Waveline24

Hey all,
We have the motor torn down due to a spun crank bearing. While apart, I am replacing the cam and need some advice. I would like to know what cam you recommend for my application. The motor is bored 30 over and other than that, completely stock. Its a 92 Mercruiser 454, weber carbed and raw water cooled. The boat is 23 1/2'. I have no idea what the factory cam specs on that motor are. My friend that works at a an engine rebuilder said to give him the specs and he will get the cam. He does not have access to the specs for the motor as they normally do automotive engines mainly. I am thinking I should just go with factory specs although I would like a little more top end and don't mind sacrificing in other areas to get it.

Any help or feedback is appreciated.

Thank you

blown1500

Need to know what the hp was stock or more specs such as oval or rectangular ports, compression ratio, etc. If the builder can't tell you that, YOU ARE IN DEEP TROUBLE. Happy to help. post or call 704-574-4020 8:00-9:00PM Eastern.

Turbojack

I'm hoping you know why you spun a bearing.

Waveline24

Well the bearing was not acutally spun yet. It was badly torn up and scored the crank due to debris in the oil.

As for the Specs

300 HP
Oval port
150 comp

I think I gave you guys a bad impression of the builder. He was only asking me what cam I wanted to run and I said whatever the STOCK spec is for a 1992 Mercruiser 454. He simply said that I should find out and let him know since he does not have the specs available. I told him that I could prolly post on a forum and get a quick reply to what stock specs are on the cam. Is there somewhere you could recommend where I could find the specs of the stock cam for my motor?

IF this may help. The motor serial is OD802596


Thanks

BADINTN

With my25' '88 Chapparrel Crane advised me to go with a cam they called their Commander. It was hyd with 535/553 lift on 112 deg center, I can't remember the duration but I still have the cam card if you need it. I got some series 049 large oval port GM heads and installed 2.19" intake and 1.88" exhaust valves in them and got rid of the peanut stock heads. I went with a Edelbrock RPM intake, a Holley 750 DP and a set of Stainless Marine exhaust manifolds. All this allowed me to jump from a 19p to a tweaked 23p Mirage and gain about 6-7mph. I figure it pushed my stock 330hp to maybe 380hp or so.

Scott72

It all depends what you are looking to do. Being a 330, you will have the peanut port heads. I don't think a cam will do much for you without replacing the those heads if you are looking for more out of the motor. You probably also have a low rise intake which will hold you back. Being a generation V 454 I'm not sure if you can use the older 049 large oval heads because the water ports on your block are larger then the generation IV 049 heads. But, like I said it depends if you just want to put it back together relatively stock or are look for more.

Griff

A stock Gen V 454mag/365hp cam is 220/220 duration and a .510/.510 lift on a 115 lobe separation.
Not positive about the specs on the 330, but it was a little smaller like a .480 lift.

With stock exhaust, just make sure to get something with a 114+ lobe separation.
Maybe go with something close to the specs of the magnum cam.

Waveline24

Thanks for all the info guys. I hope to be out on the water in the next few weeks before I miss our short but sweet summer up here in Seattle.

Waveline24

Wow,

I found my Merc Service Manual finally.

Here are the specs for my 7.4L

Lift Intake .271
Exhaust .282

Duration Intake 234*
Exhaust 238*


So, with my motor being stock. Would you recommend I stick with the Factory Spec for best all around boating? Or could I pick up a little top end speed with just a different cam and no other mods to the motor?

Thanks for your patience
guys.

Will

Griff

Those specs have to be adjusted to really figure out what they mean on a cam.

The lift #'s are valve lift. You have to multiply them times the 1.7 rocker arm ratio. 1.7 x .271= .461 and 1.7 x .282=.480

The duration numbers are probably advertised duration #'s as well, not the actual #'s usually referred to. Duration at .050 is what people ususally refer to.

The specs I just found for a stock 7.4 cam are

.460/.480 lift and 213/217 duration on a 114 LSA

A stock Magnum cam is .510/.510 lift and 224/224 duration on a 115.5 LSA

You could easily use a cam in the range of the magnum cam or a little more and pick up a few HP. You're replacing it anyway, so you might as well add some HP.