Time to rebuild?

[rich006]

I'm wondering if I need to start planning a rebuild. SlantSixDan says yes in my post about this on slantsix.org and I don't doubt he's right, but I thought I'd start a new post here since there are some smart folks here who don't frequent the .org side. This is a bone stock 1974 225 with 82K miles. Before I got it 2.5 years ago, it had 79K miles and had sat for 8 years in a garage. It does have a new carburetor.

As soon as I bought the car I noticed a raw fuel smell in the garage after parking. I finally found that a fuel/oil mixture is getting into my air cleaner via the crankcase breather, and occasionally dripping over the inside lip of the air cleaner onto the carb and manifolds. That suggests blowby pressurizing the crankcase beyond what the PCV valve can suck out, also fuel washing down the cylinders getting into the oil. Here's a list of possibly helpful information.

• The PCV valve is new and works the same as the old one: video showing vacuum at the breather at idle
• Compression test (I did it myself): all cylinders were 130-140 psi
• Leakdown test (took to mechanic): best cylinder was 22%, two were at 40%, others were 30-35%
• I'm not burning oil that I know of (nothing visible from exhaust)
• Oil dipstick smells like gas
• Fuel pump was changed a year ago (attempting to fix the problem of fuel getting into oil)
• Most of my trips are 6 miles each way to work.
• I don't feel the need for more power.
• The vision for this car is a daily driver with emphasis on economy and cleanliness.
• My son (18, heading to college in the fall) is interested in helping rebuild it.
• Money is definitely a consideration but I can spend a thousand or more if necessary.

What do you think? Oh, and here's the car so you can put a "face" on the problem.

 

[swies]

Those leak downs would worry me and so would the compression #'s.
Good news is a Ring, Bearing, and gasket rebuild is gonna be easy on the wallet.
One more point I can speak on. My son went to College recently. If you can beg, bribe, or order him to work with you on it, DO IT.
Spend the time with him while you can.
Oh yeah another thing..
DO IT, DO IT, DO IT.
Time will come when he is not around.
Sorry to be a downer. Living it now. One of the worst feelings I have had is coming home to remember that he is not in the house any more......

 

[slantsixdan]

He needs more than rings, bearings, and gaskets; his mech who did the leakdown test heard hissing at the tailpipe and at the carburetor (=valves aren't sealing, either).

Unfortunately, "Time for a rebuild" is the answer no matter which forum we ask the question on.

 

[rich006]

his mech who did the leakdown test heard hissing at the tailpipe and at the carburetor (=valves aren't sealing, either).

Yeah, I forgot to mention that important tidbit in the original post. I always forget to mention something.

Truth be told, I'm kind of excited about doing a rebuild. I didn't buy this car to be maintenance-free and reliable--I have a Mazda for that. And as Sean points out, a rebuild could be one of the best experiences I ever have with my son before he's gone into his own life (cue Harry Chapin). I guess I'll order the Boxwrench video on engine rebuilds, crack open the FSM, and turn this into a (re)build thread.

--Rich

 

[swies]

He needs more than rings, bearings, and gaskets; his mech who did the leakdown test heard hissing at the tailpipe and at the carburetor (=valves aren't sealing, either).

Unfortunately, "Time for a rebuild" is the answer no matter which forum we ask the question on.
View attachment 1715026230

Ah. Didn't know that. Sorry. That does change things.

 

[cdnEHbody]

Rebuilds are fun.

When I was into xs650 yamaha motorcycles I rebuilt a spare engine I got for almost nothing from the crank up just for fun. (After I did the one in the bike.) Sold it with the bike and didn't really make money from it. But a good learning experience.

Kind of wanting to do a slant with some light goodies.

 

[swies]

Rebuilds are fun.

When I was into xs650 yamaha motorcycles I rebuilt a spare engine I got for almost nothing from the crank up just for fun. (After I did the one in the bike.) Sold it with the bike and didn't really make money from it. But a good learning experience.

Kind of wanting to do a slant with some light goodies.

