355 SBC Misfire help
#1
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Well, hello, this is my first post here.
Anyway, I recently built a mild 355 for my Camaro. Its had as strange misfire ever since it its first startup. The no.4 cylinder does not want to run right. Its a misfire that you can hear at idle and upto about 2500 RPM but then it picks back up. This seemed to me like bad rings, so i checked and the compression on no.4 was about 165 pounds, along with the other 7. Checked plugs, wires, distributor, all getting good spark. I already know its running rich, and i plan on swapping my 750 Cfm for a 650 this weekend, but i dont think that would cause only the no.4 cylinder to not run right. This leads me to believe it is the cam. Is there anything else to try before i pull the cam and get it checked out? Im at my wits end here.![Bang Head](https://ls1tech.com/forums/images/smilies/LS1Tech/gr_banghead.gif)
Edit: Do you guys think filling it with 92 octane could help? Considering its 11.2 compression. Though i still cant imagine that would only miss only one cylinder
Anyway, I recently built a mild 355 for my Camaro. Its had as strange misfire ever since it its first startup. The no.4 cylinder does not want to run right. Its a misfire that you can hear at idle and upto about 2500 RPM but then it picks back up. This seemed to me like bad rings, so i checked and the compression on no.4 was about 165 pounds, along with the other 7. Checked plugs, wires, distributor, all getting good spark. I already know its running rich, and i plan on swapping my 750 Cfm for a 650 this weekend, but i dont think that would cause only the no.4 cylinder to not run right. This leads me to believe it is the cam. Is there anything else to try before i pull the cam and get it checked out? Im at my wits end here.
![Bang Head](https://ls1tech.com/forums/images/smilies/LS1Tech/gr_banghead.gif)
Edit: Do you guys think filling it with 92 octane could help? Considering its 11.2 compression. Though i still cant imagine that would only miss only one cylinder
Last edited by Stormdrain; 06-24-2014 at 01:33 AM.
#2
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iTrader: (5)
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is the cam solid or hydraulic, roller or flat tappet? have you checked the valve lash?
on another note 11.2:1 on junk pump gas is too much, you will have to back off on the timing to keep it from detonating. which in turn negates the power you would gain in higher compression. you will have to run a higher octane fuel once you get it running right.
on another note 11.2:1 on junk pump gas is too much, you will have to back off on the timing to keep it from detonating. which in turn negates the power you would gain in higher compression. you will have to run a higher octane fuel once you get it running right.
#5
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Hydraulic. No.4 was a touch loose but i dont believe i pushed the oil out of it. i may loosen it up tomorrow and check again but i dont believe the valves are staying open.
Edit: Yeah it couldnt be that because the compresion is good.
Edit: Yeah it couldnt be that because the compresion is good.
Last edited by Stormdrain; 06-24-2014 at 04:49 PM.
#7
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had already been broken together in with previous motor. Ill call up my pops and ask if needed. And yes i kept them matched to the cam lobes they were already worn to. Old motor had about 8k miles when i got the cam and lifters.
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#9
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Just pulled all the plugs, wet wet wet. Im thinking im overloading the plugs with fuel causing it to misfire. it may not be just no.4 because that plug is dry. Im going to try downjetting the carb before i do anything else. And the rockers all look uniform.