I HAVE USED DOWNY 6-2-1 AND MY ONLY COMPLIANT IS THE FITTMENT OF THE FLANGE AND INTAKE FOR BOTH UNITS I HAVE PURCHASED,HOWEVER THE MATERIALS USED TO BUILD THESE HEADERS LAST LONGER THAN THE MANAFRE HEADER,I HAD A 40 WHICH I PURCHASED DOWNEY HEADERS FOR AND HAD NO PROBLEM WITH WARPAGE OR RUST UNTIL ABOUT 9 YEARS OF HARD USAGE AND WELDED THE RUST SPOT AND IT STILL DOES NOT LEAK,I PURCHASED A 60 WITH A DOWNEY HEADER ,THE OIGINAL OWNER HAD INSTALLED 10 YEARS BEFORE I PURCHASD IT AND HE SAID THE HEADER HAD JUST STARTED LEAKING A LITTLE SO I TOOK IT OFF AND WELDED IT IN THE SAME PLACE THE HEADER LEAKED ON THE 40 AND PROBLEM SOLVED,HOWEVER I DONATED THE REPARED 60 HEADER TO MY FRIENDS PROJECT 40 AND PURCHASED A NEW DOWNEY HEADER FOR THE 60, AND HAD THE SAME FITMENT PROBLEM AS I DID WITH THE 40,THE HEADER AND MANIFOLD MUST BE GROUND FOR A PERFECT FIT IT TAKES ME ABOUT AN HOUR TO MAKE THE PROPER FIT,BUT I WOULD RATHER SPEND THE TIME TO MAKE THE DOWNEY HEADER FIT THAN TO HAVE TO CONSTANTLY TWEAK ON A LESS QUALITY HEADER,PLUS MOST HEADERS DONT LAST 5 YEARS WITHOUT TOTAL RUST COVERAGE AND WARPAGE THAT HAS NOT BEEN THE CASE WITH DOWNEY HEADERS FOR ME.
ON ANOTHER NOTE FOR A PERFECT NO LEAK INTAKE HEADER FLANGE FITMENT USE A LARGE DIA WASHER WITH AS CLOSE TO THE SIZE OF THE STUD AS POSSIBLE 7/16 OR 3/8 AND GRIND TO AN EGG SHAPE SO THAT THE FAT END IS OVER THE HEADER AND THE SMALL END FITS INTO THE RECESED AREA ON THE INTAKE,I HAVE USED THIS ON MY CRUISER AND MY FRIENDS AND THEY NEVER LEAK AT THE INTAKE/EXAUST AREA . AS FAR AS THE FLANGE CONNECTION BY THE EXPENSIVE GASKETS AND USE COPPER COAT I GET ABOUT 6 TO 8 MONTHS IF I AM WHEELING ALOT 12 IF NOT,ALSO USE THE FACTORY HARD MOUNT THAT BOLTS TO THE BELLHOUSING OR YOUR HEADER WILL CRACK OVER TIME.
THESE HAVE BEEN MY EXPERIENCES WITH DOWNEY HEADERS.
THE MANAFRE STYLE I HAVE ONLY SEEN THEM ON OTHER CRUISERS AND MOST OF THEM LEAKED.
GOOD LUCK AND DO IT RIGHT THE FIRST TIME!!!!!