Had two Yamaha 650's. both heritage editions! Rebuilt both motors!

 

[BillGrissom]

All cylinders 130-140 psi sounds like "as new" compression to me. Has anyone ever measured higher in a slant w/ standard camshaft? Hard to square that with the leak-down hissing, so I would question the test method. Is the mechanic certain that each cylinder was at the correct crank angle when tested? As a sanity test, turn the engine over by hand. One can usually do so on an early slant by pulling and pushing on the fan belt, though your 1974 may have a shroud in the way. If you feel 3 strong "air springs" fight you per revolution, and you hear each one hissing down slowly (>5 sec), I would say your compression is excellent. Anyone who has kick-started a motorcycle would understand.

I can't imagine gasoline getting to the air cleaner by blowing by the rings. I would suspect your carburetor is sometimes over-flowing or spitting gas, which would explain it getting into the air cleaner and also flooding some cylinders to get in the oil. Most likely cause is a bad float needle or a fuel pump with too much pressure. Sometimes people drop the needle out of the carb inlet fitting without noticing (me, Carter 2 BBD, smarter if I stopped working when it gets dark). What carb do you have? You could try an old in-line pressure-reducing regulator (dial wheel, Mr. Gasket and other brands) if high supply pressure is the problem.

 

[slantsixdan]

¯\_(ツ)_/¯

 

[rich006]

Thanks, Bill. That's the kind of different perspective I was looking for. I'll try the hand-turn test this afternoon. I do recall last time I turned the engine by hand it was pretty hard to turn, and someone suggested removing the spark plugs next time to relieve pressure. I think that was when I was changing the fuel pump.

The carb is a Holley 1945 that was installed new right before I bought the car. I haven't looked inside it.

 

[AJ/FormS]

I agree something is off. That high cylinder pressure does not match the leakdown numbers.With so many cylinders with such high LD numbers, that engine should have been darn near impossible to start.
>The first thing I would do is assume that the constant short trips have caused carbon and gum and sludge issues inside, so I would do the full-boogie additive treatment, run it on the hiway for an hour,loading it up pretty good now and then.
Then I would check/adjust the valve lash. Now I would repeat the LD test. Anything over 8% out the valves, for me, the head is coming off.Clean leaky valves never get better.After that I would do an oilchange, and get that treatment stuff out
If the LD comes up to 8% or better,I would repeat the compression test at this time. Good numbers mean the rings aren't stuck,if nothing else.
I have not seen High LD numbers and High compression numbers ever together. Those cylinders with 40/60% numbers should have been pretty much dead; perhaps mustering 30psi.
I mean, think about it;
If you inject 100 psi into a cylinder, and it shoes 60% LD, that means there is only 40% left! and 40% of 100psi is 40psi. If a perfect slanty cylinder could make 130psi cranking pressure, and 60% of that leaked away, that leaves just 52 psi.
Unfortunately cranking pressure is a dynamic thing, and at 60% LD, I would not expect 52psi cylinder cranking pressure, hence the 30psi remark.
So either the Compression numbers are off, or the LD numbers are.
Or I suppose the cam could be out of time.

 

[rich006]

When I first did the compression test, I used a borrowed tester that leaks down as soon as you stop cranking the engine. Today I bought my own tester that holds the pressure. Results:
#1 135 psi
#2 135
#3 140
#4 140
#5 140
#6 140

Possibly unrelated question: why can't I turn the engine by hand? My plan was: with the spark plugs out, make sure I can turn the engine by hand before reinstalling the plugs to do Bill's suggested "turn by hand and listen for leak down" test. Well, I can't turn it by hand. If I go to the driver's side and pull on the fan belt with both hands, I can move it a few degrees but it takes my full strength. I'm no he-man, but I'm not especially weak either. Thoughts? EDIT: Never mind--if I stand on the passenger side and pull on the belt while pushing on the fan I can turn it pretty easily.

