This whole effort to convert to electronic ignition is a road I may not have gone down if I had known these Autolite carbs need to be modified to ported to work worth a darn. Even newer ones on eBay or wherever all have this scv valve. I did manage to find a non-scv valve unit in my box of old carbs. Wonder if this will work. What about the carter or other options? Would be nice to just find one that can mount directly without to much modifications and have a smooth idle and acceleration.
All Small Six Did You Convert a Spark Control 1100 Carburetor to ported vacuum?
- Thread starter Alkraut
- Start date
This relates to all small sixes
I don't know if it should be removed or not. I've never seen a check valve ball in a vacuum port, but not sure about the svc carbs. If that's a fuel passage the ball needs to stay.
It's an option you don't seem at all interested in. But my car runs pretty good on manifold vacuum. I've got a SCV 1100 carb on it with the distributor vacuum port plugged. The distributor is a stock 1970 single vacuum can version that I think might have actually been for a 250, and it is connected to manifold vacuum. Well, it's actually an extra vacuum port on my carb spacer that I made, so technically it's not on the manifold. Any way, it runs pretty good. Idles well and runs strong (well, for a six...) without any pinging that I can hear with timing set at 12*. Hit the gas and it takes right off, no hesitation or stumbling as revs build. My long time 1100 had given up the ghost, so the carb on it is a chimera I put together using parts from a couple different 1100s I bought on ebay because most of the ones on there are pretty well used up. I spent maybe $125 on them and a carb kit. The distributor cost me about $75 as I recall. I'm not using the manifold vacuum because it's an existential philosophical choice that I've made, but because it's the easiest and cheapest thing to do with these parts. I'm hoping to find the gumption to finally get my E0 head and a non-SCV 1101 carb on it later this summer. And with that combination I'm planning on using the ported vacuum tap on the carb.
DON
Famous Member
Before buying another carb or guessing at parts to buy and try to see if they help, you might want to invest in an O2 meter. It will tell you if that high speed hesitation is lean and also give you valuable info on idle. I will never be without one. More experienced guys might not need one, but I know enough to fix a problem, sometimes finding out what the problem is, is the hard part. This is a helpful tool that gives very precise info. On a Holley triple two barrel set up( two idle mixture screws per carb and idles on all three ) I have seen a change in the meter readings with an 1/8 of a turn on one screw. I can’t see how anyone could be that sensitive with an ear or seat of the pants….i know I’m not
Thanks on inputs. Yeah, I am thinking it may be running lean. Inspecting the plugs as I have maybe 3-400 miles on the rebuild they are definitely not running rich, kind of a tanned color. Also, when sitting and I push the accelerator pump I do not see as strong a squirt of gas as I would like. So, I can take the idle mixture screw out which should bring more gas, and also the accelerator pump can be adjusted by bending the actuator rod, or maybe I replace the diaphragm. Will keep tinkering for the time being.
this is what he's referring to. I've been tuning carbs without one for many years. I made the investment in one, and it's a near-priceless tuning aid. without it I would think the carb on my fresh rebuild was doing ok, when actually it's metering irregular, the mixture is not consistent, changes need to be made. I could not deduce this by feel or ear or vacuum gauge readings.
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If you absolutely must get a replacement carb try mikescarburetors.com. I think this is correct address. Seems to be well thought of for carbs.
DON
Famous Member
The sensor goes in the exhaust pipe, just after the header or y-pipe or manifold depending on what you have. A threaded “bung” is welded into the pipe. There is a method to install it without welding, it uses a hose clamp type thing to hold the bung in. I have a meter made by Fast. It is no permanently mounted. I only use it for tuning. It is personal preference which style you get. The meter needs a 12 v power source. My meter came with a chart/ graph that tells you what readings you should have.
DON
Famous Member
Fast meter, don’t know if this link will work? This meter can be upgraded to use two sensors, read individually, which can help with multi carb set ups and split headers, one sensor on each header bank
Just plug the venturi advance port with JB Weld or whatever.
The main reason NOT to run an LOM spark valve Autolite 1100 with a centrifugal-vacuum advance distributor is the excessive advance caused by the venturi vacuum.
This main reason NOT to run an LOM spark valve carb. with a centrifugal-vacuum advance distributor has nothing to do with ported vacuum that an LOM Autolite 1100 does not have and the flawed conversion instructions will not provide.
The main reason NOT to run an LOM spark valve Autolite 1100 with a centrifugal-vacuum advance distributor is the excessive advance caused by the venturi vacuum.
This main reason NOT to run an LOM spark valve carb. with a centrifugal-vacuum advance distributor has nothing to do with ported vacuum that an LOM Autolite 1100 does not have and the flawed conversion instructions will not provide.
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