460 Head Upgrade

[WATERROCKET]

What improvement could i expect by installing a fresh set of cj heads on my stock 88 460 king cobra. Its rated at 340hp now. Thanks

[spectras only]

I would change the camshaft to fomoco part A 443 .Check the size of your carb,min 750 CFM to 850 would suffice.Make sure you get the 7/16 rocker arm studs with the 7/16 guide plates and hardened pushrods .Rocker arms [1.7 ratio] would be your choice , roller tips or full roller .Also get dual springs if you have single springs with damper springs only.Seat pressure should be min 130 pounds to 300 open ,to control valve float.you'll have over 400+HP.

[WATERROCKET]

Spectras Only, Thanks for the reply,I only have 300 hrs on the stock motor and i really don't at this time want to pull it out.The carb is a 750,it would be nice to put these heads on for now and leave it at that till the time comes to do something a little different.Where do you think with this change i will end up. Thanks
ps. i can get these heads for hardly jack.

[spectras only]

Just changing heads ,wild guess is you'll go from 340 to 365/375 HP.The King Cobra heads you got right now has 9:1 comp ratio ,so I guess going to the CJ heads your comp ratio will be bumped around 10:1 . Someone might have a different figure ,so let them chime in wink
[ September 18, 2002, 08:32 PM: Message edited by: spectras only ]

[058]

When you install those CJ heads make sure you check the piston to valve clearance as the CJ valves are much bigger than the piston reliefs for use with stock size valves. eek!

[WATERROCKET]

058, Oh shit,I thought that this was going to be easy. You say I need to do the puddy test? What kind of clearance am i looking for . Thanks

[058]

YES!!! Check with clay, Play-doh, Silly Putty, window sash...anything. What you are looking for is to check the bigger valve will fit in the piston relief, some do and some don't depending on the piston. All the reliefs are deep enough just not big enough, that is if you are running a mild cam. [They won't be deep enough if you are trying to run a .700" lift cam]

[spectras only]

058 is right ,if you're going to change cam for high lift later[I thought waterrocket wants to replace the heads only,since he's hours are low on his engine?].The A443 cam has around 560 lift on both valves and will clear with late model 460 deck heights.

[WATERROCKET]

Now its starting to sound a little better. What ratio roller rockers should i run with the stock cam. And do i really need to install stainless valves. Thanks

[WATERROCKET]

Oh, i forgot as posted above 1.7 ratio, is that what i have now?

[not guilty]

If youre adding cam and compression to BBF dont overlook the exhaust.If its stock OMC you,ll have seious reversion problems, trust my experiance on this, wiped out 2 good motors before i learned.
Last motor we used EMI BBC manifolds with FORD adapters, not really my best choice but worked. Plugs are nearlly impossible to get to and adapters need some fitting work before putting them on.Next time I will probably go with Lightning headers, little more exp.
Heres a picture of our 1986 OMC 460 w/EMI pipes.
http://free.***boat.net/gallery/Forum_Graphic_Depot/new_motor.JPG
NG

[WATERROCKET]

Not Guilty, How many horse are you pushing with your motor. I don't want to change my cam at this time, only change to the cj heads and roller rockers. Do you think i will have any problems?

[spectras only]

Warerrocket, the stock bbf rocker ratio is 1.7 ,but not guaranteed wink .A good aftermarket roller rocker will be right on.You could change the valve lift with higher rocker ratio like 1.73 to achieve more valve lift without changing the cam for now.When installing new rockers,always check for coilbind.You should have at least 0.60" gap between coils at max lift.Piston&valve clearence check should be carried out as well .Since you have the cj heads in your hand ,it's easy to install stainless exhaust valves now.I never put s/s valves in my engines ,because I've been running the wet log manifolds with risers,and reversion wasn't an issue for me.Like NG said ,the lightning headers would be my choice for exhaust replacement [if money is no object :D ].I see on NG's picture ,he has the factory airfilter [he probably has clearence problems to install a better one :p ].If you have room ,install any of the free flow aftermarket filters [uscg types]and a 1" or 2" phenolic spacer to keep the carb a little cooler.BBF's run great with 5" to 6" spacers under the carb if there's room under the hatches.Just a thought to squeeze more ounces from your engine wink .
[ September 20, 2002, 10:13 AM: Message edited by: spectras only ]