 

[AJ/FormS]

Yahoo!
Those are some very fine numbers.
The trouble you are having would be normal if the plugs are in.Especially if you are tugging on the belt. Well almost normal.
Whenever you shut the engine off, the engine does not stop instantly. The flywheel continues to rotate the engine until one piston starts to build compression. Then the flywheel gets stalled and the beast sleeps.
Now, along you come and attempt to compress the air trapped in that cylinder, and you cannot. There are about 600 cc of air in there, and it wants to act like a big spring. The only thing that prevents that is the friction of the other ring packs.
You almost cannot get enough leverage on the little fan blades. If you position one at a little above parallel to the ground, you might get enough body weight on it to crank it over a bit, if you can manage that without the belt slipping. But as soon as it moves a few degrees, it stops.
When you crank it over backwards, you have to put in enough force to break the ring-pack friction, and you may also be trying to compress some valve springs. So all in all, it is quite difficult. I can do it, but I am 210 and pretty solid.And if I slip, I am band-aiding my knuckles,lol.

But if it is difficult with the plugs ALL out, that is not right.
And listening for LD for a seasoned tech is useful. But for most, I venture to say,less so. The trick is to be able to ascribe a value to what you are hearing and simultaneously feeling on the turn-bar. A very tricky unscientific,if you will,endeavor. Useful yes to someone who has done it hundreds of times, but to Mr. Average, I'm not on board.
But at your pressures, I wouldn't even worry about LD. LD only measures ring-seal at the top of the bore,where it is the most worn, and the rings have popped out of their grooves to their maximum, and so the endgaps are wide open; and it measures the valve's sealing ability. But with a well traveled engine the valve seats look like crap with wide seats and all banged up and pitted, so you never know if a leak is due to a bad valve, or carbon stuck on it, or even rust in cases were an engine has been out of service for a long time. In your case the compression tests pretty good, so I wouldn't be suspecting an LD issue.
If it starts easy, forget about it. Engines with bad LD either start with great difficulty or not at all. Whereas even with 90 or 60 psi compression, it is going to start. I think it would start with every cylinder at 30psi, albeit with some extended crank-time.And it sure won't be excited about it,lol
One thing nobody mentioned lol, is that if this is a manual tranny, it has to be in Neutral.Another is that if the starter bendex is stuck in the ring-gear, it WILL be difficult to turn. But they usually pop out with a bit of rocking of the crank.
I bought a 1.25 Deep socket to reach inside the pulley to turn the crank. Yeah I know it's no fun cranking it from down-under, but the other option is to remove the fan and shroud.
130/140 are really pretty good numbers.
Those short trips are really hard on this old girl. Every choke start is killer. IMO you need a second car, one with EFI, for those short trips. Six miles is what? about 10 minutes from start to finish? The oil hasn't even warmed up yet. The choke could be on for two or three of those. The intake is cold, and you are just getting heat inside, so the thermostat may not even be open yet.No that's not good. That will sludge up your engine real good.
At this time of year,even if you let it run for 10 minutes first, the total running time will still not be long enough to boil all the moisture out of the crankcase.
I think your symptoms are all related to the twice daily short hops.

 

[BillGrissom]

I know I ticked off SSD and some other experts, but I hate to see people pulling an engine apart when the problem is external to the engine. It is too easy to suggest "just rebuild" at another's expense. Many people start down that path and never finish, leaving a project sitting in the garage for decades, often from frustration. The slant six in my 1969 Dart didn't idle right for decades. Two times mechanics recommended a valve job, which didn't help, I also changed intake manifold, etc looking for a vacuum leak, and ~3 Holley 1920 carburetors, plus had the engine rebuilt. Finally, when it acted the same with an entirely new long block, I tried a 4th carb and bingo it idled like a dream. BTW, that engine swap was necessary as one cylinder had 0 psig compression. Still don't understand how all those "professional" mechanics couldn't solve it. Today, I have more knowledge plus tools like O2 sensors, and avoid all shops. I am the only idiot touching my vehicles today.

