Inline 6 300 performance upgrade
Inline 6 300 performance upgrade
New here, just starting a 1985 E150 custom camper van build. My question is on improving the performance of my inline six 300. I had originally planned EFI headers and using an Offenhauser intake with a Holley 390, but on the webpage it states this set up won't fit. So I'm back to square one. I have access to a 351w but I'd like to just improve the 300 and save the 351 for a different project. Thought? Ideas?
Senior Member
Joined: Apr 2019
Posts: 1,236
I would save your money. You will not get the performance improvement you are expecting on a 4.9, especially a carburated one. . It was never intended for performance.You never mentioned what your differential ratio was. That could help but at the expense of fuel economy. If you really want a small performance improvement, go with the 351.That will help "some".You got a lot of weight you are trying to push along.
Junior Member
Joined: Jun 2022
Posts: 5
I had 1976 and 1980 E150s, both with manual 3-speeds. They would leave 20-30 feet of rubber (with only one tire), and chirp the 1-2 shift hard. I confess I don't know the rear axle ratio in either, and both were empty boxes (though long wheelbase). Never wanted for more power with either. Plenty of beans for passing on rural 2-lane highways.
Point is anything you can do to keep the weight down will help.
Next is picking a low-restriction, but still quiet, muffler. I don't remember the best brands (Google the CarCraft comparison article on them), but even the $30 Thrush Hush mufflers will free up some horsepower over the stocker.
Second, the later-model injected sixs have a much better set of exhaust manifolds. Beyond that, on the motor, there are a number of six cylinder forums that can guide you. Some of the 300 inch sixes will take a different intake manifold, which with a higher-flowing carb will increase the top end power signficantly - and burn more gas LOL. I forget which ones have a one-piece head/intake manifold.
Lastly - though much more expensive - is checking what you've got for a first gear ratio in the trans. Most acceleration that we care about is 0-40 mph, and a lower first gear makes that happen. If you've got an automatic, swapping in a 4-speed overdrive trans will let you drop the rear axle ratio, but still let a good low rpm highway cruise. Again, the above can get expensive, but IMO are less invasive than dropping in the Windsor you were considering, so thought I'd mention it.
Point is anything you can do to keep the weight down will help.
Next is picking a low-restriction, but still quiet, muffler. I don't remember the best brands (Google the CarCraft comparison article on them), but even the $30 Thrush Hush mufflers will free up some horsepower over the stocker.
Second, the later-model injected sixs have a much better set of exhaust manifolds. Beyond that, on the motor, there are a number of six cylinder forums that can guide you. Some of the 300 inch sixes will take a different intake manifold, which with a higher-flowing carb will increase the top end power signficantly - and burn more gas LOL. I forget which ones have a one-piece head/intake manifold.
Lastly - though much more expensive - is checking what you've got for a first gear ratio in the trans. Most acceleration that we care about is 0-40 mph, and a lower first gear makes that happen. If you've got an automatic, swapping in a 4-speed overdrive trans will let you drop the rear axle ratio, but still let a good low rpm highway cruise. Again, the above can get expensive, but IMO are less invasive than dropping in the Windsor you were considering, so thought I'd mention it.
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