Quote:
Originally Posted by mgarblik
We brought the Grocery Getter out in 1996 with three 1972-1974 455 stock blocks. Using Program Engineering caps. The crankshafts were stock Pontiac N cranks, carefully prepared by me with no surface treatments, just nice oil holes and large radius. Lots of tuning errors with the nitrous. Lots of time spent learning the ignition timing the engine really wanted. Even a quarter mile run starting in 2nd. gear with all that nitrous when a shift linkage part failed. Never made the kind of power Marty made, but I would argue, we may have been just as abusive to the block. We were right at 1000 HP which was allot in those days. All three blocks did eventually fail and they all failed in the same area. Right up the oil passage at the #2 oil feed drilling from the main saddle to the cam bearing. At least for us, that was the weak spot in the 455's. Overall, the Pontiac block is very tough. By the way, no lifter brace in any of the blocks. Roller cam though with .850 lift and 260 lbs. on the seat back in those old days. We also ran our blocks unfilled. Didn't want the weight, didn't want the bore distortion, did want the cooling.
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Marty had a NA block 455 HO I believe, that was run at Norwalk, 740 HP range, just prior to the Turbo project. He decided to stop racing the engine 'one pass before the engine failed' (He drove the car on the trailer and we saw the failures when the engine was torn down).
All three center 4 bolt main caps were cracked. #3 was starting to crack up the inside bolt hole in the main cap. #4 was cracked about 1/3-1/2 of the way up the inside bolt hole, and the #2 main cap was cracked all the way up the hole on one side.
The outer bolt and the center stud and nut/washer were the only things keeping the cap in place. It was now a 2 piece cap.
So my visual inspection of the block/main cap failure said: that the #2 main failed first, then the #4 main, then the #3 main was soon to follow.
That fits exactly with your failures in the "#2 oil feed drilling from the main saddle" with your 455 engine blocks, Mike.
Tom V.