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brite
03-23-2013, 03:05 PM
I have a full solid roller 468 BBC. It is currently in a pulling truck. When I pull, its at 7100 rpm all the way down the track. The comp cam is a 7-4 swap ( the firing order)... .gross valve lift: .741 intake .717 exhaust... Duration @ .050: 268 and 280 respectively. It has std stroke steel crank and rods and forged pistons 11.3:1 comp. ratio. Makes around 700hp. My question is can I run this in a weekender jet boat without having to be in the throttle all the time ?not that that's bad) but I heard alot of "idling around" can damage the valvetrain... Is this even true or just an old myth? I heard it was due to having oil restrictors in the back of the block going to the top end oiling system... Hen idling, the top end won't get enough oil to make it a reliable engine fo "street" or "in this case, "idling on the lake"

wolfie
03-23-2013, 07:16 PM
Idling in a jet boat isn't like idling in a car. You're usually running at 1200 RPM just getting out of the harbor. What I would worry about is the engine being set up for a car vs. boat. Marine engines need a different tolerance machined into the piston to accommodate the lack of expansion of the cylinder wall. A marine engine runs a lot cooler around the cylinder than a car engine.

newtojets
03-23-2013, 07:20 PM
well where do i begin?? lets start with your first question, can you run your motor in a boat( yes and no, boat motors are built a little different then any other motor. its mainly in the tolerances, i.e. bearings and piston to wall. most jet boats need torque , which is why the olds 455 was used so offen ) your next question, can you hurt your motor from idling . no , but .... you can foul all the plugs or just load the motor up so bad it dies and wont restart. hope this helps!

H20MOFO
03-23-2013, 07:42 PM
Are your lifters hippos. I dont sweat idling my crowers much because they are oil fed. Steve would do a lot better job than I at explaining that. Thi difference between a reg. roller lifter and a hippo. Mine is on its 4th season...Ya...I know I just jinxed myself.lol

brite
03-23-2013, 08:51 PM
Thanks for the replies...H2omofo; what is a hippo lifter? My lifters are comp race lifters..not sure of the part numbers, they are the ones that are lighter in weight for better rpm, but as for the clearance on the pistons, Dave, your saying that a boat engine must be tighter? I'll have to see what mine is set up at. What temps do they normally run?. Thanks

wolfie
03-24-2013, 11:21 AM
Thanks for the replies...H2omofo; what is a hippo lifter? My lifters are comp race lifters..not sure of the part numbers, they are the ones that are lighter in weight for better rpm, but as for the clearance on the pistons, Dave, your saying that a boat engine must be tighter? I'll have to see what mine is set up at. What temps do they normally run?. Thanks

Actually, the pistons have to be machined a little. I think Kreg means Hi performance, which Comp Cams lifters are.

I'll send you a You Tube video a little later today... Got caught up in things yesterday.

White Lightning
03-24-2013, 01:54 PM
Brite, let me preface this by saying that I'm relitively new to the "jet" part of boating myself, but I DO know engines! lol The answer to your question is a resounding YES, there's no reason that you can't run your puller motor in your jet boat.....WITH a few mods. What everyone is saying is that because the coolant that's run through a jet motor is the lake itself engine temps tend to be lower then that of a street driven engine (and that's not an absolute, it can be adjusted to a higher temp) so with a cooler block the cylinder diameter dosen't get as large as with a higher temp block. Easy fix. Just have the machine shop finish hone the block a few thousants larger. Depending on the piston material that you're running the finish diameter will vary (different expansion rates for cast, forged and hyperutectic pistons). Easy peasy. Now the top end oiling will depend on the RPM that you decide to run and the type of lifters that you have. Standard needle bearing roller lifters depend (more so than forced oiling) on windage (oil flung from the crank and rods) to lube the roller wheels and axles. Above, say, 1,200 RPM there's enough oiling to make them live as long as you don't have a crank scraper taking the windage away. Still, not a deal breaker. Most major valve train manufacturers make roller lifters that have a bronze bushing for the roller wheel instead of the needle bearings OR a oiling hole that's EDM'd into the bottom of the lifter that force feeds oil to the roller axle asuring long life in an engine that see's extended low idleing time. Like Wolfie said, the jet motors don't really see real low or extended idleing time. As far as your cam goes, that's just a matter of 'gearing' the impeller to your engines performance RPM. In fact, I'm running a 'puller/mud drag' cam in my 472" Ford engine in my Kona. There's no reason that you CAN'T run these type of cams as long as you run the RPM that they were designed to function in. Personally, I applaud your choice of using your puller engine for your jet build. It'll give you a good base for a VERY performance oriented Hot Rod. Bear in mind that you'll need a good flowing set of over transom wet headers to make it all breathe. Make sure that you keep the coolant pressure below 15 PSI so you don't push water past the intake gaskets and milkshake your oil and control the water in the headers so it's low, or non-existant at idle so as to not get any water into the exhaust port area and have the reversion from the overlap in the cam suck water into the port and do BAD things! lol Most header manufacturers, like the Hooker Super Comps not only make a Jet Boat header that looks kick arse but they have drain holes in the low part of the tubes to insure that there isn't and residual water standing in the header. With 700 ponies available under your right foot you'll have perma-grin for days at a time! lol My 472 is suppose to make about 734 horse and I can't wait to get it out on the water this year. I'm going to run my cast A cut impeller and I bet it will do just fine. I've been told that you can run a cast impeller as long as you hold the hole shots to a minium, otherwise go to a stainless impeller (NOT CHEAP). Now, get your wrenches out and get to work!!! lol
Rob

