Chevelle Header Suggestions??

[Texas Hotrod]

That must be when the "D" ports were popular and the round ports were your basic design. LS1 heads are round port, so I guess the D port wasn't much better.
Round port headers will work fine on D port heads. Make sure the gaskets are round port.
I learned by trial-n-error to use some red silicone to seal the headers, and throw the gaskets in the trash. Run a file across the flanges to make sure the faces are clean. The headers on my Biscayne sealed just fine, haven't had any leaks in 6 yrs.



Spend a few extra bucks and get ceramic coated headers. The will look nice for a long time, radiate less heat, and add a few extra ponies (compared to non-coated tubes).