I have a 406 SBC, 13:1, fairly radical cam (697 lift, 290 dur), solid roller, Dart block, heads. Motor runs very strong, and has gone 9.80's in a Vega, with 1 850 carb. I recently bought it, and proceeded to replace the intake with a Pro Dominator Holley tunnel ram w/ 2 660's. Again...this motor runs very strong, but blows out the front and rear intake seals as soon as I do a test burn out in my parking lot. I have breathers to the headers for crank case pressur evac. I have replaced the intake gasket 3 times....same situation. The intake looks good....like new....I picked it up from a fairly reputable seller at a swap meet......there are some of those. The motor is 23 degree. Is it possible that this intake was modified for an 18 degree application? Do you even have to modify the intake for that? Thanks in advance for any input.