I thought I'd ask for advice about my 71 Road Runner.

This is a show car I've had for almost 30 years and it's in very nice original factory condition. Aside from a repaint in the 1980's, new upholstery, and wear & tear and maintenance, it's all original. I've only put on about 6,000 miles since I bought it.

The problem is that when I bought the car it had 100,000 miles and the engine wasn't winning any 1/4 mile races. It starts and runs reliably, but the power just isn't there.

How can I refresh the engine while keeping the originality of the car? Can a rebuild keep everything original, including the bore?

Thanks.

I don't see why not. An engine rebuild does not change the originality of the car.

Not going out on much of a limb to say no, the bore will likely not be original when you are done.

An untouched 1971 engine at 100k miles it's almost guaranteed to be wore out.

When I had my numbers matching engine rebuilt I only had it bored +.010, just enough to clean the bores. Then I had custom pistons made for an extra $30 each instead of going the standard +.030 overbore.

To really do it right, and correct any issues found, it'd be best to allow for fresh machine work, pistons and so on.

That said, you may be able to get by with a hone/re-ring and valve job if it is not worn too horribly bad. But, by then, it's torn completely down and that's the golden opportunity to really get it right.

Regular stock Service manual specs are almost crazy for a performance application, allowing a whole lot...like .010 bore taper before boring was supposedly deemed necessary. That said, you can make one run reasonably well again with a hone and a fresh set of rings if the bore wear is less than that.

If you go that route it's more like an overhaul than even a rebuild...polish the crank, hone it, rings, valve job, gaskets, and that's it.

But what will you do if anything is worn past spec, which almost guaranteed it will be? Like the cam. Or what will you do if a crank journal is scored, machine it or find another one? At some point if the quality of the build vs. originality conflict with each other, it'd really be better to err towards quality.

Personally? I'd stash the original numbers engine (or just the bare block) get another similar engine to build (you didn't mention what it is?) assuming it's a 383 you can get another one, or a 400 which looks the same externally, and build it for fun with a stroker kit, etc. and have a bunch more power/fun.

Shouldn't cost a ton more than rebuilding a stock engine with what's available off the shelf today. This way you can have fun beating on it and not worry about damaging the cars numbers matching status.

.02

I agree

There are folks who prize originality - including worn-out ignition parts & hoses - over good running condition; but if you want to actually drive & enjoy the car, a stock-spec rebuild isn't going to detract from the car's market (or enjoyment) value.
I'd hold the boring & crank work to the minimum, but all of that + the valve job will depend on the wear you find when you open the thing up & inspect it.
Worst-case scenario, keeping the external appearance stock is really the only concern as far as market value.

Nobody asked the first question:

How are you using the car?

Maybe he doesn't need a stroker 400 and doesn't run the car hard.

Yep. If you're not pushing the car hard why separate it's pieces.?
Many never find themselves back together again.
Owner then has the * in his thoughts and conversations about the car; "it IS numbers matching but that motor is tucked away in my shop" blah blah blah.

Keep it together unless you run it hard.

With a repaint and new interior, a rebuild wouldn't matter. But one big to remember, nobody is going to ask to see in the bores. But one thing could be done, put sleeves in it then the original pistons could be reused. Just a thought

This post has been a little confusing to me. If the goal is everything must be original as built, then you can't do a rebuild. If the goals is OEM original, folks are really only going to see exterior parts and matching numbers block and exterior components are the most important. Certainly having a good reputable Mopar guy do the work. Internally, if not really worn, original valves maybe salvage, heads cleaned up, seats corrected, who cares if the springs are new.

Minimal work to the engine if possible. Frankly, you can still find good original pistons and rods if necessary.

Engine builder I help is freshening up for performance a 73 440. Basically only needed a cylinder honing, though it probably did not have 100K on the motor. Resized the rods, added a forged crank instead of cast, better valve springs and moved to early 440 stock high compression pistons and a mild cam. You can even get bearing and seal to rebuild the water pump. But I bet it is not original anyway at 100K and 47 years. Do you want to trust the oil pump or do you go with new, but use your old housing and just swap ring and impeller... Nothing wrong with a OEM rebuild with new rotating parts. Obviously if a survivor car or going for a gold standard, all NOS parts would be used, but cost goes through roof.

