maok Posted September 15, 2017 Share Posted September 15, 2017 G'day all, I've been trying to chase down what is causing this problem that has occurred recently. It just hesitates at any constant speed, but will even out when I pull the choke out a little, so it leads me to believe its carbie related. Its a Carter BB1 updraft. At idle and full throttle no noticeable issue, only at constant speed. I have played with the float level many times now but with no success. Its set about 1/32 to 1/16". I don't have the tool for setting the float but the brass float soldered SEEM is almost the top of the fuel bowl. The float tests ok. An electric fuel pump that I have been using for some time now is set about 2psi with a fuel pressure regulator, I have played with it at higher and lower levels with no success either. The spark plugs look ok, except #1 probably the cause of the missing sound at the exhaust pipe., see pic below. The gaps are all about 0.027". The ignition looks to be all good as well, dwell at about 37o angle, new rotor button and cap. I have tried new insulated spark leads as well. It does start perfectly, so the timing is good, set at about 4o BTDC. #6 to #1 #1 Any ideas? Link to comment Share on other sites More sharing options...
maok Posted September 15, 2017 Author Share Posted September 15, 2017 Ok, problem solved....Anyone want to guess what the issue was? Link to comment Share on other sites More sharing options...
r1lark Posted September 15, 2017 Share Posted September 15, 2017 Vacuum leak? Link to comment Share on other sites More sharing options...
maok Posted September 15, 2017 Author Share Posted September 15, 2017 That was my first thought last week besides the float level. But nah. Link to comment Share on other sites More sharing options...
JACK M Posted September 15, 2017 Share Posted September 15, 2017 Partially clogged hi speed jet? Link to comment Share on other sites More sharing options...
Spinneyhill Posted September 15, 2017 Share Posted September 15, 2017 Flooding? dirt in float valve. Vacuum leak? Link to comment Share on other sites More sharing options...
maok Posted September 15, 2017 Author Share Posted September 15, 2017 Nope. I pulled the carbie off many times thinking the issue was hidden inside. Yeah nah. Link to comment Share on other sites More sharing options...
PlymouthPE Posted September 16, 2017 Share Posted September 16, 2017 Bad spark plug? Link to comment Share on other sites More sharing options...
viv w Posted September 16, 2017 Share Posted September 16, 2017 Spark plug gap too small, open gap to 35thou Link to comment Share on other sites More sharing options...
maok Posted September 17, 2017 Author Share Posted September 17, 2017 WoW! 0.035" really? I will try it and see if it likes that much of a gap. It was actually the bolt that holds the distributor, this Einstein forgot to tighten it enough... Link to comment Share on other sites More sharing options...
Guest Posted September 17, 2017 Share Posted September 17, 2017 I have done that. If I was starting out on a long trip at night I would loosen the distributor clamp and advance the timing about an eighth of an inch. Cool night air and advanced timing just like supercharging especially if I had added a gallon of alcohol or stove oil or kerosene to my ten gallon tank. Only one had to be sure to fully tighten the clamp. Younger and foolisher I knew where everything was on my engine and what wrench fit but was not smart enough to carry a flashlight. Sure hard to reset timing in the dark. Link to comment Share on other sites More sharing options...
maok Posted September 17, 2017 Author Share Posted September 17, 2017 Well its got this young Einstein stuffed. I hope I don't have to apply E=mc2 or some of his difficult equations. It doesn't do it when engine is cold but will at full operating temp. I'm going check the float level again for the infinite time.... Link to comment Share on other sites More sharing options...
