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KOZY
10-09-2000, 11:39 AM
looking to replace my standard performance oval port heads, would large oval be the way to go.

BlackWidowBowTies
10-11-2000, 04:38 PM
I would highly recommend the "rectangle port" heads you speak of.
I recently put the finishing touches on my latest 454, actually a .30 over. I prted and polished the heads to improve flow.
With a few other goodies I achieved a naturally aspirated 630 hp. Not the greatest number in the world but its as solid a motor as I have ever seen. Forged bottom end and all. After porting and polishing I gained 27hp.

hoolign
10-12-2000, 06:40 AM
just curious,ive just done 5000.00 {cdn} on a 1970 454 which was already bored .30 over with 11 1/2:1 trw pistons had the heads ported and polished {peanut heads},5000rpm cam,roller rockers,valves and guides,it runs 114 octane through a 850 holley dbl pumper and it dyno'd at 525 horse,what {goodies}did you add? yo get630

spectras only
10-12-2000, 10:50 AM
Hi guys,I have a legitimate 454 LS6 in my 24 daycruiser.They come with forged crank,pistons,rectangular heads, solid lifters,11,1/4 compression, heat treated rockers and forged rods.The factory rated horsepower is 450.To gain 180 HP you need a lot more than polishing and porting.Polishing and porting only gives an advantage well over 6000RPM.If you contact Lingenfelter racing,they tell you not to bother with porting and polishing unless you are running in the 7000 RPM range.I turn 5000RPM with my stock LS6 on a 14/13 OJ 3 blade prop that gives me a theorethical 57/58MPH.To obtain 630HP I would need to change to a radical cam,a much higher comression ratio.I also run a 800CFM double pumper Holley.Lingenfelter is the undisputed Chevy guru when it comes for serious engine building.I would take his advise in future modification on my engine.By the way Cheetah boats built their boats in the 70's.You see some examples in reader rides.So go back some issues and yuo'll find some owners who would share their information.

BlackWidowBowTies
10-12-2000, 03:40 PM
Originally posted by spectras only:
Hi guys,I have a legitimate 454 LS6 in my 24 daycruiser.They come with forged crank,pistons,rectangular heads, solid lifters,11,1/4 compression, heat treated rockers and forged rods.The factory rated horsepower is 450.To gain 180 HP you need a lot more than polishing and porting.Polishing and porting only gives an advantage well over 6000RPM.If you contact Lingenfelter racing,they tell you not to bother with porting and polishing unless you are running in the 7000 RPM range.I turn 5000RPM with my stock LS6 on a 14/13 OJ 3 blade prop that gives me a theorethical 57/58MPH.To obtain 630HP I would need to change to a radical cam,a much higher comression ratio.I also run a 800CFM double pumper Holley.Lingenfelter is the undisputed Chevy guru when it comes for serious engine building.I would take his advise in future modification on my engine.By the way Cheetah boats built their boats in the 70's.You see some examples in reader rides.So go back some issues and yuo'll find some owners who would share their information.
Engine was an origional LS6 as well, Contact Kim Barr Racing Engines in Dallas for actual Dynoed numbers 628hp to be exact. As the motor came from its origional manufacturer Guardian Marine it produced 572 hp with Bassett racing headers, which I am using.
The origional LS6 was quoted by GM at 450. Actual numbers were 525 to 540 hp. Check out HP books BigBlock Chevy power,
decent source for info. With all due respect, John Ligenfelter does build a mean motor, but Kim Barr has been a prostock racer and has been building race engines for 22 yrs. Hes on the all time fastest ProStock top 250.
Anyway, I dont claim to know everything, by any means, but I do know I gained a realistic 29 hp from porting and polishing the heads, degreed the cam, and fine tuned the 850 dbl pumper Holley. Other than that I have a big Lunati cam, solid lift.
I built the engine myself, very meticulous, gapless rings, 5 angle valve job, general goodies.
I dont mean to offend anyone but I can produce dyno charts to attest to my engines hp rating of 630hp

spectras only
10-13-2000, 07:39 AM
Hi bowties, can you give any cam specs,compression ratios and maybe some info on your boat's performance,ie; RPM-speed and drive specs?

SPECTRABRENT
10-13-2000, 11:23 AM
I believe Cheetah boats is in Lake Havasu Az.
SpectraBrent

BlackWidowBowTies
10-20-2000, 04:52 PM
Spectras Only..
My boat is a 1972 Cheetah. 19' 86"beam, full length stringers. Hull weight 900lbs. 18 degree deep v design.
Pump is a Dominator MB12s with an "AA" SS impeller, 2 5-degree wedges. Place diverter. Pump has beem ballanced.
Engine 454 bored .30 over. LS6 1972.
Peened forged steel, cross drilled and chamferred, tufftrided crank.4 bolt mains.
Completely balanced rotating assembly. Balancer to flywheel. Lunati solid lift cam model #SPB-2 550, 550. 110 degree centerline degreed to 108 degrees.
Valve lash set to .22.
Edelbrock TM2R Tarantula single plane manifold matched to heads, topped by a Holley Double pumper w/ mechanical secondaries at 850 cfm.
Large rectangle port, ported and polished heads, 5 angle valve job, hardend seats. Competition spring job set for each valve.
Gapless piston rings.
11 1/2 to 1 compression forged aluminum pistons. Indexed spark plugs. Peened 7/16ths cap bolts.
Vertex magneto and Bassett racing headers.
Dyno tests done 3 months ago showed 628 hp at 6000 rpm.
BWBT

BlackWidowBowTies
10-20-2000, 05:00 PM
Not that it matters but I meant vlave lash set at .022 hehe sorry. some of you must have gotten a kick out of that hehehe.
BWBT

spectras only
10-23-2000, 04:20 PM
Hi Bow Ties,the camshaft specs sure indicate substantial increase over the stock LS6 camshaft and the racing headers help too,impressive figure anyway.What I'd like to know what RPM you running with the AA impeller with your present setup.Your compression ratio only went from factory 11:1 to 11.5:1.I have the HP book also and the maximum HP ever recorded in there is for the LS7 at 465HP.I'd like to know what did Guardian Marine to your engine prior to your rebuild to go to 572HP?!Let me know what speed you get out of your Cheetah with a GPS.Thanks

BlackWidowBowTies
10-23-2000, 06:58 PM
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

spectras only
10-24-2000, 11:50 AM
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.

BlackWidowBowTies
10-24-2000, 03:49 PM
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