Need to make sure this rebuild will work

chris0061

Chief Petty Officer
Joined
Jun 17, 2007
Messages
446
I'm getting a 350 block bored out 40 over and 882 heads already ground with Z 28 springs in it. I'm taking that and a 260 Mercruiser block with crank and cam and all bottom half with the pistons and rods out to a machine shop. He's going to take the 260 apart and make sure the crank is good and the cam is good, If so he's going to take the new block and heads and of course new pistons and rings of the ones he says needs to go in there build the long block then I'll transfere the other parts and install in the boat. Any tips on what I can do to help build a good engine, IE buy certain pistons, rings, lifters, exc, exc.
 

Attachments

  • th_IMG00038.jpg
    th_IMG00038.jpg
    4.2 KB · Views: 0
  • th_IMG00043.jpg
    th_IMG00043.jpg
    3.5 KB · Views: 0
  • th_IMG00044.jpg
    th_IMG00044.jpg
    4.1 KB · Views: 0
  • th_IMG00040.jpg
    th_IMG00040.jpg
    3.9 KB · Views: 0
  • th_IMG00041.jpg
    th_IMG00041.jpg
    4.5 KB · Views: 0

Bt Doctur

Supreme Mariner
Joined
Aug 29, 2004
Messages
19,093
Re: Need to make sure this rebuild will work

Keep it under 320hp and train your right hand to be weak on the throttle
or you`ll need a new Bravo setup to go with the new motor
 

chris0061

Chief Petty Officer
Joined
Jun 17, 2007
Messages
446
Re: Need to make sure this rebuild will work

What gives it the horse power anyway? Is it the cam, or being bored out, The cam in the 260 that he is going to take out is stock I'm sure.
 

Bt Doctur

Supreme Mariner
Joined
Aug 29, 2004
Messages
19,093
Re: Need to make sure this rebuild will work

Just wanted to say just take it easy .I know how some people get trying to squeeze a bit more out of the 350 block.The hp rating is for alpha drives.
The did use the 330BBC with the alpha but found out it couldnt take a heavy throttle hand even in a light boat.Thats where Bravo came in.
 

chris0061

Chief Petty Officer
Joined
Jun 17, 2007
Messages
446
Re: Need to make sure this rebuild will work

OK I'm not really looking for more horse power just a solid engine and I found the block and heads for sale for 300 so I thought that would be my cheapest and best way to get a good engine for my boat.
 

180shabah

Rear Admiral
Joined
Mar 26, 2005
Messages
4,995
Re: Need to make sure this rebuild will work

Solid engine and bored 40 over don't mix.
 

chris0061

Chief Petty Officer
Joined
Jun 17, 2007
Messages
446
Re: Need to make sure this rebuild will work

I don't know what you mean.
 

xltier

Chief Petty Officer
Joined
May 20, 2004
Messages
636
Re: Need to make sure this rebuild will work

I don't know what you mean.

.030.over would be alot better..040 is kind of pushing it on a couple of the cylinders.at least thats what our engine builder claims.
 

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
70,465
Re: Need to make sure this rebuild will work

I'm getting a 350 block bored out 40 over and 882 heads already ground with Z 28 springs in it. I'm taking that and a 260 Mercruiser block with crank and cam and all

Ayuh,... What's wrong with the Merc block,+ heads,..??

Vortec heads are the prime Choice of heads for a Marine motor,...
Especially with compression ratios up around 10:1...
 

chris0061

Chief Petty Officer
Joined
Jun 17, 2007
Messages
446
Re: Need to make sure this rebuild will work

number 8 busted a exhaust valve Bondo and cracked the cyl wall. I just thought that this 40 over block and heads would be the best way out of this engine problem.
 

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
70,465
Re: Need to make sure this rebuild will work

I'm getting

Is any of this a Done Deal,..??

I prefer to have my Machinest to bore the block to match the pistons, usually at .030...
Rather than trying to match new pistons to an already bored block...
You end up with closer tolerances,+ there's more choices of .030 pistons out there...
And as I said, Vortec heads are a No Brainer....
 

chris0061

Chief Petty Officer
Joined
Jun 17, 2007
Messages
446
Re: Need to make sure this rebuild will work

It's not a done deal yet. I have the old block ready to take to the machine shop and I'm supposed to get the other block and heads Sat. If that crack in the sleeve is more than 30 over what am I looking at?
 

MikDee

Banned
Joined
Jun 6, 2007
Messages
4,745
Re: Need to make sure this rebuild will work

Solid engine and bored 40 over don't mix.
I Agree! All I know is, .030 is the Maximum safe overbore on a 350!
See what your machinist says if you cylinder is cracked, maybe they can re-sleeve it? Or, If not it's junk!

Heed what Bond-o is saying, he's right on with the info here, it all has to match closely. Another thing to note, whatever heads you use, if you have to go over .450 lift on the cam, you must either machine the valve guide seats down, (so there's no spring binding) or get the "bee hive'' springs, & thin retainers, that will let you go to a Max of .550lift
 

dan t.

Lieutenant Junior Grade
Joined
Feb 28, 2008
Messages
1,131
Re: Need to make sure this rebuild will work

882 s are not good heads, shure they flow pretty good, BUT, they are thin, stick your finger up inside an intake port, you can feel the bottom of the rocker stud, this is a missing water passage that was deleted for weight savings. the 993 is a far better casting,or as suggested go vortec, free horsepower and probably no more cost than guides and hard seats for old style heads
 

AZSenza

Chief Petty Officer
Joined
Mar 11, 2008
Messages
521
Re: Need to make sure this rebuild will work

I agree also with .040 being too much. It leaves little metal for heat transfer and strength. The vortecs can be bought brand new for under 600$ a pair. They flow better than anything chevy made before and will do it longer (Reliability). Last time I went in for a valve job, it was $300, for a new set of heads I'd have spent the additional 300. When we used to go past .030 overbore, we had the blocks sonic checked for thickness, this was usually reserved for vett blocks so the numbers would match, too many blocks new and in junk yards to over bore past .030 in my opinion...I know of a place that sells new GM 330hp (at 5000rpm) engines for well under 3000$ for a long block with vortecs.
 

Howard Sterndrive

Rear Admiral
Joined
Nov 5, 2008
Messages
4,603
Re: Need to make sure this rebuild will work

my advice is buy a GM 290 horse crate long block. Part # 12499529
It makes 260HP at boat rpms. Same as your original.
Put brass core plugs in and swap all components over.
12499529a.jpg

You can be back in the water in 1 or 2 weekends and the engine is new, not rebuilt.
They seem to be avail for around $1500 - $1700 at places like JEGS

It's easier to sell a boat down the road with a new engine - rather than something hot rodded to turn high rpm's in a car.
 
Top