216 rebuild initial settings and cylinder compression questions (For advanced dummies

My 1949 216 L6 rebuilt-engine has low compression and I’m curious if this is normal until the rings have seated fully? Also, the idle speed is not 100% stable.

Perhaps I’m worried about nothing again? I just don’t know?

After much effort, I finally have my rebuilt 216 running on an engine test stand. This is my first build. All bolt-on components are either NOS, rebuilt, or remanufactured. Essentially, everything has been replaced in an effort to gain longevity and dependability. I’m trying to do everything by the book.

http://www.adchevy.com/info/1949_216_specs/

I first ran at 1800 RPM for 20 mins to break in the cam as the rebuilder suggest. And yes using a zinc additive. The motor has about 1-1/2 hour of total run time (no load other than generator) and I do my best to vary the speed as not to wear in any particular spot. The temperature holds steady at ~180 deg at ~5-6 PSI engine coolant pressure.

I’m now making sure all components meet “Shop Manual” specs, and tuning it up accordingly. The first thing I noticed is, the idle speed is not stable. It varies by about 50 RPM to the low-side for no apparent reason. (It is hardly noticeable by ear and sounds sort of like a slight occasional cough. It can really only be detected on the Tachometer. A 50 RPM drop happens about every 6 seconds.) Vacuum pressure is stable and solid as a rock at 22 lbs. The Carburetor is NOS and meets all adjustment criteria. Fuel pressure is also stable. The ignition timed up perfectly and returns perfectly on ball at idle. It runs extremely smooth, and I can hardly feel any vibration at all.

See Video: http://s1126.photobucket.com/albums/l606/chevy1948/movies/?action=view&current=idle.mp4 (Full screen to read gauges)

I purchased a good screw-on compression gauge yesterday, and the initial compression came back at 46-49 PSI on all cylinders. It is very consistent between cylinders; however it should be about 110 PSI according to the book? I tried it again today, after warming it up fully and removing all plugs again, and the compression on all cylinders is between 65-70 PSI? Are the rings finally starting to seat?

However, the idle variation has not improved, despite higher compression today and checking everything again. Shouldn’t the RPM’s be solid as a rock? Or is this just the way it is? The book says idle speed should be 475-500 RPM.
Any advice will be greatly appreciated.

Thanks!

 

You checking the compresion with the throttle blocked fully open ? If not try it that way with engine warm.

 

Squirt some oil in the cylinders and check compression it might be the gauge. Crome or cast rings really need to be put under a load to seat. Years ago I went to a Perfict Circle clinic they wanted you to set everything as close as possable before starting start it up check for leaks and take out and make it accelerate from 40-60 in high gear 10 times then take it to the shop and adjust timing valves ect.

 

Yes, I did both those things. Putting a few squirts of oil in the cylinder didn't do anything, and I was surprised about that?

The gauge is fine, I checked it against a known source of PSI and it was perfect.

Can low compression be the cause of the idle variation? Shouldn't the idle speed be steady as a rock? The every 6 seconds dip, has me baffled? What could cause that?

Thanks!

 

Another thougth cam timing off 1 tooth?

 

Cam timing greatly affects cranking compression. Aren't those very low compression motors to begin with. Maybe 6.7:1. A hand crank was even a dealer option, telling you it is a low compression motor.

If you advance the cam 4 degrees, I bet the cranking compression would be where you want it.

 

I find what you are saying quite interesting. Yes the compression ratio is very low 6.60 : 1. And yes there is a hand-crank flange on the harmonic balancer!

As far changing timing gear goes, I think it is beyond my capabilities, and requires all types of gauges and valve adjustments. I’m going to use what the rebuilder set it at. I would be opening a can of worms for sure. From what I have been reading about it, High pressures can cause issues of their own.

But I’m leaning towards thinking the compression issue is the rings breaking in period. Because all the cylinders read about the same and all increased in PSI together from one day to the next. (20 lb increase in one day.) I called the rebuilder and he said, “Giving some more time for the rings to settle in is the best thing to do right now, before condemning it”.

