indydoug

Well the time has come for an engine rebuild, hopefully just the top end. My 1980 has the original L-48, completely stock down to the exhaust, less most of the emissions bolt-ons. I've had it three years and put 11K miles on it, total mileage is 85k. It always starts right up and idles smoothly, but I get a lot of blue smoke on start-up if it has been sitting all day. Most of the gaskets around the heads are perpetually damp, and I'm ready for more HP anyway. I am planning on new heads, intake, roller cam and exhaust. I also intend to keep the engine in the car.

My question is - what should I do before I start removing parts? This is my first time going deeper than the sheet metal. So far I have done the following:

- I added a quart of Marvel Mystery Oil to free up a stuck lifter (worked great!) I'm leaving it in for at least a few day to let the detergents do their work.

- Cooling system clean - running Prestone cleaner for a few days after draining everything, including pulling the plugs out of the block, busting through the wall of crud and letting out the chocolate milk. I'll keep cleaning and flushing until it drains clear.

- I plan on running a compression check and a leak down test to ensure the block is worth keeping. The is a good weather driver, will probably never see a track or dragstrip, so I don't plan on anything a stock block can't handle.

Is there any other prep work I should be aware of, keeping in mind I prefer to keep the block in the car?

jnb5101

Pull the engine, have the block hot tanked and have it and the crank magnafluxed, and fully machined. If you're going to upgrade the engine, start with a known foundation.

Easy Mike

Up the balance in your checking account and make sure your credit card is not maxed out.

Got beer in the fridge?

CaseyJones

This is a sad truth. No matter what you plan to do, double what you plan to spend and add 20%.

Beer helps.

I have an 80. Trust me...

hugie82

Usually blue smoke on start up is valve seals. Do your compression test just to be sure but most likely it will come back to that. If your oil pressure and compression are good, a head swap will have you running in no time!
It's also a great opportunity to gain 50hp with higher compression, better flow and weight saving aluminum heads

Rich's'78

I don't think you will see anywhere near 50 ponies with the stock cam. Just get some GM Viton valve seals installed and be done with it. Newer heads are great, but are not cheap. If you are happy with the stock performance, leave it at that. Otherwise there is a lot of info here on the forum.

kanvasman

When you do the compression test, make sure the engine is fully warmed up first. Migth burn your fingers, but it is a lot more accurate way of doing it.

indydoug

Roger that! I know this won't be cheap, but it will still be a budget build. I would love to drop in a $8k crate engine but I still have kids in college.

Thanks - I've been doing a lot of forum research and have a pretty good idea what I am getting in to. Unfortunately I am NOT happy with stock performance, so the stock heads, cam and exhaust will be replaced. I'll start another thread to solicit component recommendations once I'm comfortable with the stock block.

Thanks, I'll check compression with the engine as hot as I can handle.

One other item of prep I forgot to mention - I ordered David Vizard's "How to Rebuild Your Small-Block Chevy" based on several forum recommendations. Thanks to all for your suggestions.

68Thunder427

A 1980 L-48 only had 195 hp which isn't much. There are a lot of options out there for 350's the main question is what is your real budget ($$$$)! and that can help us lean you in hte right direction. I had my heads ran through and the valves, valve seals (new GM VIton), and valve guides for $800 (doing my own labor of course) including Felpro gasket set and new fluids.

scottyp99

You can purchase brand-new, assembled, aluminum high-performance heads, (that will beat up on a stock head and take its lunch money) for not much more than 800 bucks. Re-habbing those old, stock heads is just not cost effective anymore.

Scott

68Thunder427

That was to do the heads on my 68 427 L-71

68Thunder427

http://www.speedwaymotors.com/BluePr...ine,52467.html
http://www.speedwaymotors.com/BluePr...ine,60347.html
There are a lot of 350's out there ready to roll like these you just have to decide what you want and what you want to spend.

REELAV8R

The best you'll get with the existing pistons is about 9.0:1 CR. That's not too bad compared to stock though, and might be all 85000 mile rings can handle in any case.
You could easily run a 265 ish duration cam on a 110 LSA with that I would think, and get decent performance.
Kind of depends on your leak down results. If you ring seal is weak your gonna have an oil burner on your hands with plenty of excess blowby.

7T1vette

Here's the deal.....

Your engine probably only NEEDS new valve seals. This is a simple task for a mechanic and it is a relatively low-dollar repair. Likewise, replacing valve cover gaskets (and/or pan gasket) is relatively easy and not expensive. When you do those repairs, you will not get blue smoke at start-up, nor will you have those testy leaks.

