Attempt/Mistake #2

[68 TT]

Originally Posted by El Campo

I am at work right now but I will get you all that when I get a chance. I know it's 11:1 compression, and has a Xtreme Energy 292 mechanical roller. Has a Proform 950 carb ( the fuel/air was perfect when it was dynoed). The shop that I had it at thought that the reason it fell off at those RPMs was because of the 4.5 inch stroke. Seemed odd to me that it peaked at such low RPM though. The cam isn't massive (which the heads woul benefit from) because the truck is street driven. I called Comp Cams before I bought everything and this is the one they recommended. Another thing that was odd to me was that it made max power with only 32 degrees of total timing!! That was before I had the MSD though (not sure if that makes any difference) I would be happy to spend some money on the engine if it would help my power if I knew what to do. I had old trashy 1.5 inch no name headers on it when was dynoed. I have since gotten these 1 7/8 inch primary Hookers. 3 inch dual exhausts.

The 565 in my best friends dragster makes the best power at 34 degrees so 32 is not far off. I wouldn't go any higher than 34, on the dyno it fell off in power quickly above that. The stroke will lower the power band but not that far. You should be in the 6500 to 7000 rpm range for peak power with what you have.

Your headers are tiny for that big of an engine and may be the reason it falls on its face at such a low RPM, it just can't breathe. A 2" tube is a little small for that engine so look for a set of 2-1/8" tube headers. It would probably be happy with 2-1/4" tubes like we run on the 565 with the combination you have as well if you find a good deal on a set.

3" duals should be OK as long as the bends are mandrel bends and not crush type. Typical muffler shop crush type hydraulic bends in a 3" pipe will restrict its flow down to that of a 2-1/2" pipe or smaller depending upon the bend radius. Way too small for your engine.

The rest of your package sounds like a good parts match for the cubes. I think most of your problem is in the exhaust side.

You could also be getting some valve float from too little valve spring pressure if the wrong springs were used. Check your seat and open pressure to make sure they match up with what Comp says the cam needs.