Please Help No R.P.M

[Kevin Crane]

Hope someone can help me out here ! Built BBC468 10-1 motor and it hit's a wall at4300! Heavy 75 Tahiti hull 19'6" Spinning a A impeller Pump is fresh Berkley With Loader And new wear ring. Motor is 468 TRW forged ,Balanced , Stealth Intake,Holley 850,All MSD, Crower Cam Intake: Duration: 311 / Lift: .578 Crower Spring's ,Crower Lifter's , Crane Roller Rocker's , No Headers Yet Just Log's . Boat has about 1/4 " hook which I will take out this winter . Have been told that this cam might be to big any one have any ideal's ????????? Thank's Kevin

[HammerDown]

Ya should be getting more R's than that.I'll tell ya my engine combo...468 Chevy,Comp Cam # 11-314-4 Lift 550/t554,Dur.232/237,Lob cen.110.Comp.springs.Crower roller rockers Also using TRW pistons 270 dome at 9.75 comp. with oval 049 iron heads bigger valves,bowl blend,flowed out 116cc.Stealth intake topped off with a 715 vac.Holley.Mallory dual point Dist.36 degrees total (thats were it made the most rpm) Bassetts O.T. Berk. Aggressor A. On a good air day no baffels the motor spins up to 5400 rpm,baffels in hot humid East Coast weather I'll drop 51-5200.Daytona 21 footer.Don't think that little bit of hook would drag ya down that much? What is the state of tune with the motor? Total advance,jetting.I would think the 850 is way big,but the item that's hurting you the most is those log exhaust...ya cant make power unless ya get that air out as well as in!
[This message has been edited by HammerDown (edited October 10, 2001).]

[77charger]

sounds low to me im runnin a bbf429 with a 248@50 .590 lift 108 cntr hydraulic cam,10.5-11-1 comp.stock dove heads ot headers,19' boat,a impeller,energizer pump.With baffles 4800@68 5k witout(dont know the speed there but faster).Timing is at 34 total but can bump38 with 100octane.The ot headers will help your cam choice is good,have you ran a comp check on your cylinders whats your timing set at.I would expect 5k on that set up.

[Kevin Crane]

HammerDown, Have 34 in it and I belive jet's are 82&84 plug's look good just a little dark ..Indeed log's killing me but think this motor should turn in the area of 5500. Good set of header's would give me ruffly 50 Hp. more and that would be 12 to 1300 more rpm gain if that could only work like that it would be nice huh?? It's some little thing but what that thing is I don't know !!

[Kevin Crane]

77charger, Timming also at 34 compression is fine have about 40hrs. on this motor. I was hopeing to turn around 5500 with this motor!!

[fryzll]

I have a 18.5 Challenger and my #'s are about the same as 77charger, 4800 rpm at 67mph. I am runnin a Jacuzzi w/ a A impeller (I think). It sound like you have all the good stuff. What kind of shape is your carb in? Was the cam installed straight up or advanced? I cant remember if it was MSD or Mallory but the gap between the pickup and the rotor opened up and had a simalar prob on my buddys car. None of this is probably it but hey, its my .02.
Chris

[Kevin Crane]

Originally posted by fryzll:
I have a 18.5 Challenger and my #'s are about the same as 77charger, 4800 rpm at 67mph. I am runnin a Jacuzzi w/ a A impeller (I think). It sound like you have all the good stuff. What kind of shape is your carb in? Was the cam installed straight up or advanced? I cant remember if it was MSD or Mallory but the gap between the pickup and the rotor opened up and had a simalar prob on my buddys car. None of this is probably it but hey, its my .02.
Chris

[Kevin Crane]

Carb is new ,All is new Pull's real hard but hit's a wall at 4300!!!!!!!

[custom-cruiser]

Kevin,
If you give me complete cam card or grind # and what size valves you have I can run it on a computerized dyno program and see if your torque curve is falling off early,Then i'll throw in a couple different cams and see what happens.
If anyone else is intrested I need motor type,bore,compression,valve sizes,cfm,manifold type(single,dual,blower,turbo),exhaust type,lifters,and complete cam card at seat to seat or .050 and if your cam is forward, up or back. It's not 100% real world but gives you a good idea and lets you try different combos without all the time and money,like how much hp would a superchiller give? or a different cam ect. ect. http://free.***boat.net/ubb/biggrin.gif
Currently I turn an "A2" 5500 rpm and with a little help from this program I think i'll be Knockn' on 6000.

