Andreas1924 Posted June 3 Share Posted June 3 i bougt my 1927 chevrolet earlier this year and have driven it a little bit but now it starts to pop and backfire, and im wondernig if its my carb or my timing that needs adjustment. Ive ran some cleaning additiv through the carb to loosen up old gunk and dirt. Theres no airfilter on it is that a part of the problem ? Should i take the carb off and clean it more, and if so where can i get new gaskets, and dose anyone have a manual for taking it apart, putting it back together and adjusting it back in to run like butter again? Thank you for your time and have a great day. Link to comment Share on other sites More sharing options...
demco32 Posted June 3 Share Posted June 3 check the timing 2 Link to comment Share on other sites More sharing options...
EmTee Posted June 3 Share Posted June 3 Have you checked the cylinder compression? There could be one or more burned or sticking valves. 4 Link to comment Share on other sites More sharing options...
mikewest Posted June 3 Share Posted June 3 Sounds like it's starving for fuel. Running to lean. 1 Link to comment Share on other sites More sharing options...
mikewest Posted June 3 Share Posted June 3 Does it help to run it on half choke?⁸ Link to comment Share on other sites More sharing options...
Axial_Flow Posted June 3 Share Posted June 3 I can't see the pictures you posted, however, if the carb pre-heat stove is not connected, it will not run properly even with today's gasoline. The "stove" is the metal can that surrounds the exhaust pipe just after the exhaust manifold and is connected to the carb with a flexible metal pipe. The stove also has a small pre-cleaner device to let air enter the stove. I am not saying this is your issue, but its a good place to start if all the "normal" items are checked out. If you need pictures of these various components, I can supply them. 2 Link to comment Share on other sites More sharing options...
rocketraider Posted June 3 Share Posted June 3 An exhaust backfire (more correctly called an exhaust explosion) is usually related to ignition. Checking timing is a good place to start. Then check the points, condenser, rotor and distributor cap. If points have to be adjusted or replaced, you'll need to recheck and reset timing. Worst case your distributor may have enough shaft, bushing and bearing wear to affect its operation. Only solution there is remove it and have it rebuilt. Rebuilding services usually have a distributor machine and can set it to near perfection. 1 Link to comment Share on other sites More sharing options...
chistech Posted June 3 Share Posted June 3 (edited) The 27 chevy uses an air filter that is part of a can on the exhaust. A flexible metal hose goes from the side of the exhaust can around the rear of the engine and is attached to the carb. This allows only warm air to enter the carb. If you don’t have that the intake manifold will ice up and not atomize properly causing a lot of the issues you mentioned. Also, those engines were designed for low octane gas that burned faster than today’s higher octane. Open your spark plug gap to .040 or .045. That will help but at idle you will still get a little popping. Had to do this on my ‘31 and while it runs terrific, it still has a small popping at idle. Advancing your timing off of the stock settings also helps. Note: I didn’t see axial flows post when I posted this but he is correct. Also, do you have a single exhaust port or two ports. The ‘27 used a single but were prone to heads cracking and were replaced with the ‘28 cylinder head and exhaust manifold. Edited June 3 by chistech (see edit history) 3 Link to comment Share on other sites More sharing options...
Andreas1924 Posted June 3 Author Share Posted June 3 thank you for your good answers/ advise. So check timing, thicker mixture, get at stove/airfilter and open up sparkplugs up to .040-.045 inch? mm? 1 Link to comment Share on other sites More sharing options...
Andreas1924 Posted June 3 Author Share Posted June 3 4 hours ago, mikewest said: Does it help to run it on half choke?⁸ yes if i choke it a little while driving it runs good again, so its too lean in the mixture ? 1 Link to comment Share on other sites More sharing options...
Andreas1924 Posted June 3 Author Share Posted June 3 6 hours ago, EmTee said: Have you checked the cylinder compression? There could be one or more burned or sticking valves. if i cant fix it with thicker mixture and timing and a propper airfilter, removing the head and check gasket and valves to make sure the compression is optimal? Link to comment Share on other sites More sharing options...
Andreas1924 Posted June 3 Author Share Posted June 3 2 hours ago, rocketraider said: An exhaust backfire (more correctly called an exhaust explosion) is usually related to ignition. Checking timing is a good place to start. Then check the points, condenser, rotor and distributor cap. If points have to be adjusted or replaced, you'll need to recheck and reset timing. Worst case your distributor may have enough shaft, bushing and bearing wear to affect its operation. Only solution there is remove it and have it rebuilt. Rebuilding services usually have a distributor machine and can set it to near perfection. can you recomend any good places to get distributor rebuilt ? i was planing on making it 12v during the winter so itll be running 12v from next year, can i get the distributor made so that itll be the orginal that runs 12v or will i have to get a newer one installed when time comes ? Link to comment Share on other sites More sharing options...
mikewest Posted June 3 Share Posted June 3 24 minutes ago, Andreas1924 said: yes if i choke it a little while driving it runs good again, so its too lean in the mixture ? Its my opinion ... not seeing it . 3 Link to comment Share on other sites More sharing options...
chistech Posted June 3 Share Posted June 3 There is a very good chance your intake is icing up which is leaning it out. Choking it is adding more raw fuel and it’s getting more fume to burn. When it’s running check the intake manifold. If it’s cold, wet, or it might actually have ice on it, you definitely need the warm air intake from the exhaust can. Look at pictures on the web of ‘27-‘28 engines and you will see the exhaust can and the metal flex pipe rom exhaust to the carb intake. I had a ‘27 for a short time and it was missing the warm air pipe. When I first started it ran great but it only took a few minutes before the intake would start to ice and it would misfire badly. Once I got the exhaust can/filter and added the flex pipe it ran fine. 1 Link to comment Share on other sites More sharing options...
roysboystoys Posted June 4 Share Posted June 4 When I worked at an Ignition/carburetor shop in the 1960's, we started every tune up or diagnosis with a compression test. All these suggestions may be your problem, but do you know your engine is in good condition? Very simple procedure on your car. One suggestion not mentioned is the valve adjustment, seems to get ignored a lot, but was normal maintenance when the car was daily driven. Good luck on your repairs 2 1 Link to comment Share on other sites More sharing options...