BUT, you will still have only a stock L-48.

If you decide to beef it up, you really need to do it right...or you can end up with a broken L-48 engine. Throwing higher power parts on a worn engine is not the way to do it, if you want the engine to live very long. The engine should be pulled and disassembled; the block should be cleaned out, Magnafluxed, re-bored, and the head surfaces stoned smooth (at least). If you have the block 'decked', make sure that the machinist knows NOT to mill off the I.D. numbers on the front pad.

Once the block is ready, you will need new pistons/rings, cam, heads, intake and exhaust manifolds PLUS all the sundries (gasket set, pre-lube, paint, etc. etc.). By the time you get done, it will cost you $4K+/-if someone else does all the work.

IMO, you should just fix what it needs now and keep it running as well as it does-- and save the money for gas and FUN STUFF!!! When the engine develops some REAL problem(s), then you can go big.

REELAV8R

I think a top end on a L48 is fine if you have a decent ring seal, are willing to put in new main bearings and con rod bearings along with the new heads and cam and everything else checks out ok.
the CR is going to dictate how radical the cam can be. And if you put on some Vortecs or even aluminum heads that are mid range units your HP should be limited enough to not blow the bottom out. You might get 300 to 340 HP if all goes well. Seems like stock L48 should be able to handle that if you keep the revs below 5500 rpm.

Jartanyon

My thinking is if you are gonna go as far as pulling apart the top end, might as well pull apart the bottom end and check it. It is just a little more work to build on a solid foundation and well worth the peace of mind. These are old engines and with 85k on it, I'm sure it could use some TLC. I had a local racing shop clean the block and parts, hone, put in new plugs, new mains, polish the crank, magna flux, etc. for around $400. In the grand scheme of the rebuild, that was a drop in the bucket and well worth it.

BEFORE:


AFTER:

Dustup7T2

Just curious. Is your reason for leaving the short block in the car a lack of tools or space issue? It's understandable if you have limitations but the end result from your current plans may not satisfy your expectations.

Removing it for a proper cleaning and inspection is a lot less trouble and safer to conduct while it's out. That would offer a chance to also clean and freshen up the engine bay "while you're at it", as we like to say.

Good luck, whatever you choose.

cv67

If your rings are good go for the heads/cam and have fun with it. Not everyone can afford a dream build

You wont "blow the bottom end out of it" unless youre getting stupid with rpm. Its not the added compression that does this its the right foot

indydoug

Thanks again for the recommendations, all inputs and opinions are welcomed and considered. I would love to pull the block, stroke it to 383 and turn out 450HP, but that is not happening for several years. Here is my justification for leaving the block in the car:

- Lack of tools and space is a big one. I do not have an engine hoist, and if I did, I doubt I have room to pull the engine in my small garage. I also know no one nearby to help, so I am going solo, with forum support. I do not want to attempt pulling the engine by myself, when I have never even seen it done before (apart from youtube). I am comfortable pulling off the top-end myself.
- Engine budget. My target is $2000, realistically I hope to keep it under $2500 after nickel and dime stuff. Pulling and rebuilding the block would require me to rent/purchase a hoist and stand, buy more replacement parts and likely more tools, and outsource work.
- I do not plan on anything outrageous. As noted above, the final product will be less than 9.0:1 CR, between 300-340 HP, and stay under 5200 RPM. As noted in my original post, the car is a good weather driver, and will not see a track or dragstrip.
- Research on CF has identified many reputable sources stating no need for bottom-end work on a mild street build, barring obvious warning signs. One in particular:
Assuming pre-tear down testing and post-tear down internal inspections do not turn up anything of concern, I consider the risk minimal. If I have problems with rings or cylinder walls I'll reassess the whole plan.


I did get the compression testing done this weekend. Here are the results:

Cyl. Compression
1 148
2 154
3 150
4 152
5 158
6 157
7 166
8 155

I bought a compression leakage tester and small air compressor from Harbor Freight this afternoon. Hopefully this weekend I will have some leak down numbers. Then I'll ask you experts what those numbers tell me about the block.

REELAV8R

Take a look at you tube to see how to do a leak down test.
everything can be done with engine in the car including bottom end bearings if you decide to change or check those.
From what I've read 20 % leakage is not unusual. You're just interested in ring leaks of course, not valves.