Powering up the 403 Tech Q@A

Hello everyone. I'm new to the forum. I hope that I'm posting this in the correct place. Anyway, I just finished reading the August 2009 issue of High Performance Pontiac. On page 88 in the Tech Q&A, John Vaccaro from Scottsdale Arizona asks questions about a 1977 403 Trans Am. Terry Fritch answers quite nicely. What Terry says about the 403's stock cast iron manifolds being restrictive is true and the requirement for headers creates other difficulties such as fitting the vehicle. This no longer needs to be a problem as Thorton Reproductions have had GM licenced restoration exhaust manifolds since March 2008 for "dedicated dual exhaust" that fit 64-88 Oldsmobile 307, 330, 350 and 403 engines . They will fit all GM A body, G body, F body, (Trans AM with a 403)and 1971 and newer B and C body cars. These manifolds are based on the 455 but modified to be much better flowing than anything stock. If it's a street driver with a 403 in it I would think that the tradeoff in horsepower for the aggravation of headers is negligible. I'd use the cast iron manifolds in a New York minute. Just a suggestion. The last time I inquired they were $291 a set plus shipping and handling. Thorton Reproductions, 832 Mine Road, Quakertown,Pennsylvania 18951. Phone 610-282-2494. Fax 610-282-2484.  

Great info for the Olds power crowd! I agree with your point about manifolds for the street, especially nearly stock cars. I haven't checked in along time, but doesn't anyone make headers for 403 cars anymore?
Steve  
Trying to help... 'cause we don't all have to learn the hard way!