Barney Eaton Posted June 4 Share Posted June 4 (edited) The 2 cylinder Onan motor on my mower does the same thing when the points are bad or out of adjustment. Edited June 4 by Barney Eaton (see edit history) 1 Link to comment Share on other sites More sharing options...
demco32 Posted June 4 Share Posted June 4 (edited) 20 hours ago, chistech said: The 27 chevy uses an air filter that is part of a can on the exhaust. A flexible metal hose goes from the side of the exhaust can around the rear of the engine and is attached to the carb. This allows only warm air to enter the carb. If you don’t have that the intake manifold will ice up and not atomize properly causing a lot of the issues you mentioned. Also, those engines were designed for low octane gas that burned faster than today’s higher octane. Open your spark plug gap to .040 or .045. That will help but at idle you will still get a little popping. Had to do this on my ‘31 and while it runs terrific, it still has a small popping at idle. Advancing your timing off of the stock settings also helps. Note: I didn’t see axial flows post when I posted this but he is correct. Also, do you have a single exhaust port or two ports. The ‘27 used a single but were prone to heads cracking and were replaced with the ‘28 cylinder head and exhaust manifold. adjust the ignition advance a little later to drive with higher octane gas, the combustion ends +/- 8 degrees after TDC Today's gasoline contains a lot of cetane, which is detrimental to the knock resistance of the gasoline + the ethanol evaporates at 35 degrees Celsius, which reduces the quality of the gasoline. Incorrect dwell angle can lead to inconsistent spark plug firing result in misfires, rough idling, and poor engine performance. Over time, this can also lead to fouling of the spark plugs, reducing their efficiency and causing further issues. also check the valve timing and do a compression test. Edited June 4 by demco32 (see edit history) Link to comment Share on other sites More sharing options...
Frank DuVal Posted June 4 Share Posted June 4 On 6/3/2024 at 2:44 PM, Andreas1924 said: i was planing on making it 12v during the winter Why? It just makes more problems to fix. That 4 cylinder motor should be easy for the starter to turn over. It will start and run great on a six volt system. 12 volts will not fix mechanical issues, points issues, etc but might band-aid them for a short while. Then you still have to fix them. Fix the issues first (above recommendations) and enjoy the car.😄 1 Link to comment Share on other sites More sharing options...
TTR Posted June 4 Share Posted June 4 7 hours ago, roysboystoys said: When I worked at an Ignition/carburetor shop in the 1960's, we started every tune up or diagnosis with a compression test. All these suggestions may be your problem, but do you know your engine is in good condition? Always start with This ^^ Anything else can be a waste of time if the engines internal, compression related condition is unknown. You can check and adjust carburetors, distributors, timing etc until you’re blue in the face, but if the compression is bad … Link to comment Share on other sites More sharing options...
Andreas1924 Posted June 5 Author Share Posted June 5 1 hour ago, chistech said: The 27 chevy uses an air filter that is part of a can on the exhaust. A flexible metal hose goes from the side of the exhaust can around the rear of the engine and is attached to the carb. This allows only warm air to enter the carb. If you don’t have that the intake manifold will ice up and not atomize properly causing a lot of the issues you mentioned. Also, those engines were designed for low octane gas that burned faster than today’s higher octane. Open your spark plug gap to .040 or .045. That will help but at idle you will still get a little popping. Had to do this on my ‘31 and while it runs terrific, it still has a small popping at idle. Advancing your timing off of the stock settings also helps. Note: I didn’t see axial flows post when I posted this but he is correct. Also, do you have a single exhaust port or two ports. The ‘27 used a single but were prone to heads cracking and were replaced with the ‘28 cylinder head and exhaust manifold. its a singel exhaust port, but i havent seen any craks or signes thereof, but ill keep it in minde thanks 1 Link to comment Share on other sites More sharing options...
a sell Posted June 6 Share Posted June 6 If you don't have one already get the owners manual for your year model. I would also recommend getting the monthly service bulletins for your year of car and the following year as well. That is when the previous year model would be brought back to the dealership for repairs, and the mechanics would come up with tricks to make their jobs easier. I think the manual is $20 to $25 and the service bulletins per year are $15. It will make your life so much easier when you need to work on your car. The Filling Station in Lebanon OR sells all of these. They have an online catalog. 1 Link to comment Share on other sites More sharing options...
Andreas1924 Posted June 8 Author Share Posted June 8 On 6/3/2024 at 5:36 PM, Axial_Flow said: I can't see the pictures you posted, however, if the carb pre-heat stove is not connected, it will not run properly even with today's gasoline. The "stove" is the metal can that surrounds the exhaust pipe just after the exhaust manifold and is connected to the carb with a flexible metal pipe. The stove also has a small pre-cleaner device to let air enter the stove. I am not saying this is your issue, but its a good place to start if all the "normal" items are checked out. If you need pictures of these various components, I can supply them. do you know where i can get a stove airfilter? Link to comment Share on other sites More sharing options...
Axial_Flow Posted June 10 Share Posted June 10 On 6/8/2024 at 12:18 PM, Andreas1924 said: do you know where i can get a stove airfilter? I would start with Gary Wallace at http://www.earlychevyparts.com/. 1 Link to comment Share on other sites More sharing options...
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