brite
03-24-2013, 09:07 PM
Rob, thank you for taking the time to help answer my question. I will be taking my engine out of my truck this week. I was hoping to be able to "adjust" running temp of the motor once in the boat, but even with that you say I won't be able to run it at a hot enough temp to avoid having the cylinders honed to a larger dia? Head gaskets for this engine aren't cheap (bought some last winter when I went to lower compression pistons). If I have to tear it down to get it honed I will......Also, what is the reason for running water thru the headers other than to keep them from blueing and to keep heat down ? Thanks again..... I feel better about running a solid roller cam.

wolfie
03-24-2013, 09:36 PM
Rob, thank you for taking the time to help answer my question. I will be taking my engine out of my truck this week. I was hoping to be able to "adjust" running temp of the motor once in the boat, but even with that you say I won't be able to run it at a hot enough temp to avoid having the cylinders honed to a larger dia? Head gaskets for this engine aren't cheap (bought some last winter when I went to lower compression pistons). If I have to tear it down to get it honed I will......Also, what is the reason for running water thru the headers other than to keep them from blueing and to keep heat down ? Thanks again..... I feel better about running a solid roller cam.

First off, water is run through the headers to keep them from bluing and to quiet the exhaust down a little. Some run dry headers, but Mr. Ranger usually loves to write tickets for noise.

As far as the engine/piston issue, I sure hope we're all wrong. I hope you're running forged pistons and not hypereutectic pistons if you plan on this. Again, maybe I don't know enough about building engines. I just know that I would rather follow what my engine builder as well as a whole lot of other performance boat guys that have been doing this for years than to pay to rebuild. Rob may be completely correct on this issue, and I don't want to piss on anyone's advice and mean no disrespect towards Rob and his knowledge. I just want to go on record as saying I don't recommend not clearancing it for marine applications.

"THE ADVOCATE"
03-24-2013, 11:13 PM
I don't mean to jump in, but I think this is what I have learned. 70deg. lake water will keep your BB around 160deg unless you plumb in a thermostat. Which doesn't work, because the constant flow of 70deg lake water doesn't change. Thus your thermostat will have to be fine tuned for a temp. Which means lots of plumbing and problems. Yes some guys want 180 to 210deg. F. Ford guys don't care, they run better cooler, Chevy guys want hot (thinner blocks) and Olds guys just ask why their motor blew after thirty years? Plan on running your temp around 120 idle and 160 peddle down. 180 if the throttle sticks!!!

White Lightning
03-25-2013, 02:08 PM
Rob, thank you for taking the time to help answer my question. I will be taking my engine out of my truck this week. I was hoping to be able to "adjust" running temp of the motor once in the boat, but even with that you say I won't be able to run it at a hot enough temp to avoid having the cylinders honed to a larger dia? Head gaskets for this engine aren't cheap (bought some last winter when I went to lower compression pistons). If I have to tear it down to get it honed I will......Also, what is the reason for running water thru the headers other than to keep them from blueing and to keep heat down ? Thanks again..... I feel better about running a solid roller cam.

Yup, you'll have to finish hone the cylinders for more initial clearance. Like I said, it'll depend on the type of piston that's in there. Any competent machinist will have access to that particular piston manufacturers' info, and they DO have very specific clearances for lake fed Jets, I've seen the paperwork for the KB hyperuetectic pistons.
Worse case scenario is that you have a small amount of piston slap noise before the engine comes up to temp.
Wolfie, I never take offense when someone critiques my info lol. I AM human and I DO make mistakes! lol As far as running the Hyper pistons in a lake jet set up, well I've run 2 sets in my boat but I didn't get to run them for a long time (detonated and melted 2 sets) But, I'll find out when my boat hits the water this summer! lolol Realistically I don't expect to have any problems running them as long as everything is clearanced accordingly.
Rob

H20MOFO
03-25-2013, 03:42 PM
Thanks for the replies...H2omofo; what is a hippo lifter? My lifters are comp race lifters..not sure of the part numbers, they are the ones that are lighter in weight for better rpm, but as for the clearance on the pistons, Dave, your saying that a boat engine must be tighter? I'll have to see what mine is set up at. What temps do they normally run?. Thanks

I was hoping Steve or someone would jump in......my crowers are oil fed....I have always heard that type of lifter being referred to as either hippo or hi-po. I know my solid roller lifters are being well oiled at all r's. Not all roller lifters are hippos.

H20MOFO
03-25-2013, 03:45 PM
http://www.performanceboats.com/dyno/76410-how-often-rebuild-lifters-cam-opinion-2.html

read posts 9 and 11

brite
03-25-2013, 04:35 PM
Wow.... Ok, I now understand why and how a boat engine must be set up differently than a car engine. I talked to the machine shop who built my pulling engine, and he said that with the TRW forged pistons I used, it is around .006 clearance at the wristpin and .004 measured further down the piston... He said I should by fine as long as I let it warm up before romping. ... I hope he's right on these numbers being acceptable........ Thanks again to all who replied.

brite
03-25-2013, 06:00 PM
Also, thanks for the link h20mofo. Very informative