I also think there is a carburetor or ignition issue as far as the RPM drop is concerned. If it was valve timing, it would “cough” more than once every 6 seconds or so? I think? I’m going to first re-check point gaps (on all distributor peaks) and change out the capacitor. So, let’s see what happens? It is like a charge is building up?

Any additional suggestions will be greatly appreciated!

I want to get this engine into the car ASAP!

 

I think that you are thinking too much, worrying to excess, and stressing for no good reason.
It is a 64 year old engine based on a design much older than that. Modern test equipment will pick up burps and bumbles that drivers and mechanics didn't notice in 1949. Despite a total rebuild it still ain't new, but renewed. Driveit. Enjoy it. Don't worry. Old Chevy 6's did not run like a watch even in 1949.

 

I believe "48 Chubby" has your best advice at this moment in time.

From past experience I can tell you, running the engine on that stand with NO LOAD will give you only part of the picture. Fine for getting everything set and checking for leaks.

Your rings (and valve seats) will probably not provide their best seal until you get it under a load and get the heat up. My 235 can run for a half hour and not completely warm the oil up on the stand - because it is not under load and not producing power.
Sure the water temp gets to 180° but it's loafing. My 235 also drops a few RPM occasionally with no harm.

If you really think you need to chase a problem I would recommend a Leak Down test which can tell you whether it is intake leaking, exhaust leaking, or ring leaking. Any one of them can wear in and seat better if you DRIVE it with a load.

Paul

 

The last two post, for sure. Relax.

 

I agree! To much fuss about so little. Surely I could have some real problems, and a slight, nearly undetectable cough is nothing to get my pants in an uproar about.

In my younger years, I drove cars that had real problems and they still held up for years! I had a 283 that smoked and over heated for many moons until it finally went kaput! And only because I ran it dry out of oil. You've heard of the blue-flame engine? Well I had the blue-cloud engine!...lol. It did help keep down the mosquito population however.

This rebuilt engine is old! 65 years old and yes, to expect it to be perfect is to much to ask of the old bugger. I doubt anyone would even notice the burp unless I hooked up a tach and showed it to them. To be honest, it runs sweet and I can't wait to swap it out of the car. Certainly, running under load is what is needed next.

So back to work, I will try adjusting the points and replace the capacitor (just to see) and let the swap begin!

 

If you don't have any ticks, knocks, slaps, pops, sputters, coughs, shimmies, or shakes I'd say its running about as good as you can expect. If it idles smooth and doesn't die, comes off idle and holds a higher RPM smoothly pat yourself on the back and call it good! Got to remember these engines were not much more advanced than tractors of that era. As for the 50 rpm idle drop every 6 - 9 sec, you might consider fuel delivery, could be your float setting or you could try removing the cap from the tank you are using, it might not have enough vent. The compression issue is probably valve seats if it does not change when you do a wet test, and they will probably work in after a few hours of running.

 

Just saw the video of it running, it sounds great, the vac. is rock solid (much better than I can say for mine), but the RPM drop does look a little strange, could the meter have an issue? Because it doesn't sound like the motor drops any RPM at all when the meter drops.

 

Thanks 4doorsRfun2! it is nice to hear that you think it sounds great!

I welcome advice from everyone, and I thank you all!

I reworked the ignition, new points, capacitor, checked wires and connections and it didn't help at all. Still getting the RPM drop. It leaves me to believe it is a carburetor issue. The carb is NOS (so they say) and it may need to be rebuilt after all. However, I'm going to wait and see if it is just a symptom of the valves not being 100% seated yet. I will wait until the motor is installed into the car, and after I put a few miles on it.

HOBBS carburetor rebuilding service located locally (Still in business after 60+ years) said they would rebuild it for $99. Not bad considering their spotless reputation.

