Hi!
About 400 miles ago I replaced the engine with a rebuilt HO.
This was my first engine swap fwiw.
I've got it running great, but, I've got terrible fuel economy. Like 13mpg last tank, when I'm used to 18-20mpg the way I drive. My first tank I had too much fun with the engine, and the 10mpg didn't worry me yet, but my last tank, all commuting and no fun, was 12.5mpg!
Anyway.
I never retightened the header bolts: I only tightened them once, while the engine was out of the car before installing. Could heat cycles have loosened them? I might have an exhaust leak there, which could lead to rich running, which could kill fuel economy.
I'm also wondering since I put in new headers and an h-pipe --stock 2.25"-- that maybe at that ball and socket they might not be sealing perfectly? It's just metal on metal, the hpipe sockets didn't seem perfectly spherical, the hpipes weren't from the same car as the headers, so they may not be sealing right.
I tried asking at pepboys if they had gaskets; they had these really thick donut gaskets that just plain didn't fit.
Can gaskets be found to put here? Maybe you even have a NAPA part # for me?
Might try to do this tonight if possible.
Finally just idly thinking that, as I have no idea of the history of these hpipes, how would I know if the cats were clogged, and would that affect fuel economy anyway?
Seems to have alright power in the rpm range I drive it in (700-4000), so if the only symptom of clogged cats is poor power from being restrictive, and no effect on fuel economy, then I'm not going to worry about that.
thanks!
-Bernard
About 400 miles ago I replaced the engine with a rebuilt HO.
This was my first engine swap fwiw.
I've got it running great, but, I've got terrible fuel economy. Like 13mpg last tank, when I'm used to 18-20mpg the way I drive. My first tank I had too much fun with the engine, and the 10mpg didn't worry me yet, but my last tank, all commuting and no fun, was 12.5mpg!
Anyway.
I never retightened the header bolts: I only tightened them once, while the engine was out of the car before installing. Could heat cycles have loosened them? I might have an exhaust leak there, which could lead to rich running, which could kill fuel economy.
I'm also wondering since I put in new headers and an h-pipe --stock 2.25"-- that maybe at that ball and socket they might not be sealing perfectly? It's just metal on metal, the hpipe sockets didn't seem perfectly spherical, the hpipes weren't from the same car as the headers, so they may not be sealing right.
I tried asking at pepboys if they had gaskets; they had these really thick donut gaskets that just plain didn't fit.
Can gaskets be found to put here? Maybe you even have a NAPA part # for me?
Might try to do this tonight if possible.
Finally just idly thinking that, as I have no idea of the history of these hpipes, how would I know if the cats were clogged, and would that affect fuel economy anyway?
Seems to have alright power in the rpm range I drive it in (700-4000), so if the only symptom of clogged cats is poor power from being restrictive, and no effect on fuel economy, then I'm not going to worry about that.
thanks!
-Bernard