Author Topic: 1937 346 basic tests  (Read 669 times)

Offline Steve Rinaldo

  • Posts: 96
1937 346 basic tests
« on: June 18, 2017, 08:01:25 AM »
I have been doing some engine tests on my 1937-60 and I would like to get have some opinions on the results So here goes.

1. Compression test- I did a compression test on a warm engine and here's what I got. Dry all were around 90 and the wet test showed 95. The shop manual spec. is 100-105. I don't think this is an issue. Thoughts?

2. Vacuum test- At hot idle the gauge shows about 15 inches. The wiper hose was pinched off. I can get the reading to increase to 18 by advancing the ignition timing. Thoughts?

ignition timing- When using a timing light should I still us the IGA mark with the engine a slow idle and the distributor advance line pinched off?  I had a Chevy that the damper ring with the timing marks slipped causing weird timing readings. Does this happen on these engines?

Thanks, Steve

Online Steve Passmore

  • Posts: 4677
  • Name: Steve Passmore
Re: 1937 346 basic tests
« Reply #1 on: June 18, 2017, 03:31:47 PM »
That's not bad if it's still the original engine. I think it's more important to have them all within 10%  I have engines running well on 90psi

You should still work to the timing marks IGN

I have never heard of a problem with the crank pulley marks on these engines.
Steve

Offline Steve Rinaldo

  • Posts: 96
Re: 1937 346 basic tests
« Reply #2 on: June 18, 2017, 03:48:29 PM »
Thanks

Offline Brad Ipsen CLC #737

  • Posts: 737
    • CLC Member
      CLC Member #737
Re: 1937 346 basic tests
« Reply #3 on: June 18, 2017, 04:01:49 PM »
There is no rubber in the vibration damper.  All is metal to metal so very unlikely that the marks would ever move in relation to the keyway.
Brad Ipsen
1940 Cadillac 60S
1938 Cadillac 9039
1940 Cadillac 6267
1940 LaSalle 5227
1949 Cadillac 6237X

Offline Carl Fielding

  • Posts: 332
    • CLC Member
      CLC Member #10797
  • Name: Carl Fielding
Re: 1937 346 basic tests
« Reply #4 on: June 18, 2017, 09:29:35 PM »
"...................distributor advance line pinched off.." ? I am wrong about something almost every day. Are you referring to vacuum advance ? I do need to know if I am wrong , but I didn't think vac. adv. came in until '40 for Cadillac. What year is your 1937 346 engine ? Thank you , Carl

Offline Steve Rinaldo

  • Posts: 96
Re: 1937 346 basic tests
« Reply #5 on: June 19, 2017, 06:07:06 AM »
It is the matching engine. This is the distributor that was on the car when I got it about 15 years ago. If it is a later distributor should the vacuum advance hose be connected to manifold vacuum? the fitting on the carb. shows 2 at base idle which leads me to believe it is ported vacuum. What do you think?

Online Steve Passmore

  • Posts: 4677
  • Name: Steve Passmore
Re: 1937 346 basic tests
« Reply #6 on: June 19, 2017, 09:59:44 AM »
Someone fitted a later distributor. Happens a lot but you need the later carb base. It attaches just below the idle screws Steve.
Steve

Offline jackworstell

  • Posts: 135
  • Name: J L Worstell CLC #7558
Re: 1937 346 basic tests
« Reply #7 on: June 19, 2017, 12:06:04 PM »
Steve P

If a vacuum advance type distributor has been substituted....is it  OK to simpiy use straight intake manifold vacuum for it....ie  tee-off of the vacuum fitting  which goes  the fuel pump and then onto the vacuum wipers ?

Jack Worstell      #7558      jlwmaster@aol.com

Online Steve Passmore

  • Posts: 4677
  • Name: Steve Passmore
Re: 1937 346 basic tests
« Reply #8 on: June 19, 2017, 01:19:06 PM »
I honestly don't know Jack. Never seen it done and don't know why anyone would want to. The pipe and fittings are tiny compared to the wiper pipes so that would be an issue. Easier to pipe it where it should go.
Steve

Offline Steve Rinaldo

  • Posts: 96
Re: 1937 346 basic tests
« Reply #9 on: June 20, 2017, 11:28:04 AM »
Here is a follow-up to my post. I teed into the line that went to Wipers which is manifold vacuum and ran a line to the vac. advance. I removed the distributor and reset the points to .015 and bench checked that the mechanical and vacuum advance operation. They are working fine. I retimed the engine using the IGN marks at very slow idle with the vac. advance removed.   I checked both the vac. and Mech. advance while running they are working fine. I checked the amount of vacuum at the advance hose and was reading about 19 inches. This proves to me that port on the carb is a ported vacuum pickup.

