Replacing 305 w/350, HAVE BUILD-UP QUESTIONS

[knotperfect]

I recently posted that I picked up a 19.5 1977 Wellcraft cuddy-cabin with a pre-alpha sterndrive and a locked up Mercruiser 5.0.



There as water in one cylinder and it was scored pretty deeply. So on the recommendation of my local machine shops, I obtained a used 350 to rebuild instead of re-working the 305. I have a few goals with the re-power in mind, not necessarily in order. 1-LEARN SOMETHING and share the experience with my son. 2-AFFORDABLE. If I had $1500 laying around I would just order a long-block. 3-RELIABLE.. We are not WOT all day kind of people. I am not so concerned with this getting done immediately as this is a family project and I am replacing stringers, decking etc so time is on my side. I will re-use most of the accessories from the original engine and I fully understand using the marine alternator, fuel pump, starter, etc....

So, my questions are

1) what would you recommend as a reasonable rebuild for this 350? Meaning overbore, piston types, etc? I have seen kits from Summit and Jegs ranging from $235-$400 but not sure of the direction to take. Also, I don't yet know if this engine has been bored or not.

2) re-use (after rebuilding) existing 2-bbl Rochester and cast manifold, find a 4-bbl carb/manifold, maybe Edelbrock 1409 and manifold?

3) What can I expect the HP range for this to be (with 2-bbl and 4-bbl)?

The used longblock that is the basis for this project is a 1977 model 3970010 (010) block and 333582 heads. It was running strong when pulled and I paid $100 less carb and starter. It came with a Weiand Stealth 4-bbl manifold but I have heard that a cast intake is better, so I may just turn this into ebay.



I will have my machine shop prepare the block, heads, and crank and any other items that need attention and I will assemble. I understand there is machine $ associated, but again, I am working this as a project. I don't think this is outside my expertise and I will rely on Vizards "How to rebuild your small-block chevrolet" as well as a few friends that have done this type of thing a few times in the past.

I appreciate the advice given on these forums, and all help would be appreciated.

 

[Lyle29464]

Re: Replacing 305 w/350, HAVE BUILD-UP QUESTIONS

Sounds like you have a good handle on it. I would do a search on this site and you will find many threads on what type of gaskets, core plugs and oil pump to use and not to use. It will talk about marine Carbs, starters and Alternators. I would bore it the minimum and not use the aluminum intake if your going to do much salt water boating. The MAIN THING is getting the right cam. Be sure to get advice from some one that has built marine engines. good luck

 

[LAC_STS]

Re: Replacing 305 w/350, HAVE BUILD-UP QUESTIONS

You have to add on machine shop bills to that too. I am revulsion a 350 and I got $700 in shop costs already.

It's gonna cost you at least $300 to have the block bored 30 over (or 60 over or just honed) clean block and heads, check for cracks, check mains for algnement, install cam hearings, install freeze plugs, check rods/balance rods, check heads and fix (valves etc).

Your probably looking at about $1500.

 

[ussoldier_1984]

Re: Replacing 305 w/350, HAVE BUILD-UP QUESTIONS

Do not go over .030 on a chevy 350 you are pushing your luck the cylinder walls are not gonna be strong enough. the max you should bore is .030 Take your bare block with the main caps on to the machine shop where they can measure the bore and see if it needs punched out or not. Usually when I come across 350's that have been bored the top of the piston will be stamped with what size overbore it is. I would recommend making sure the head surface and block is true at the machine shop. while its there have them press in new cam bearings. is it a large journal or small? 2 or 4 bolt main? This might be a good cam for your build if you dont already have a marine cam http://www.jegs.com/i/Comp+Cams/249/12-232-3/10002/-1

 

[Bondo]

Re: Replacing 305 w/350, HAVE BUILD-UP QUESTIONS

Ayuh,... I Agree, it's generally Cheaper to buy a long block, than it is to build 1...
If you build, yer Machinest will determine how much the cylinders need boring...
It's a function of clean-up, not power...
Hyper-pistons are a Good choice,...
Shoot for 9 to 9.5:1 compression ratio...

If you run the 2bbl. carb, expect about 230/ 240 hp...
'bout 260hp with the 4bbl..
That intake you have now, I believe is a single plane, 'n Not a good choice for a boat motor...

 

[knotperfect]

Re: Replacing 305 w/350, HAVE BUILD-UP QUESTIONS

Got off the phone with my machinist. Provided I deliver the block disassembled, he charges $300 for prepping a rebuildable block/crank and worst case scenario would be $500. Included would be the wham-a-dyne cleaning, bore (if necessary), hone, deck, new cam bearings, polish or grind crank (whichever is necessary) press out/in piston pins, brass freeze plugs, etc. He would price me a rebuild kit or give me the specs for what I need so that I can order myself. He re-works heads for $120 a set (typical), and $150 if thy need to be decked. This is a local father-son business that has a lot of respect in my area and is highly recommended. Since my dead 305 has a good cam and crank, he said we can probably re-use the cam and he can give me an allowance for the crank. With all that being said, do I start looking for a 4-bbl or rebuild my 2-bbl? Looking for a cost/benefit for both options. Again, this will be used for cruising and maybe pulling a tube once in a while. Also, will my original cast 305 2-bbl manifold be acceptible, or do I look for something more "modern?" Thanks

 

[LAC_STS]

Re: Replacing 305 w/350, HAVE BUILD-UP QUESTIONS

I would def go for the 4 bbl. You can get an Edelbrock 1409 new for about $275-300. Or get a rebuilt one.

