5.7L Cam Choice

[ALEXT77]

Hello everyone,

I am currently in the process of repowering my Four Winns Horizon RX (1997). My plan is to drop a 5.7L in place of my current 4.3 Volvo. The 5.7L block I have is from a 1985 Cobalt. To pair with this block, I have a set of Vortec heads, intake, and roller lifters. I will be running a 4 barrel carb and through prop exhaust. I was hoping to get some suggestions on a cam and set of springs to help me get some more power without reversion.

Let me know what you guys think!

 

[Lou C]

1) the 1985 GM (Chevrolet) block is a 2 piece rear main seal, vs the 1986 and newer 1986 and up one piece main seal. When they went to the one piece the flywheel changed, and I don't think your coupler (Merc or Volvo) will work with the 2 piece style rear main flywheel. So you have to check on that...
2) the 1985 block didn't come with roller lifters so if you want to install roller lifters/cam you have to have it modified to do so.
I think you'd be better off using a '96 and up that already has a one piece rear main, Vortec cyl heads and roller cam.
3) the outdrive gear ratio for the 4.3 isn't really right for a 5.7, it will give you good power out of the hole but it will limit top speed

What size Four Winns do you have?
If it's a 20' or smaller, you might be better off with a reman 4.3 Vortec with an Edelbrock marine intake and 4 bbl carb.

 

[ALEXT77]

Lou,

My apologies, it is a 1 piece main. I must be off on the year. The boat is an 18'. I built a 1.50 gear ratio outdrive to account for this power increase. I have roller lifters and Vortec heads off of a newer 5.7L. I am wanting to know what cam/ springs I should run to get a bit more power out of it.

 

[Scott Danforth]

Skip the pre 1995 block. It will not be machined for the lifter spider for the roller lifters

If you get the heads worked on, get them modified for thread in studs and cam lifts higher than 0.45". Then you can look at the XM264HR cam. With some additional work, you can look at the XM270HR