The Stovebolt Site Forums The Shop Area Engine Shop tune up help 53 GMC

I thought the information would be easy to find on-line but its proving more difficult then it should. I have a 53 GMC that I want to find the Dwell/point gap specs (I have found between .016 to .022) and 26degrees to 33degrees. I know these number are all close but what should I use.
Second, Ignition timing. I think I found that it should be 5 btdc at 600 rpm. Is this with the vacuum hooked up or not. Then I'm reading posts about 3450rpm and timing should be 32.5-39.5.

Can someone simplify this for me or point me to a web site?

thank you in advance (design)

Pletch,

What size engine do you have in your 1953 (New Design) GMC? Your profile says you have a 1953 GMC 3100?

If you have 1953 GMC 1/2 ton long-bed (model 102-22, I think), I think the standard GMC engine was a 228?

Tim

Sorry for this bit of important info. It is a 228 Long bed 1/2 Ton.

Pletch,

I cannot find tune-up specs for a 228 on Rob English's oldGMCtrucks website; however, I'm dumb enough to try to answer your questions (and, I hope and I know that someone will correct my errors - I just hope it comes from a GMC person who knows the 228):

1. "Dwell/point gap specs (I have found between .016 to .022) and 26degrees to 33degrees. I know these number are all close but what should I use."
-> Go for the middle number; but, if you have new points, use .022" and check the setting(s) after 500 miles (many people reset every 1,000 miles thereafter).

2. "Ignition timing. I think I found that it should be 5 btdc at 600 rpm. Is this with the vacuum hooked up or not."
-> I do not think that you need to worry about the vacuum hook-up but I am not certain about any/all 228 carburetors: WHEN IN DOUBT, it never hurts to disconnect the vacuum line to the distributor and plug the line on the manifold side of the line. My uninformed understanding of the 228 timing is to set the distributor so that the clutch-housing-pointer points to the "U" on the flywheel. I hope someone with a late 228 will confirm or correct.

3. "Then I'm reading posts about 3450rpm and timing should be 32.5-39.5."
-> I do not know what this means. Maybe this is referring to total ignition advance at 3450 rpm? Someone else can address this one (and split a few hairs)

Tim

Pletch,

I have the shallow distinction of having a non-running 228 in my GMC 52 pick up.

If you use Tim's link to the GMC website and click on the links, you will find that info for the 228 is also included, even though they say "248-270".

So, from the site..

Dwell/Point Gap specs .016-.021" 38-45 degrees

Initial Ignition timing point is UDC (upper dead center) for the 228 and 248 and
5 deg BUDC for the 270. I believe the mark reads "UC" on the flywheel.

I believe all readings are with the vacuum hooked up.

From p 173 from the GMC site, under ignition system it shows maximum centrifugal advance for the distributor is 10-12 deg. at 1475 rpm and then a footnote that states these are one half of the engine degrees and engine rpm. (Maximum advance in engine degrees is 20 deg.) Perhaps this answers your last question.

Hope this helps, you'll have to excuse me now it is 60 degrees outside on this 5th day of Jan. in Kansas. Too rare to not enjoy.

OK...

I think I got dwell/point gap where I want it. Now here is my next problem.
I got it timed 700 rpm, the pointer is at the "o". It runs perfect... but it is hard to start only when its warm. Any suggestions?

Congratulations on getting it going.

Just for the record, the "o" is the 5 deg BUDC mark.

Your timing marks should look like this:

U I C o 5

The mark between the U and the C is UDC or TDC if you like.

The 5 refers to the "o" mark.

Hopefully someone with more experience can answer your question on starting
when warm.

I may have found the problem when starting warm. When the engine is warm I have not been touching the gas pedal at all. If I give the gas pedal a pump or two it will crank over a few times then start. I'm assuming this is normal. Is it?