viv w Posted September 17, 2017 Share Posted September 17, 2017 I had a 54 Chev 6 and at a steady speed it jerked about, I had the plugs set at 0.025in. I was advised to open the plug gap to 0.035in and it cured the problem. However, you say it doesn't do it, when you run with the choke partially closed??This indicates a lean mixture from the carb. I read in a vintage Chev club of america magazine, that, if you are using alcohol blended gas in a Chevy six, and it gives this problem, you may need to open up the main jet a size or two, as it has been found that these engines run lean on blended gas. I don't know what gas you are using. If it is blended, then I suggest you drain this gas and try and buy some regular gas, say 85 to 87 octane and try it in your car. If the problem goes away then you know it is the gas. Blended/alcohol gas has a much higher octane rating than regular gas and once your motor has warmed up, it may be causing problems. If the problem disappears with regular unblended gas, then you have 2 options, run with regular gas, or drill out the main jet a size or two to enrich your mixture. You have not said what car you have, but I assume with an updraft carb, it is pre 1932. I did a bit of searching, on problems with alcohol blend gas with older cars. One interesting thing, that came out of the articles, was that the older cars, do NOT have the compression ratio's of todays modern engines, to deal with high octane gas. They were designed to run on gas that had a much lower octane rating than today, and gas then, probably had an octane rating in the region of 45 to 65 octane. They said a problem with low compression and a high octane gas, is that the gas is not fully combusted inside the cylinder, and leaves the cylinder still burning when the valves open, this can also lead to overheating in the manifold and a hot running engine. They recommended lowering the octane level by adding some diesel or paraffin to the gas to help lower the octane rating. I had a 1928 Chrysler 52 and it used to run so hot that the exhaust manifold glowed red in the dark, I ran a Ford A carb and even making the mixture richer, I could not cure this problem. The car ran sweetly and I eventually just assumed that's the way they were. After reading the article, I now assume it was caused by too high an octane gas. Keep us posted on what you find. regards Viv. Ps, wrong heat range plugs can also give you problems. Link to comment Share on other sites More sharing options...
maok Posted September 17, 2017 Author Share Posted September 17, 2017 Yeah sorry, I should have mention the vehicle in concern. Its the green machine in my profile pic, '28 Chrysler. Its not a fuel octane or ethanol issue. Ethanol gets blamed for almost every problem in old cars, I feel sorry for poor ethanol, not that I use it. I fill up from the same servo every time. I do agree with your octane comments. The problem definitely (maybe) is more noticeably at higher constant speed. But non existent at idle, partial or full throttle situations. I will try my another carb (JR5 Tillotson) to see if the issue is still present. This should eliminate the carb or ignition. Link to comment Share on other sites More sharing options...
maok Posted September 18, 2017 Author Share Posted September 18, 2017 (edited) Did the carb swap today, it was actually a JR2, not a JR5 Tillotson, my grey matter is getting greyer. After a hiccup with the starter motor and some fine tuning of the Tillotson, she is now burning rubber like a F1 car. Well almost. After making sure it was at full engine temp., took her for a 10 minute drive and I am glad to say the problem was totally non existent. It actually really liked the Tillotson, had noticeably more get up and go than the BB1. Probably more to do with my tuning capabilities of the BB1... I will do more testing tomorrow and look further into the Carter BB1. Edited September 18, 2017 by maok grammar error (see edit history) Link to comment Share on other sites More sharing options...
Spinneyhill Posted September 18, 2017 Share Posted September 18, 2017 There was discussion somewhere not long ago about using a marine carb. on a car. It would cause it to run lean and eventually damage the engine. I wonder if that is the correct model BB1 you have, or is it a marine version? I can't remember where the discussion was, perhaps Technical? Link to comment Share on other sites More sharing options...
maok Posted September 18, 2017 Author Share Posted September 18, 2017 Thanks spinney, I will check the casting number on the BB1 and hopefully someone will identify it. What would be the difference between a marine and auto carb? Jetting? Probably smaller pump? I would have thought that the jetting would be larger on a marine carb. Link to comment Share on other sites More sharing options...
Spinneyhill Posted September 19, 2017 Share Posted September 19, 2017 It was in this thread: This was related to a Zenith carb. but I am sure I have recently seen similar discussion concerning the BB-1. I think The Carburetor Shop list a few variants of the BB-1? Link to comment Share on other sites More sharing options...
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