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Thread: heads for 454

  1. #11
    BlackWidowBowTies
    Max RPM with the AA is 5400.
    Non GPS speed has been 82 mph.
    Factory compression on the LS6 was 11 1/4 to 1. The factory rated this motor at 450 hp. It was well known in within the hotrod public that the motors produced well over 500 hp.
    As for what Gaurdian Marine did to it to get 572 hp at 6000 rpm on the dyno, your guess is as good as mine. All the parts that were there from the origional motor I reused(it only had 14 hrs of operation on it),except for the block, which had been cracked from freezing. ( long story )
    I replaced the block with a raced prepped unit from Kim Barr Racing from Dallas Tx.
    I had the rotating assembly balanced and I spent alot of time Plasti-gauging and fitting the crank and connecting rods, pistons and rings. Added dry sump oiler.
    As I have been told often, every little thing helps and its all in the details. All the work that I did was based upon recommendations from several, old school racers from my youth. I have been building car engines for 20 yrs. But I had never built a Jetboat motor. Different stresses going on inside, so it was different. I have made well over 600 hp from a bigblock Buick 455 engine for my '70 GS.
    I dont claim to know much about this whole thing. It was as big a surprise to me to get those results from the Dyno as anyone. But the whole time I was being told to expect 600 hp or so. This was from Kimm Barr and others. The rebuild took me 4 months, I took my time and I am very proud of what I accomplished. As for the numbers, well it matters not to me if I am believed or not, I let the boat speak for itself.
    BWBT

  2. #12
    spectras only
    Hi Bow Ties,your boat "speeds" for itself and I'm not disputing dyno figures by reputable engine builders.We used to get Guardian Marine crate engines, they were basically marinized engines.Harman and Hardin Marine did the same.They used to put slightly hotter cams to bring the horsepower up from stock.I've built 460 engines with cams similar to your cam's specs and get good power increase with higher compression figures.You must remember the LS6's compression dropped significantly after 1971 when they went open chamber heads.Horspower was still rated at 450HP but you could tell the difference in performance in boats.My friend just sold his 1970 chevelle with the LS6, #match car and it went better than later chevelles.Your speed is in the rigth bracket with your HP figure but I would try to go to an A impeller to get the RPM to get the performance out of your engine.A truly balanced LS6 could take to 7000RPM occasionally.I have the tm2r manifold as well as most LS6's were equipped like that in the seventies.Life was good back then huh?Good boating and dont'loose your hat.

  3. #13
    BlackWidowBowTies
    Spectras only.
    Thanks, I really didnt mean to sound as if I had an attitude. I had planned on going to the "A" impeller. Seeing as how I dont push the RPMs into the engines max hp range. I appreciate the comments, and yes those were the good ol days.
    BWBT

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