MadMat

Will the headers from a 496 CMI sport tube package (http://www.custommarine.com/headerap...ncePackage.php) fit a 540 Bulldog OK (ie Mk IV block, tall deck, NA motor ).
Do the 496 headers have an O2 sensor in them already?
Thanks in advance
Matt

22 DAYTONA

They will fit. No o2 bung but they do have a heat sensor bung. The heat sensor bung might work for o2. I would call cmi and ask.

MadMat

Thanks

Raylar

Yes they will work on your big block. No the heat sensor bungs are only plumbed into the water jacket of the headers and not into the exhaust areas and they are not 18mm as the O2 sensors are. If you have a good stainless welder in your area, go to NAPA and buy the 18mm stainless bung fitting and have the shop carefully drill or cut the hole thru the inside face of the collector area through both inner and outer tube and carefully weld the bung to the inner tube and the outer tube of the header. After its welded be sure to pressure check for leaks. To install a wide band O2 sensor we use two 18mm spark plug extensions fittings (used in the old days to stop oil fouling on plugs) we weld or fit them together and thread the new fitting into the header with a small amount of anti-sieze on all threads but not so much it fouls the O2 sensor. This trick keeps the O2 sensor out of the moisture better in the header when taking readings. Also pick up the stainless 18mm plug so you can remove the O2 sensor when you've collected your readings and need to plug the bung. I have never been able to leave O2 sensors in place and get them to last very long at at about $85 a piece we hate to burn through the sensors. Write down your O2 air fuel reads at 100 rpm increments from idle right up to WOT and you will have the data you need to make fuel and some spark changes to your engine under loads.
If someone knows the type and number of the new O2 sensors some marine manufacturers are using on these new catalytic emission systems on the marine engines I would like to know how they hold up continously to salt water especially and if they can be adapted to our current wide band O2 meters??

Have fun

Best Regards,
Ray @ Raylar

MadMat

Thanks Ray! Damn, that p!sses on my plans to run it closed loop then. Is it possible that sensors that survive are narrowband so don't have the air pump? Or titania sensors and therefore fully sealed?
Also, not familiar with the spark plug extenders you mention - have you got a link/pic?