Hey everyone, this is my first writeup on here. Seems that most everyone has the 302, 351, or a EFI 300, so I thought I'd give some eye candy to the carb 300 enthusiasts.
The stock carb 300 has about 120hp and 255tq. The engine is known to be a tank, and you definitely can't stop it. Unfortunately, you can't exactly get it going very quickly either.
Last summer I swapped out my stock log exhaust manifold for the dual manifolds from a stock fuel injected 4.9. (I'll have to dig up my pictures and put them in here too). The 1bbl exhaust had a 2" outlet, which is about a 3.1 square inch exit. The EFI manifolds have two 1.75" outlets. Together, that's about 4.8 square inches. About a 30% gain. I also went from the stock 1 7/8" exhaust to a high flow 2.5" exhaust. Not to mention the cat was original and was so plugged I was blowing manifold gaskets. The difference was amazing. Est. 145hp/270tq. Total cost from engine block to tailpipe: ~$400
This spring it was time for an intake upgrade. The stock Carter one barrel on the 300 is about 180 - 200cfm (heard quite a few different numbers). It does well up until around 3000 RPMs and then gives out. With the stock setup, you can't get it up much over 3000 anyway so this is okay. However, with a much higher flowing exhaust, it was time for some more carb.
After doing about a year of research (might as well since I had the time, not the money), the Offenhauser dual port intake with a Holley 390 was agreed to be a very good upgrade. I found one used from a guy who threw a rod in his engine for much less than new. Normal price was about $800, picked his up for about $300.
The hardest part was making an accelerator bracket for the engine since the stock bracket bolted to the stock intake. Just took some ingenuity.
After wading through and removing the stock tangle and mess of vacuum lines and removing the stock intake, I bolted the new intake in and connected the carb. It fired up nicely and after a little tuning we took it for a test drive. Even with a 3.00 rear end, it snapped
the RPMs right up to around 4000 and definitely wanted more. Without some head building, I probably shouldn't be taking it much higher than that, although it seemed like it certainly wouldn't care. My easy going 300 has suddenly become a force to be reckoned with. I couldn't believe the difference, it basically felt like I just removing 1500lbs from the vehicle and it felt as light as a toy.
Est: 170hp / 290tq.
The new intake, prepped and ready to go.
Fitting on the Holley carb to check for accelerator bracket alignment.
Comparing the old Carter 1bbl with the new Holley 390.
Here's a comparison of the venturi sizes. No wonder...
My brother working away with the grinder making the cable bracket.
The mostly stock engine bay, just ready and waiting.
Another view of the engine bay.
Here's a view of the previous intake and exhaust. Gotta love the mess of vacuum lines.
A view of the stock carb on the engine. It's put in some good work, but it's time to go.
A cleaner view of the intake/exhaust with all the lines out of the way.
A clear view of the dual exhaust manifolds from the fuel injected 4.9. Those things are sweeeeet.
The new intake set in place on the engine. No work required, it fits perfectly.
Here's me working away, torquing down the manifold bolts.
My Bronco with my brother's Jeep. Another awesome straight six. (4.0L high output.)
The finished custom accelerator bracket. Simple, effective, and hidden from sight under the air cleaner.
Hooking up the necessary vacuum lines and hoses. There were so few, it took me a moment to believe it.
The final touch. Tuned, and ready to go.
Next on the list is a distributor recurve. This moves the distributor's vacuum advance from an emissions oriented curve to a performance curve and will really wake this whole setup right up. The kit cost $4 and is sitting on my work bench. After that, it's a head P&P (maybe this summer), and a cam. From what I've read, this should be setting the engine right around 210hp/325tq. Should have come like this from the factory...