Originally Posted by
badaml
On the stock engine (427), does the head need to be shimmed to run 30%? Also, how is the engine with the jp1 pipe?
I wish I could tell you to shim or not to shim. Here in Central USA I did not use head shims on my Mach when I switched to 30%. I used it for 7 more gallons (11 total) before getting a second engine in a trade. The engine will need to be retuned. I fattened the high speed about 6 hours to be safe and backed out the idle mixture screw a bit, tuned from there.
If you have this engine in the buggy the JP-1 pipe be too much bottom end. The chassis gets overloaded with torque and there is a lot of wheelspin, tires wear very fast, no traction. I would get a jp-2/3/4 instead. The jp-1 is for bottom end and this engine already has a ton of it. The pipes make a difference in the way an engine performs so read about what they are designed for and go from there. This engine is a great budget engine.