Well i've tried a million different things and id like to see if anyone has any more ideas. i have a 1969 gs400 with a 462 BB th400 ati 3500 stall and 355 gear, the old motor ran 12.60@105 with no problems with a stock stage 1 fuel pump over the winter i built a new shortblock the new motor makes approx 50-75 more hp and ever since ive installed it, the car gets a miss or cutsout above 5k rpms, ive swapped carbs, fuel pumps to a carter hi volume mechanical, ign coil, ign control box (stinger box) checked the valve springs, checked fuel pressure at WOT never dropped below 5.5#s i was told by mike at TA that the car may need an electric fuel pump to feed the manual pump because of the acceleration forces the manual pump may have trouble pulling fuel. cam was degreed and the motor was built by a very reputable race shop with knowledge of buicks. For those or you who were at norwalk it was the green 69 that ran several 12.30s with the high rpm miss, and its pictured on this board under the norwalk pics, thanks to whom ever posted that pic. thanks for any and all help, \ Shawn :spank:
Just because you don't drop below 5.5 psi does not mean you have enough fuel. You might have enough pressure , but do you have enough volume? Your set-up should be able to move 1 gal of fuel in about 30 to 35 seconds, this test is easy with an electric fuel pump, not so easy with a mechanical pump. Your miss could also be a jetting issue. These are only suggestions as you say nothing is wrong with the engine itself. Jim Burek
Make sure you don't have too much oil pressure. I had 90-95 and it would lay over and breakup at high rpm. 75-80 now and it revs no problem.... Just a thought since you said new shortblock.... Bruce
