The Stovebolt Site Forums The Shop Area Engine Shop TIMING DEGREES BTDC 1955 235

Hello, I have a 1930 Chevy 1 1/2 ton with a 1955 235 under the hood. Now I know about the timing ball but that does not apply here. I have modified the flywheel from the 1930 194 so it's bolted up to the new motor this way I'm able to use the 1930 trans and drive train.

So my question is, what would be the degree before top dead center that would be correct?

Also at what RPM should the motor be turning when setting the timing?

Now I have a mark on the flywheel setting TDC also a mark on the crank pulley.

So I just need to know the best RPM and degrees to set the timing at.

Thank you, Mike

Try using a delay-flash timing light and begin with an initial timing setting of 5 degrees before top dead center. Set the idle speed at 500, and set the light delay at 5 degrees, and align the TDC mark you've made on the flywheel with whatever reference pointer that's on the bell housing. Then you need to check the centrifugal advance. With the vacuum line to the advance unit disconnected, hold the engine at a steady RPM of around 1800-2000 and dial the mark back to zero. There should be around 20-25 degrees of advance at that speed. Then reconnect the vacuum line and rev the engine up again. There will probably be around 30-35 degrees of total advance with initial, centrifugal, and vacuum added together.

Jerry

Would it be the same process for a stock 228 ? I can't find the marks on the flywheel and mine has a Petronix electronic ignition.

It would be hard to run fast enough to give me a Pertronix system, so I can't offer any opinion on how to test one. You'll need to establish TDC and make your own pointer and timing mark if there's not an obvious way to establish when a piston is exactly on top. Once that's done, the delay flash light can be used to test all the above functions.
Jerry

Jerry,

Thank you for your response I believe this is the info I need to get started. The flywheel has the factory timing mark on it an sense I'm using the original mating bell housing it all matches up. When I made the adapter plate so I could bolt the 1930 194 flywheel to the 1955 235 motor I made sure I had it clocked correctly so I could time. But I just couldn't find the degrees BTDC or the RPM's for timing. As far as a vacuum line I don't have to worry about that. I was able to remachine a MSD distributor an install in my 235 so now I have an all electric fire. I will work on the truck over the next few days and I will update you with my progress.

Again thank you, Mike

Mike, the only additional thing I'd suggest doing is using a "positive stop" to be sure the TDC mark is accurate. Use an old spark plug shell with the porcelain removed and a piece of 3/8" all-thread rod a couple of inches long tapped into it. You'll need to put about a 45 degree angle bend into the rod and secure it with a jam nut so it points straight down once the plug shell is screwed into the head. Turn the engine slowly by hand until the piston stops against the rod, mark the flywheel at the pointer, then turn backwards to the stop point and mark again. TDC will be exactly halfway between the two marks, which is where the ball should be if your indexing of the bolt holes in the flywheel is correct.
Jerry

I am getting ready to start my 235 and found this thread in a search. I got a HEI distributor from Tom Langdon and said the initial lead is 20 degrees. He said the 235 with a stock cam likes 30-32 degrees advanced which would be the initial plus 10-12 with a timing light.

Is a delayed timing light the only way to do this? There are no indicators on the flywheel except the little ball and the triangle that precedes it. Does anyone know how may degrees the triangle would be advanced from the ball?

I have wasted literally billions of electrons trying to give people advice, which they promptly ignore. Once anything in a stovebolt ignition system gets modified, the wrench jockey is on his own regarding setting the timing, and there are plenty of self-appointed gurus who will be happy to give you reams of advice that doesn't make good nonsense. Different years and engine sizes have widely varying flywheel markings, and using the above "positive stop" method of establishing TDC is step number one. Any attempt to skip that step means you're shooting in the dark. My email is in my profile. If you'd like to have a discussion of ignition timing off the main forum, please email or PM me and I'll share a phone number. A 2-way conversation can accomplish more in a few minutes than a couple of dozen written messages can. That's why I spent 30-something years in a classroom, putting the next generation of auto mechanics out there.

The advice you've gotten about initial timing is a good example of insufficient, or downright incorrect information. If you use an initial timing of 20 degrees before top dead center, keep a fire extinguisher handy for the inevitable backfire and carburetor fire. 5-8 degrees of initial advance is much more appropriate.
Jerry

Wasted electrons Jerry , I think not.
I'm sure there are many on this site like myself that read these articles without commenting due mainly to a lack of expertise , but we read and absorb all that we can to be used at a later date as needed.
You might never know how helpful this info is to us fence sitters!!
Keep up the good work

Thanks John

I agree, 20° BTDC is too much for an engine with mild cam timing. This will kick back and fight the starter, and "pop", and (unless the advance curve is slow) ping on hard acceleration at low speed.
Typically, between 5-10° is closer to what the engine wants.
With significantly longer cam overlap more advance will help idle quality and tip-in response. Overlap does not completely "flush" the chamber at low speed, and the remaining exhaust gas slows down combustion.

