Well we just put in our new 350 crate engine (330 hp). The problem is it seems to be running rough and going across the frozen lake in the dark today and looked back at the pipes and they were glowing and flames were shooting out of the exhaust at about 4000 rpms I have seen this when you are stuck and have it floored but never at this low of rpms could this be caused by the timming to advanced? we set it at idle it was 8 degrees btdc. it also seems to be missing a little now any ideas would be great.
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need help with 350 chevy
- Thread starter elk
- Start date
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Anonymous
Guest
sounds like it got hot, like the radiator froze
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Anonymous
Guest
sounds like timings off
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Anonymous
Guest
sounds like you run it way too lean
purplepeople5939
Member
I would do a compression check
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Anonymous
Guest
Is this a bran new motor how many hours are on it? I have seen several new GM crate motors with a weak hole due to bad ring seal or bad valve seal. You need to do a leak down test or at least a compression test. Make sure all your cylinders pressures are good before you start trying to solve any problems and chasing ghosts. If you do have a weak cylinder it will require the other 7 to make up for it. So they run harder and hotter. 90% of the time when this happens people miss diagnose it as running lean or too much timing. Which maybe the case but you should start your trouble shooting at A and end at Z. If you find all your cylinders to be with in 15lbs your O.K. in the motor department. Now you can start chasing jetting and timing issues.
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Anonymous
Guest
Good luck let me know what ya find. Remeber to pull out all the spark plugs before doing your compresion test.
Well here is the update pulled all the spark plugs and tested compresion is was fairly close the highest was 148 and the lowest was 140. Now here is a strange part the #1 and 4 plug had zero carbon on them and looked just like new now all the others looked like it is running very rich. It also sounds like it has a slight miss when you stand behind the boat and between 3-4 k it runs very rough then smooths out. when you stand behind the boat everyonce in a while it will shoot out a little fire. Help please where to head next. BTW timming is 32 at 4k and have disconected the vacum advance.
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Anonymous
Guest
Well you have good cylinder pressures so you can move on. The good news is that would have been the hardest and most expensive thing to fix. If you have a pyrometer check your header temps when the motor is running this will tell you immediately if a cylinder is too rich or too lean. If you don’t have one do it the old redneck way and lick your finger tips and very quickly just touch the header tubes on the cylinders just to make sure their all firing. If any header tubes are cold then you have an ignition problem such as bad wire, cap, or plug. If the tubes are hot you know their firing and you have a jetting problem. If the jetting is that inconsistent between cylinders it will be hard to find the problem. If two plugs are dead white it could just be a vacuum leak or a carb problem that is leaning out just those two cylinders. When you looked at your spark plugs was the porcelain bright white and the ground strap was a greenish, goldish color if so they were firing and are too lean. Since the white plugs come out of 1 and 4 and ’m sure you are running a dual plane intake. Look at your intake and see if one and four run off the same carb barrel on some dual planes they do. You could just have an open vacuum port or a venturi booster not flowing properly inside the carb. If you want look at you two white plugs and your intake runner layout and let me know what ya find.