If you are going to add a bunch of performance parts on the top, I would not trust the bottom end to hold up without at least going through and rebuilding the bottom end.

My stock L48 (with the exception of a Crane 266H cam) lasted about 90,000 miles. I was the second owner and bought it with about 45,000 miles.

 

True, you will need shorter pistons if you use 6 inch rods. If you use the stock length (5.7 in) rods you will be have a little more top end rpm. on the top end. You still will have a stump puller up to 5500 rpm with the 6 in rods.

 

I read most of this thread and figured I'd let you know what happened when I rebuilt my 74 L-48. My engine had about 92000 miles on it and I fretted a lot about the condition of the block, pistons, etc. I didn't have the money to purchase a new engine and didn't have confidence in anyone to rebuild the one I had. I took a chance and rebuilt (freshened?) it myself. I bought a few books on rebuilding small block chevy engines and read a lot before I started. I removed all the accessories from the engine and pulled the engine out without the tranny without having to remove the radiator. I did however remove the fan shroud to gain some clearance. Once I had the engine out I tore it down, keeping every part in order so I would know where it went back. I then measured the bores and to my surprise they were still within stock specs. A few of the cylinders still had the original hone marks. I was amazed to say the least. I then cleaned the block, crank and pistons thoroughly. I used hot soapy water and a pressure washer on the block and cleaned the pistons by soaking them in carb cleaner. I also cleaned the crank with hot soapy water and brushes. Once everything was cleaned up I had a friend come over and remove/install the cam bearings. I could have done this myself with the proper tool but the guy only took $20 for the 5 minutes work so I was ahead of the game. I bought a rebuild kit, including gaskets, from Summit and proceeded to assemble the engine. Some clearances were a little on the wide side but still within stock limits. I could have gotten the bearings a little tighter by buying .001 undersized bearings but I felt it was good enough if it was within specs. Everything went together easily and the books I bought got quite a workout. I replaced the stock heads which were shot with SR Torquers with 2.02 and 1.60 stainless valves and 67 cc chambers. I replaced the cam with a Crane Powermax 272 cam with 216 degrees intake and 228 degrees exhaust durationand replaced all the lifters and pushrods. I also replaced the fuel pump, oil pump, oil pan (chrome) and water pump (chrome) and also installed Summit aluminum roller rockers. Everything else got a good painting and new gaskets.Once the engine was reassembled I reinstalled it. To date the engine has run strong and has not used a drop of oil. It starts easily and runs much better than stock due to the cam and heads. I use premium gas but could probably get away with a lower grade. All in all the rebuild cost me about $1000 total and I'm very happy with the results. As time has passed I've added headers and some more chrome but overall in the 10000 miles I've driven the car it's performed flawlessly. Don't be afraid of doing it yourself. The worst that can happen is that once you tear the engine down you find the bores out of spec and need to have machine work performed and/or a new engine. With only 70K miles on your engine I doubt that is the case. The best, you don't need anything more than a freshening. Give it a try, you may surprise yourself.

 

Thanks for the reply. Sounds like I am just where you were prior to making the plunge. I have read everything I can get my hands on but still doubt my abilities to tackle the rebuild of the shortblock.

I am finding that if I stay with a rebuilt 350 shortblock I can pick one up for around 700. This may still be my best option.

BTW - Did you keep your original pistons and intake? Any other performance mods beyond the cam and heads?

 

Yes, I kept the original pistons, rods and intake. The only other mod was to change the points to an electronic setup. I'm using a Crane XR1 conversion now which has worked much better than the Pertronix I originally installed. As you can see by my pic I also added at a later time a Performance Plus polished manifold and an Edelbrock Thunder Series AVS 650 cfm carb. Other than that the internals are all stock.

 

Top end only. (I don't do that!) I know a guy w/ a shop that guarantees his work & used to do that on stock engines- no longer since he says that it can be expected to need rings shortly after.

Power wil be dramatically up from stock.
Anywhere from less than 1 drag run (could blow) to several years.

The other part of that is replace rings. Some rebuild by pulling the heads & pan to replace rings & bearings (& heads or valve job).

 

I just finished a top end vortec rebuild (heads, cam, lifters, pushrods, intake) on a stock L48 with 92,000 miles. So far so good in the first few miles.

Before the rebuild compression was good, so I kept the pistons and rings for the time being.

When I pulled the oil pan everything looked good and after measuring everything I was comfortable that it is going to hold up for a while longer.

I am with Lars and others who say "Go for it!!!" Of course there is a chance that some component of the engine is going to fail with added horsepower, but I say don't let that stop you!!!

Now for a disclaimer...Everything can be fixed or replaced if you have the money to do it. That being said, if you don't have the money to replace broken parts, then don't push the limits of the engine. If you have a good running L48, appreciate it for what it is.

 

I am in the process of finishing my 76 L48 with 114k. I pulled the motor apart sent the block to have it cleaned and honed. We measured bore, taper crank journals, etc. Everything was good. We replaced all bearings and used the original pistons crank etc. Put a set of 202 heads (64cc)( the heads have been ported etc. comp cam, I think it was 454 lift on in. and exh., Edelbrock RPM manifold and we will use the Q jet and rebuild it. I am putting a set of shorty headers on it also. We also replaced oil, water, & fuel pump.

I was amazed that the engine was in such good condition when we pulled it apart. Still had the original bearings in excellent condition. Could still see the machine marks in the cylinders. I don't plan on racing, just wanted a little more from it.

It all started as an engine compartment detail......LOL

 

I know you don't have much confidence in yourself, but a cheap short block is just that. One of my favorite sayings is "Pay for it right the first time...and weep only once." There are a lot of junk short blocks put together with crap coming out of China. It seems you are comfortable with doing the top-end...Find yourself a mentor and use this forum and do it yourself. That way you know what you have. It sounds like your engine is sound...just some miles. You ought to see what passes for cores that those reconditioned shortblocks start from...and most (a lot)of the production shops will cut any corner they can. Sounds like money is tight, just like with most of us so just be smart.