350 heads on 403
#1
350 heads on 403
Anyone have any insight on which heads to use on a 403 to boost compression? Have choices of 5A 68cc, 6 has &70cc and 7 has 69cc. Need information on what these heads came out on, and what they would cross over as far as part #. I know a 403 is not a good candidate for high horsepower, due to the bottom end just trying to get compression above 8.5-1. Thanks The #s are located on the left front and right rear of the heads.
#2
A 403 moves as much air as a 400 big block. Why handicap it with small port heads from an SBO. Use BBO heads, port-match the intake as required, and either mill the heads or change the pistons to get the CR you want. The only reason to use SBO heads on a 403 is if you have a Trans Am and need to retain the stock intake so the shaker scoop still fits.
#3
The heads you have are all around the same as far as flow rate. You can install larger valves if doing a valve job to increase the flow.
As for what they came on, all SBO engines used the same heads during any given year:
5 = 1968-1969
6 = 1970
7 = 1971
7A = 1972 (small size capital A)
As for what they came on, all SBO engines used the same heads during any given year:
5 = 1968-1969
6 = 1970
7 = 1971
7A = 1972 (small size capital A)
#5
Consider 330 heads as well. #3 and #4 heads have a smaller combustion chamber than the 350 heads. Even #2 heads, if you can find them, will work however they'll have 3/8 stud holes at the rocker arms. They require the same work and most #3 and early #4 might require some clearance on the pushrod holes due to the different bank angle of early engines. Any standard replacement head gasket is also ~.025" thicker unless you get MLS adding another ~4cc of volume.
#7
I have two sets of #4 heads - One set is bare castings - Magged NO CRACKS - light rust. I can BB them in 10 mins and look better, but then I want more for them. . Plus, I have a set of take offs from a 330 complete.
I've ran #4's on 403's and my favorite head - other than a set of race port #5s or #6''s
$300 for the bare set and $250 for the take off's as IS. Plus the ride. Each head is about 47 lbs and will be roughly $100-$120 to ship.
Each head takes about 1hour to wrap and single box. PITA ! I hate shipping heads.
If you want/need the 330 forged crank out of the same motor I pulled heads - its available as well to. Bigger PITA to ship. NO Flex plates....
My zip is 78681.
Email is sigtauswt@yahoo.com
I've ran #4's on 403's and my favorite head - other than a set of race port #5s or #6''s
$300 for the bare set and $250 for the take off's as IS. Plus the ride. Each head is about 47 lbs and will be roughly $100-$120 to ship.
Each head takes about 1hour to wrap and single box. PITA ! I hate shipping heads.
If you want/need the 330 forged crank out of the same motor I pulled heads - its available as well to. Bigger PITA to ship. NO Flex plates....
My zip is 78681.
Email is sigtauswt@yahoo.com
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