Looking for 454 w/ 990 head setup's

[KonaJet74]

Hey Guys,
I'm looking for all setup's for a 454 with
990 head's. Please post what U got and what
U use the boat for (race,skiing,cruising etc...).
Please list as much info as possible, I'm not
looking to copy anybody, I'm just interested to
see what works best in all situations & what is
definately NOT a good idea to do. I've got a 74
18' Kona w/ a 454 Ls6 & "A" impeller & i'm just
searching for info before I start buying everything
& I don't want to make any mistakes. Thanks in
advance!

[QuickJet]

The Bahner in the pic does a solid 82+ mph. I say "+" because it was done with two people and a cooler sittin shotgun. It's a typical LS6, Isky Z-89 solid cam, TR2X tunnel ram with two 750's, 990's MSD. Pump has a droop with an A and an extreme loader. Nothing crazy just a good lake combo. People have gone slower with alot more.
http://www.hotboatpics.com/pics/data/500/10278IMG_0337MA14195371-0005-med.JPG

[RICHARD TILL]

my boat is a 1997 youngblood tx-19 with 990 heads that were on it when i bought the boat in 1982, comp roller rockers, jomar stud girdle, venolia pistons, edelbrock intake, two 750 holleys no. 6109, lunati roller .680/700, b impeller. boat has full interior and turns 5850 rpm`s at wot. dont know the mph. its a lake boat. lots of fun.

[FASTRAT]

There are 2 "ole" sayings:
#1 Speed costs---how fast do u want to go?
#2 If it ain't broke---don't F__K with it!
IMHO--#2 applies to u!...if it runs good now...leave it alone & go have fun
make some mods to the hull, add a loader, shoe, ride plate, droop, diverter & u might be pleasently surprized at what the results will be!
just my .02 cents
fastrat

[KonaJet74]

make some mods to the hull, add a loader, shoe, ride plate, droop, diverter & u might be pleasently surprized at what the results will be!
The boats completely torn down now, I'm installing a shoe, ride plate
and loader & we're going to blueprint the bottom. The cam was a
smaller solid lifter cam and it was too tame, so I'm looking for
more power & just checking to see what people have done &
their experiences. I know there's potential in her, I just want
to make sure I do it right!

[SmokinLowriderSS]

From what I have been able to find ......
Stock "LS-6" Heads: (Mortec)
3946074....69&71...rect...OPEN...'69 427 L88, ZL1, Aluminum, 118cc chamber
'71 454 LS6, "round exhaust port"
Port sizes:320-326/120cc
'990 heads:
6272990....70-up...rect...OPEN...454 service replacement, used on some MKIV crate engines, 118cc chamber
Port sizes: 318/125cc
Same stock valve sizes, 2.190"/1.880"
Basically, same spec heads. Why spend $$$$? You're not going to change much, if anything.
The only port flow Stan Weis site lists for both is .600" lift, here it is.
'990 - 292cc I/204cc E
'074 - 331cc I/201cc E

[SmokinLowriderSS]

Just how tame is "too tame"?
I've seen quite a few engines, jet-boat engines, come in here OVER-cammed to where they can't spin the pump hard, sure lok good on a dyno, till you look at WHERE the HP & Tq numbers come in at.

[FASTRAT]

Smoke...i agree...not much difference in the heads...why spend the $$$...maybe put in some 2.225 valves to breathe better...chng the manif to a Air-Gap & add a different carb...get a cam similar to urs & along with the other chngs IMO it would run great!
fastrat

[KonaJet74]

I do have the 990 heads & everything else has casting
#'s of a Ls6. I can't ID the cam that was in it. It had
165r & 951812 stamped on the gear end. I tried looking
at all popular cam manufacturer's & came up empty. As
I remember it was pretty mild from when my buddy had
it. It is a solid cam though. What RPM range do you guys
like the torque at? Is 2500-5500 or so a good ballpark? I'm
a car guy and I'm new at this, so please bear with me. Do
these motors come up really quick to a certain RPM like a
torque converter? Thanks for all the info & recommendations,
I really appreciate it. Keep It Coming!!!

