VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 Won't rev past 2000RPM?

Hi all, first post - hopefully many, many more :)

I've never dealt with pre-war cars until a buddy of mine bought several a few weeks ago. He wound up buying two '37s and a '41 along with a handful of other cars that are all in unmolested, very good shape.

In the midst of buying all of these, another friend of mine caught the bug and bought a '48.

Since I'm the most technical of the bunch, I offered to bring 'em back to life and have had good luck on all but a common problem with all of the Chevy sixes!

They had all of the basic symptoms of sitting for decades - frozen carburetors, brittle hoses, stuck intake valves, etc.

I've been through them all and as far as running conditions go, they all run PERFECT. Butter smooth idle, very quiet, plenty of torque.

The common problem to all of them is the motors seem to hit brick walls at 2000RPM or so my ears tell me. Taking them up and down the road results in very short gear changes and top speeds of 40MPH or so.

The only things that's been changed that aren't OEM spec are the plugs and wires. I didn't purchase them so I don't know if the plugs are resistor plugs or not, but I'm pretty sure the wires are.

Does anyone have any advice on tracking this problem down? I'm definitely not an expert on pre-war cars, but felt more than comfortabe tackling the projects.

When it hits the brick wall, it sounds like a late model rev limiter - it's not bogging, just hitting a wall like it has more power to give and not able to. Occasionally it will backfire through the exhaust if the RPMs are held at this point.

Carb?
Ignition?
That's the way they're supposed to run?

I really hope it's not the way they were supposed to run. Putting a 100MPH speedometer in a car that struggles to hit 40 would be a sick joke :)

The 216's, depending on year, will scream up to 30 MPH in 1st gear and 55 MPH in 2nd....85 or so tops. You do have a problem.
Possible causes: points,condenser, spark plugs, low fuel pressure , obstructed fuel line or fuel passages in carb.,weak or broken valve springs.
I use resistor plugs in all of my cars with no problem.
Good luck and keep us posted.

Hi Team 140,

Gene has given you a good list of possibles. In addition you would be wise to shoot some WD-40 or any other product in that family, at the base of each valve. Do this while running.

I suspect the problem is the fuel pump. Disconnect the fuel line at the distributor and attach a low pressure gage. You should get around 3-5 lbs of pressure.

Your problem is odd in that all the vehicles are doing the brick wall stunt. The backfire is an indication of lack/low fuel pressure. However, it could be caused by the electrical circuit. If electrical, you will get a miss, or uneven torque.

I still vote for fuel system.

I forgot to welcome you to Chevy Chat II. You will find that when you bring a problem to us you will get serious replys. So, hang around.

Thanks for the welcome!

They do have fresh points and condensers. I'm also leaning toward a fuel issue and somewhat curious about the electronics.

I've coated the valves with PB Blaster. On one of the 37s and the 41 they had about 5 valves siezed between the two. I managed to free them up without much fuss.

Where specifically is the high speed circuit in a W-1? I've found a rebuild guide, but it's not very informative as far as pointing out which jet does what.

I call myself thoroughly cleaning the carburetors, but I may have missed that circuit if it's well hidden. The only information I had was basic carb theory and the rebuild guide that gave me adjustment specs more than anything.

Oh, forot to mention, we did install a reman carburetor on one of the cars and it had the same result so I'm going to rule out the carb for now (thinking out loud here)

Fuel - Spark - Air. Air seems OK. I'll tap into the fuel line and get some pressure readings tonight and go from there.

Also, is there an easy way to hook up a 12v tach for diagnostic purposes on these 6 volt systems?

I agree...probably the fuel system (fuel pickup plugged? line clogged? fuel pump?). Symptoms sound like fuel starvation.

You might also want to adjust the timing Remember when these cars were built the octane rating was not near what we get today. Most if us advance the timing by 8 to 10 degrees when using 87 octane.

Coach

Just about forgot about timing!

I haven't set the timing on any of them yet - mainly because I haven't found out where the timing mark is and whether I can run a 12v timing light attached to standby battery and get a reading or not.

Is the timing mark window the hole in the bellhousing above the starter? If so, will a timing light hooked up to an external battery work to run the timing light? I'm not an idiot - I've ust never tried that and I'm not at home to do so!

Power the timing light with any 12 V battery. I use my booster pack.
The "hole" in the flywheel housing has a pointer, marks are on the flywheel. Ball in flywheel is the starting point. Can be advanced from there a bit. May be rusty and difficult to see. Loosen distributor clamp a little and turn distributor to where the engine "sounds" the best and play around from there. Turning dist. counter clockwise will advance the timing and that sounds like what you need.

The timing ball on the flywheel is really hard to see (for me anyway). :grin: A dab of white paint on the ball will help a bunch while you're standing on your head in the engine compartment.

I agree that fuel is most likely the problem. With the Carter W-1 carb coordination of the throttle plate with metering rod is critical. Fuel starvation is a common problem if metering rod is delayed. The metering rod slipped onto a short shaft on the pump arm and counter shaft assembly is the primary high speed control. If you remove the float bowl cover you can inspect the metering jet.

One other item to put on the list is partially plugged exhaust system though I seriously doubt it is the problem in these cases.

As Gene wrote any 12 V battery strong enough to fire the light is ok. Use No. 1 plug wire to fire the light as usual.

If you attach a vacuum gauge to the intake manifold you will be able to check valve operation as well as general condition of cylinders. Timing, valve adjustment and a bunch of other stuff can be checked or verified with a vacuum check.

Any information out there on how to properly coordinate the throttle blade and metering rod? It's all connected and appears to be working freely, but is there an adjustment that can be made?

