write a quick post about the new 331 I installed in my 66. I had a few issues because I updated the accessory drive to a March serpentine set up. The main problem was that I needed to use a new style reverse rotation water pump. however I had an old style (even though new) timing cover. So after sorting it out by finding the correct water pump (85 mustang) which had the correct bolt pattern and port layout It was on.

Its all installed and buttoned up and I AM Happy. It is really really strong. All I heard on here was that I was choosing the wrong cam, and that my heads were WAY TOO small. Also that my carb was wrong and too small. I went ahead and did my research and went with a forged 10:1 331 rotating assembly. (instead of a 347 becuse I drive a lot of miles. I was told that the rod angle on the 331 was much better and would wear bettter.I took my nearly new trick flow 170cc heads and had them ported, I also had my stealth intake ported and installed a x303 cam.

It is so strong that I cat hardly seem to get traction in 1st, 2nd, and 3rd. It also drives like it has a power band similar to a 2 stroke. Once it hits 2800 rpms it goes wild. I have the ignition red line set to 5500 rpms, I dont want to wind it up much higher than that until it is good and broken in.

I had Tuff Dawg here in AZ assemble it for me and do the machining. They were great. they always answered the phone and had the answers I was looking for. they were very professional.

all in all it was very worth it. i was told it should be about 440HP I dont actually know but it sinks my *** in the seat.

 

Nice!

 

Awesome! Glad to hear Just be careful shifting that T5 if you ever put sticky tires on it. Lots of fox body guys blow up main shafts due to excess traction/poor shifting.

 

347 will last just as long as a 331 these days. The wear from rod angles and such are a thing of the past (347 kits these days use different piston setups). The heads aren't terrible, and won't really hold you back unless you want tons of top end power; they work decent for something with broad power (still using my AFR 165's on my 331). But the X cam is seriously holding you back though, it's basically 80's technology. Not a huge problem, cams can be changed easily enough...especially roller cams (if you're ever so inclined).

I doubt it's 440hp though, especially with that cam. With smaller heads like that you need a pretty good cam to get up over 400hp in a 331. Prolly more like 385-400hp, but with a lot of torque. The reality, is most people are happier on the street with an engine that makes less power than they think they want; but with broad torque and good manners.

If you have money later, you could throw a custom cam and a Vic Jr on it and prolly make close to 400rwhp, which would be like 450 at the crank (you'd likely want a better carb with a single plane at that point though).

You'll prolly want to shift at like 6k or just a tad over.

 

As long as it makes enough power to peg your buttometer and has you grinning like an idiot then you did it right.