I have a '73 Coupe, 350/190hp Auto, factory a/c, original motor and transmission, 150,000 miles. All original, smokes a little when started after sitting overnight, leaks oil from oil pan, timing cover, valve covers. In 2,000 miles of driving it hasn't leaked enough oil to require any to be added, so it can run as is for the foreseeable future as it is a weekend knock around play car. For shows and bragging rights it isn't "pretty".

I've been doing a rolling restoration and now need to decide whether to clean up, paint and repair the various items listed in place or pull the motor and trans so that I can get to everything and do it "right".

If I pull motor I have thought about four options:

1) Clean it up, paint, replace the various gaskets to repair the leaks and reinstall as is otherwise.
2) Doing a full tear down, overhaul keeping everything to original spec replacing items as needed and then reinstall.
3) Instead of all stock overhaul, punch it out and juice it up, perhaps to the 250 CLD spec.
4) Buy and install a mildly upgraded crate motor vs juiced up overhaul and storing the current motor for bragging rights to say I have the original motor that runs. I could always "clean it up" and reinstall it at a later date using the crate motor for a future project.

Regardless of the option chosen, I would like for things to look relatively close to original under the hood, to the degree possible. As such, even using a quadrajet would be desirable.

Although it is a nice car with no rust and luckily one of the previous owners spent a fortune on suspension, exhaust, brakes, tires, paint and interior, I realize it is a car that will never be worth what I have already and will be investing...and I'm ok with that; however, I don't intend to go completely overboard. Having a bit more spunk would be desirable as the semi-tired 190hp 350 has great exhaust to make it sound big, but it's bark is much bigger than its bite.

I do most of my own work, have a well equipped shop, including lift, but have done a motor rebuild for 40+ years. So most of the labor is sweat equity, but I'm out of touch and practice and will probably farm out any internal motor work/assembly

I have set a goal for the most expensive option to be no more than $5k with a desired target of less than $3k.

I would welcome any thoughts, suggestions and advice, including same for a crate motor....too many options and not enough knowledge on the various pros and cons.

Sorry for the long explanation. Thanks in advance.

 

With your target of less than 3k I'd say that your number 1 is your best option.

I'm not sure that a rebuild- and all the extras that go with it-- will hit your 5k.

 

If it were mine (and I wouldn't want a spare engine taking up space) I would rebuild the bottom end and upgrade the pistons to bring the c/r closer to 10:1, replace the heads (you need bigger valves) with either the old iron Double Hump 2.02 heads (this will keep an OEM look) or new aluminum heads (better flow than iron), a better cam (the L-46/L-82 cam is great for the street), a high rise aluminum intake manifold and a set of headers. This will give you 350hp-400hp (gross) and shouldn't be too expensive.

I'd keep the auto tranny just to keep the costs down.

 

Year one has a 400 hp crate for $3100 right now. I've just been window shopping

 

Kind of depends on your time frame and goals for the car.

If you got the time, rebuilding it is a good project. Going stock or just above stock power to say 350ish HP you could keep the stock con rods and crank and hone the block for new pistons and rings.
Then put on some after market iron heads with smaller combustion chambers, 64cc's or so to bump up the compression and improve flow.
I would not waste any money or time on the stock heads.
Drop in a better cam and your going to have a much improved engine.
That could be done for $3000 or so and plenty of sweat equity.

If you want it up and running sooner then the crate engine is a decent option. Farther from stock, but probably better components and you can pop for a little more and get one with a roller cam, then oil types will not be an issue.
$3000 to $5000 depending on what you choose. A stock replacement engine can be had for around $2000 last time I checked.

I chose the former when I had to make that decision. Up to 400+ HP on a stock bore 350, cost about $4500 so far. However I replaced everything but the block and oil pump and converted to a roller cam with full roller rockers.

 

if you rebuilt an engine 40 yrs. ago, the same applies to your '73 small block. nothing has changed in technique. gaskets/seals/lubes, etc. are better quality, that's all. dropping in a crate motor of same generation would still look stock, and is the easiest route, especially if money is no object.

but I would do option 2. change the leaking gaskets, and test for compression, and determine if it needs rings (probably) and valve seals before I would spend the money replacing an engine that just needs a typical refresh. if needed, MAYBE put in a better cam/switch to a roller.

where it gets complicated is when you start upgrading for more power. then it's the old "while I'm at it" routine, which could easily be more expensive than a crate motor would be...

 

There is also the "poor man" engine rebuild option 1.5. I just completed this myself.

If the engine only burns oil after sitting for a few days that is likely the valve stem seals.

1.5) Pull the pan and replace the rod and main bearings, and oil pump. New gaskets and rear main seal. Pull the heads and take them for a basic rebuild of tank/lap valves/new seals (or aluminum as suggested above). New timing chain.

You get everything new but rings and camshaft. This approach only works when all else is otherwise fine and nothing needs machining. Which you really don't know until you pull the pan and inspect.

Your parts cost is about $200-250, head work another $250-300 and about 3-4 partial weekends of your labor.

