New cam for 5.7 - am I going too big?

[Uncle Binky]

I'm doing a bit of a freshen up on my 260 HP 5.7, A1G2 drive in my 1999 Trophy 2352. The engine is a 1991 5.7 4V.
I bought a pair of 906 Vortec heads and took them to my machinist for a checkup, new SS intake valves, and a 3AVG. In discussing an appropriate cam to complement the new heads, dual plane intake, and possible carb, he suggested a 224/224/.450/114 LSA cam. This is bigger than I had intended to go, as I was looking at a Comp Cams 262 which is a 218/224/.505/112. My boat is heavy, and although the point of this exercise is to improve cruise and time to plane (when loaded for a tuna run), I worry about missing the opportunity to improve the low end for working through the big chop and swells we deal with offshore. Is this cam pushing my power band up the RPM range to an unusable limit? I don't see ever turning this engine over 5000 RPM, so I don't see a need to cam it that way. Any engine builders have experience here? Thanks.

 

[Bondo]

Re: New cam for 5.7 - am I going too big?

Ayuh,.... Welcome Aboard,... I like Yer choice, over yer Machinist choice,....

Especially in a big heavy hull,...

 

[Walt T]

Re: New cam for 5.7 - am I going too big?

Make SURE your machinist has upgraded your heads to take that .505 lift. That may be why he recommends the .450 as unmodified Vortecs cannot be use with more than .460. That being said, I agree with Bondo if the heads are modified.

 

[NHGuy]

Re: New cam for 5.7 - am I going too big?

Also,
I recommend the Comp Cams 262H. I have one in a box right now, I'm planning to install it in March when the snow lets me get my engine out of the boat.
Things to know. The recommended springs for that cam make more pressure than you should use during lifter/cam break in. So after you have the heads worked, check to see if you can use your old springs for that.

 

[Uncle Binky]

Re: New cam for 5.7 - am I going too big?

He told me that the 224/224 cam is a standard high performance marine cam. I trust him, but I want to keep my power where I'll use it, which is below 5000 RPM. I wonder if I'm tossing money around - will I see gains that warrant replacing my existing cam?

 

[Bondo]

Re: New cam for 5.7 - am I going too big?

He told me that the 224/224 cam is a standard high performance marine cam. I trust him, but I want to keep my power where I'll use it, which is below 5000 RPM. I wonder if I'm tossing money around - will I see gains that warrant replacing my existing cam?

Ayuh,.... I wonder too,.... The Vortecs, without lower end work, should be a Noticeable kick,....

If you were doin' a full on Rebuild, Ya, different cam, 'n different pistons too,....

 

[Uncle Binky]

Re: New cam for 5.7 - am I going too big?

Any known, verified improvements by swapping a cam while still using the stock exhaust? I've heard (another free opinion) that I won't see a performance gain from a cam change without spending piles of lovely cash replacing the stock Mercruiser exhaust. If I'm not going to see a noticeable improvement from the cam, I'd rather spend that money on bait...

 

[Fishermark]

Re: New cam for 5.7 - am I going too big?

If I'm not going to see a noticeable improvement from the cam, I'd rather spend that money on bait...

Since, as you say, opinions are free... I say spend the money on bait and gas. The vortecs alone will give you some extra oomph. I also would not replace all the intake valves unless necessary either. Have your machinist give you his opinion as to the condition of the existing valves.

 

[Uncle Binky]

Re: New cam for 5.7 - am I going too big?

Since, as you say, opinions are free... I say spend the money on bait and gas. The vortecs alone will give you some extra oomph. I also would not replace all the intake valves unless necessary either. Have your machinist give you his opinion as to the condition of the existing valves.

When I took thew heads to him he took one look and knew these were out of a truck. He told me that when Mercruiser first started installing vortec engines in their drives he was taking in several sets of heads every week from the local boat dealers due to "tuliped" intake valves. He was adamant that I have him install stainless intake valves, and who was I to argue? A magnaflux, surface, valve grind, SS intakes, and new seals came out to @$250. I wasn't complaining. His is one of the leading shops in the Seattle area, and I am happy to spend my money with him. I just couldn't help but err on the side of caution regarding the cam recommendation. I have another issue with the engine, which may turn out to actually be a Crusader, but I'll post that in the "other brands" section.