Want to add power 351

[davidcflorida321]

Just pulled out my engine, about to sandbloast it and paint it and was wondering if someone could tell me how to add power and maybe some websites that i can get info on?

 

[DJ]

Re: Want to add power 351

What's it bolted to? An old OMC stringer drive? If so, be careful, that drive won't take much more.

 

[Don S]

Re: Want to add power 351

Just a thought here david, you might want to get your tranny/drive slipping problem cured before you start trying to up the horsepower. If you can't get that drive/tranny combo fixed, no since throwing money into the engine.

 

[davidcflorida321]

Re: Want to add power 351

thnx, i have a b/w velvet drive 71c, i am rebuilding the tranny, so i def want to up the horspower while i ave the engine out

 

[WillyBWright]

Re: Want to add power 351

It looks like you already have a 4-barrel. Thru-transom exhaust might give you a significant boost. A set of marine headers would also give more performance, but I think they're about $1600/set. That would allow mounting a 4-barrel with more CFM to boot. With the manifold you have, going more CFMs won't help much. Just keep in mind that nobody has any idea of just how many ponies that odd drive will tolerate. Shear a gear tooth and it's Game Over. You might consider an aluminum hig-rise intake manifold.

 

[Laddies]

Re: Want to add power 351

The Velvet Drive 71-C is one of the most widely used marine gears in the world and I have scene them on 454s, 350hp and above---Bob

 

[rodbolt]

Re: Want to add power 351

yes but that funky outdrive may not. no telling the shape the u-joints and yoke is in. now will be a good time to pull and inspect that as well. hope this project goes your way

 

[Laddies]

Re: Want to add power 351

Rod bolt, I guess I didn't see a picture of the outdrive and he don't mention it in the post--Bob

 

[Laddies]

Re: Want to add power 351

Ok I found the other post, it looks like it sure could use some TLC. I have never seen one like it----Bob

 

[davidcflorida321]

Re: Want to add power 351

well sounds like some good tips to boost power, i have had the stern drive apart, i didn't check tolorences or anything but the gears and everything inside looks to be in perfect order, nothing wrong that i could see. i think the headers and through hull exuast would be nice but do i have to take out the manifolds from the hull and patch it all in or something?

 

[WillyBWright]

Re: Want to add power 351

The profile of the manifolds you have looks fairly agressive. There are manifilds that breathe well, looks like those might be. Here's a site you might find interesting.<br /><br /> http://www.tresmartinoffshore.com/aspcart/CMI.html <br /><br />There are exhaust tips you mount to the transom and route the exhaust hose there rather than out the drive. The old system would have to be removed and capped, or at least capped. Or there's the cutout system that can let the exhaust go either place at the flip of a switch. Those are illegal on cars, but apparently not on boats. I was about half right on the price. Looks like $3K+.

 

[f_inscreenname]

Re: Want to add power 351

Are you looking to rebuild or just bolt on’s for more HP? If bolt on’s. I think you may cause more problems then you have now. If that is a 351W you have a awesome (and semi rare these days) motor there if it was right. I killed 3 hopped up 302’s before I built a very good 351W. I must say it was one of those motors that you tend to remember if you are a gear head out of the hundred I have done (well maybe not that many but it is close). In a boat you can not beat the longer stroke. When I bought that boat over there it came with a 318ci (mopar’s version of a 302ci). The first thing I did was find a 360ci (mopar’s version of the 351W) to replace it with. Just because of the way the 351W preformed. Again it the longer stroke!<br />With that said I again encourage you to rebuild the motor. It looks very tired. If you add a bunch of stuff to “hop it up” you are distend to break something. If you are going to rebuild I will put a complete motor together for you but it is a lot of leg (finger) work for me so I will not bother if not. I have built a couple motors for folks here. Well they did the work but I found the stuff to do it with and in most cases cheaper then they ever thought. I think if they had problems with the build we all would have herd by now. Let me know.

 

[davidcflorida321]

Re: Want to add power 351

i have a lot of work ahead of me, i have the tranny out andthe engine. ready to start opening the engine and rebuilding her. I'm looking to get all high performance parts. i want this engine to be all it can be...lol I can do the removal and reassembly, but i will need a machine shop to do the heads and block. i think i am going with the through hull exuast with the headers, i'm going to put a high rise intake manifold and a new carb. if i'm going to do it i want to do it right, any help will be a plus. thnx

 

[Boomyal]

Re: Want to add power 351

Don't use a high rise intake and a cam to go with it. You will kill your usable torque, right where you need it. Seek advice from a good engine shop before you jump. Tell them what it is being used for and they will likely know the most suitable mods.