5.3 jet boat cam
09-02-2013, 07:41 AM
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5.3 jet boat cam Been through a couple of motors this year so far. If you've never run one of these in a jet boat, this is probably the hardest duty a motor can run. Imagine putting your motor on an engine dyno, loading to 100% max power, then hold it there for 10 minutes, NOT 10 seconds. They operatre at two speeds, idle and wide open. There is no mid RPM driving.
Anyway, broke a few rods over the summer. Broke the bottom half of a 6 liter GTO piston clean off. Unfortunately that one tore up my nice little 226/229 .575/.578 112 lsa cam. Now I'm running a stock 5.3 bottom, ported 5.3 heads with PSI 1511 valve springs good for up to .630 lift. Heads have been milled .010 also. Current cam is a stock LS1 grind, 2001 era.
Any ideas for cam that will get me the most available right about 5,000 to 5,300 rpm? Peak might be higher, but the impeller in my Berkeley jet drive will hold a 5.3 down to that range. I'm thinking of something a little closer to .600 lift and about 230-235 duration on this next one. See if I can grenade one more before the summer is over.
FYI, this current motor is a straight $200 junk yard short block with 90k on the ticker. Just put my heads and oil pan on it with a Camaro cam and although it's slower, it about runs better than any of it's predicessors. GPS'ing 58 right now. Was getting 65 out the 6.0 liter. The stock 460 Ford big block that came in the boat ran 57. Would like to get it back over 60.
Looking forward to some great discussion on this one. Remember, mid range power NOT needed at all. When you hammer the throttle on the jet boat, the tach snaps to about 200 rpm PAST where it runs at till the pump loads up. Take just under a second for the pump to load, then it hold tight at max rpm.
Anyway, broke a few rods over the summer. Broke the bottom half of a 6 liter GTO piston clean off. Unfortunately that one tore up my nice little 226/229 .575/.578 112 lsa cam. Now I'm running a stock 5.3 bottom, ported 5.3 heads with PSI 1511 valve springs good for up to .630 lift. Heads have been milled .010 also. Current cam is a stock LS1 grind, 2001 era.
Any ideas for cam that will get me the most available right about 5,000 to 5,300 rpm? Peak might be higher, but the impeller in my Berkeley jet drive will hold a 5.3 down to that range. I'm thinking of something a little closer to .600 lift and about 230-235 duration on this next one. See if I can grenade one more before the summer is over.
FYI, this current motor is a straight $200 junk yard short block with 90k on the ticker. Just put my heads and oil pan on it with a Camaro cam and although it's slower, it about runs better than any of it's predicessors. GPS'ing 58 right now. Was getting 65 out the 6.0 liter. The stock 460 Ford big block that came in the boat ran 57. Would like to get it back over 60.
Looking forward to some great discussion on this one. Remember, mid range power NOT needed at all. When you hammer the throttle on the jet boat, the tach snaps to about 200 rpm PAST where it runs at till the pump loads up. Take just under a second for the pump to load, then it hold tight at max rpm.
09-02-2013, 09:10 AM
#3
I would aim for some overkill on the springs as the sustained high rpm will tax them more than typical car use.
I also think 230+degrees in a 5.3l is going to need more rpm than you are going to be able to give it. How restrictive is the exhaust? Guessing pretty bad at idle but not a problem at speed? Might consider a tightish LSA to narrow up the powerband.
I also think 230+degrees in a 5.3l is going to need more rpm than you are going to be able to give it. How restrictive is the exhaust? Guessing pretty bad at idle but not a problem at speed? Might consider a tightish LSA to narrow up the powerband.
09-02-2013, 10:11 AM
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Very free flowing exhaust, like open headers free. I know a 230 cam makes peak power WAY above 5,000. But what make the most power at 5,000? A 230 cam or a 205 cam? PSI springs built for .630 should have a little room at .600 I would think. Just asking. I gotta fix the floor in the boat this week and it would be a great time to swap cam with the back seat out. Or may just leave the Camaro cam in it. Sure liked that 226/229 .575/.578 112 lsa cam that came out though.
09-02-2013, 01:00 PM
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Maybe a COMP Cams 54-446-11 with 232/234 duration and .595/.598 lift on a 112 LSA. Peak TORQUE for this cam comes in at 5,000 rpm, on an LQ4 with the right springs anyway. PSI springs should handle this just fine, right?
09-02-2013, 09:04 PM
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No kidding. Seat pressure and coil bind are well within tolerance with these springs. Lift is the only thing that's close. They good or not for a .598 lift cam?
Seat pressure closed 130lbs@1.800", open is 370lbs@1.175", coil bind at 1.100". Also heads are milled .010 but running dished pistons so PTV should not be an issue. Ran these heads on the 6 liter with flat tops and the old .578 cam with no issues.
Seat pressure closed 130lbs@1.800", open is 370lbs@1.175", coil bind at 1.100". Also heads are milled .010 but running dished pistons so PTV should not be an issue. Ran these heads on the 6 liter with flat tops and the old .578 cam with no issues.
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02-03-2014, 01:07 PM
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Went with a 125/129 @ .050 and .575/.575 on a 114 cam profile. Haven't sprayed it yet, but on straight motor it's about the same top end on GPS. It's hitting pretty hard from the dig though. The sound is WICKED. Might need shorter pushrods? I'm getting 1-1/8 turn from zero lash on the rockers till I hit 22lbs on the torque wrench. Got a couple more pieces till the nitrous set up is complete. Then we'll see how she does.
Plan to be at Lake Hugo, Oklahoma first weekend in May at the boat drags. Gonna spray it hard there.
Plan to be at Lake Hugo, Oklahoma first weekend in May at the boat drags. Gonna spray it hard there.
02-03-2014, 03:14 PM
#11
Went with a 125/129 @ .050 and .575/.575 on a 114 cam profile. Haven't sprayed it yet, but on straight motor it's about the same top end on GPS. It's hitting pretty hard from the dig though. The sound is WICKED. Might need shorter pushrods? I'm getting 1-1/8 turn from zero lash on the rockers till I hit 22lbs on the torque wrench. Got a couple more pieces till the nitrous set up is complete. Then we'll see how she does.
Plan to be at Lake Hugo, Oklahoma first weekend in May at the boat drags. Gonna spray it hard there.
Plan to be at Lake Hugo, Oklahoma first weekend in May at the boat drags. Gonna spray it hard there.
1-1/8 turn is about .053" preload. So if anything you might need longer PRs; NOT shorter.
You're on the low end of preload (w/stock lifters), but unless your are issues like louder than normal valve train you're likely fine.
BTW, .047" = 1 turn