[WATERROCKET]

Here is what it looks like now,will i need to change the valve covers to clear the rollers.
http://free.***boat.net/gallery/Forum_Graphic_Depot/Im0003241.JPG

[not guilty]

Im running 1.73 full rollers in this motor and clear the stock steel valve covers ok, have the alum lke yours on our new boat and look like they have as much if not little more room.his motor runs about 425 hp.Keep in mind compression is a factor to reversion slightly too, the cams in omc 460 is on the edge already.When your done pay close attention to youre idle characterisics,if it acts like it loads up a lot it could be water.
That actually is a 3" holley 900cfm arrestor with the omc decal on it.We have plenty of room in there, at one time we had a velocity stack with aK&N on it , looked cool but a water cop gave me shit so I got the holley and put the decal on it so he could stick it in his $#@% next time !!NG

[spectras only]

WR, your valve covers {they look similar to the M/T cover that clears the roller rockers] look tall enough to accept the rockers.However try to just put it on loosely with all sparkplugs removed ,and crank the engine over fast.If there isn't enough room ,the rockers will throw your covers off :D . It looks like NG's block has the old chromed valve covers ,that wouldn't clear 'SOME' of the aftermarket full rollers.I repost some specs I did for Gnarly before; http://www3.telus.net/spectrasonly/OMCKingCobraspec.jpg http://www3.telus.net/spectrasonly/OMCKingCobra.jpg
[ September 20, 2002, 11:39 AM: Message edited by: spectras only ]

[HOSS]

By the extra thick valve cover gaskets.
Gotta love thosebench racing fags!

[not guilty]

WATERROCKET-double check your carb if thats what you said was a 750- looks like the stock 600.
SPECTRAS-thats a great spec shhet, printed that out last time put on photo sheet and made a nice wall novelty. thanks. Whats the deal with omc and the HP ratings on the 460,seems it changes from boat to boat but the motors the same.The 1988 mach-1 we bought this year has twins and thier tagged at 365 hp ??Guess they thought they perform better in pairs huh !!??
[ September 20, 2002, 02:35 PM: Message edited by: not guilty ]

[spectras only]

NG ,you're probably right about WR's carb.Lots of 460's were equipped with 600 holleys :rolleyes: .I would use the 850 holley vac secondary marine carb with big jets; 88 primaries 94 secondaries.Will move a big heavy boat real easy :) .

[Blown 472]

Not to rain on your parade but I think you would be better off with a set of dove's the rpm range of the cj's might not be what you are currently running, aside from the larger ports the cj and dove have the same chamber. Just my 2 cents. :p

[WATERROCKET]

Blown 472, Sorry for late reply, Have been out of town. I am currantly running 4800 to 5000. Do the cj heads like a lot higher r's to get the hp? Or do i need to sell these and get a set of doves. Are the valves the same size in the doves as what i am running now? sounds like it may be an easer change out with out having to worry about the pistons. jd

[Blown 472]

The dove's have 2.08 and 1.66 valves and probably the same size as what you have now. if you checkout www.reincarnation-automotive.com (http://www.reincarnation-automotive.com) there is a great section on porting. I had cj heads on my jet boat and went to a set of dove's and the boat ran better, just my opinion but I think you would get better velocity with a smaller port. There is also a forum there you can ask all the ford guys as well. The biggest improvement you will make over what you have is raise the compression and a better exhaust port. Keep in mind though you may need guide plates and studs.

[WATERROCKET]

Blown 472, Man that was quick, think i will have any problem getting rid of these heads? The doves going to take me to 10 to 1 comp.

[Blown 472]

If you post them on that site I told you about they will sell, the truck pull guys like them cuz they turn all kinds of rpm. :)
One more thing, you probably have a cj intake on your boat, check the casting numbers on it, if you have the room and you go with the dove's you should consider a weiand stealth intake. Hell I just sold a set of heads, intake, cam and carb. :p
[ September 24, 2002, 07:11 AM: Message edited by: Blown 472 ]