 

[rich006]

If I push the fan blades without also pulling on the belt, the belt just slips. Maybe it's not tight enough or maybe it's too covered in power steering fluid that has leaked out of the pump. Anyway, I was able to get a small fraction of a turn at a time by pulling on the belt with one hand and pushing the fan with the other. It helped to remove the coolant overflow bottle. I did feel the "air springs" but I couldn't tell for sure if there were 3 per revolution because I couldn't turn it fast enough. I'd hear hissing for a second or two, then on the next pull I might get another second or two of hiss, then nothing until the next cylinder. The bottom line is, as AJ said, I can't really tell anything from that method.

I'm just trying to understand how the compression can be so good if there's enough pressure in the crankcase to push air the wrong way through the breather.

I added 2 cans of BG 44K when I filled the gas tank today. Per Dan's recommendation, I'll let that work for a while and then do the Italian tuneup. I did notice that my spark plugs were a much lighter color after a couple of good highway trips than they were last time I looked at them. Previously they were brownish, today more of a light tan or yellow.

My typical commute is about 15-25 minutes depending on traffic, and the engine coolant always reaches 190 degrees according to the gauge. I know it takes more high-power running to get all the components up to full temperature. Anyway, I'm going to make sure I mix in some longer, higher speed trips from now on.

 

[slantsixdan]

I know I ticked off SSD

You didn't tick me off.

It is too easy to suggest "just rebuild" at another's expense.

It's even easier than that to shout out random part names that have nothing at all to do with the problems being experienced by the car owner, thus sending him off on goose chases at his own expense. What's harder -- but necessary -- is to match the response to the symptoms presented, and ask for clarification if not all the details are known.

 

[rich006]

The rebuild won't happen until summer anyway, so I have time to try a few things first. Regarding the float needle: I assume if it were gone, the engine would be completely flooded and not running, but is it possible that somehow the carb bowl could be overflowing occasionally? On a possibly unrelated note, my idle mixture screw has a plastic cap that prevents it from turning more than a half turn. Does that mean I shouldn't need to adjust it?

One thing is for sure: the engine runs reasonably well, although I've noticed just in the last few weeks that it starts right up but then after a few seconds starts to bog down and doesn't idle well until it gets warm. Once warm it's fine. Then again, I don't have a lot to compare it to. Maybe after rebuild I'll be laying down rubber at every intersection, ha ha.

The PCV valve is correct: it's stamped 2103 and is the one listed for a 1974 225. I'm still holding out hope that my valve cover baffle is simply clogged with crud, preventing good ventilation. It is very caked with black crud. I'll see where I stand after cleaning that out, adjusting valve lash, and running the fuel cleaner treatment. Just in case gunk is interfering with the valves, maybe I'll run the fuel treatment through before opening up the valve cover.

 

[slantsixdan]

The rebuild won't happen until summer anyway, so I have time to try a few things first.

Yup. Summer's a much nicer time than winter to do heavy-duty car work.

Regarding the float needle: I assume if it were gone, the engine would be completely flooded and not running

That's correct.

is it possible that somehow the carb bowl could be overflowing occasionally?

Sure…and you'd know it. If it were happening after you shut off the engine and park the car, the whole area would reek of gasoline. If it were happening with the car running, the engine would gag and belch clouds of black smoke, if not stall.

my idle mixture screw has a plastic cap that prevents it from turning more than a half turn. Does that mean I shouldn't need to adjust it?

No, the adjustment is still very much needed — as described after the links to carburetor operation and repair manuals in this post. Idle mixture limitation was mandated early on in the sequence of cleaning up car exhaust emissions. That doesn't necessarily mean the optimal adjustment is within the range allowed by the limiter cap. I routinely remove the caps (pry off with screwdriver and/or pliers) and then adjust the idle mixture optimally.

it starts right up but then after a few seconds starts to bog down and doesn't idle well until it gets warm. Once warm it's fine.

The '74 choke is factory-set on the lean side, and it is not adjustable. A № 1234 electric choke kit will drop right on and enable you to adjust the choke tension and duration to get rid of the mushy acceleration during warmup.