I checked the timing and fuel pressure. The fuel is a bit low at 3psi at idle and 2.5 when it acts up. Brand new pump too...

The best I could get the timing to was 8*BTDC before she started to stumble all over the place.

140 I have noticed you said you have replaced the points. Here's a problem I found with a friends '52. He had changed and reset everything. And it still wouldn't go over 40mph and would backfire also. After trying to help him via email I went over and found he had forgot to put in the spring in the points. The only thing that was returning the points to the closed position was the copper strip. Therefore allowing them to float. This sounds like the exact same problem and the common denominator is new points. I would check it out. Hope this helps you out.

I hesitate to mention this because you stated that more than one vehicle had the same problem, but a clogged or partially clogged exhaust system will cause the same problem.

Lots of good info here guys. Thanks a bunch :)

I'm going to take another look at the points this evening and make sure the spring is in there. That's a very good possibility as to what's going on and it makes a lot of sense.

Not all brands of points have the seperate spring. The originals did not have it as it was permently attached and performed both functions. The spring is silver and if the seperate ground connector was used it was copper colored.

yep, Mickey and his family can cause some grief. I once perchased a 56 pickup that couldn't pull the hat off you head. The 235 had "just been rebuilt", a term that is very subjective. I pulled the motor and went thru it, reintalled it and it ran great....untill I hooked up the exhaust. Mice had pack the muffler with leaves, twigs, seat padding, etc. a lesson learned

The metering rod adjustment is made by bending the coordinating rod (connects arm on throttle shaft to pump arm). With the throttle plate centered and fully closed the distance from the main jet to the bottom of the short shaft should be 2.795". Carter supplies a gauge to set this distance as part no. T109-25 for most Chevrolet W-1 carbs. Some early models use T109-15 or T109-20 gauge. They are listed as 2.797" and 2.795" respectively.

There are a few of VCCA members who have years of experience rebuilding Chevrolet carburetors and list their services in the Services to Members section of the G&D. They have the specialized tools, parts and specifications to do the job properly. Many generalist carb rebuilders can clean and reassemble but may not have the experience, parts or special tools. I have found they often charge more than the experts.

Does the engine actually rev higher than 2,000 rpm? If it does here is an even dumber question...are the parking brakes engaged? Maybe frozen while engaged?

No, it does it in neutral. I've ordered a set of points and they should be here tomorrow. I won't have much time to work on it as I'm leaving tomorrow evening on a road trp to pick up a '46 Chevy 1 1/2 ton truck. The bug has bit us good around here!

I'll swap out the points and give an update before I leave if I have time!

The best way I've found to tune these old engines,is with a vacuum gauge.Just disconnect the vacuum line to the distributor advance unit,and connect the vacuum gauge to the carb fitting.
It should show up any problems with the engine,eg carb,timing etc.I usually time my engines without a timing light.
Just set the points to the correct gap,bring No.1 piston up to the firing position,loosen the distributor clamp.Then remove the H.T. lead from the center of the distributor cap,and place the end of it near a good earth point.
Turn the ignition on and slowly rotate the distributor until you hear or see the spark,and lock the distributor clamp tight,and thats it.It's proved very accurate for me over the years,and you don't have to play around with timing lights that need a 12volt battery.

A variation to CJPs suggestion instead of watching for spark connect a test light between the points wire and ground, when the light just comes on lock the distributor.
Tony

Dear all,
With a new fuel pump (and 3 psi fuel pressure) and new points and condenser (all put in by the same hand), I am having an itch about the points.

My 38 sat undriven in a barn for a couple of years when I moved from Ohio to Massachusettes and when I went back to bring her back with me I fired her up and she ran "OK" but I could not keep up with my wife who was driving the family car ahead of me. I found I had to undulate the gas pedal and floor it and let up for the car to gain speed slowly, but she kept fading to slower and slower top speed until finally I could not get her over about 45 mph and lost more speed on hills. I thought I was having fuel problems for sitting too long so I did not want to stop and baby her but kept going. When I got to our home in Massachusettes I scratched around and discovered the points had worked loose and had no gap at all !!. I was lucky she ran at all. Reset the gap and she leaped down the road with all the power a mighty chevy 216 should have at more than 60 mph with the gas pedal only a fraction of the way down to the floor (as oppossed to having to have it on the floor all the way from Buckeye land). Hope that helps and let us know how your problem is resolved, hopefully soon. I find that setting the points gap is easiest if you turn the engine slightly beyond the peak of one of the 6 lobes and then hand rotate the shaft back slightly to get the top of the lobe exactly (the spring in the system will allow a backward rotation somewhat but not a forward one). It is really great, driving a 38. Mike

It was the points! Apparently, the fellow that was helping me get these cars back in running order has never fooled with points and left out the return spring. I dug through some of the Borg arner boxes laying around and found a few of them :)

The '41 runs like a champ! I took it up to 60MPH and decided that was all I wanted to do on 40 year old tires.

Many thanks for the help and I'm sure I'll have more questions here and there.

For those of you interested, I have some photos of the cars I'm working with as well as the 1 and 1/2 ton I picked up Yesterday at: http://picasaweb.google.com/w.brian.smith/JoelSCars

Findin' the problem and then Fixin' the car is all part of the enjoyment of driving these old cars.
This site is one tool that is avaliable for us to Find and Fix our old cars.

Good for you!

Great!! Who would of thunk it, eh? It is nice to be able to pay it back once in a while as this site has been priceless to me in my '46 build. Happy motoring.

Awesome news...congratulations and 'well done'!

Coach