[SmokinLowriderSS]

Take a Micrometer (or hell, a caliper for the purposes of this) and find out what the cam lift is/was. Personally, I would not go over 290* seat to seat duration, and for most of the time, I think closer to 280* is more useful.
That cam doesn't cross to any Chevy part numbers I have so it's a major question mark.
Find out it's lift and you have a reference to start with.
According to my data, a vactory LS-6 ran a solid, non-roller, .500" lift cam with 306* seat-seat duration, Number 3863143 or 3904362, depending on which manual I check. The newer manual says 307*/298*.
Personally, I'd go .560" to .600" lift, not over 290* seat to seat duration, I think that's somewhere arround 240* @.050" lift. or you're gonna hurt the torque curve and push it up high, perhaps so high that a missmatch occurs and your motor can't make enough mid-range power to stay ahead of the pump.
You're already gonna have some trouble with the large rectangle ports at moderate RPM (4 to 5-grand) cylinder filling, try to avoid making it worse and it should run good.
I'd put as much CR in it as possible, measure and calculate it, don't just take the catologue reference for what it says. Quite a few of us on here can figure out the calculated CR if you give us enough information.
Chamber cc
Piston style & dome size
piston depth below deck top @ TDC
gasket thickness
bore & stroke
Aim for a MAX RPM of 5500 on a lake motor for the cam, not a peak at 5500, or it may push you too high IMO.
I'm real happy with only 8.5:1 (so far) running a hydraulic .565" lift, 280* duration. There's a lot of breathing still left in her held back by the small-valve stock heads.
I'm also running the Performer RPM Air Gap and love the response, but I have large oval ports the whole way down.

[KonaJet74]

Thanks Smoke,
I kind of figured I'd be whipping out the mic's, I tried
the easy way but everything's not always simple. I got
some other suggestions to bring the heads in to get
some pocket porting & a good valve job & then get them
flowed (thx 2 cstraub69). Then I could match a cam up to
that. I'm also looking at a roller cam for the extra durability
& break in simplicity & a full roller rocker setup. I guess I'll
start there & go from that point. Thanks for the info!

[SmokinLowriderSS]

Sounds good, accurate flow numbers would help the planning. Just don't get them hogged out for a bunch more flow, IMO, or you'll cause yourself troubles.
cstraub is a good resource from all I have seen in here, listen to him, he knows his stuff. :)
Best of luck to ya.

[MikeF]

990's here on a 469.
Get about 52/5300+/- rpm w/a prepped B impeller.
Cam is a solid flat tappet w/ about an average of .600 lift for both lobes and around 260 average for the durations at .050. Previous cam.
New build is not yet together, but is basically same build w/ different flat tappet cam. Know nothing yet. :crossx:
Still a little out on the whole Oval port/Square port discussion on what is best for a jetboat application. But am trying figure it out. :boxed:

[SmokinLowriderSS]

990's here on a 469.
Get about 52/5300+/- rpm w/a prepped B impeller.
Cam is a solid flat tappet w/ about an average of .600 lift for both lobes and around 260 average for the durations at .050. Previous cam.
New build is not yet together, but is basically same build w/ different flat tappet cam. Know nothing yet. :crossx:
Still a little out on the whole Oval port/Square port discussion on what is best for a jetboat application. But am trying figure it out. :boxed:
It's an RPM/usage thing. Several factors occur via comon physics.
Port volume is related very directly to mixture flow velocity at a GIVEN rpm. at ANY rpm, the larger the port runner volume, the slower the airflow is (and the reverse)
Below a certain flow velocity (I do not have the figure), fuel droplets start falling out of suspension ("puddling" occurs), which reduces mixture concentration.
Also, given valve timing, higher velocity in the port causes the mixture (since it has weight (mass) and velocity, it has inertia) to keep rushing fwd as the valve closes, squeezing a bit more into the cylinder, even after the piston starts up and cyl pressure starts to rise.
Also, there is a point where it is very difficult to increase flow velocity by using vaccume ahead of the port, thus, every port size has a maximum flow volume, normally aspirated (unpressurized) and that point is a factor of engine size x port sixe x RPM (also valve area but leave that equal here for sake of port area discussion).
Smaller port volume reaches a good flow velocity soonest, and reaches it at a lower RPM the larger the engine displacement.
Larger port volume, reaches a good flow velocity next, and reaches it at a higher RPM on the same engine, but the point depends on the engine displacement. (ie, say the max port flow on a given head is at 5,000 RPM on a 396, may be reached at 4,000 RPM on a 502, 3400RPM on a 572)
Largest port volume reaches a good flow velocity last, and reaches it at the highest RPM on the same engine, but the point again depends on the engine displacement.
Now, what engine size used and desired opperating RPM dictate best port volume size.
Where a 572 with the largest port runner size, 320+cc intake, might be reasonably happy on a street car driving 3,500 RPM down the highway (tall gears), a set of small ovals measuring 200cc might be maxed out with that engine by 3,000 RPM. Those large ports may still not be at their best untill 5,000 RPM or so in that setup (consider a 3500 to 5500 RPM "band" at that size against a "1500 to 3,000 RPM "band").
On the other hand, that 396 with the "peanuts", may work very well untill it maxes them out arround 4,000, 4500RPM, but will have trouble with the largest ports untill a certain RPM is reached, say, 5,000 RPM where the puddling in them stops by the now high enough flow velocity.
Now for some real numbers to try to relate it to.
My Taylor SS, 454, 8.5:1 compression, Headers. Valves 2.30x1.90 to get them out of equasion. Peak info.
Peanut heads: 200cc runner
Torque, 450@2500 / 460@3000 / 463@3500 / 456@4000
HP, 348@4000 / 368@4500 / 364@5000
Her '049 Large Oval ports: 253cc runner
Torque 465@3000 / 474@3500 / 480@4000 / 474@4500
HP, 406@4500 / 430@5000 / 428@5500 / 401@6000
Rectangle port '188's: 317cc runner
Torque, 459@3000 / 467@3500 / 470@4000 / 459@4500
The 454 isn't big enough to pull thru the Rect ports with the current (.565" lift, 280* duration) cam, and they hurt it.
572CID, .700 lift cam, 300* duration, 1000 CFM carb, single plane, headers
Peanuts:
Torque, 566@2500 / 567@3000 / 570@3500 / 556@4000
HP, 423 @ 4000 / 435@ 4500 / 403@5000
'049's
Torque, 576@3000 / 590@3500 / 599@4000 / 588@4500
HP, 456@4000 / 504@4500 / 514@5000 / 500@5500
'188's
Torque, 572@3000 / 583@3500 / 587@4000 / 567@4500
HP, 447@4000 / 486@4500 / 484@5000 / 460@5500
Those 188 heads don't max the ports untill .800" lift (or after, they stoped at .800") according to flow numbers.