The typical 2403 Delco distributor gives about 12-14 distributor degrees of mechanical advance so the motor sees 24-28, with 24 being the more common. So with a stock distributor, if you wanted to get to 30 degrees advance total, you would set it at 6 -8 degrees of advance (at the flywheel) and yes, a dial back light is pretty handy. Now all of that centers on how accurate your flywheel bb is.

You put one of tom Langdon’s v6 hei distributors in. So you will need to sort out total mechanical advance for that distributor. If it’s 20 total (that is 10 degrees at the distributor) then you can easily get 6-8 initial and tinker from there to see what your motor likes. 10-20 is a lot for a stock motor so I would not start there. just go slow and bump it until the motor tells you it’s to much.

I didn't see what distributor you are using (OEM or Aftermarket) but having the specs for a typical 216/235 engine may be helpful. My experience has been that greasy 65 year old OEM distributors don't provide full mechanical advance (measured in "engine" degrees) and should be checked and cleaned.

The 216/235 engines have poor combustion chambers for high compression and high RPM. They are low speed, low compression, high torque engines running on poor fuel when new. This combo requires a lot more advance than what we usually think is required. To this point I believe the original specs for 1950-51 235, car or truck, is as follows:

Distributor 1112358 & 1112363
Mechanical Advance (engine degrees)
2° @ 600 RPM
12° @ 1400 RPM
33° @ 3700 RPM

5° initial + 33° mechanical = 38° total when fully wound out at 3700 RPM (not counting vacuum advance)
(Same vintage 216 would be 5°+38°=43° at 3400 RPM)

I would suggest you start there with original 235 initial+mechanical curve. Later tweak for your cam/carb combination from that point.

Paul

Blue flame 235 engines did not have near that much timing:
straight up at low idle and 28 crank degrees in the mechanical running on [censored] for gasoline,
Most can run 5 degrees initial lead on regular gas though, more on premium.
Run them to they start to pre-ignite and back it down two degrees or so and you are golden.

Tom said the initial is 20 in the distributor and that the engine should like 30-32 total. Means I should have 10 advance at the flywheel. Just trying to figure out where ten is in relation to the bb

Depends on the flywheel, check this link out:
http://chev235guy.blogspot.com/search/label/Flywheel%20Timing%20Marks

There are two with balls on the flywheel. One is set at 2 degress after top dead center(retarded), that flywheel came off a blue flame 235, believe 55 and later, the other is more commonly found on 216 engines and is 5 degrees advanced or before top dead center,
The third is straight up.

Link courtesy of Pre 68 Dave

For others coming later to this thread I am posting info I have found for the late 1112403 distributor. Pay attention to "distributor" degrees versus "engine" degrees, don't get them confused.

http://restorecarsclassifieds.com/wiki/articles.php?n=161 “Page #0854"
NOTE: Listing for 1959 6 cylinder cars. Latest distributor 1112403 for service or retrofit.

IGNITION
FIRING ORDER: 1-5-3-6-2-4.
SPARK PLUG GAP: .035".
Spark Plugs - AC No. 44.
COIL: Delco -Remy 1115120.
Ignition Current: 1.8 amps, idling, 4.0 amps, stopped.

Resistor - Resistance type cable used in harness between bulkhead disconnect plug and starter solenoid bypass terminal (in coil primary circuit for regular operation). Bypassed during cranking when coil energized directly from starter solenoid bypass terminal. (resistor is for 12V system)

DISTRIBUTOR: Delco-Remy 1112403.
Condenser - Delco-Remy 1928111. Capacity .18-.23 mfd.
Contact Point Set - Delco-Remy 1924571.
Breaker Gap - .016".
Cam Angle - 28-35° with .016" gap.
-BREAKER GAP CAUTION: Manufacturer recommends final check with feeler gauge or dial indicator if dwell meter used to set points.
Breaker Arm Spring Tension • 19-23 ozs.
Rotation - Clockwise viewed from above.

Automatic Advance (mechanical)
Degrees----Distr.-----RPM-------------Degrees----Eng.------RPM
0-2°--------------------375----------------0-4°------------------750
4-6°--------------------700----------------8-12°-----------------1400
9-11°-------------------1350--------------12-14°----------------1750
18-22°------------------2700-------------24-28°-----------------3500

Octane Selector: Adjustment on distributor provides 10° spark advance or retard from center "0" position.

Vacuum Spark Control: Delco-Remy 1116140.
Vacuum Advance
Distr. Degrees-----------------Eng. Degrees---------Vacuum (" of Hg)
Start-----------------------------0°---------------------4-6"
10-12°---------------------------20-24°----------------15-16"

IGNITION TIMING Setting - 5° BTDC at idle speed with vacuum line disconnected.

NOTE - Supersedes previous specification of TDC and will give better economy. Timing Mark - First short vertical line on flywheel, clockwise from steel timing ball (TDC) insert. Line
up with pointer in inspection hole in right front face of housing with Octane Selector set on "0".

Paul