To rebuild or not?

[Jred]

I have a 1970 Avanti II with the original sbc350 in it. 65,000 miles. 
 

A few months back I replaced a freeze plug that was leaking on the passenger side. That was easy to get to, just behind the starter. Today a freeze plug started leaking but this one is on the driver side just behind the motor mount. as far as I can tell, I’ll have to pull the motor to replace that plug. 
During the last plug removal I noticed a good amount of build up in the water jacket of the block. I back flushed the block but I know there’s more in there. Seeing that the driver side plug is now going, and considering the various oil leaks from the front and back of the engine… I’m considering a full rebuild as opposed to a simple reseal.
I’d like to perform as much as possible of the rebuild myself, taking the block to the local machine shop for machining. while I’m at it upgrading the internals to run on modern gas and maybe give it few more HPs. 
this would be my first engine rebuild. 
What suggestions might you all have?

Edit: about a year or so I installed an aluminum intake and had the Rochester 4 barrel rebuilt

thanks,

Jason

Edited July 4, 2022 by Jred

[Gunslinger]

It's probably more cost effective to buy a crate engine and drop it in...they're available in many horsepower/torque levels.  When you rebuild the current engine it's all too easy to go down the rabbit hole with modifications.  When it comes to Avantis having the original engine has never really been an issue among collectors.  

[Avanti83]

Agree with Gunslinger unless you are bound and determined to assemble it yourself. A complete engine rebuild kit for the 350 including crank, cam, pistons all gaskets etc is about $1400 from the usual suspects. You would then need to have your engine cleaned and bored as well as the heads and valves redone. If you want a better cam etc then the costs go up.

$3000 will get you started in a crate motor from the same sources.

I suggest that you take a look at Jegs or Summit Racing's site and compare the performance level you want between a parts cost for a rebuild and a similiar crate motor and then decide which way to go. Your machinist should be able to give you a ballpark number for the block and head work.

I have rebuilt several SBC's because I enjoy doing it and I have the tools and other odds and ends to do so.

Edited July 5, 2022 by Avanti83

[John D]

with only 65k, if the engine has good compression and doesn't burn oil, the freeze plugs and oil leaks can be attributed to age. Pull it and pull heads, look at cylinders and measure taper and/or significant ridge. Check a couple bearing caps for wear/scoring, gotta pul rear main to replace the seal anyway. If you don't see anything amiss I'd replace gaskets and freeze plugs and timing chain and run it. If you do see issues, rebuild or crate it.

[Jred]

Thanks all. 

Another friend suggested checking to see if its a 4 or 2 bolt. He mentioned that the 4 bolts from 1970 are good for building. 

 

[Avanti83]

14 hours ago, Jred said:

Thanks all. 

Another friend suggested checking to see if its a 4 or 2 bolt. He mentioned that the 4 bolts from 1970 are good for building. 

 

Four is better than two but, in reality, the vast majority of SBC's were two bolt and they hold up just fine for the HP levels you were discussing.

[Jred]

On 7/6/2022 at 5:27 AM, Avanti83 said:

Four is better than two but, in reality, the vast majority of SBC's were two bolt and they hold up just fine for the HP levels you were discussing.

I like sensible way of thinking. 

[Gunslinger]

Use ARP bolts and a two bolt main cap will be just as safe as a four bolt main of standard grade bolts used.  But...four ARP bolts will do even better if you have an engine with four bolt mains.  

Essentially...regardless of what engine you have...you'll be golden with ARP bolts.  They're considered the best bolts on the market.

[wildfelr]

RQB3263/81/305.... I suggest you go for it ....its not rocket science... ive done a dozen over the last 60 years....one was a 92 Buick roadmanter (GM350)...2 bolt main/roller cam and 2 barrel throttle body injection from the factory........ and other Ford 460, 4.3 chevy v6, seagrave v-12  to mention a couple....when I could the first thing I did was ...BUY THE BOOK, and read it twice... "how to rebuild your chevy v8".... second.... locate a reputable machine shop.... third ...read the book again... fourth ... enlist help from friends .... have fun... pic coming

[wildfelr]

[wildfelr]

RQB3263/81/305.... YOUR ENGINE IS actually a low mileage re build and should be very  straight forward. If your lucky It may go together standard (std) the machine shop will determine that and provide the matching  bearings/rings etc... and for a couple extra bucks they will even build up the short block for you...only brass freeze plugs and dont forget the one behind the flywheel....paint all cast iron parts etc before assembly....keep in touch here ...RQB3263

[wildfelr]

RQB3263/81/305.... Amazon has the book for 26$.......... 2 bolt///4 bolt mains  doesnt make any difference at all itsa a cruiser not a race car...a torque cam is a good idea, sold by all cam mfg also called an RV cam it will come with lifters an new valve springs ...I used Crane cam lifters and springs....that mod will help if you have an overdrive (700r4) trans but is good in any case..... my anemic 305 loves it with the OD.... WRG

[Gunslinger]

If you plan on rebuilding your present engine…call Summit Racing and talk to their techs.  They will ask specific questions about how the engine is to be used…what is wanted from it.  They will give solid recommendations on the parts…intake, carb, heads, etc….regardless of brand to match everything together for best performance for the job.

[Jred]

Thanks @Gunslinger and @wildfelr