Thinking About Refreshing a '66 340-4v

Hi All,

I've got a 340-4v in my '66 Skylark and I want to replace my 2spd with a Tremec which I am pretty sure means I need to take my crank down to a machine shop and get it drilled for a pilot bearing. The engine has about 45k on it and other than an odd miss that I can't track down seems to be in pretty good shape with around 150psi per cylinder. Here are my questions:

1. Forgive me for being an absolute novice here, but if I pull the engine and then *carefully* take out the crank, is there a reasonable scenario where I could put it all back together assuming that bearings and journals all look fine and I put everything back where it came from and in the same order?
2. Still assuming that everything is fine internally, if I decide to go further and there wasn't a ridge in the cylinders, could I get some STD rings and bearings and do a mild refresh after doing a ball hone on the cylinders?
3. Building on #2, how important would it be to take it all down to get hot tanked and then also replace freeze plugs? If I have the block hot tanked, that pretty much ruins the cam bearings, right?
4. If I go even further and have the heads rebuilt, are there any important things to tell my machine shop who might not be super familiar with Buicks?

Thanks,
Ray

 

Dick Miller racing makes a pilot bearing adapter that enables you to run a manual transmission without taking the crankshaft out to have it machined

 

Pull trans and check it first

 

X2, if the engine runs fine, try not to mess with it if you don't have too, pull the trans. and see what yah have or need to do.
If you need to remove the crank, then its a complete tear down of the engine, heads off, rods/pistons out.
You can TRY to remove the crank with the rods/pistons in, but the 340, like the 350 is a deep skirt block, I don't think there's enough room to squeak the crank past the rods.
I DID do this once on a 455, but the 455 is not a deep skirt block.
With the 340 apart, may as well do rings, bearings, valve job, ohhhh its gonna snowball on yah

 

X3 - Don't mess with it - the 340 is a very durable engine, expect to get over 100K on the factory build. While it's only a 2 year engine(66 and 67), its still a Buick. Be very careful selecting a shop to do any work on it.

 

Your crank already has the bore for the pilot bearing. Do not tear down the engine.

45K original miles is nothing on one of these. Do a thorough clean up, replace the gaskets, maybe swap in a new timing chain set and water pump. Do a leak down test and a thorough tune up. That should be all you need. When loosening water pump and timing cover bolts proceed carefully and use heat as needed. It's much better if you do not break those off.

TA Performance is looking into new 1 piece rear main seals, possibly with a silicon lip. Before you change the main seals see if they have that sorted out. Often times the old ones just need a little oil on them to seal just fine after a short time period with regular running.

Jim

 

Thank you for all of your inputs . It sounds like I am going to pull the engine, clean it up, re-gasket it, but generally leave the inside parts inside on this go-round. Well, I have a miss that I can't track down and I am starting to think, after doing some more reading today, that I could have a lifter issue or a flat lobe- fingers crossed for this investigation.

 

I agree with Jim, I put a 66 340 from a LeSabre in my 64 Special 4 speed and the crank was already machined for the pilot bushing. If it's not leaking and running well I'd leave it alone. I have a 65 Special with a 300, 52K miles, runs like a top, untouched. Your car came with a 2.78 rear, to convert to a 5 speed you'll probably want to change that to at least a 3.23 otherwise you'll be shifting into 5th at 90 mph.

 

Barely enough room. If it gets knicked it will need ground either way.

 

While you have it out, replace the timing set so you don't have to worry about the stupid factory nylon cam gear falling apart!

 

You can check for a flat lobe while you have the valve covers off. Just check to see that all the valves open fully. More likely to be an ignition issue, or even an exhaust leak that is being mistaken for something else but it is possible.

Jim

 

The exhaust manifolds on the 340's can crack very easily. You will get a noise (phiff) each time that cylinder fires.

 

At least on my 350s and how those manifolds crack with a cold engine you can feel around for the spent gases shooting put for a few minutes.

 

If here is a miss, do a compression test before it comes out so you know if it needs to be gone into or not.

 

Leakdown test should also show that.

Jim

 

340 engines are prone to have cam wear,mine was bad at a 120,000. other than that they are great engines.