Only the L16/18 had this 4 into 2 manifold. The L20B is 4 into 1. Congrats! I did the same thing on my 76 L20B.

Pretty much a header that never wears out...

I had to make my own dual down pipe. Modified a 240sx pipe...

What did you do about the intake joined to the exhaust manifold.

Randalla 29

Posted March 15

Do you know that the 68-73 510 down-PIPING is the same for the 710?  I agree if you are using the earlier exhaust manifold, you want the matching upper flange++ of the downpipe, but I bet the down-PIPING won't fit the 710 chassis......??  When you find a complete downpipe, you might just have the seller (sorry, I'm out of spares) cut it about 3-4 inches down from the flange, which will also save you mulla in shipping!  Any good muffler/exhaust shop can bend the down-PIPING to suite your 710 chassis.  If you know the 510 down-PIPING will fit, then never mind!! 🤪

Also, from what I have gathered, all of the 510 OEM downpipes were LONG, having the Y pipe (dual pipes) stretch almost down to the bend under the chassis.  I have seen a few really SHORT Y pipes, figured they were aftermarket replacements from back in the day, which might work well for you.......??  The LONGER the Y pipe, the better for performance, but I would think it would be marginal........??

Hope that helps!

510/710 use the same L series engine and transmission. Steering box is generally the same. I would take the chance. Truck L16 down pipe has to bend around the torsion bars but no steering box so it may not fit in a car????

My down pipe (pictured) is from an '90s? S13 or 14 and it fits. Flange had to be swapped to an L series but...