New Muffler=run like poo? (1 Viewer)

[k91]

History....75' 40 had 2F head rebuilt last summer,

-finally got it all assembled in October, took off the Holley carburetor and replaced with a 76 Aisan.

-Had the rusted out, barely hanging on cherry bomb muffler replaced with a thrush last month.

-Ran just fine before the muffler, when I picked it up...ran like poo. no power, sputter, backfire through carb.

-I'm thinking it needs valves adjusted at this point? Ive tested the fuel pump, reset timing and rebuilt the Aisan. Ive checked for vacuum leaks, tested vacuum, Still doing it. Any thoughts? Thanks, Matt

 

[Michael Hanson]

I dont think its the mufler,but turn it on put in park,see what kind of air is coming out the back . Mike

 

[grant5127]

Vacuum gauge......

A handy non-expensive diagnostic tool..........

 

[k91]

Grant, I have one and have found that the vacuum at idle is about 17in. When I accelerate, the needle drops significantly indicating worn rings. This the reading I get when I run the vacuum guage off the manfold, not the port on the carb. Thanks for your input, Matt