[cstraub]

Power under the Curve. My issue with the rags, flow benches, and dyno's is the hyp of Peak numbers. Woopty Doo I say. What is important is the overall power curve within the rpm range you plan on operating. I love seeing these dyno numbers on marine engines that hype the peak power at 6500 rpm. Then the engine goes into the boat and peak rpm is 5700. Yeah the engine makes 700hp but you can't get there.
Cylinder head selection is relative to the "curve theory". Cylinder head cross section, runner volume, valve area should all be considered when selecting a head. SS has done a pretty good job with examples. I will just add a few things. Boat engines have to get from an idle to max rpm and speed without the luxury of a transmission or converter. Take an IO boat, once you stab the throttle it is up to the engines ability to accerate on its own to reach max speed/rpm. Air speed feeds the cylinders. At lower rpms this speed is slower so IF your heads are OVERSIZED for the engine then the port velocity will drop. When this drops the ability to fill the cylinder is slow doggy air, kinda like filling a 2" diameter hole with a 3" glass pouring the liquid all at one time. By doing so this makes the engine lazy in the acceration mode. Now take the same engine with a MATCHED set of heads. At low rpm sure the heads are still large for the rpm and the CID but not as bad so the induction does not overwhelm the engine therefore it accellerates faster.
I just cammed a pair of 572's (4.600 x 4.375"), 9 to 1 with 990's on the engines. With hyd rollers (they were stout, .670" lift) the best one made 680HP and the worst made 671HP. Now the general concensus would not have gone this route feeling the heads would be to small, but for the customers goal of a peak of 5800 rpms I told him we could use them. The boat had a pair of Merc Bulldogs (500HP underated I say myself) and over the old power the boat has picked up 14mph. The customer is happy.
So I say to you, select heads for "Curve Power" not peak power. Curve power is what you are going to use, Peak power is what your going to talk about.
Chris

[KonaJet74]

Chris, so on this particular instance with a 18' jet & a
454 w/990's, when the go pedal is mashed, how far
does the rpm jump instantaneously? I'm not all that familiar
with jets, so I've got torque converter on the brain here.
Do you look for around 2-5500k for a torque curve to
work with?

[cstraub]

Chris, so on this particular instance with a 18' jet & a
454 w/990's, when the go pedal is mashed, how far
does the rpm jump instantaneously? I'm not all that familiar
with jets, so I've got torque converter on the brain here.
Do you look for around 2-5500k for a torque curve to
work with?
Working with a few of the jet guys here on the forum I have learned we can be a little large on cylinder heads and induction be with a jet boat. Take Steelcomps build, he is HUGE on induction and I was worried about throttle response when Scott got the engine in the boat but he has been very pleased. The impellers allow the engine to rev quicker I feel and not load the engine like an I/O does.
I feel your combo with bowl blending on the heads, a good 3 angle valve job and a matched cam and lifter ( I would go hyd roller for longevity) it should be a good bullet for you.