Need Help Timing a 270

[renovate7]

I'm trying to time my 270 in the DUKW. The TM9-802, pg. 201 #C, says to lower the rpm to 350 so the centrifugal advance hasn't kicked in, and align the ball on the flywheel with the needle. The ball is set at 5 BTDC. The power plant manual TM9-1802A, pg. 238 section 130/B/5, says to have the engine running at normal idle rpm, which is 510 rpm, big difference. Any ideas?...Assuming it's supposed to be the 350 rpm, which my vehicle won't idle at, the 1802A, pg. 218/Data/Centrifugal Advance, says there should be 2 degrees of advance at 400 rpm and 10 degrees at 800 rpm. Interpolating I get 6 degrees at 600 rpm, which I can idle at quite nicely. My timing light allows me to advance the timing flashes. If I set it to 6 degrees of advance this will put the ball under the needle at 600 rpm. Correct?...The 9-802, pg. 202 #2 at the top, also says to advance it another 3 degrees if your using fuels over 75 octane, which we are. This would put me at 9 degrees of advance on the light, at 600 rpm..I talked to an expert this week who says they "time them by ear", turning the distributor by hand to get max rpm and then retard it about 3 degrees, anyone do it this way?...If anyone has expertise in this I'd really like to talk to you by phone, please PM me your number. Thanks Hank in FL

 

[saddamsnightmare]

July 3rd, 2015.


The "Time by Ear" method worked for the Model T, Model A and a lot of other vehicles. If you look at an old Ford T or A shop manual, they will give you the distributor setting information. BUT on a Massey Ferguson MF65 Gas tractor, the set by ear and back off 3 or 4* worked very well at getting the maximum power output on the least gas consumption, so find a really old respected auto mechanic to show you how if you have concerns about doing it right.

That's the nice thing about these primitive gas engines, you don't need a computer to get them running, only common sense and common tools. Good Luck!

 

[elkhtr]

The old school method was to advance the timing, then test drive under load (high gears on hill) until it pings. Then back off a little. This will be max horsepower on the fuel you are currently burning. Raise the octane and you can get a little more advance.

 

[renovate7]

I ended up timing it by ear. I set the idle mixture screw until I had max vacuum, I think it was 20-21, well in the green zone. I turned the distributor until I got max rpm, then backed it off a bit. I was able to get the rpm's to go from 600 to 750 just by turning the distributor, without adding any more gas (rpm screw or idle-air screw). I backed it off until it was running 700 rpms. That tells you how rich I was running. I now also don't have the dieseling on shut off problem, that's what started my timing quest. I do let it idle for a few minutes after returning from a run and then it just turns off, like it's supposed to...I can't tell you how valuable my new timing light was. It gives rpms in a little window in the back. No more separate tach and dwell gauge. I ran the tach of a spare 12v battery I have.

 

[dmetalmiki]

The method you have used is the best way on those vehicles, and you seem to have got it just right. As said previously, if it does not ping in high gear pulling, or on hills then your fine.