up a time to go up and let him show you the basics and get it running. Once it is running right, be sure to turn the fuel pump off and let it run the fuel out of the carb each time to stop the engine. That will keep you from having carb problems in the future. Also, once you get it right, about all you need to do to "tune" the carb is to change the air and fuel jets based on Altitude and Temp. The way to do that is to look at you exhaust gas temps.
It could also be your MSD box or several other things.
You can look on the internet for a parts breakdown of the Webber Side draft carb.
I hope that helps. it is not that hard once you read up on it and do it a time or two.
Dale
Last edited by dmccallum; 06.18.16 at 12:34 PM.
Carb issue
Chris,
FYI, You could also remove the carb, box it up and send it to Moses. He will rebuild it for you and you will be good to go.
Dale
more info
Has the car every ran since you have owned it or was this the first outing?
Did you do any work on the car recently?
It sounds like a self induced issue...main jets not on the emulsion tube, rag left in the air horn, throttle linkage not opening carb, etc....or not
1st outing for me. Got the car in January, and started it and let it idle (so as to not annoy the neighbors!) every month. This was the 1st time I'd tried to rev it over 1K. The only things that have been done to it are the fuel cell was removed so that I could do the rollbar update. Nothing else engine related has been done.Originally Posted by Darryl Wills
Through the marvelous wonders of the internet, I've managed to find a couple of Weber books online, along with some videos on youtube showing how to assemble the carb from scratch. I plan to see if I can fix the problem today. I'll report back.
Plan:
* Remove jets, and verify that they're not fully, or partially clogged.
* Verify that they get reinstalled correctly.
* Etc.
check the fuel flow rate...SHould be a minimum of 1 quart/min from the down stream side of the fuel regulator. Make certain the flow stream is solid and not arated.
one more quick thought: if you started it several times & only let it idle and did not rev it up a little, the plugs can foul pretty quickly & then the engine won't rev well at all, although usually it won't start very well the next time you try either... (it might be that setting a few weeks, it would "dry out" enough to start, but still not run well).
It is a little hard to tell from just looking at the plugs, but they should not be wet. Change to a new/good set if you have them & try that.
& be sure to use the proper NGK race plugs, which are a little (OK - a LOT) expensive. the standard street plug should start & idle OK, it will not pull good & it will not rev much over about 5,000 rpm.
we usually do a "10 cent warm-up", meaning we insert a dime under the idle adjuster in the carb linkage, to just give it a few more rpm (maybe idle @ ~1,000 to go up to 1,400 rpm for warm-up). that seems to work well & we don't get fouled plugs, even without continually revving it up (although you should "clear its throat" once in a while, after it is warmed up a bit...). Daryl says not to rev it up too much until it is warm, maybe ~140 deg F or more.
just don't rev it so high that you bend the valves (Sorry - couldn't resist...)
so - check the timing and the plugs. (and just be sure all the carb venturis (SP?) & other pieces are properly secure in place)
I know your engine has been "warmed up" a bit, but the basics should all be the same.
we gotta get you on track !!! (FYI - I'll be @ PIR this coming Wed thru Sun)
How do I check the fuel flow rate?
take the fuel line off at the carb.
place it into a quart jar.
should fill the jar up in less than a minute
observe the stream..should be solid fuel
So, I was curious about the fuel pressure regulator. I got the info from it, and looked it up online. Holley 12-804. (aka 34R-6657B). The specs for it say that it works up to 4 PSI. Then, I check Racing Beat, and they say that weber carbs expect 5 PSI. Could that be my problem?
Do I need a 12-803 (4.5-9 PSI)?
-Chris
(And then I see that the rebuild kit includes *2* springs. Evidently, the SPRING is the difference between the 803 and the 804).
Last edited by FrankRizzo; 06.30.16 at 7:13 PM. Reason: I dun lernt something!
Yes change the spring you need at least 5psi. You are running out of fuel.
Is it possible that the diaphragm is the cause of my problems? (Ordered a repair kit, will change it when I get it).
I'll assume they are DCOEs - have you seen Dave Andrews page? It has a pretty comprehensive look at jets, etc. Much Pinto info, etc; http://www.dvandrews.co.uk/webers May not be directly applicable.
I'm just now building a manifold for the Spec Outlaw Renault engine. The engine is out so no help in tuning/testing etc.
Cheers - Jim
Then, I made a weird discovery.
It is my understanding that with the Holley regulators, the INPUT is the bottom, and there are 2 outputs, 1 on either side. The way that MINE is hooked up, the input is on the SIDE, and the output is hooked up to the BOTTOM. This seems WRONG, but I want to make sure before I go move a bunch of stuff around.
Anyone know for sure?
-Chris
Well, the oddly connected regulator appears to function correctly, as once I replaced the plugs it appears to be MUCH MUCH better. So, I had temp 10 plugs (NGK Iridium 10's) in it, and I replaced them with NGK R 11's. Now, it starts RIGHT up, and runs much smoother.
Thanks to everyone that offered suggestions, and to StarFMGuy for the gracious gift of 2 sets of used plugs. to aid in my debugging.
See you at the track!
-Chris
NGK number?
Ok, new question...
What is the full NGK number for the plugs in our engine?
Different for leading and trailing or all the same?
Thanks!
All the same. All NGK N6725-11.
Thank you Frank!
Hope I can meet ya at a race soon.
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