[Beavertim]

Custom Cruiser,
Does your Dyno model have an input for turbo boost (blower boost is probably OK)? If so, could you run my engine specs? I have a pretty much stock Ford 460 with log manifolds and a draw through twin turbo setup. Max boost is 8 psi. CR is 8.25 to 1, cam specs are Intake .500 in lift 234 deg duration @ 0.05, Exhaust .510 lift 224 deg duration @ 0.05, I'm not sure of the lobe centers, but lets assume 114 deg sep. Holley 750 vac secondary with 72 jets in primary, 90's in secondary, PV's in both. Manifold is stock 429 CJ. Have done some mild porting of heads which are stock closed chamber. Intake does have intercooler (70's era design). Thanks Tim

[Beavertim]

Custom Cruiser,
By the way, where did you find the Dyno program? Tim

[Blown509Liberator]

Let me tell you a story about exhaust.
I have a 502/502 motor in my baja. This motor was originally in this boat them move to my tunnel hull now is back in the Baja.
The pump is a JF with an A cut legend impeller. Motor is a stock 502/502. With Gil Off Shore Exhaust 5100 RPMS.
Gills stayed with the tunnel and the new blower motor. Put a set of Merc. Center risers on it and it dropped to 4400 rpms. I have 4" hose out of the manifolds to 4" tips but that was the only change to the Baja. So in my book I think the first modification anyone should do is a good exhaust system.
Also if that Duration of 311 is at .050 I would rethink your came choice.
Heck I am running 260Int 270ex @.050 and .669int and 680ex of lift with a 112 lobe separation on my blower motor making 850 hp
MikeW
[This message has been edited by Blown509Liberator (edited October 11, 2001).]

[BLOWNDRAGBOAT]

Your cams got WAY to much duration, especially using restrictive water log type manifold. Also, recheck your impeller size, it might be a double A. That motor combination is pretty basic and should be turning around 5200-5400 rpm with a single A impeller. My feeling is if you changed cams and switched to a header you would pick up the extra torque needed. I am gonna list a few cam numbers for ya. The cam your using is a topend cam designed for much higher rpm usage. MOST cam's with duration numbers of 308 or larger have a power band of 5000-9000 rpm depending on the cam manufacturer. Think of it as the longer the duration the higher the rpm range and since jets don't see that type of rpm your cam is on the wrong end of the scale. It would be a much better cam for a V-drive that can turn more rpm. Go look at these cam numbers I have provided you with. I use LUNATI cams pretty exclusively in the engine's I build for myself AND my customers. To anyone else checkin this out, these cams are suited to just about ANY NATURALLY aspirated motor from 396-468. I go a bit more on duration and lift for bigger engines. The cams I use in my 500 plus cubic inch motors would kill anything under that. These cams also like small doses of nitrous upto 150-175hp settings and single stages. I have some favorite nitrous grinds as well as blower grinds. Anyway, here are the numbers:
LUNATI Hydraulic part number 30207
244/244 duration @.050 572/572 lift. Power range is 2800-6300. This is a 454ci bracket cam OR jetboat. Produces a broad torque curve and you won't have a valve to piston clearance problem. Nice idle
LUNATI Solid part number 40208
247/255 @.050 558/556 lift. Power range is 2500-6500. Same as above with a bit more loppey idle. I like this cam and use it alot for 396-468 ci motors.
LUNATI hyd. Roller part number 50249
232/242 @.050 578/595. AWESOME camshaft. Power is in the 2000-6500 rpm range. This is THE cam that I would put in your motor. It's a little pricey but it provides that strongest and widest torque curve. It also rev's quicker and won't wear the lobes as fast. This is my favorite cam grind when I build a small motor such as a 468. Combine this cam with a Weiand Team G manifold, bassett's,a properly tuned 850 also, recurve your ignition to provide all your timing in by 2600 rpm. This combination with a 10.5:1 final compression ratio is VERY strong and should turn ANY A impeller about 5600 rpm. Most importantly, it rev's much quicker and provides much more torque than what your using now. If you want to contact my shop for more detailed info I can be reached from 9-6 eastern. I don't give out my number over the net so contact me thru my email address and I will give you the number. I would also like to know what your running in the way of heads. BLOWNDRAGBOAT@YAHOO.COM