Partial Rebuild

[meadowbrook]

My 50 dodges 230 has 90k miles and has not been rebuilt. It has great oil pressure, 50 psi at speed and never less than 10 in the hottest idle at 500 rpm. 

But compression is low, about 60-80 psi cold. No head gasket leaks into coolant (I tested for  in coolant Exhaust). It runs fine and starts readily but it does idle kind of rough, even after a carb mixture adkustment giving me the highest vacuum. 

Would it be worth it to pull the head and perform a valve job? Maybe a re ring and hone if the cylinder walls look ok? 

[dpollo]

You could do what you are planning but by 90 000 miles, there will be a fair amount of taper in the cylinders and the timing chain will also need replacement.  A valve job alone may result in more oil consumption due to higher vacuum in the cylinders on decelleration. 

Lots of these cars received in-car overhauls back in the day and the results were often satisfactory but relatively short lived due to wear which was not addressed.  Assess how much you are going to use the car in the next ten years and consider that parts are relatively easy to get now but the supply will ultimately dry up.

[dale]

Dont know if its true but Ive been told a new valve and ring could be a no-no unless the rod bearings are replaced too....Might be an urban myth though.  You can take a compression check with just turning the motor over and then remove the spark plug and then squirt some heavy oil into the cylinder and take another reading.  If the reading is much higher then it signals bad rings.  Og corse if the motor doesnt smoke Id just do the valves and valve seals.

[Don Coatney]

55 minutes ago, dale said:

Dont know if its true but Ive been told a new valve and ring could be a no-no unless the rod bearings are replaced too....Might be an urban myth though.  You can take a compression check with just turning the motor over and then remove the spark plug and then squirt some heavy oil into the cylinder and take another reading.  If the reading is much higher then it signals bad rings.  Og corse if the motor doesnt smoke Id just do the valves and valve seals.

Where are the valve seals located?

[Bingster]

Are you going to go 90,000 miles with your vehicle?

[RobertKB]

Many years ago, I had a weak cylinder at 72,000 miles in my '53 Plymouth. Pulled the head and had a burnt valve. A mechanic friend and I pulled the pistons after removing a slight ridge, honed the cylinders, re-ringed the pistons, replaced the burnt valve, and ground the other valves and lapped the valve seats. I did not replace the rod and main bearings as they were plastigauged and were right in the middle of factory specs. Oil pressure was at 55PSI at speed and never below 40PSI at hot idle. The car now has nearly 101,000 miles, does not burn oil, and maintains the same excellent oil pressure. Maybe I have been lucky but that is my story on a partial rebuild.

Edited November 2, 2016 by RobertKB

[sser2]

60-80 psi on cold engine doesn't sound bad. Compression is actually measured on HOT engine, and it is likely that hot compression will be higher. You need to ascertain that compression is within plus or minus 10 psi in all cylinders.

High oil pressure means that main. rod, and cam bearings are all in good shape.

Rough idle is an issue of tune-up rather than engine wear. It could be due to vacuum leaks, ignition problems, or your rpm too low. 500 rpm is on the lower side.

I wouldn't try to fix what isn't broken.

[55 Fargo]

Why couldn't you do a ring and valve job, if all is well.

For the amount of miles you will put on it, this could very well work out.

Do a wet and dry compression test, and a cylinder leak down test, and discover exactly what the problem is.

Perhaps a valve job will be all that's needed for another 30-50k miles.

 

Edited November 2, 2016 by Rockwood

[55 Fargo]

3 hours ago, dale said:

Dont know if its true but Ive been told a new valve and ring could be a no-no unless the rod bearings are replaced too....Might be an urban myth though.  You can take a compression check with just turning the motor over and then remove the spark plug and then squirt some heavy oil into the cylinder and take another reading.  If the reading is much higher then it signals bad rings.  Og corse if the motor doesnt smoke Id just do the valves and valve seals.

Where did you read or hear that.

Of course the best course of action is to measure the cyls and journals for wear, replace timing chain and gears all new guides valves, pistons and rings.

