dejh22 Posted June 2, 2018 Share Posted June 2, 2018 I'm having an issue with a 396 that was rebuilt last year. At first before I dialed it in, it was smoking on the left side. I had colder plugs (AC 44's) pulled them out and they were wet and black. After tuning and replacing with a hotter plug (AC 45's) plugs looked better and for the most part the smoking went away. I have been driving it some this spring and even went to a couple car shows. Been noticing some smoke again on and off but this time on the right side. Drove it last weekend and did not notice any smoke. My friend said it smelled like "gas" when I passed him. Today I went to a car show and just got home. I noticed it smoking a little again on the right side. I backed it in the garage and my wife said it burned her eyes. The smoke is a light blueish color. I just pulled the plugs on the right side and they look good to me. Starts good and runs good. Could it just be rings not seated yet? I don't think it even has 500 miles on it. Here are some pics of the plugs. Quote Link to comment Share on other sites More sharing options...
ripleydale Posted June 3, 2018 Share Posted June 3, 2018 Are you using oil? A compression test would be a good place to start. 1 Quote Link to comment Share on other sites More sharing options...
dejh22 Posted June 3, 2018 Author Share Posted June 3, 2018 Are you using oil? A compression test would be a good place to start. Well it does have a small rear main drip. So it does use a little oil from that. Just going to live with it for now. I did find trans fluid in the vacuum line from the trans vacuum modulator to the vacuum port on the carb. So I'm thinking that might be the source of the smoke? Was just getting ready to order a new modulator online. Quote Link to comment Share on other sites More sharing options...
monte70car Posted June 3, 2018 Share Posted June 3, 2018 Burning the eyes sounds like its running rich. Looking at the plugs you pulled on the right side there is one that's black compared to the rest on the side. Check the plug wire and make sure it doesn't have a burnt section on it maybe even change that wire. What type of carb are you running on your 396? could have too much gas going in the motor. I had a similar issue back when I had a Holley on my 402 and even changing the jet size and the pump cam still had a rich smell. Now it has a Q--jet on it and it runs better. Quote Link to comment Share on other sites More sharing options...
dejh22 Posted June 3, 2018 Author Share Posted June 3, 2018 Burning the eyes sounds like its running rich. Looking at the plugs you pulled on the right side there is one that's black compared to the rest on the side. Check the plug wire and make sure it doesn't have a burnt section on it maybe even change that wire. What type of carb are you running on your 396? could have too much gas going in the motor. I had a similar issue back when I had a Holley on my 402 and even changing the jet size and the pump cam still had a rich smell. Now it has a Q--jet on it and it runs better. I adjusted the carb yesterday. But I think it is about set were it was. The spark plug wires are new and in good condition. I'm running a 750 Holley vacuum secondary. It has a comp cam 280H It has a 520 lift 280 duration. The compression is about 10.25 - 1. It runs really well Quote Link to comment Share on other sites More sharing options...
dejh22 Posted June 15, 2018 Author Share Posted June 15, 2018 UPDATE, Rear main has been changed and not leaking as of yet. I also changed the transmission modulator that was bad. I was hoping that was the cause of the light smoke on the LEFT side. ( The Topic says right side, my bad) The light smoke is still there. Tonight I did my first ever compression check. Here are the results. 1. 180 3. 175 5. 170 7. 170 2. 180 (little less) 4. 180 6. 180 8. 180 As you can see the lower compression side is also the side that is smoking a little. What should this be telling me if anything? The engine doesn't run hot. I really don't think the smoke is from coolant. I had someone tell me it smells like fuel and they also said it smells like oil. I have Parkinson's and don't have a sense of smell so I can't tell. The color of the smoke is a blue/white color. Thanks Quote Link to comment Share on other sites More sharing options...
monte70car Posted June 15, 2018 Share Posted June 15, 2018 Number 3 is within 5psi of the rest. 5 and 7 could have stickie valves which is allowing air to go out or could be a crack ring on both of those pistons. Sine you are unable to to smell have some smell the oil on the dipstick. A crack ring will let gas into the engine wiping oil off the cylinder walls. I know I had an engine in my 70 with a 750 Holley and it ran so rich it would make you cry. 1 Quote Link to comment Share on other sites More sharing options...
