cylinders 5 & 8 not firing

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rocky yo

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Hey guys,

I just brought my 71 bb vert to the local mechanic for oil change and transmission oil service, just some minor stuff. He noticed that the car was not running right and says hat 2 of the cylinders are not firing # 5 & 8. Now when I first got the car I had the original points system replaced with an HEI distributor. I noticed the car was a little shaky but I thought that maybe it was due to sitting for so long. Also, I have been noticing a really strong smell of fuel. Just wondering if any has any thoughts.

Thanks
 
When we bought our L78 Chevelle in '97 it had an HEI. When the HEI died, I put a good condition L34 396 distributor in the car. It worked just as well as the HEI ever did. If you want to turn higher rpm the Delco D112P heavy duty points are nice to have but for anything under 6K rpm the stock Delco points worked fine. With a points distributor, there isn't much you can repair on the side of the road. On the other hand, our old '87 S-10 has its original HEI with well over 150K miles and it works just fine, so the HEIs can be as reliable as any. I just prefer the simplest route. I'd be checking for a cracked distributor cap and bad plugs. Make sure that these two wires are not running parallel with each other for any distance. Induction can cause problems too. Check under the hood when it is dark out to see any arcing.
 
the fuel smell will be due to loading up with 2 cylinders misfiring. don't forget that the fuel is ending up in the crankcase and fouling the engine oil. if it was me i'd install new plugs, wires, cap and rotor and do an oil and filter change.
 
buckhorn76 said:
the fuel smell will be due to loading up with 2 cylinders misfiring. don't forget that the fuel is ending up in the crankcase and fouling the engine oil. if it was me i'd install new plugs, wires, cap and rotor and do an oil and filter change.
Click to expand...
Ya just hit the head on the nut :agree:
 
Isnt 5 and 8 fed of the same intake runner one cyl not firing could be killing the other one on the same runner, if its a automatic isn't the modulator fed of that runner? Vac line could be off down at trans or valve spring on one cyl or if it hydraulic cam a lifter can do this by holding valve open or hopefully not a cam lobe maybe even a valve spring.
 
One more thing isn't the vacuum fitting for the vacuum system on the 5 and 8 runner? If so take a pair of needle nose pliers and pinch the vacuum hose off right at the intake if the miss clears you've got a leak in the vacuum system which will kill these 2 cyls leak could be anywhere go over to vacuum tank under left fender and pinch line off going in if miss stops either tank is leaking or leak is somewhere in system pinch line off coming out of tank if miss doesn't stop tank is leaking if miss does stop leak is somewhere in system
 
Still at the shop. Getting a tune up plus some other work I've been putting off. She should be ready tomorrow. I opted to upgrade the wires from the HEI distributor to a set if performance wires. Hope that helps the situation.
 
All done, she is back on all 8 cylinders. Sounds great but they want me back at the shop soon to "tune" the carb. She seems to be running a little rich. Also, I have a new question on a separate post.
 

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