Timing Question - 262
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heres what i do I use a vacum gauge turn dist to highest vac reading and see how it runs, i have found that i get a littel starter kick back at full vac when motor is a runnig temp so I decrease vac -2 lbs, you can fine tune to what works for you you can lern alot about your engine with a vac gauge read up on it, your engine tells youwhat it needs. Dan.0
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I had tried the vacuum method initially with this motor but I didn't trust the readings since the dizzy position didn't seem to be close using the two methods. I'll give it another go because it seems like the vacuum method is much easier and more reliable. Thanks!0
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Hi Ken - Yes, I have all of the documentation....bored 30 over, 10 under mains, new valves, seats ground new guides, new cam bearings, new chain, oil pump gear as well as some other odds and ends. I haven't checked the lash but the leak-down tests I performed didn't signal any issues.The twin h has the proper intake and carters for the 262 and they have been rebuilt and synchronized. I'm fairly certain I have the Hudson built 4.11 rear.Ken U-Tx said:50ClubCoupe said:I have a hunch that my curve is off since the engine seems to be revving pretty high at 55 mph. Thanks in 'advance!'
You have a three speed non overdrive tranny, and the standard rear axle for that was 4.11:1 . That equates to about 2700 rpm at 55 mph. The distributor advance does not change engine rpm, if that is what you are implying....... Your car may even have a 4.55 rear axle, which would push the rpms at 55 to about 3000.
This engine is supposedly "rebuilt". Do you have documentation of what all was done, replaced on it? Did it get a new timing chain? Did it get a new bronze distributor drive gear? Are the valves all set to correct lash? There are many other things that can make it feel weaker than it should be. How about the Twin H's two Carter WA-1 carbs, are they rebuilt and synchronized? Out of synch Twin H carbs can adversely affect performance.I appreciate your note on the rpm at 55 mph. I'll see if I can rig a tach somehow (mine is digital and has to be close to the dizzy) to see what I'm running at 55. I understand the distributor won't change the rpm....I was implying that the motor is working harder (higher rpm) to produce power when the advance isn't correct. There may be nothing wrong with the setup, I just don't have a reference point. I was expecting a little more punch on acceleration due to the twin h but maybe that's just do to the car being 4,000 lbs.One last suspicion I have is my head gasket. I've been getting some seepage around the perimeter but I've been torquing the head and it's helped. I'm not losing any water and she's not bubbling through the rad so I don't think it's an issue but I ordered a new head gasket from Dale last night to have on hand.0 -
".......the dizzy position didn't seem to be close......"
Although timing is the question here, I'm still curious about this statement. If you are unable to get the distributor to rotate within it's normal range of the slotted attachment plate, the oil pump may be installed a tooth or two.....or three, off of the designed position. Did the individual who installed the pump realize the significance of the pump-shaft position as it relates to the camshaft? The distributor should be approximately in the orientation shown in the MPM (the book to which Ken referred).
The attached images are rotated into the actual position you should see on the engine as in the photo on the left.
Sure.......one can re-arrange plug wires on the cap to make almost any arrangement work but I'm a fan of starting where the book shows it. Have a look and see if it's a match.
F
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4009A...new points, condenser, gapped myself....not my first rodeo. I stated I was checking the vacuum and mechanical advance mechanisms in my original post. I have the manual with above listed information and I also referenced the information on Ken Cates' site which led to my original ask of having the advance in reference to crank rpm, not in Hg. Didn't mean to waste anyone's time.0
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I had a similar problem with rebuilt engine & carbs w/Pertronic igniition. My issues & solutions were: 1- Pertronic timing isn't always the same as stock distributor, adjusted timing to max vacuum retard 2 degrees. 2- valves were to tight gap close up at high speed, Got help to increase valve clearance.003" more than book. 3- twin-h carbs out of sink. Adjusting carburators so uni-syn bubble was at the same height on both carbs. The first attempt was a very time consuming frustrating experienceg back and forth rpm & balance carbs multiple times to get it all right made a significant difference in power and drivability. The Pertronic was telling me the timing was ok but vacuum was way down and very poor power. That's when I used high vacuum reading to get power back. I didn't notice much difference after replacing bad vacuum advance with good one. Probable help improve mpg a little. Stock valve adjust it would run ok around town but when exited freeway after a 50 mile trip to club chapter meeting it would not want to keep running until the engine cooled down. Ran great after opening valve gap a little after that. I hope this is helpful Lee O'Dell ,0
