speed update

[jet21]

OK thks for the info everybody,We've been discussing it here,and I think maybe I'll smack on a bottle of NITROUS ,what do you suppose that'll do for me,anyone use it much?.looking at the charts and with what lvjetboy has said a impeller alone wont cut it,if you burn nitrous for a few sec's say 5-6 will you gain much on your top end,and if so will a jet hold that speed or drop off quick or slow,I've never used it so some info would be great.nitrous setup here is around same cost as impeller,which is about the same size as my shrinking funds,and declining marital status.ltr.p.s.boats a 71cv-21 glas/carlson.

[jeff-in-ky]

My boat (21' Edge tunnel) with a 454 goes from 74 mph @ 5600 rpm to 89-90 mph @ 6800 rpm on nitrous. Just make sure your motor is built to take the strain and that you have adequate fuel pressure, you may also need to back of the timing. Mine is set so that a separate electric fuel pump kicks in when the nitrous is activated. You can go with a smaller system and alleviate a lot of the problems if you only need to gain a few mph.
BTW- It is instanteous power when you kick it in. The downside is that nitrous where I live is $3.50/lb and a 10# tank is probably only good for about a minute of use, but I have a big system.
JB

[flat broke]

I'd lean away from the bottle for a while. Jeff is right but his motor was probably set up for a system that big. You are going to have to buy a timing retard device, extra fuel pump, plumbing etc on top of the nitrous kit if you want your motor to last. And even then theres no guarantee it will survive repeated use. I think you should look at your engine first. Consider that a stock marine 454 gets you 330 hp. The data we have so far suggests that you are only at that state currently. Do you have details on your engine setup? Block type, rods, pistons, compression, heads, carb, manifold, etc? You should know all of this before you decide to roll the dice on nitrous. It is very concievable there are some free hp sittin in your setup right now as well as other mods that are less strenuous on your setup than nitrous. If you have specifics on your engine, share them as the more information we get the better we can steer you based on our experiences. My recommendation would be to find a hard parts solution (cam, ignition, exhaust, etc) combined with some pump work to get you to 65 reliably time after time without the added expense of filling up a bottle every friday before you head out. Don't get me wrong, if the motor is setup to run on nitrous, it works well, as Jeff's and many other guys numbers will prove. But their motors/fuel systems/ignition systems have been altered to make the juice a little safer to run.
Let us know whats in that 468 and maybe we can help you out without turning to the bottle.
Chris www.liquidaddiction.net (http://www.liquidaddiction.net)

[Beavertim]

Jet21,
I put a simple throttle plate NOS setup on my old Hallett 19/stock 2-Bolt main 454 chevy (except for the roller rockers and forged pistons). The gas bumped up the RPMs from ~5200 to ~5700 w/150 HP jets. Never had any problems with it. I don't know what the speed increase was. NOS is a cheap way to go in the short run, but as jeff-in-ky stated, it can be more expensive in the long run, depending on how often you use your boat and the laughing gas. Just my 2cents. Tim

[jet21]

Ok,block=396512 bored 60, flat top pistons.heads 386781 new valves,springs etc.castcrank 353039 . torker2 intake ,torker2 cam.true roller chain/gears.holley 750 v/s.carter 120 gph pump.stock gm hei ign.glenwood logs. not 2 impressive but im still buying lotto tickets.

[flat broke]

Originally posted by jet21:
Ok,block=396512 bored 60, flat top pistons.heads 386781 new valves,springs etc.castcrank 353039 . torker2 intake ,torker2 cam.true roller chain/gears.holley 750 v/s.carter 120 gph pump.stock gm hei ign.glenwood logs. not 2 impressive but im still buying lotto tickets.
With the information you provided, assuming 9:1 compression and using the curent specs from Edelbrock for the Torker cam, you should be pushing about 443hp at 5500RPM according to desk top dyno. The catch is I selected a small tube header to get that number. If I change it to H.P. manifolds which we'll say you're closer to with the ones you have right now as automotive manifolds would be backed with mufflers, the numbers drop considerably to 356HP at the same 5500RPM. Basically your cam and manifold are designed to breathe and your corking your motor up with the logs. Swapping out to a better manifold or headers would be a good step with or without the nitrous. Besides, if you have good exhaust the nitrous will work better if you ever decide to run it. A guy that posts by the name of Blown509Liberator had a 502 that he swapped from stock manifolds to lightning headers and got good results. You might want to look him up and shoot some questions his way.
By comparison I thought I'd give you the numbers if you ran a 100hp shot on your current setup with current exhaust. The simulator baically assumes that 100hp shot increases the hp 100 points at the peak of the curve. As such with the log exhaust and a 100hp shot you get 456hp instead of 356hp. If you run that same 100hp shot on the motor with better exhaust youre looking at 543hp. Bear in mind that these numbers are not to be taken as gospel as Desktop Dyno is only a tool to gauge the difference between changes and not absolute values. I hope that gives you a little more information to throw into the mix and maybe come out with a better end result. Try plugging in the new HP numbers on LVJetboy's Jet Performance Calculator at http://www.angelfire.com/extreme2/dr...erfomance.html Then see if you'll get past 65.
Talk to you later,
Chris www.liquidaddiction.net (http://www.liquidaddiction.net)

[jet21]

RIGHT STUFF, flatbroke,thks for the advice,ltr.....jet21

[77charger]

thta kind of mootor sounds like you need a b cut impeller to get it into that rpm range of 5500 say at 4700 you are not in the peak range and you are not using all of the hp.