Despite the problem being almost insignificant in the scheme of things, I still want to know what it is causing the RPM glitch. OCD (Over compulsive disorder) is rampart from what I can see in this hobby, and I'm developing a bad case of it! I guess that is just the way it is going to be!

Youz guyz is OK!

 

Have you checked it with a different meter just to rule that out? Might be worth a shot. As for rebuilding the Carb, if its a Rochester B, BC, BV it is a very simple Carb and real easy to rebuild. Mike's Carburetors has kits for around $20 and an online video. I can tear mine apart and put it back together in under 20 min. Its really easy.

 

Valves if done right should not need any seating in time, are you sure you got them adjusted with enough clearance. If squirting oil in the cylinders did not make any difference, then it is not the rings either. Did you have the head done by a pro. ?

 

You have the engine idling for long periods while you check out the random RPM drop? Not the best for a new engine,it needs a load on it for proper break in,as in driving the car.
That rpm drop,it is random? Might be just a lean idle misfire caused by a carb needing attention or fuel quality.

 

Apparently not the distributor (NOS, rebuilt, or remanufactured). A bad diaphragm in the vacuum advance can do what you describe. So can weak springs and/or wear in the mecanical advance parts.

 

You can see the video of what it is doing here: http://s1126.photobucket.com/albums/l606/chevy1948/movies/?action=view&current=idle.mp4
It is a Carter W-1 carburetor. And I have a manual called Carter Carburetor Repair which has detailed instructions on testing and rebuilding. Despite the W-1 Carburetor being a simple device, overhauling does require some specialized gauges and experience, for which I have none. I appreciate the potential cost savings, but I think I will have the pros do it, if I have actually have it done.
It sure wouldn’t hurt to try a different tachometer, but I don’t have one. However, when the RPM drop happens you can hear it slightly in the exhaust. Sounds like a very mild cough. So it is there alright.
And yes, the valve/rings machine work was done by a professional company, and they are quite reputable. They tell me it does take time to seat the valves. The distributor is working fine and meets all specs. I put a new vacuum advance mechanism, just to be sure, and tested everything in accordance with the manual. So, I think the distributor and vacuum advance are fine.
I don’t idle the engine for very long, and I try to always run it at a different RPM, with the exception of running it at 1800 RPM for 20 mins as the rebuilder suggest to break in the cam. Otherwise, I can see the RPM drop immediately. Engine hot or cold, the RPM drop is there.
Again, I think most people wouldn’t even worry about it as it is very slight and nearly undetectable, but I do want it to idle properly. Perhaps running under load will help things? Maybe the carb needs to be rebuilt? Perhaps the new diaphragm does have a tiny leak? Inquisitive minds want to know!...lol
I do enjoy the advice, and surely I will figure it out eventually.

 

Does this mean that the timing gears were not changed when engine work was done???

 

It runs too good (if you watch the video) for the cam timing to be off. I is almost an imperceptible drop in RPM. I think we are all getting spoiled with EFI! These motors are always going to have little tiny burrbles and sputters at idle, especially when using NOS carburetors etc. It just seems strange that it is almost a steady (every 6 - 9 sec.) drop in RPM, then right back to normal.

 

No the timing gears are new. The re-builder says they. are set up as they should be, and there is no reason to change things. If I'm not happy, they will fix what ever needs to be fixed, but really want me to try and break in the motor before I panic about anything. I need to get this engine in the car ASAP, and I think many things might just work themselves out under load.

They provide a 3 year unlimited mileage warranty, Pro-mar engine re-builders Paramus, NJ. They came highly recommended by a local "Old Schooler" who said he has had excellent luck with them.

Thank you for your thoughts, and I do appreciate all advice and the different ways to look at issues I'm having.

 

That's good to know 4doors! Yes it is basically a big lawnmower engine, and such a slight variation in RPM is probably par for the course. The motor I'm replacing runs far rougher than that, and the car works perfectly. (Except for the rear-main seal which leaks terribly.)