Frankly no one will know what was done internally unless you show them documentation and pictures.

If this is going to be a cruiser and you don't change the way you use it, I would find a good engine machine shop near you and at least rebuild the long block, send the carb to Scott Smith at Harms (i am assuming you still have the original carb?) and then once the motor is home, have fun putting it all back together detailing it, reinstall..

Happy deciding and tinkering...

Had 100k on it when you got it, but you do not know if it was ever apart, right? If it was me, I would remove it, take it apart for inspection etc. If all orig, it is WAY overdue for valve stem seals and other wear items, timing chain etc. Cool thing is date of mfg is usually on rod and main bearings, gives you an idea if ever rebuilt and all. If the bores are close enough to re-use, maybe just re-ring and replace freeze plugs, cam bearings and whatever else looks bad. The problem with stem seals is the way they love to become brittle, crack apart and find their way to oil pick up screen. And that would cause you expensive grief when out motoring around one day. Hopefully the timing chain is steel based cam gear that won't fall apart and also jam up pick up screen like the older ones.

Two things come to my mind.
One. Check the engine condition to get an idea of what specifically may be worn. That also will give an idea of whether condition relates to seeming lack of power.
Spark Plugs.
Compression check dry and wet
Leakdown test.
Vacuum at idle

Two. Winning or losing races has a lot to do with whom your lined up with. But I'll take it that the top end seems disappointing. Go over the tune. On a factory stock setup, the factory specs are a great baseline. See that everything is in top condition. Make sure it has the factory timing curve. Then start experimenting at the strip. Might want a little more timing. Maybe a change in jetting. One step at a time. Use the mph and check the plugs each time a change is made.

For your use id look at a simple hone, rings, bearing, vj, cam, ect..... I think alot of us forget our youth and working hard just to keep a car going.

A very budget rebuild with a good cam can go 40-60k miles of good driving, I used to do it often, even with alot more taper in the bore then the book said was cool.

I used to do it to many 440s including my 440-6 runner and with a mild cam it ran stronger after the re ring, ect then it ever did and I beat it hard for nearly 60k before selling it.

Dont be spinning it past 5500 and a simple job goes a long way and runs like new.

Thanks for all the good replies.

To answer the questions:

It's a 383. I've never raced this and I don't drive it hard at all. It's a nice clean cruiser, something to take to shows.

Really, because I don't drive it much nor race it, is why it's lasted so long in its current condition. It's just that when I most recently took it out for a drive I kept asking myself "what if it had better pickup, what if I tightened up the steering, etc". I've never even taken off the heads the whole time I've had the car.

Shouldn't need to.
As far as what you're asking. Better, quicker throttle response, could just be a matter of some tuning. Tuning can take two forms, and in this instance both forms apply.
The first is tuning to factory. Mostly making sure its got the carb and timing to factory specs along with the matching emissions equipment.
The second form more applies to hot rodding, but can be done with a stock baseline as well. That is tuning (adjusting) for best performance.
It might just take some adjustment of the timing, and maybe some minor tuning of the carb, to change how it feels.

My suggestion is to establish current baseline. Check the initial timing and advance. See if there is any anti-smog equipment that might cause a delay either because it is or is not hooked up. Check manifold vacuum for indicaitons of problems. That would be the starting point. Then a compression check and leakdown if you want a better picture of the engine condition.

Tech guide shows '71 383 likely came with a timing retard solenoid
http://www.imperialclub.org/Repair/Lit/Master/287/Page11.htm
and possibly a solenoid controlled vacuum advance valve.
http://www.imperialclub.org/Repair/Lit/Master/287/Page12.htm

If either of those is stuck in 'retard', then the timing will be late and the throttle will feel sluggish.

You'll have to check your car to see if it has either or both, and if so whether they are working correctly, or at least not retarding the timing.
Those are the only emissions items I see in the guide that could effect throttle response. But they are big ones.

What is the rear gear ratio? Even if the engine was new/rebuilt it may not ever feel frisky off the line like you think it ought to if you have highway friendly gearing.

If the engine compression numbers are good and it's not using any oil you may not gain a lot rebuilding it back to stock specs. If it's apart and you change the camshaft, mild head porting work, etc. then you can expect more power.