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Borla · 10-21-2005, 05:32 AM

Food for thought........the car is basically 10 years old. Unless the rest of the exhaust has been replaced recently, it's likely to have a fair amount of build-up in the cat and the muffler........the header is even less likely to have a positive effect on performance if there is added restriction further down the line.

Imagine it this way.....you are pumping gas into a gas can, using a funnel. The pump can pump faster than the narrow end of the funnel can pour into the can. What do you do if you want to be able to fill the can faster? Make the top of the funnel bigger? No, because the narrow part of the funnel still isn't going to flow any faster. You have to widen the narrowest part first to see any real improvement. The same principle applies to air flow from your engine through your exhaust. You have to improve the most restricted places to see improvement. You can put a huge 4" tip on the exhaust, but if the pipe further up between the muffler and cat is only 2", it was a waste. You can put a higher flowing header in, but again, if there is restriction downstream, you are still not going to see much difference. ESPECIALLY if the install causes you to have an exhaust leak somewhere, like because there is no exhaust gasket. Aside from the mention of warping valves, having a severe exhaust leak (like what would occur from having all kinds of air rushing in where a gasket should be), could cause your engine to run very lean (i.e. not enough gas for the amount of fuel it is mixing into the combustion chambers). If you run too lean for too long, you are going to put a hole in a piston, or comparable severe damage can occur. I wouldn't drive the car around much with the current issue. Worst case I'd return to the old manifold, with a gasket, then do research to be SURE the header is appropriate, the gasket will fit, and (for any real benefit) replace the rest of the exhaust too.

Just my $.02.

10-21-2005, 05:32 AM	#16 (permalink)
Borla Junkie	Food for thought........the car is basically 10 years old. Unless the rest of the exhaust has been replaced recently, it's likely to have a fair amount of build-up in the cat and the muffler........the header is even less likely to have a positive effect on performance if there is added restriction further down the line. Imagine it this way.....you are pumping gas into a gas can, using a funnel. The pump can pump faster than the narrow end of the funnel can pour into the can. What do you do if you want to be able to fill the can faster? Make the top of the funnel bigger? No, because the narrow part of the funnel still isn't going to flow any faster. You have to widen the narrowest part first to see any real improvement. The same principle applies to air flow from your engine through your exhaust. You have to improve the most restricted places to see improvement. You can put a huge 4" tip on the exhaust, but if the pipe further up between the muffler and cat is only 2", it was a waste. You can put a higher flowing header in, but again, if there is restriction downstream, you are still not going to see much difference. ESPECIALLY if the install causes you to have an exhaust leak somewhere, like because there is no exhaust gasket. Aside from the mention of warping valves, having a severe exhaust leak (like what would occur from having all kinds of air rushing in where a gasket should be), could cause your engine to run very lean (i.e. not enough gas for the amount of fuel it is mixing into the combustion chambers). If you run too lean for too long, you are going to put a hole in a piston, or comparable severe damage can occur. I wouldn't drive the car around much with the current issue. Worst case I'd return to the old manifold, with a gasket, then do research to be SURE the header is appropriate, the gasket will fit, and (for any real benefit) replace the rest of the exhaust too. Just my $.02. __________________ Coimhéad fearg fhear na foighde!!!!