The engine starts very easy both hot and cold. It also idles very smooth with a setting of about 500 rpm.

So I learned some things in this exercise and I hope this helps some other guys. Steve

Offline DaveZ

  • CLC #26097
  • Posts: 43
Re: 1937 346 basic tests
« Reply #10 on: June 20, 2017, 04:35:52 PM »
Steves:-)
I know you guys will know this....
Where does the positive ground bolt to on the 37's? Is it a cable or ground strap? Many thanks, Dave Z
Regards,
David Zitzmann
1932 345B
1937 5019

Offline jackworstell

  • Posts: 135
  • Name: J L Worstell CLC #7558
Re: 1937 346 basic tests
« Reply #11 on: June 20, 2017, 05:10:10 PM »
Steve R     pls clarify...why do you think the carb port     is ported vacuum and not straight manifold vacuum ??

Jack Worstell

Online Steve Passmore

  • Posts: 4677
  • Name: Steve Passmore
Re: 1937 346 basic tests
« Reply #12 on: June 20, 2017, 05:12:06 PM »
Mine was a ground strap straight to the chassis, but who knows if it was original?
Steve

Offline Steve Rinaldo

  • Posts: 96
Re: 1937 346 basic tests
« Reply #13 on: June 20, 2017, 07:35:43 PM »
Manifold Vac. is below the throttle blades at idle and reads about 18-21 inches. Ported vacuum is above the throttle at idle and strength is directly related to the port position in the carburetor bore. It generally reads about 5-15 inches, again related to the throttle blade position. The is one more named venturi vacuum and it is picked up at the restriction in the carb bore. It is strongest at wide open throttle and only reaches about 5 inches Steve.

Offline Brad Ipsen CLC #737

  • Posts: 737
    • CLC Member
      CLC Member #737
Re: 1937 346 basic tests
« Reply #14 on: June 20, 2017, 09:48:20 PM »
Without going into all of the exact engineering that goes into the port location for vacuum advance which I may not know completely correctly the easy answer is not to question Cadillac engineers.  It took a lot more cost and effort on their part to locate that port exactly right in the carb than just tapping into the intake manifold.  There must be a good reason for it to be where it is. 
Brad Ipsen
1940 Cadillac 60S
1938 Cadillac 9039
1940 Cadillac 6267
1940 LaSalle 5227
1949 Cadillac 6237X

Online Steve Passmore

  • Posts: 4677
  • Name: Steve Passmore
Re: 1937 346 basic tests
« Reply #15 on: June 21, 2017, 06:35:34 AM »
Without going into all of the exact engineering that goes into the port location for vacuum advance which I may not know completely correctly the easy answer is not to question Cadillac engineers.  It took a lot more cost and effort on their part to locate that port exactly right in the carb than just tapping into the intake manifold.  There must be a good reason for it to be where it is.

Agreed. otherwise, why would they bother?
Steve

Offline John Washburn CLC 1067

  • Posts: 1145
  • Call me on my shoe phone 303+885-3545
Re: 1937 346 basic tests
« Reply #16 on: June 26, 2017, 06:34:58 PM »
Steve,

I am confused as always. Since you are running a later distributor with the vacuum advance and a later carburetor with the vacuum port on the base plate that is where the vacuum advances connects to.

If you look at the specs for 1940 and later (original vacuum advance cars, not including the trial in 36) you will notice that to set up for the distributor you need to have a certain amount of vacuum at different RPM's. If you run the vacuum line into the manifold you are negating what the vacuum advance is engineered to do.

Long story can send you the specs and we can chat, unless I am confused as to where you are getting vacuum to supply the advance for the distributor.

The Johnny

John Washburn
CLC #1067
1937 LaSalle Coupe
1938 6519F Series Imperial Sedan
1949 62 Series 4 Door
1953 Coupe DeVille
1956 Coupe DeVille
1992 Eldorado Touring Coupe America Cup Series

Offline Bobby B

  • Posts: 1470
  • Mendham, New Jersey
  • Name: Bob Bender
Re: 1937 346 basic tests
« Reply #17 on: June 26, 2017, 07:37:10 PM »
Steve,

I am confused as always. Since you are running a later distributor with the vacuum advance and a later carburetor with the vacuum port on the base plate that is where the vacuum advances connects to.

If you look at the specs for 1940 and later (original vacuum advance cars, not including the trial in 36) you will notice that to set up for the distributor you need to have a certain amount of vacuum at different RPM's. If you run the vacuum line into the manifold you are negating what the vacuum advance is engineered to do.

Long story can send you the specs and we can chat, unless I am confused as to where you are getting vacuum to supply the advance for the distributor.

The Johnny

John,
Hi. Good Reading......
This was the post I found on a MOPAR forum during a google search.

This was written by a former GM engineer as a response to a similar question on a Corvette board:


As many of you are aware, timing and vacuum advance is one of my favorite subjects, as I was involved in the development of some of those systems in my GM days and I understand it. Many people don't, as there has been very little written about it anywhere that makes sense, and as a result, a lot of folks are under the misunderstanding that vacuum advance somehow compromises performance. Nothing could be further from the truth. I finally sat down the other day and wrote up a primer on the subject, with the objective of helping more folks to understand vacuum advance and how it works together with initial timing and centrifugal advance to optimize all-around operation and performance. I have this as a Word document if anyone wants it sent to them - I've cut-and-pasted it here; it's long, but hopefully it's also informative.

TIMING AND VACUUM ADVANCE 101

The most important concept to understand is that lean mixtures, such as at idle and steady highway cruise, take longer to burn than rich mixtures; idle in particular, as idle mixture is affected by exhaust gas dilution. This requires that lean mixtures have "the fire lit" earlier in the compression cycle (spark timing advanced), allowing more burn time so that peak cylinder pressure is reached just after TDC for peak efficiency and reduced exhaust gas temperature (wasted combustion energy). Rich mixtures, on the other hand, burn faster than lean mixtures, so they need to have "the fire lit" later in the compression cycle (spark timing retarded slightly) so maximum cylinder pressure is still achieved at the same point after TDC as with the lean mixture, for maximum efficiency.

The centrifugal advance system in a distributor advances spark timing purely as a function of engine rpm (irrespective of engine load or operating conditions), with the amount of advance and the rate at which it comes in determined by the weights and springs on top of the autocam mechanism. The amount of advance added by the distributor, combined with initial static timing, is "total timing" (i.e., the 34-36 degrees at high rpm that most SBC's like). Vacuum advance has absolutely nothing to do with total timing or performance, as when the throttle is opened, manifold vacuum drops essentially to zero, and the vacuum advance drops out entirely; it has no part in the "total timing" equation.

At idle, the engine needs additional spark advance in order to fire that lean, diluted mixture earlier in order to develop maximum cylinder pressure at the proper point, so the vacuum advance can (connected to manifold vacuum, not "ported" vacuum - more on that aberration later) is activated by the high manifold vacuum, and adds about 15 degrees of spark advance, on top of the initial static timing setting (i.e., if your static timing is at 10 degrees, at idle it's actually around 25 degrees with the vacuum advance connected). The same thing occurs at steady-state highway cruise; the mixture is lean, takes longer to burn, the load on the engine is low, the manifold vacuum is high, so the vacuum advance is again deployed, and if you had a timing light set up so you could see the balancer as you were going down the highway, you'd see about 50 degrees advance (10 degrees initial, 20-25 degrees from the centrifugal advance, and 15 degrees from the vacuum advance) at steady-state cruise (it only takes about 40 horsepower to cruise at 50mph).

When you accelerate, the mixture is instantly enriched (by the accelerator pump, power valve, etc.), burns faster, doesn't need the additional spark advance, and when the throttle plates open, manifold vacuum drops, and the vacuum advance can returns to zero, retarding the spark timing back to what is provided by the initial static timing plus the centrifugal advance provided by the distributor at that engine rpm; the vacuum advance doesn't come back into play until you back off the gas and manifold vacuum increases again as you return to steady-state cruise, when the mixture again becomes lean.

The key difference is that centrifugal advance (in the distributor autocam via weights and springs) is purely rpm-sensitive; nothing changes it except changes in rpm. Vacuum advance, on the other hand, responds to engine load and rapidly-changing operating conditions, providing the correct degree of spark advance at any point in time based on engine load, to deal with both lean and rich mixture conditions. By today's terms, this was a relatively crude mechanical system, but it did a good job of optimizing engine efficiency, throttle response, fuel economy, and idle cooling, with absolutely ZERO effect on wide-open throttle performance, as vacuum advance is inoperative under wide-open throttle conditions. In modern cars with computerized engine controllers, all those sensors and the controller change both mixture and spark timing 50 to 100 times per second, and we don't even HAVE a distributor any more - it's all electronic.

Now, to the widely-misunderstood manifold-vs.-ported vacuum aberration. After 30-40 years of controlling vacuum advance with full manifold vacuum, along came emissions requirements, years before catalytic converter technology had been developed, and all manner of crude band-aid systems were developed to try and reduce hydrocarbons and oxides of nitrogen in the exhaust stream. One of these band-aids was "ported spark", which moved the vacuum pickup orifice in the carburetor venturi from below the throttle plate (where it was exposed to full manifold vacuum at idle) to above the throttle plate, where it saw no manifold vacuum at all at idle. This meant the vacuum advance was inoperative at idle (retarding spark timing from its optimum value), and these applications also had VERY low initial static timing (usually 4 degrees or less, and some actually were set at 2 degrees AFTER TDC). This was done in order to increase exhaust gas temperature (due to "lighting the fire late") to improve the effectiveness of the "afterburning" of hydrocarbons by the air injected into the exhaust manifolds by the A.I.R. system; as a result, these engines ran like crap, and an enormous amount of wasted heat energy was transferred through the exhaust port walls into the coolant, causing them to run hot at idle - cylinder pressure fell off, engine temperatures went up, combustion efficiency went down the drain, and fuel economy went down with it.

If you look at the centrifugal advance calibrations for these "ported spark, late-timed" engines, you'll see that instead of having 20 degrees of advance, they had up to 34 degrees of advance in the distributor, in order to get back to the 34-36 degrees "total timing" at high rpm wide-open throttle to get some of the performance back. The vacuum advance still worked at steady-state highway cruise (lean mixture = low emissions), but it was inoperative at idle, which caused all manner of problems - "ported vacuum" was strictly an early, pre-converter crude emissions strategy, and nothing more.

What about the Harry high-school non-vacuum advance polished billet "whizbang" distributors you see in the Summit and Jeg's catalogs? They're JUNK on a street-driven car, but some people keep buying them because they're "race car" parts, so they must be "good for my car" - they're NOT. "Race cars" run at wide-open throttle, rich mixture, full load, and high rpm all the time, so they don't need a system (vacuum advance) to deal with the full range of driving conditions encountered in street operation. Anyone driving a street-driven car without manifold-connected vacuum advance is sacrificing idle cooling, throttle response, engine efficiency, and fuel economy, probably because they don't understand what vacuum advance is, how it works, and what it's for - there are lots of long-time experienced "mechanics" who don't understand the principles and operation of vacuum advance either, so they're not alone.

Vacuum advance calibrations are different between stock engines and modified engines, especially if you have a lot of cam and have relatively low manifold vacuum at idle. Most stock vacuum advance cans aren’t fully-deployed until they see about 15” Hg. Manifold vacuum, so those cans don’t work very well on a modified engine; with less than 15” Hg. at a rough idle, the stock can will “dither” in and out in response to the rapidly-changing manifold vacuum, constantly varying the amount of vacuum advance, which creates an unstable idle. Modified engines with more cam that generate less than 15” Hg. of vacuum at idle need a vacuum advance can that’s fully-deployed at least 1”, preferably 2” of vacuum less than idle vacuum level so idle advance is solid and stable; the Echlin #VC-1810 advance can (about $10 at NAPA) provides the same amount of advance as the stock can (15 degrees), but is fully-deployed at only 8” of vacuum, so there is no variation in idle timing even with a stout cam.

For peak engine performance, driveability, idle cooling and efficiency in a street-driven car, you need vacuum advance, connected to full manifold vacuum. Absolutely. Positively. Don't ask Summit or Jeg's about it – they don’t understand it, they're on commission, and they want to sell "race car" parts.

                  Bobby
1947 Cadillac Series 62 Convertible Coupe
1968 Mustang Convertible
1973 Mustang Convertible
1969 Jaguar E-Type Roadster
1971 Datsun 240Z
1979 H-D FLH

Offline 35-709

  • Posts: 2680
  • The most valuable antique is an old friend.
  • Name: G. Newcombe
Re: 1937 346 basic tests
« Reply #18 on: June 26, 2017, 08:47:33 PM »
Great stuff!
1935 Cadillac Sedan resto-mod "Big Red"
1973 Cadillac Caribou - Sold
1950 Jaguar Mark V Saloon resto-mod

Offline The Tassie Devil(le)

  • Administrator
  • Posts: 7198
  • Name: Bruce Reynolds
Re: 1937 346 basic tests
« Reply #19 on: June 26, 2017, 09:32:54 PM »
Thanks Bob,

It reinforces my use of full manifold vacuum on my cars, after I have removed the Anti Pollution Controls.(no need for it down here, as we don't have pollution testing stations, anywhere), plus all our pollutants end up over in New Zealand, but that is another story.

Bruce. >:D
'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'55 Buick Special Post Coupe (LHD)
'74 Chris Craft Gull Wing RHH
(Past President Modified Chapter)