340 TA Build Question

[challengermaniac]

Hey guys,

I just pulled the numbers matching 340 out of my TA (with 35k original miles) that is in need of a rebuild.  The motor is original from top to bottom, which brings the question; do I rebuild/machine the original internal parts (crank, pistons, camshaft, valves, etc), or go with new?  A friend of mine said to consider my use/purpose for the car, and if for show only, rebuild with original parts and if for crusing/driving & shows, build with new internals for improved performance and set aside the original parts.

Any other thoughts or recommendations?

[Cooter]

My experience has been alot of what the factory produced was a victim of mass production. Tolerances were not right, maching was middle of the road at best. I'd redo the original parts. Unless your doing a full on stroker build for massive power gains (Which I can't see in an original type car), the stock internals should be just fine.

[Topcat]

My experience has been alot of what the factory produced was a victim of mass production. Tolerances were not right, maching was middle of the road at best. I'd redo the original parts. Unless your doing a full on stroker build for massive power gains (Which I can't see in an original type car), the stock internas should be just fine.

 
But change out the pistons. Todays stuff is far better than back then.

[RB2929]

Recommend keeping all the parts that you replace.  If/when you sell your car, the next owner will appreciate it - and you'll get a few more dollars.

[femtnmax]

If truly only 35K miles, and considering your use of car, the engine may not be perfectly exactly like new, but with that few miles all it needs is hone the cylinders, then add new rings, main&rod bearings, and gaskets.  Clean Everything spotless, and I mean CLEAN.  Maybe a new timing chain if you really wanted to get fancy. I always replace the water pump and fuel pump on cars that have sat awhile.
With that few miles there will be no ridge on the cylinders, minimal to none wear on the valve stems or guides...basically nothing worn out, Period...
I tore my 340 down after 130,000 miles and the crank still met factory orignial spec, the cylinders by then had a good ridge so needed rebored w/ new pistons, and needed valves and guides in the heads.
Like said, yours has so few miles it won't need all these parts.

But if you want to spend the money go for it, keep the old parts... because someone out there would love to put together an all-original engine from perfectly good OEM parts.

[jimynick]

Charlie, when you meet the guy who can tell what's inside your engine by looking at it-run! As mentioned, with the low mileage, you might get away with a hone and re-ring/bearing job.The 340's were all forged (pistons/rods/crank) so if they measure up-literally, then reuse them. If memory serves, I believe they used a chrome top ring and I'd change that to a plasma moly ring which is current technology. Personally, I'd put a cam in it, but be careful with break in these lousy oil days. You can now buy nitrided cams and they're the cat's a$$, but are more expensive. If you have to go over-bore, shoot for a CR of under 10:1 due to lousy gas octane. Get a GOOD machine shop to measure/hone it and make sure they have torque plates for it, too. Good luck

[Cooter]

The 340's were all forged (pistons/rods/crank)

Not exactly true..I had a 1973 340 that had a cast crank and pistons.

[cwestra]

You'll also want to install hardened seats in your heads.

[femtnmax]

You'll also want to install hardened seats in your heads.

Yes, with unleaded gas the heads MUST have hardened Exhaust seats, intakes won't need them.