However, it would be cool to get rid of the RPM drop, but certainly can live with it, if I have to. Without a sensitive tachometer you wouldn't even know it was there.

I guess we are all spoiled with modern computer controlled engines!

 

Take off the distributor cap and rotor.Rotate the engine until the points are opened. Grab the top of the distributor cam and try to wiggle it back and forth with moderate pressure while watching the points. Do the points open and close when you wiggle the cam? Is it a lot,like .006 is a lot .If so,the slight change in timing from random points gap will often cause what you describe.Is the fuel in your area 10 percent Ethanol? On some engines,the Ethanol causes a slightly lean idle and misfire but otherwise the engine runs fine............

 

Sounds just like a good running old chevy six is supposed to sound! I dont think you can make it idle better than the video.. put it in, It needs to be under a load to break in properly.

 

Truckedup, I really like what you proposed, so I went and checked it out right away. Unfortunately (I mean fortunately) there is absolutely no play what so ever. It is tight as a drum. I used a tool to grab onto the shaft and gently tried to wiggle it also. Nothing, everything is tight.
I even went the extra mile and checked the gap at each peak, and remarkably, they were all the same! I found it hard to believe myself, so I checked it twice. I cleaned everything with some silicon spray, and assemble it all up again. No change still the RPM dip. But great try!!
Yes 10% alcohol, and I use the new Stabil to treat it as it is suppose to eliminate any alcohol issues.
Ottoman, and others, your right, the key words are: PUT IT IN!! RUN IT UNDER LOAD!! BREAK THIS BABY IN!! STOP FOOLING AROUND!!
Tomorrow is going to be dedicated to doing just that. If I can get the old motor out in a day, I will be thrilled. I never did it before, so I don’t have a clue how long it should take. I also want to clean up the engine compartment and fire wall before installing the new motor. So that will probably add a day.
Perhaps I will start a thread about the engine swap? Surely I will have questions.
You guys are the greatest! H.A.M.B. rules!

 

Just to give you an idea, I pulled the 235 in my 53 all by myself in a little over 2 hours (adjusted for breaks and about 45 min. of pre-prep [drain fluids, take pictures, etc.]). I was really surprised how fast it was done! My intention that day was just to pull the radiator, core support, and grill, but next thing I know the motor and trans were hanging on a hoist in front of the car! Cleaning the engine compartment however took over 3 weeks (at least 2 hrs per weeknight and 8 hrs minimum on the weekend) of washing, scrbing, and sanding, before it was even ready to prep for paint.

 

Nice! I should be so lucky!

I'm off this morning to start the job. Let's see how far I get?

Nice to hear all went smooth for you. Did you replace it with another (the same) 235 or did you do something else?

Thanks!

 

Same motor rebuilt with some performance upgrades. Got some before and after pics. Still need to get the exhaust installed, and it is running a bit lean so I have to do some tuning there.

 

Outstanding! What a difference! I really get charged up when I see something like that. I bet it looks even better in person!

I took a stab at removing my engine yesterday. Didn’t get it out all the way, but will have it out by tomorrow for sure. The most time consuming effort was unbolting the dam grill. My work space is narrow, and that slowed me down even more. Still, if you got yours out in a day, that’s really something!

I did notice the bell housing on the rebuilt 216 doesn’t have the starter-linkage-mounts. So hopefully, I can use the bell-housing that is in the car. If not, I’m going to have a major delay. It is a ’49 - 216 and they must have done away with the foot-starter that year?

I attached a couple of pics, and I can see it is going take longer than I thought to clean up the engine compartment (especially after seeing yours…wow!) and need more time to mess with the bell housing. I’m changing my estimate from 3 days to 6.

I love those dual-carbs! I have Fenton-headers and dual exhaust already; I might like to do the dual-carb thing also after the 235 is rebuilt. I wonder if there is something I can have the rebuilders do to spice it up even more? Perhaps a cam of some sort? I also wonder how expensive it would be to have the ports enlarged to get the most from the dual-carbs? Can it be done?