Ford Muscle Cars Tech Forum banner

1 - 1 of 1 Posts

·
Premium Member
Joined
·
1,065 Posts
Discussion Starter · #1 ·
1 5/8" vs. 1 3/4" headers- how much power is lost?

I am temporarily forced to use a set of 1 5/8" headers ( MAC longtubes with 3" collectors)in my 393 due to several reasons.I am not happy with that since the exhaust ports in the AFR 185 heads are almost round and the header ports at flange are traditional Ford sb rectangular.I ported the headers at flange area as much as possible in order to smoothen out the flow reducing step but I quess it does not help too much.This step is something like 1/5" inch both sides of the port.Floor and roof are ok, except for the corners. This mismatch and the smaller pipe size will no doubt reduce the power output but how much? Lets talk about open exhaust, no mufflers.This engine should put out someting like 530-540 horses at 6000 with 1 3/4" headers and open exhaust.
One last point: to me it looked like the AFR exhaust port size is very much the same size as the 1 5/8" header pipe size.Do we need larger header pipe sizes than the port itself? Is the only problem the mismatch between the shapes of the header port at flange vs. the exhaust port or does this engine need the bigger 1 3/4" pipe as well?
 
1 - 1 of 1 Posts
Top