Performance upgrade questions

[CharlieB]

Re: Performance upgrade questions

Cyl heads on the 305 used smaller valves than many 350's, you need to check, some elect to 'notch' the top of each cyl to provide clearance for the larger intake valve. Personally, I'd rather see you swap in a decent 350, with vortec heads and a mild marine cam. The combination would give you a noticeable improvement in power without breaking your bank account, leaving you enough to think about a new prop to utilize your new-found power.

 

[mybadford]

Re: Performance upgrade questions

Cyl heads on the 305 used smaller valves than many 350's, you need to check, some elect to 'notch' the top of each cyl to provide clearance for the larger intake valve. Personally, I'd rather see you swap in a decent 350, with vortec heads and a mild marine cam. The combination would give you a noticeable improvement in power without breaking your bank account, leaving you enough to think about a new prop to utilize your new-found power.

I will check valve reliefs in the pistons. The 305 is in there and I figured I'd just use it since it has relatively low hours, but I am not opposed to a larger power plant. I've got a couple 350s needing to go in something. Also have a 400 in need of a home. None of them are set up for marine use but can be changed and set up for marine use "I think". Doesn't the marine engines use a forged steel crank vs a cast steel crank?

 

[Bondo]

Re: Performance upgrade questions

Doesn't the marine engines use a forged steel crank vs a cast steel crank?

Ayuh,... Generally speakin',.... Nope.....

 

[mybadford]

Re: Performance upgrade questions

Ayuh,... Generally speakin',.... Nope.....

HHHMMM Well, Maybe I will re-cam and change freeze plugs in a 350 I have and do all of the above stated changes in some sort of fashion. Undecided on the heads so far. It'll probably be next winters project. Boating season is right around the corner.

 

[mybadford]

Re: Performance upgrade questions

Cyl heads on the 305 used smaller valves than many 350's, you need to check, some elect to 'notch' the top of each cyl to provide clearance for the larger intake valve. Personally, I'd rather see you swap in a decent 350, with vortec heads and a mild marine cam. The combination would give you a noticeable improvement in power without breaking your bank account, leaving you enough to think about a new prop to utilize your new-found power.

I have elected a non-roller 350 that I have lying around. It has around 30,000 miles on it. It holds 40psi of oil pressure at idle warmed up to 195 degrees. Goes past 60 psi pretty much as it comes up from an idle. It currently has a standard oil pump.

Still undecided on heads between a vortec or afr 180cc. Heads will probably be an impulse buy. Before the end of summer I would like to purchase a set of headers if I can find a good deal on a set of used headers. Id like to fit those on first just to see if I can pick up a mph with that fire breathing 305 my boat has.

Scott Danforth, I'm curious to see how your boat differs from before and after with your mods once you get it lined out and running right.

My boat has a 14x19 factory volvo prop. I was told it is a high speed prop. It will hit 47mph at 4700rpms with me and another 200lb passenger. I'm 250lbs. Its pretty much a mph per 100 rpm from 2800rpms and up according to gps. How much more power would you guys think I would need to go to a 23 pitch and spin it 5,000+ rpms? My goal is to be able to hit 60-61mph. The boat doesn't seem to have a real deep v compared to other boats. It's 2900lbs dry weight. It gets on plane "ok" if the load is right. If I put a couple biggins in the back seats if just about won't even go on plane from an idle to wot. If I ease into it it will do fine getting on plane.

 

[bigbadbowtie]

Re: Performance upgrade questions

I suggest a vortec head and less than a 480 lift cam so you can utilize stock diameter valve springs. Anything more than 480 lift will require a behive spring and pinned studs(or screw in). Stock vortecs have some NICE flow numbers for a factory chevy head. You want the 062 or 906 casting heads. My opinion............

 

[LegacyT]

Re: Performance upgrade questions

Mybadford:

How you making out? Did you end up getting that 350 in there or did you stick with the 305? To the other guys: I'm looking into installing a set a Trick flow super 23 175CC aluminum heads Edelbrock performer intake and Comp cams Xtreme Marine 12-232-3. This is all low end torque and midrange hp stuff. Do roller rocker arms do anything or are they mostly for show. Thinking of just using the stock rockers...