dejh22 Posted June 16, 2018 Author Share Posted June 16, 2018 Number 3 is within 5psi of the rest. 5 and 7 could have stickie valves which is allowing air to go out or could be a crack ring on both of those pistons. Sine you are unable to to smell have some smell the oil on the dipstick. A crack ring will let gas into the engine wiping oil off the cylinder walls. I know I had an engine in my 70 with a 750 Holley and it ran so rich it would make you cry. Well I just replaced the rear main seal so the old oil is gone. But I remembered I changed the oil filter and it was still out in the garage. So I poured the oil from it into a cup, I tried to smell it and I could smell anything. I had a couple other people smell it and they said without a doubt it smelled like gas. This engine is a true 396. My machine guy said it was in specs and could keep it standard bore. But was on edge. I went ahead and kept it standard. This is the first engine of have done without having it punched. It really didn't smoke at first start up. But then it started smoking both sides and then went a away. My thought was I need to get some miles on it and seat the rings. Then it would smoke on and off. This last time it would smoke all the time on the left side not a lot. There isn't very many miles on it, I would say less then 500. It really does run great. I think What I may need to do is pull it and bore it .030 over. Like I should of done in the first place! Quote Link to comment Share on other sites More sharing options...
dejh22 Posted June 16, 2018 Author Share Posted June 16, 2018 Well I just replaced the rear main seal so the old oil is gone. But I remembered I changed the oil filter and it was still out in the garage. So I poured the oil from it into a cup, I tried to smell it and I could smell anything. I had a couple other people smell it and they said without a doubt it smelled like gas. This engine is a true 396. My machine guy said it was in specs and could keep it standard bore. But was on edge. I went ahead and kept it standard. This is the first engine of have done without having it punched. It really didn't smoke at first start up. But then it started smoking both sides and then went a away. My thought was I need to get some miles on it and seat the rings. Then it would smoke on and off. This last time it would smoke all the time on the left side not a lot. There isn't very many miles on it, I would say less then 500. It really does run great. I think What I may need to do is pull it and bore it .030 over. Like I should of done in the first place! Update.... I just did a wet compression test on a couple cylinders. #1 dry was 180 and wet 190 #7 dry was 170 and wet 180. Could it be I just need to put some more miles on it to see if the rings will seat? Quote Link to comment Share on other sites More sharing options...
dejh22 Posted June 21, 2018 Author Share Posted June 21, 2018 Another update. I pulled the intake and looked down into the intake ports of the heads and found small pools of oil in all cylinders except one and two. This has me stumped. The heads don't have very many miles on them. They are iron heads ( 3993820 ). I read somewhere that the rocker arm studs can protrude into the ports. That they found the studs had no sealant on the threads and oil was leaking past. I know that on aftermarket heads this can be true. I didn't think the rocker arm studs on stock big block heads did. Quote Link to comment Share on other sites More sharing options...
Monteman1971 Posted June 27, 2018 Share Posted June 27, 2018 If it wasn't all new I'd say.....Chevy idas..... Meaning leaky valve stem seals. although this is typically on start up, if you have pools of oil it is possible. Maybe they were installed dry and got torn up? I'd go to the valve with the biggest leak and pull the spring off (remember to use something to hold the valve up during this procedure). 1 Quote Link to comment Share on other sites More sharing options...
dejh22 Posted June 28, 2018 Author Share Posted June 28, 2018 If it wasn't all new I'd say.....Chevy idas..... Meaning leaky valve stem seals. although this is typically on start up, if you have pools of oil it is possible. Maybe they were installed dry and got torn up? I'd go to the valve with the biggest leak and pull the spring off (remember to use something to hold the valve up during this procedure). Heads are off and going to be installing another set after I have them gone thru. We believe it is the valve guides leaking past the outside of the valve guide (between the guide and head). 1 Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.