Posted: Wed May 20, 2020 6:36 am Post subject: Timing an M38 with a vacuum gauge std engine 134 Flathead
Hi my M38 has been timed the normal way.
Check point gap with feeler gauge when breaker lever on high point of cam.
Turn engine over and on compression stroke and aline pointer with 5 degree TDC. Checked with Vac gauge and finger even a balloon for good measure.
Turn distributer anticlockwise until points closed then back clockwise until points start to open. Rotor should point to No. 1 position. Yes it does. Tighten clamp.
Set up timing light and adjust distributor until the timing marks line up.
Tighten clamp.
Went for a run, okay but seemed lacking power.
All okay so far I think.
Did a check with the Vac gauge and it reads 17Hg and normal motor.
I moved the distributor clockwise a few degrees and the revs increased, sounded smoother and the gauge went to 20 Hg, I backed it off 1 Hg and went for a run.
Went the best ever ,but on return I put the timing light on and it was miles out,about 13 advanced at 700 rpm.
Not wanting to damage anything I would ask if I am doing anything wrong?
On the Vac gauge instructions it does talk about on old engines it is difficult to get reliable timing from the original guidelines.
As a tool it is very easy to use but how accurate on my timing not sure.
Comments would be appreciated. _________________ 1952 M38
Vacuum gauge timing is for the old muscle car era where easy starting, and no pinging were not on their priority list. It is a technique used to squeeze all the juice out of your 134 giving great top end performance and ignoring startability and engine longevity. The choice is yours but if you want that performance level that can be very damaging to your 134 why not just get the right engine for the job. A V-6 is the best all around performer with the running gear these jeeps have. The V-8's dictate an upgrade in tranny, transfer and axles since the original jeep equipment was meant to be used with 60 or 72 HP L or F 134's. All the choices are your. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Listen carefully for any indication of pinging. I time all of my MVs (gas ones at least), with a dwell meter followed by the vacuum gauge. I do it exactly as you do. Ive been doing this since the sixties and I have yet to loose a single MV engine, other than to high miles on the freeway, and that was just a need for a rebuild, not a failure as such.
When I go to meets I just shake my head at the guys who seem to be in a competition for how long they can crank their Jeeps without them starting. They all tell ya, that they are tuned "by the book".
The carb is as important to easy starting and great running as anything else.
All of my MVs (Willys, Ford, Dodge and White) start instantly hot or cold. No cranking, just touch the starter and they are running. _________________ '52 Dodge M37, '42 GPW, '48 FrankenJeep CJ2A/M38, '50 CJV-35(U), '51 M38, '42 WC-57 Command Car, '44 WC-51 Weapons , (2) M1941 Sperry 60" Anti-Aircraft Searchlights, John Deere M-gator, '44 White M3A1 Scout Car
When we used to play with Hot Rods we tuned them using the poor mans dyno.
Get them warmed up and ready to go. Start the engine. Run the idle up high, then pull out ever other plug wire (so the engine is only running on half of its cylinders. Using a tach run the rpms up to where the advance is full in, then adjust the distributor timing for highest RPM's. shut it down and return the idle setting and plug wires to normal. Worked great! _________________ '52 Dodge M37, '42 GPW, '48 FrankenJeep CJ2A/M38, '50 CJV-35(U), '51 M38, '42 WC-57 Command Car, '44 WC-51 Weapons , (2) M1941 Sperry 60" Anti-Aircraft Searchlights, John Deere M-gator, '44 White M3A1 Scout Car
Just an opinion, but the Military carb is not a performance part, it had other tasks that it had to do, like run under water. The Weber is probably far more tunable than the stock M38 carb. But even with the stock carb they can be made to purr. _________________ '52 Dodge M37, '42 GPW, '48 FrankenJeep CJ2A/M38, '50 CJV-35(U), '51 M38, '42 WC-57 Command Car, '44 WC-51 Weapons , (2) M1941 Sperry 60" Anti-Aircraft Searchlights, John Deere M-gator, '44 White M3A1 Scout Car
The YS637S had another feature important to jeeps. It's ability to operate smoothly irregardless of the jeep's relative angle to the ground.
Notice in my original reply I did not say it was a bad way to time your jeep. I said it can result in some bad things. If you believe you are a super knowledgeable mechanic and it works for you great. If you do not feel comfortable or confident timing that way then do not do it that way. And although not mentioned here a few degrees advance is a good thing with modern 80 plus octane fuels. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
That is the only way I time engines; using a vacuum gauge and my ear. Never fails to make them run better than using the timing marks. I do not even own a timing light!
You broke the code on how to do it. _________________ M38 23100 June 51
M38 34523 Sep 51
M606/CJ3B 1964 Kaiser 57348 118458
M37B1 1963
Willys MB 1944
Ford GPW 1942
Dodge WC63 1943
Dodge Power Wagon WM300 1967
Plymouth Barracuda, 1973, 340 4 barrel
All ground up restored by me.
Lots of others.
Another fan of the Vacuum gauge, just need to train my ear for a few years.
I am going to advance the std 5 BTDC to 8 degrees as Wes suggested for modern petrol. Will see how she sounds/runs then as it will be part way between the two systems of timing the motor. May be a happy compromise. _________________ 1952 M38
So she is now set on 8 degrees advanced with the timing light and then set base idle with the Vac gauge(better than my novice ear) best reading 18.5Hg.
Went for a run out and happy with the results, runs well with hopefully no engine explosions.
Thanks for all the input. _________________ 1952 M38
Joined: Mar 08, 2020 Posts: 60 Location: SW Wisconsin
Posted: Fri May 29, 2020 4:11 pm Post subject:
dpcd67 wrote:
That is the only way I time engines; using a vacuum gauge and my ear. Never fails to make them run better than using the timing marks. I do not even own a timing light!
Well this explains a lot... I can name 1 Jeep where your method failed.
You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum