VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 1938 216 lack of power

I have been noticing lately that my newly rebuilt 1938 216 engine runs real good, sounds smooth, no backfiring, but going up hills it lacks a lot of power. I used to have a 1954 Chevy 235 in the car so maybe I'm just spoiled. However I have read in the past in VCCA's G&D that adjusting the timing in a certain position will give the engine more power. Does anybody know the secret?

Keep advancing your timing a couple of degrees at a time until you notice pinging under load or a dragging starter. Once you hit that limit back it off a degree or two until the pinning or dragging stop then lock it down. I don't use a timing light. I time to the fastest idle when warm then fine turn using my octane selector.

I set the timing right on the pointer and the ball at the flywheel and set my octane selector to the owners manual specs. To advance the timing do you rotate the distributor clockwise? Should I use the octane selector to set it?

a timing light made my 54 engine run worse ! I timed it by "ear" . it has tons of power & snap . frank

Frank,
What's your procedure to time it by ear? I've always used the book settings but I'm willing to try a new way.
Jim

I believe advancing the timing is turning the distributor CCW but it's been a while since I did mine and I've slept since then. To verify pull the cap & crank the starter. Opposite of the way the rotor turns will be advancing the timing. The ball and pointer were set up for gas in the 65 octane range. You should be able to get a minimum of 10 deg. advance timing over stock with no problems. Just loosen the clamp with the engine warm and running then turn the distributor both ways until you get max idle speed then lock it down and take it for a drive. If no pinging and the starter doesn't drag you're not too far.

That makes sense! Thanks!

If it is a Master or a Master Deluxe with a 3.73 rear end it will be a little flat on hills.
The timing may be retarted due to the rubbing bllock on the points wearing down and slowly closing the points. Check the point gap.

Hey Fast,

Gene suggests that a 3.73 rear gear might make it seem slugish. I'm over in the "Wine Country", not far from Danville, in the mountains between Santa Rosa and St. Helena. I've converted my '36 PU with a bone stock 207 engine from 4.11 to 3.55 rear gears. There is a long 11% grade near my home that my PU pulls easily in 2nd gear, and in fact often catches up to modern econoboxes that are maxed out on that hill at about 25 MPH.

If I were you I would verify the initial timing, point gap, valve adjustment, function of the vacuum and centrifugal advance mechanisms, corerct jetting in the carb (and alter it if it seems to be running rich/lean) and do a compression test.

My '36 ran too rich with current California gas and stock jetting and power was noticably down because of that. Jetting is easily altered by calculating the effective main jet opening area with the metering rod in the cruise, power and transition positions and using different metering rod and jet combinations to finess the mixture under all conditions.

In my case the engine likes a 0.094" main jet and a 1-step lean 1937-38 metering rod in a 1939-40 W-1 carb. The metering rod is designated as 70-47, meaning the rod diameter that is actually in the jet at light throttle is 0.070" and the tip of the rod that is in the jet at full throttle is 0.047". That 0.047" is too lean for my engine so I reduced it to 0.0445". The steep hills around here are an excellent "dynomometer" for experimenting with jetting, finding too lean, too rich and "just right".

Gene: When I rebuilt the rear end I thought long about the gear ratio so I could get on the freeway. I decided to leave the gear ratio as-is with the standard master deluxe ratio. Now I hope I didn't make a mistake.
Brino: You lost me! I'm a pretty good mechanic, your explanation sounds good but how do I change the main jet and get the metering rod you mentioned? The engine is newly rebuilt and the points are new too. I did adjust the points to the owner manual specs. I just had the valves adjusted by a race car mechanic. I can do a compression check, hopefully that's ok since the engine was just rebuilt.
Thanks!

If it is a Master Deluxe it has the "performance" 4.22 ratio....If it was never changed. With that ratio it should climb all hill with ease in high gear. It should cruise efffortly at 55 + MPH.
When I changed my '39 from the 4.22 to the 3.73 hill climbing, especailly with four passengers suffered.
It would still check the point gap and advance the timing as far as possible. If you advance it with the octane selector you can run it up at a controlled rate and see what you are doing with out using a timing light.

My 37 Master with 3.73 gears does very well but I can tell the difference between 2 and 4 passengers. Back in the day we used to pull boat trailers and other utility trailers with no problems but one time I hauled a 35 Pontiac 8 on a heavy home made trailer and I never got it out of 2nd gear! lol The Pontiac alone out weighed the Chevy.

But there are no hills in Iowa.

Ha Ha, Well there are a few but you are right it is mostly flat!

If I lived in Iowa instead of northern California then I wouldn't have this hill problem with my 38!

"Brino: You lost me! I'm a pretty good mechanic, your explanation sounds good but how do I change the main jet and get the metering rod you mentioned?"

Fast,

I'm not one of the designated "Experts" here. I leave it to others to claim that distinction. But I bring a street rodder's approach to the restoration side of the car hobby. I have 5 carbureted vehicles, a '71 Dodge van that I bought new, my '36 PU, a small block Chevy powered '32 Ford roadster, a '78 El Camino and my wife's '60 Mercedes 190 SL with Weber carburetors. All of these vehicles have improved power AND fuel economy from carefully fine tuning the carburetors to give the engine an optimum air/fuel ratio under varying conditions.

Because I'm an amateur maechnic I don't have a dynomometer and none of these vehicles has an O2 sensor that would allow installation of an air/fuel ratio gauge. So I do my experimentation with carburation by "seat of the pants" trial and error, keeping notes on how the engine runs with various combinations of main jets and metering rods.

The concept of adjusting actual fuel delivery orifices in a carburetor is well explained in a number of resources. One of the best is Doug Roe's book on Rochester carburetors. On page 241 Roe presents a table of the actual area of a wide range of jet and metering rod sizes. The effective open area that the gasoline actually flows through is the jet area minus the metering rod area.

If you send me your email address I'll send you photos of where in your carburetor you'll find the jet and rod and the simple gauge that MUST be used to properly synchronize the metering rod and throttle plate to each other. Mine is raywaldbaum@gmail.com.

These Carter W-1 carburetors are very basic devices and were widely used in the 1930's and 40's. Therefore, there is an abundance of jets and metering rods available to a guy who is willing to go looking for them.


"The engine is newly rebuilt and the points are new too. I did adjust the points to the owner manual specs. I just had the valves adjusted by a race car mechanic. I can do a compression check, hopefully that's ok since the engine was just rebuilt".

A "professional" engine assembler is just a person who charges money to do the work. No skill level is implied. Unless you asembled the engine yourself you have no way of knowing the quality of the machining, parts and assembly. That is why I suggested a compression test and verifying all the components of the "tune up". If you find a genuine NOS Carter carburetor kit it has an instruction insert with that same recommendation; verify everything before diving into the carburetor.

A compression test tell tell you what the actual cylinder pressures are. There is a minimum psi specified for your engine and all the cylinders' measured pressures must be very close to each other or there is a mechanical problem.

Once the basic mechanical condition of your engine is verified at 100%, fine tuning the distributor and carburetor will optimize its power delivery and economy. These antique engines are pretty wimpy and benefit from all the fine tuning you can give them.

There is even a point set for later model Chevys up through the 1960s that fits your '38. Some "Experts" dispute that because it is not listed as fitting 1930's and '40's distributors but I have that point set in my '36 and it is a huge improvement over the old 2-piece point set.

If you ever come over to the "Wine Country" stop by and say "Hi".

Gene: I had the octane selector at "0" so I advanced it up to "10". The engine seems to be running better. I'll drive it this weekend to see the difference.

Brino: that's pretty technical. I will need to read it a few times to understand. I advanced the distributor 10 degrees. I will double check the compression and points.
The carb stuff is a bit over my head but I would like to learn more. I like all the power I can get and street rods too!
jdeddy@pacbell.net
BTW: I am in the wine country sometimes for my work related meetings (irrigation @ vineyards). I'll let you know when I'm up there and I'll stop by to see your rides.

How was the power before the rebuild?
If it has lost power since the rebuild either the timing gear timing is off, the ignition timing,etc.
If the valves are set too tight it will have a rough idle. If the compression is low the rebuilder did something wrong. The first and most simple thing to try FOR THE AVERAGE PERSON is to play with the ignition timing.

