Ford 300 HD exhaust and attached intake manifolds - used

The real deal.

https://www.ebay.com/itm/134300114447?hash=item1f44e91e0f:g:DToAAOSws~NjWR-R&amdata=enc%3AAQAHAAAAsGaPSaEsJUzlOY0IOi8cV%2FioWnwDcDwTZu52KNB3j0K8AfzVxTcQLW6muG3AXKifzI4AAj7p8RQ38Xp6NHAe%2FJ3lkZbzsDHWiZ2bdtbHCo%2BRd%2FaY%2B6VmUnLJu%2Ft9W%2B1jBnAB7Xf5XI2UiYd6rS0kz6JF7%2BeQF6kRgtFXhHtPrcvoqfGOh6mkUd0OpTa6RYpoHQDf4LxDTmudffQjnnWQ5nuCzYsC%2FfScrp6HBbmVuL4i%7Ctkp%3ABk9SR8Kj3beRYQ

Compare to aftermarket:

https://www.ebay.com/itm/275532046393?hash=item4026fd6039:g:2hcAAOSwakRjao34&amdata=enc%3AAQAHAAAA8PUp%2FFZdmIYL%2F2vwYWBp67eToEw9LOyCm4a%2BpGoz4Wo0df3bTXo7Ep3shSRVxh9p%2BPbM7YIobNNP4ytVRGIuMtls6Q20ZSUcWNSEoHEEPdFRxlYfrR3Sl35PHGGLCpk6Y37JRTc38ScfWOkW5t3ekND2DCa%2B0Q64LSKHmhvcscVopFP14zmmOHxRZL1osycGtQdEEKNiXRmdU1hqQheHSV5N48NHAb96K8XiDbF4K4VUF2YpYvxBvBkgvmcSz%2BsfGKqJKMa8qlm2fyORqZMMETM4IC10eVZQ%2FHha6xG4NSsMUvnG%2BF878HfDyq6sFwzvjQ%3D%3D%7Ctkp%3ABk9SR8Cj3beRYQ

David - Is the second set actually aftermarket?  But the first set sure is a lot less expensive.

How much do those help the 300?

The 2nd listing is aftermarket: "New aftermarket exhaust manifold. Manufactured to exacting standards. Quality inspected for your satisfaction."

The opening at ~2 1/2" is larger than the standard log manifold and was designed to allow the engines in the F600 to run at 3000 RPMs and higher under full throttle. The F.I. exhaust [more modern] had almost the same flow capacity and some say the FI manifolds are superior due to the smoother bends, but the FI exhaust manifolds had additional bolts to hold them in place relative to the exhaust ports. Since the F.I. exhaust manifolds were not attached to the intake manifold, the exhaust manifolds can shift downward [without clips to hold in place] which can result in exhaust leaks and restrictions, when used on pre-FI heads without the additional bolts.

The HD intake manifold does not have the thermostatically controlled plate to direct the exhaust to the underside of the intake manifold, so it would not be "happy" when cold and some think it would get too hot when at operating temperature. There is a large opening where the plate would have been. I personally don't believe the latter part in that FORD engineers had a reason for doing what they did.

I was not able to obtain the exhaust manifold when I was trying to get the best gas mileage, but would have loved to install an Edelbrock SP180, which was designed with smaller runners than the stock log intake manifold to enhance low RPM torque and install the carburetor I had from a 1970 F350 with 300 engine and use these with a HD exhaust manifold flowing through a larger diamater single exhaust and a freer flowing Magnaflow muffler.

Thanks for that explanation, David.  It helps me understand.  And, given that the HD pieces would be an interesting addition to someone's 300 build.  

1986F150Six wrote

The real deal.

https://www.ebay.com/itm/134300114447?hash=item1f44e91e0f:g:DToAAOSws~NjWR-R&amdata=enc%3AAQAHAAAAsGaPSaEsJUzlOY0IOi8cV%2FioWnwDcDwTZu52KNB3j0K8AfzVxTcQLW6muG3AXKifzI4AAj7p8RQ38Xp6NHAe%2FJ3lkZbzsDHWiZ2bdtbHCo%2BRd%2FaY%2B6VmUnLJu%2Ft9W%2B1jBnAB7Xf5XI2UiYd6rS0kz6JF7%2BeQF6kRgtFXhHtPrcvoqfGOh6mkUd0OpTa6RYpoHQDf4LxDTmudffQjnnWQ5nuCzYsC%2FfScrp6HBbmVuL4i%7Ctkp%3ABk9SR8Kj3beRYQ

SOLD!

Someone saw the benefits thereof.  Wonder who?