What are the best sources for y-block headers?  I have been out of this game about 40 years but am now building a 312 with ported 411 heads and a Paxton blower setup.  I plan to run a toploader on it, so have clutch linkage.  Does anyone build a good 2-inch header that will fit this in a 57 Fairlane with manual steering?  I see some advertised but need advice based on experience.

Well maybe I'm just stupid but I call it "old" but I don't guess I understand "boost". The only experience I have with "boost" is my Banks turbo on my '92 Ford 7.3 diesel pickup. It cruises a 5 psi and under a load it is at 11 - 12 psi. If the wastegate sticks it will peg the needle at 15 psi. I think any powerstroke is at 14 psi. I realize that it is diesel vs gas and detonation is a way of life with a diesel. I remember when Ford first came out with turbo's in '94 it made about 4 -6 psi and it was almost like not even having a turbo. I think tractor pullers have like 200 psi through up to 4 turbos. How in the world can they make that much boost if 6 psi is too much for a Y-block? Is turbo boost different than supercharger boost? I think old airplane motors had like 75 psi and they used 115/145 octane fuel. I know the experts on here, and I mean that, you guys are experts, can explain this to me ...

Doing Fords for 45 years. '56 Customline Victoria

E.J. in Havana FL

It's all in how the engine is designed.  An engine running 200psi has been built for it.  Everything from the block, crank, rods, pistons, heads, etc is beefed up to handle the power.  Most of the Y-blocks running around have cast pistons.  With cast pistons about 6psi is the most it should take.  Cast pistons are fragile.  One episode of detonation and something is probably coming appart.  The Y can take a lot more if it is built for it.  The same is true for most other engines.

Turbocharger and supercharger boost is the same.  A turbo system is a little more dynamic.  Since it's not belt driven, the boost pressure is not a function of engine rpm.

Lawrenceville, GA

The boost typically added to a Y-block by a supercharger or turbo ultimately is not the issue, unless someone is going above 11-12 psi, measured at the supercharger outlet.  The issue is horsepower.  Your answer hits the nail on the head.  As you increase boost, horsepower increases.  If you add too much horsepower to an engine that is not made for it, you will break something.  Elsewhere in this forum are some pictures by Ted Eaton of sbf engines that were built up to more horsepower than they can take.

My earlier comments about boost were made to provide some idea about how much air I need to run through the engine as one factor to consider in selecting headers.

I may have mentioned somewhere above that if you measure boost from the supercharger I plan to use, at about 6200 rpm it will show 11 to 12 psi at the blower outlet.  If you measure the same pressure in the intake manifold, after various losses through the carbs, etc., you will see no more than 6 psi, maybe less.  That is because of friction loss in the system.  Typically, boost has traditionally been measured at the blower outlet, but measuring manifold pressure is a better indicator of what may be reaching the valves, where even more friction loss occurs as air flows through the head to the cylinder.  I am not sure where you are measuring the tubo boost on the Powerstroke, but it is likely somewhere near where the air enters the head, thus 15 psi of boost on your diesel is probably equivalent to the 6-psi I would read in a Y-block manifold when the supercharger is putting out 11-12 psi at its outlet.  If so, the diesel turbo is adding a lot more boost than I plan to add to a gas Y-block for street driving.

Getting back to the header issue, everyone seems to agree that going to more than 1-5/8 inch primary pipes on the header will cost low and mid-range power on a street car, even with the supercharger.  I accept this, but I am not sure I understand exactly why this happens.  Can anyone explain this?