Gene: My 38 originally had a 1954 235 six which I put in when I was in High School back in the 60's. I bought an original 38 engine from a street rodder and it was running just fine on blocks at the time. He had bought the car from a grandma who just had the engine fully rebuilt. I had the engine re-rebuilt just to make sure it was in good and brand new condition. I plan on checking the compression to make sure and today I set the distributor at 10 degrees advanced. So far so good, the engine starts up fine and idles good. I'm taking it for a spin tomorrow.

Fast,

I will email you a picture of where the main jet and metering rod are, assuming you have a Carter W-1 carburetor. In its over 3/4 century of life that engine could easily have acquired another carburetor along the way like a Rochester.

The "technical" stuff is really simple. On it's way to be burned by the engine gasoline passes through a precisely sized orifice in the carburetor called a main jet. Because the engine requires a different air:fuel ratio depending on whether it is working hard or loafing along, a tapered rod called a metering rod moves up and down in the main jet to vary the amount of gasoline that can actually flow through the main jet.

The opening in the main jet has a certain area. The tapered metering rod also has a certain cross sectional area that restricts the main jet. The actual opening of the main jet with the metering rod partially blocking its opening is the effective open area. The metering rod is raised and lowered in the main jet as the throttle position is changed. It's just like adjusting a faucet to vary the flow of water.

By experimenting with different main jets and metering rods you are altering the air:fuel ratio delivered to the engine to see what it likes best. By keeping detailed notes of the results you will soon zero in on the optimum jet and rod combination. If it seems like you need a rod between 2 sizes you can reduce the size of the "fat" rod by spinning it in a lathe, drill press or even hand drill and polishing the too-big part with fine crocus cloth. That leaves tiny scratches visible with magnification that you then polish out with an abrasive like valve grinding compound, paint polishing compound or even toothpaste.

When you get it right your engine will seem like it's on steroids. Then you'll have a big grin as you say to yourself "I did that". That's a feeling that people who never try anything or pay others to do everything will never have.

I used to ALWAYS set my timing "by ear" on all the cars I've ever owned. There was always a "sweet spot" where it would run beautifully.

Fast,

I'm emailing you a photo of a disassembled W-1 carb showing where you'll find the main jet and metering rod. Also in the photo are an assortment of jets and rods and the gauge used to synchronize the positions of the throttle plate and rod.

The W-1 is really a stone age device that anyone can handle, unless you're getting into putting bushings into worn throttle shaft or accelerator pump shaft bores. The Carb Shop has an excellent online tutorial on this carb,it's evolution from 1932-49 and how to service them.

If you want to see a highly evolved, complicated carburetor open up a Carter Thermoquad or Rochester Quadrajet. They are highly tunable and excellent performers when dialed in but that comes at the price of complexity. It's quite an exercise changing the jets and rods on a Quadrajet so I have 2 for my '78 El Camino. One to run well and another to pass a smog check. It's way faster to switch carburetors than to change the jetting.

As for setting initial timing "by ear", my hearing is gone. When I'm experimenting with carburetor and distributor setups I bring my wife along to listen for pinging.

6cyl o t.

Your timing by ear method sounds (pun intended) intersting and I would like to try it. In order to do that I have a few questions.

What is the actual sound that indicates the sweet spot?

Do you listen for it with the engine running under a load or no load? Idling, mid RPM or revved up?

Do you vary initial, centrifugal or vacuum advance, a combination of these or all 3?

Once you find the sweet spot do you record data on where it is using a timing light and degree wheel so you can go back to it quickly without repeating the whole process?

Does the process include any objective measurement such as what speed the car can maintain on a particular hill that really challenges its power output and measured fuel ecopnomy?

I just advance the timing as far as I can with out causing the engine to kick-back or turn over "hard" when using the starter. Also if advanced too far it will "flutter" at about 1500-2000 RPM when under no load.(in neutral)
Due to the ultra low compression it will never "ping" under a load. With the low ocatne gas available in the '30's they would ping with too much advance.
If you set the timing first set the octane selector to the center (0). Then set the timing with a timing light "On the ball". Then advance the octane selector to 10 Deg. advanced. If any of the above problems appear set it back to 8 Deg. advanced.
At an average that is about the right amount. Frm that point on you can fine tune with the octane selector with out using a timing light.