 

[knotperfect]

Re: Replacing 305 w/350, HAVE BUILD-UP QUESTIONS

If I wanted to save gas, I'd buy a kayak. But what is the relative fuel consumption of a new 4-bbl compared a 35 year old, rebuilt 2-bbl?

 

[wifisher]

Re: Replacing 305 w/350, HAVE BUILD-UP QUESTIONS

It sounds like your local machine shop could be a huge help for you. I would say buy as many parts from him as you can, and he will probably be happy to help you with any problems you run into.

 

[Bondo]

Re: Replacing 305 w/350, HAVE BUILD-UP QUESTIONS

If I wanted to save gas, I'd buy a kayak. But what is the relative fuel consumption of a new 4-bbl compared a 35 year old, rebuilt 2-bbl?

Ayuh,... Any 'n All fuel consumption questions are answered by the righthand of the operator of said carburetors....

The 600/650cfm Edlebrock has smaller primaries than the 2bbl. you have now...
'n,...
I've never had an Over-powered boat, but have driven alota Under-powered craft...

If the Power is there, ya don't Have to use it,..
But,.. It's nice to know it's there if ya Want it.....

 

[knotperfect]

Re: Replacing 305 w/350, HAVE BUILD-UP QUESTIONS

4-bbl gets the thumbs up! The Weiand Stealth is indeed a dual plane manifold. I will be using in brackish water, so add zincs and use, or replace?

 

[picklenjim]

Re: Replacing 305 w/350, HAVE BUILD-UP QUESTIONS

The Weiand Stealth is a good intake but I'm not so sure you can get a carb like you need for it. I believe their made for a square bore Holley so the Edelbrock's probably won't work. As for the cam I wouldn't even consider putting a used cam from a motor that had water in it into a new rebuilt motor. Definitely get a new cam and lifters. The one linked to above would be a good choice.

 

[treehugger165]

Re: Replacing 305 w/350, HAVE BUILD-UP QUESTIONS

hello knot, were r in the same boat, i mean upgrading a 305 to a 350, lol. i have a 78 seastar 23 foot cabin. how are all of your controls lining up, on the 350? how did u know the cam and such would fit? obviously, im not as knowledgeable as u, so i am looking for any info to make an informed decisions about my boat. thanks.

 

[knotperfect]

Re: Replacing 305 w/350, HAVE BUILD-UP QUESTIONS

My consideration for the 5.0 cam was that the water in the cylinder was due to winterization (or lack thereof) and looks brand new. It is a shame really that everything in the motor looked factory-fresh except #6. I will have my machinist look everything over from the old engine and go from what he says. I have a feeling that he will be able to put together a package deal at a good price, making the old stuff a moot point. Thanks for the input. Want to buy a Weiand Stealth?

 

[StevNimrod]

Re: Replacing 305 w/350, HAVE BUILD-UP QUESTIONS

Have a cam spec'd. It will probably be the best money you will spend on the build. It has to take in account compression ratio, exhaust type, etc. so there is no real one-size-fits-all. There are off the shelf cams that are good for a range of engines, but you're in this deep so why not give your engine what it wants.

 

[knotperfect]

Re: Replacing 305 w/350, HAVE BUILD-UP QUESTIONS

The price of my free boat is creeping up. Machine shop says my block is excellent so a cleaning, hone and cam bearings are all it needs. The heads however need work. New valves, guides, and the usual will puch the entire process from $400 to just shy of $800. At this point I feel that I am more than 1/2 the way to a Rapid-o rebuild delivered. Where is the fun in that. Decisions....

 

[knotperfect]

Re: Replacing 305 w/350, HAVE BUILD-UP QUESTIONS

Today I pick up my block. The bores were good so we did a hone, cleaning, blocking, etc. and are sitting at .040 over. I will use the pistons (flat-top with 4 valve recess) that came out of the engine now that I have cleaned and inspected them. Now I am on a quest for heads. A craigslister has a set of Vortec heads. Can I use these provided I swap my manifold to the vortec style? Since my old manifold and 2-bbl were the original 35 year old parts, I will be replacing them anyway. Do you all have recommendations for vortec intake and appropriate carb set-up?

 

[fastimz]

Re: Replacing 305 w/350, HAVE BUILD-UP QUESTIONS

Knot, congrats on all you have done so far. I live in New Kent, what machine shop are you using? Go ahead and put a good cam in the motor, I run the comp cam from post above and it is an excellent piece. I run on the York River and it gets brackish towards the end of the season. I have used the same aluminum intake for 7 years now without any issue. Just make sure it gets flushed out good when you pull it out. To save you some money, keep the intake you have and buy a Holley 4bbl squarebore and the throttle bracket for a mercruiser (since you already have to buy a carb). I have always been a Holley guy and use one on my 350 and my 454.

 

[knotperfect]

Re: Replacing 305 w/350, HAVE BUILD-UP QUESTIONS

Using Apples in Yorktown. I will build the engine myself and will order the re-ring kit this week. I was planning on using the original marine cam that was in the old 305, machinist says it looks like its hardly broken in. The heads I dropped off at Apples were beyond economical repair, so now that is my current search. I am also on the York (Queens Creek and Cheatham Annex) So... you say keep the stealth manifold and find a holley squarebore. Do I need to track down a throttle bracket going from the 2bbl to 4-bbl? I am sort beginning from scratch since I junked the last block and the old logs. I bought a set of center risers last week and am trying to figure out how to run the cooling set up. I am running the transom/stringer restore and the re-power in tandem. This is like a puzzle but its fun.

 

[Flysfloatsor]

Re: Replacing 305 w/350, HAVE BUILD-UP QUESTIONS

Did you say you had a lead on vortec heads? If so, use them!

I just built a 383 Stroker with vortec heads, its a good combo.