Precision

Tim,

Hp = torque x RPM/5252

That HP at 6200 is making 579.4 ft lbs. of tourqe. It's like a small block that makes 900 HP at 8500 RPM is generating 556 ft lbs of tourqe.

Horse power is much easier to make if you are willing to turn the motor that much to get it there. In the end that comes down to having the correct camshaft to do it.

Edit*

Oviously the small block example has high compression and runs on race gas. Just illustrating the HP vs TQ numbers. Not making a comparison from BBC to SBC.

kvogt

Yes Mike

Compression ratio went from 8.2 to 7.9. But boost was at 6.7 lbs (not a Livorsi gauge) before and to 7.3 lbs after the build without changing the pulleys Rick then changed pulleys to 8 lbs and the boat ran the same, no speed increase. Doesn't make sense. The motors just go flat around 5300 rpm and slowly work up to 5600. Maybe Haxby can explain it, sounds like he has seen similar stuff on the dyno. Just looking at the numbers you would think that cam would pull on the top end, but it lays up with two different exhaust systems.

Eliminated572

It definitely sucks having a build setup for 6400 and the cam falls over at 5900. Cant make the power up there if the cam has other plans....

MILD THUNDER

Kris, do you think the boost level has gone up, from possibly not enough exhaust duration?

Ive noticed on most dyno pulls with basic roots combos, the boost usually starts out say at 7.0 lbs, then around peak torque drops to maybe 6.5lbs , then begins to climb again, maybe to around 7.5lbs at peak rpm.

I dont know if that little extra boost at peak rpm, is from the blower spinning faster, or the engine simply incapable of moving the air at high rpm, and the boost backs up the intake. I believe the latter kinda, because when you compare the HP gain per 100 rpm data, while you may see the boost climb, the power simply isnt. Say you might see 20hp gain between 5300-5400 with no change in boost, but see only 6hp gain between 6200-6300, with an increased boost level.

Panther

Any idea how the lifters where adjusted? 1/2 turn, 3/4 turn, 1 turn, bottomed out then back off 40 thou? Which lifters are being used?

I learned a bit about lifters and spintrons recently and a different method that Kaase uses for adjusting them when turning higher rpm, which is why I'm asking. PM me if you have a chance.

mike tkach

i don,t know if you had them on a dyno .to me a dyno is a tuning tool.i don,t know any of the info on the build like what size carbs,what heads,or boat info like gear ratio or props.i do know that if you build an engine to make peak power at 6400 and over prop it the results may not be good,i am not saying this is the issue.without knowing the mentioned info it would be imposible to figure out why the boat has less then optimal performance.i guess it would be easy to say the cam is the issue but without knowing the rest of the information i thing it would be wrong for me to say that.edit in,i will say that imo, a 10.71 seems on the small side for a 598.

kvogt

1 turn. Morels not the high rpm ones. Lifters were not changed when the motors were rebuilt and are adjusted the same in each case. The same lifters and adjustment method were used with new current build also.

kvogt

Since the boost went up after the build we looked primarily at the exhaust side. The new cams had more lift and duration than the 651 so, we looked at putting a larger exhaust on to see what effect that had. We learned Rick had to spend many thousands of dollars and speed didn't change so we didn't address the problem. We went as high as 10 pounds of boost to make sure the carbs and blower could keep up - didn't help.

Remember we are off a solid 5 mph in a 43 No-Tech floating condo. We are way off in power

kvogt

Panther your PM box is full.

Thanks for the input in your PM

HaxbySpeed

I would bet the lifters were bleeding down as a result of the new cam profile. On the motors I wrote about earlier that broke the rockers, etc. That customer originally purchased all hi top end components from MK, and it came with the standard morel 4603 lifters. They were doing the same thing on the dyno. They would bleed down, boost would go up, (cam essentially lost a ton of lift) and the motor would lay over. We swapped in the high revs, and the power picked up everywhere, even low end torque. Boost was still a bit high for the power, but not terrible. Unfortunately, those 4603 were acting like shock absorbers, when we put the high revs in, it transferred it all to the top end resulting in broken rockers, and eventually killing a couple of the high rev lifters too.