1979 GMC C3500 Blowby

1979 GMC C3500
100,000 MILES • 7.4L • V8 • 4WD • AUTOMATIC
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CSE2_27
  • MEMBER
  • 4 POSTS
What are the causes of blowby on a 1979 454 GMC and how can it be fixed?
Mar 5, 2014 at 5:28 AM
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HMAC300
  • ✓Experienced Mechanic
  • 48,601 POSTS
blowby can be caused by many things but biggest culprit is a clogged pcv system and valve replace the vale and check hose and where it connects for good vacuum. the hose may be soft and sucking together. The engine could have detonated then went into preigniton blowing a hole in piston as well.
Mar 5, 2014 at 7:24 AM
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