But if the engine is in need of a valve grind and maybe just rings, you could get a lot more miles and time out the engine, for a lot less money.... BTW what valve seals, that's for a Chevy stovebolt 6s which is an overhead valve engine with valve guide seals

[Dave72dt]

Replacing the rod brgs when doing the valves and rings may or may not be a myth, but it does make common sense to do so.  You have to take the rod caps off to remove the pistons for rings.  For the small amount of money it takes to replace them when you already have the rods out, it's simply insurance money well spent.  The amount of work is the same whether you put in new or use the old brgs and at 90,000 miles, there has to be wear on them.  Main brgs, timing chain and gaskets. seals while you're at it.  There again, you're already half way there with disassembly and repair.   Might just as well do it right the first time.  Going back over the same ground the second time to fix something you were really close to and didn't the first time spends your money and time twice.

[55 Fargo]

2 hours ago, Dave72dt said:

Replacing the rod brgs when doing the valves and rings may or may not be a myth, but it does make common sense to do so.  You have to take the rod caps off to remove the pistons for rings.  For the small amount of money it takes to replace them when you already have the rods out, it's simply insurance money well spent.  The amount of work is the same whether you put in new or use the old brgs and at 90,000 miles, there has to be wear on them.  Main brgs, timing chain and gaskets. seals while you're at it.  There again, you're already half way there with disassembly and repair.   Might just as well do it right the first time.  Going back over the same ground the second time to fix something you were really close to and didn't the first time spends your money and time twice.

Well if a complete rebuild is in order than thats what should be done, but not just replacing bearing inserts.

New valves, pistons/rings, new guides, new cam bearing timing chain all new bearing, possibly the crank needs regrinding and on and on.

The OP is asking about a valve grind and maybe a set of rings, infact he has not completed a diagnosis to determine what he exactly needs yet.

It sounds like he wants to freshen this engine up, while it is in the car, then get more use, which if the car is driven sparingly could last a long time.

As Lou Earle once put it, do you know how much oil you can buy for the price of an engine rebuild.

Many ring and valve jobs were done, and most likely got a lot more miles on an engine because of it.

[meadowbrook]

Lots to think about.

Will perform a hot compression check and leakdown and update you guys.

Thanks for the responses.

[Don Coatney]

By the book.

[55 Fargo]

10 minutes ago, meadowbrook said:

Lots to think about.

Will perform a hot compression check and leakdown and update you guys.

Thanks for the responses.

My biggest concern is your oil pressure does drop to 10 psi, this is when hot and idling slow I understand.

If you have a lot of clearance, then perhaps a complete overhaul could be justified.

If all is well except the valves and/or rings, then you may be able to do a ring and valve job n car and call t good.

Do the diagnostics and report back, both wet and dry compression tests and a cylinder leak down test.....Good Luck

[dale]

On 11/2/2016 at 0:30 PM, Don Coatney said:

Where are the valve seals located?

I meant valve guides that seal the space where the valves go thru the block.

[Dartgame]

After you run your compression check- if the results are good, I'd consider the following -

For what its worth, your rough idle could be: idle mixture, a worn out carb, vacuum leak, valve adjustment or an ignition problem. Low oil pressure at idle indicates worn rod & main bearings, worn oil pump or both. Its easier to drop the oil pan and put in new bearings than pulling the head and honing cylinders etc...new oil pump is easy to install too. All depends on what your compression tells you.

[meadowbrook]

My carb has been rebuilt, the ignition is excellent and the valves adjusted to spec. I don't think the oil pressure is bad, it is per spec by my shop manual and 10 PSI at a very hot idle seems reasonable based on past experience and the '10 psi per 1000 rpm' rule. I really think the issue is likely rings or valves, I'll check. Thanks for all the responses.

[MarkAubuchon]

Speaking from experience this is what I did on my 49 with less miles but had been sitting for years.  Pulled head, valve job, new valve springs and replaced a few valves, cut the head . 50, new rings stock bore just honed it, new rod bearings.  Did this while the motor in the car.  I'v driven this car 25m since this repair. Runs cool, 22 mpg, solid 40# of oil pressure. Your current compression #s seem ok,  Id rebuild the carb, make sure its tuned up and drive it like a rental.