The PCV valve is correct: it's stamped 2103

That doesn't tell us anything.

is the one listed for a 1974 225

Listed where by whom?

I'm still holding out hope that my valve cover baffle is simply clogged with crud,

Would be nice, but that's probably not it. You'll see why not when you turn the valve cover upside down and look at how the baffle is configured.

 

[Killer6]

Yeah, I forgot to mention that important tidbit in the original post. I always forget to mention something.

Truth be told, I'm kind of excited about doing a rebuild. I didn't buy this car to be maintenance-free and reliable--I have a Mazda for that. And as Sean points out, a rebuild could be one of the best experiences I ever have with my son before he's gone into his own life (cue Harry Chapin). I guess I'll order the Boxwrench video on engine rebuilds, crack open the FSM, and turn this into a (re)build thread.

--Rich

1) Were there any signs the engine had gotten hot prior to your purchasing it.(new rad,thermo& gasket,recent flush tee, hoses etc)?
2) I have seen decent compression readings & piss poor leakdown readings, it doesn't automatically mean the rings are fine at all.
3) Does the engine stall immediately if You pull the PCV out of the valve cover, & is it difficult or impossible to restart like that?
4) Did You in fact have a leaking fuel pump diaphragm, or was that a dart at the wall guess?
5) How experienced is the tech doing this checking for You, esp. old school units.?
6) Does this car have the catalyst on it?

 

[whitepunkonnitro]

You dont need to rebuild that thing.
Your compression numbers are fine.
Throw out those leak results. Whoever was doing it either had no clue, or was trying to sell you a job.
Assuming both intake and exhaust valves were completely shot, there would still be no way for them to introduce raw fuel into the crankcase.
The only way for that to happen is past the rings. You would almost need to have a cylinder completely dead with zero fire to see a notable amount of fuel in the oil.
I am thinking your problem is simple and external.
Example, a malfunctioning choke pull-off that is washing the motor down with fuel at a point before piston and ring expansion really gets things to seal up.
A float adjusted just a bit too high will wash the motor under certain circumstances..hard braking or turning.
I have also seen cars and that will boil over fuel after they are shut down and underhood temp rises momentarily.
Do you have to crank the engine excessively and open the throttle to get it to start after it has been sitting hot for ten minutes?
Cover all the external bases before you go ripping into an otherwise sound engine.

 

[slantsixdan]

'74s like the OP's car don't have catalytic converters.

 

[pishta]

have you checked the valve lash? That would be the first thing I would check and adjust before I did anything else to an old slant. Next would be a carb float level check/adjustment. I have a pre 67 and it idles like a Singer sewing machine, and that was with 2 feet of exhaust!

 

[rich006]

The Echlin part number on the PCV valve box is 2-9207. The reason I mention the "2103" on the valve is that you can see that same number on the pictured valve (Standard V165) when you search on RockAuto or NAPA for a PCV valve for a 1974 225.

 

[slantsixdan]

I like the Chrysler valve, but Echlin 2-9207 should be suitable, yeah.

 

[rich006]

Yesterday I got out on the highway and did the Italian tuneup. I didn't notice any smoke. This was after adding 2 cans of BG 44K to a full tank of gas, and driving until the tank was about 1/3 full. After I got home I hooked up a vacuum gauge to the intake manifold vacuum port. At idle the needle reads 18.5-18.8 inches. It flutters but only within that narrow range. If I open the throttle, on acceleration the vacuum drops to 5 inches or less depending on how quickly I pull the cable, and on deceleration it climbs to 23 inches. According to Petersen's repair manual, a piston ring defect would be indicated by a deceleration reading less than 2-5 inches above the idle reading, but my reading is right in that 2-5 range.

Another note: lately the idle has been really rough when cold, but fine when warm. Previously the idle was pretty smooth all the time. Today I repeated the vacuum check while the engine was not yet warm, and I noticed that the idle improved dramatically when I opened up the vacuum line from the intake manifold. Does this suggest that the choke is not coming off the way it should?