krcaddis
Junior Member
- Joined
- Sep 7, 2013
- Posts
- 21
- Reaction score
- 0
- Location
- Santa Margarita
- First Name
- Gene
- Truck Year
- 1985
- Truck Model
- C20
- Engine Size
- 350
My recently re-powered crate 350 (TH400) suddenly backfired cruising about 40 MPH and now sort of lugs, less power and sputters on decel. I suspect the timing. I changed harmonic balancers to match the rest of the pulleys, located the TDC (different place than marked), set timing based on that ran crappy. Limped it to a retired expert who set it quite a bit different by ear. Found a shop to replace all the rotted emissions spaghetti and it runs pretty good for about 50 miles for a new tank of gas. The backfire happened about 10 miles later. There's two pieces missing on the Quadrajet 4 BBL carb after the rebuild: dashpot for the idle and the diaphragm for the choke. Those vacuum tubes are temporarily plugged and there seems to have little effect. Other than that, the crate engine is a used one w/20k+/-. Truck has 42k.
Might the timing chain have jumped a tooth? Distributor loose and rotated? Bad gas reached the freshly rebuilt carb? (unlikely)? What else?
Might the timing chain have jumped a tooth? Distributor loose and rotated? Bad gas reached the freshly rebuilt carb? (unlikely)? What else?