I pulled the pan on my 55k engine and everything looked and measured out fine so that is that I did. I ended up using rebuilt C4 aluminum heads and exhaust manifolds in the process as I found them on CL cheaper than having my original heads redone. That was a lot of used up weekend time though so in retrospect I probably would just buy a crate engine

DR

 

I vote for a crate engine and keep the engine that you can rebuild later if/when needed. Watch out for the while I'm at it jobs. Once the engine is out, you will find other issues to take care of.

 

Here is my suggestion:

Do a good compression check on your engine. It is important to do this check correctly. If you don't have the proper gauge or are unsure of the process, take it to someone who can do this and give you the info. Why? Because this test will let you know if you have any serious concerns about piston rings sealing and/or valve problems.

If this check shows the engine compression to be OK, I would NOT pull the engine, but only pull the heads and have them reworked. You definitely need to valve seals and probably guides. You also need to get the cup plugs (freeze plugs) replaced with brass plugs (won't rust in future).

You can replace most all of the gaskets/seals on the engine without removing it. But, if removal is easier for you (considering all the 'stuff' you have to remove to get it out), go for it. Otherwise, get it on your lift while still running, then pull heads, oil pan, damper, etc. and install new rear main seal, oil pan seal, front cover gasket and front crankshaft seal (don't forget to check whether you have metal or plastic cam drive gear...change if not metal; change gear and chain if you feel it necessary). The upper engine gaskets can be replaced when you reinstall heads/intake. You might want to replace water pump while you are at it.

A full engine seal/gasket kit is more economical than buying them separately. But, if you want better grade of gaskets than what comes in the full kit, so be it. Maybe Fel-Pro makes a complete kit with silicone one-piece oil pan gasket and Vyton rear seal.

As far as your engine's performance goes, you can check out some simple, but effective, items BEFORE you do the engine work. You may think some items in this list are 'silly'; but many folks have found that these simple issues are their biggest problems with engine power:

1. Have someone sit in the driver's seat and depress the accel pedal completely while you hold Q-jet's choke plate completely open and also hold secondary airvalve open and look down the carb secondary bores. When pedal is depressed, the lower throttle plates should be completely vertical. If they are not, there is a problem with improper accel pedal/throttle cable/carb linkage/carb getting the proper travel to fully open the secondaries. Many have found that the nice, new, thick floor mats they installed won't allow full pedal travel.
Just to clarify, moving the carb throttle linkage with your hand IS NOT THE SAME as moving accel pedal with foot. So, you MUST use the pedal to determine proper carb action. The Q-jet's secondary throttle linkage opens very late in the process. If cable travel is just 1/4" short, you may get NO secondary opening at all.

2. Set timing for 'performance'...not per factory specs. When setting for performance, timing at idle is irrelevant! To set for performance, you need to modify distributor curve by installing 'weaker' return springs in the mechanical advance mecanism. With vacuum advance vacuum line removed (from the dist. advance can) and plugged so there is no vacuum leak. Hook up timing light and tach readout; then rev engine slowly until the timing line on the damper STOPS ADVANCING. Record engine rpm when mechanical advance ceases. Stock engines may reach this point at over 3500 rpm. For performance, you want to reach maximum mechanical advance somewhere between 2600-2800 rpm. And, you want the advance reading at that point to be 34-36 degrees BTDC. You can rotate the distributor to match the 34-36 degree reading. But you will have to swap out some advance springs to lower the rpm for max advance. Most auto parts stores sell mechanical advance kits for GM distributors and they aren't much money. I have had good luck with swapping factory advance springs with 1 soft spring and 1 medium spring (the springs don't have to match...you just need the max advance to be reached at the proper rpm).
Once you get the timing curve set, you can take a timing reading at idle, if you want. You don't want to change anything...just read timing at idle (with vacuum advance removed and plugged) and record what you get. Nomally, you would get something in the 14-16 degree BTDC range. But, it might be even a little higher.
Lastly, you want to take a test drive and do a WOT test in second gear to see if you get any 'spark knock'. If you do, you can back off the timing a bit so that it goes away. Also, you will likely have to reset idle mixture screws and idle speed when you recurve the distributor.

These two simple things can make you anywhere from 15 - 100 HP improvements with the same engine! If your carb secondaries are not opening, you probably think you have a "Dog" under the hood. Get the carb and the dist. working well and you will see a BIG difference. If so, you may be happy with just a reseal and a head rework on your existing engine.

 

Pick your poison! Brand New with a Warranty!

http://www.chevrolet.com/performance/crate-engines.html

 

If youre not happy with the performance and setting the orig aside go nuts and dont worry bout it looking stock. Nice to have the orig as an enticement come sell time but dont think it will make a huge difference your call

Nothings worse than going to the trouble of pulling it out rebuilding old stuff only to find out it runs about the same. Youll enjoy the car more thats what its all about.

 

Many thanks to everyone for taking time to comment. I leaning toward pulling the motor and trans to get everything cleaned up (engine and firewall etc)...it's only sweat labor...but not before I run a few tests (compression and otherwise). After that, and based on its condition, decide the ultimate direction.

I'm sensing it is best to pull the engine and transmission together, especially given I have it on the lift and supporting the transmission on the lift would requiring a bit of bridging.

I will post status, progress and ultimate direction I take, although I may drive it a bit this spring before taking it out of service. I also have an '01 C-5 to drive, but this '73 delivers a special Corvette experience.

Thanks again.