When to use TFS heads
| Since I get asked this all the time here is my OPINION on the matter, along with the reasoning for it. Some might agree, some might not, but these are my thoughts with how I see things at the moment. In comparing the TFS heads they have about the same exhaust flow as a well ported PI head, but much more raw intake flow, much more intake valve to piston clearance, and do not have spark plug thread issues. So what is logical to me is to use the TFS head where any one of these becomes an advantage. Another point to consider is that the intake flow is only better up to about the 200CFM range if using the stock plastic PI intake as that is about all it will allow. The TFS is a ton better in the mid intake lift range and this is where IMHO the gains NA are being found when its used with the plastic intake. Combos I would use them in: NA 4.6 with a stock bottom end and you absolutely positively will not remove the pistons to notch them. In this case you can get another 10-30RWHP mainly because you can fit a better cam spec, typically 220-233 of intake duration advanced well into the 106 intake centerline range. This holds true only for the PI plastic intake as once you use these heads with any other real intake the RPM will skyrocket past what the stock shortblock can handle. NA 4.6 with an aftermarket bottom end, real intake manifold and HP peak at 7000RPM or higher. There are race cars with these heads unported shifting at 9000+RPM, that should tell you what these heads are capable of. Roots/KB/Whipple blower 4.6 or 5.4 - you finally get to use all the extra intake flow. For Lightnings with aftermarket blowers this is a really good choice to consider. Turbo or blower 4.6 with a real intake manifold, aftermarket bottom end, and 6600+ shift points. Remember we are getting 500-600RWHP with a blower and 600-700RWHP with a turbo with our PI heads on a 4.6 So for me to tell you to spend the extra for the TFS means you are wanting to surpass these numbers and stay 2V. 5.4 with a HPS intake will gain a little bit over a well ported PI head but not much as the HPS intake is becoming a restrictor just like the plastic PI intake is with the 4.6 version. NA 5.4 with an Edelbrock intake with adapter plates and a carb. If either TFS or Edelbrock make a 5.4 version of their intake I will modify this statement. Both companies have expressed interest but both wonder if the market is there to support it. Adaptor plates with a 4.6 intake on a 5.4 and fuel injected is not going to run as good as it should and IMHO the HPS intake will not support the RPM range this combo would do. A carbed TFS head 5.4 with a heavy dose of nitrous could make one serious race 2V engine especially with a big bore. Basically the issue with these heads is that you have a ton of potential, but the plastic PI intake manifold is only going to allow so much of it to be realized in a typical street operating range. If you don't want to touch the bottom end, and want to be as fast as possible NA then you can use these heads to up your compression ratio and fit a much better cam than is possible with a stock PI head. Once you go past that range they get race ready quickly. They are the ultimate high RPM race head for many of the rules restricted classes. There are other features that are better on the TFS also, they have the best valves I have seen used yet, and the cam caps are not only replaceable, they don't scratch near as easily as the stock heads. In all honesty, both of those features would be noticed by maybe 5% of the population using them. Guys tearing down race motors constantly would instantly love both features. I really like the TFS heads myself but I do not recommend them to everybody as some shops are doing. Not everybody can use their full potential and the last thing I want is someone spending $2000 plus and not going as fast as they thought they would. The engine is a combo and part of a larger combo - your car. You need to consider all the ingredients involved and match everything well together. |