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Excellent, thanks so much Lee....it seems to be a consensus that timing via vacuum gauge instead of the light is more accurate. I'll give it another go after I install the Pertronix and double check the vacuum advance. If I don't see an improvement I'll move on to the tappet adjustment. As I understand it, the ported vacuum that feeds the advance is only used for idle/low rpm and decreases as engine speed increases. If my vacuum unit is malfunctioning that may cause the difference in crank position that I noted between the vacuum and the timing light tests. Using straight vacuum should identify the issue. If my timing marks stay static with the advance connected and disconnected I know I've got a bad unit which would cause my low idle to be off and then affect my entire range since the mechanical would be too far retarded.Frank - My distributor had enough travel to get it close to where #1 should be but it's currently situated somewhere between #1 & #4 in the picture. I had referenced that photo and Ken's site (in additional to the manual) when I pulled the distributor after installing the motor (other issues) and I noted that it said to not be too concerned with the exact positioning so I just moved all of my plugs counter-clockwise one position. I probably have enough travel to get it closer to the reference picture but I've left it for now. Also, I know the engine shop was very reputable but the owner that had it rebuilt has since passed away so I can't verify they knew what they were doing but, based on everything else I've seen and checked, they did things by the book.0
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50-I agree with Lee, above. Experienced same issue with Pertronix. Book's a starting place, but vacuum was out of whack, along with timing not being at dead center. Muddled the problem more with a hot cam. Timing has to be quite advanced. Balancing carbs IS a test of one's patience, trying to get the balance right along with the rpm and good vacuum. In the end, my car is not a great idler, it wants to go and that's probably more the cam than the timing. Once it gets a load, it's a strong runner, though. Back to your original question, I believe the Pertronix wants more advanced timing. Also, the jury is still out, but it is my belief that modern gas also requires a little more advance.As you know, don't be too retarded on your timing or your plug issue, along with overheating/superheating can cause serious problems.0
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The TDC initial timing spec in the book is based on the assumption of using 1950-vintage Octane ratings which require less advance. The catalysts in modern, higher octane fuels (meaning higher than fuels of 1950) make them burn more slowly and thus want a slightly advanced timing over the book spec. I've found that 6 degrees initial timing works best in our Hudsons, a 212, Hornet and Jet.
The latter two have a Pertronix conversions but I see no difference in timing. Since the timing is the relationship between crank position and the point at which the spark occurs, it doesn't matter what kind of triggering device is used. TDC is still TDC, 6 degrees is still 6 degrees.
Explain?
F
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Thanks to both of you...everything you've stated makes sense and I hope to get some time with the car this weekend to reattempt the vacuum method. The car seems to run decent without any overheating issues (never above 175*) and she's getting right around 13.5 mpg with the twin h so it's probably pretty close but she just feels like she's got a little more power to give. I'll start out with a 6* advance and see how she reacts and then adjust from there.Russell - I recently saw a pic of your nostalgic racer and it looks awesome. I'm hoping to do a similar theme with mine in the near future.Scott0
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Just to give this thread some closure…..I had some time on the car last night and used the vacuum gauge method to set the initial timing. Boy, what a change!! She seems really happy now and I've got good pedal response, power and she's running slightly cooler too. I have no idea what advance degree she is currently running but my UTC mark is essentially right in the middle of the view hole, instead of aligned with the "pointer" while idling at 550-560 rpm. I also used the vacuum gauge to dial in the carbs and that also worked well….it was much more sensitive to adjustments than I imagined so it gets it pretty close.After installing the Pertronix (kit 1362P6), adjusting the advance, re-sync'ing the carbs, replacing the u-joints/carrier joint and dialing in the carbs she's running great and she's happy at 55mph. I still need to adjust the linkage a little bit to provide more pedal range but she's fine for now. Now it's on to fixing the dash lights and installing the new fuel sender!Thanks to all for the help and guidance.0
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Working with the EFI conversion and translating the factory specs to the computer controlled timing table, I have found a lot of difference between what an engine likes and what the specs are.
Some basics:
Base timing- is the distr setting.
Mechanical advance- is the fly weights in the distr and are rpm dependent only. The faster it spins the more advance you get.
Vacuum adv- is only applied at part throttle. An engine does not have any vacuum in the manifold at wide open throttle(WOT). It doesn't matter if it's ported or manifold vacuum. See below.
The rebuilt 308 I just completed the EFI tune on would only take a few degrees more then the factory specs. I run the idle timing at about 4-5*, wide open throttle (mech adv equivalent) right at 20* and light throttle, Mech+vac adv=33*
If you look at the factory specs above
Mech = 18*
Vac = 7.5*
Base = 0*
So light throttle total = 25.5* max/ depending on the rpm.
If you bump the base timing 5* then that adds to the mech adv and the total adv numbers.
I've tried to find the specs for the lines on the flywheel and based on measuring it, it seems like each line would be about 2-2.5* per line?
Now my old used 49 262 won't hardly even run with those timing specs. The compression is 90psi across all 6 cylinders. I have a 54 cam in it.
For it I run my idle timing at 15*
WOT=32*
light throttle =43*
Keep in mind that I have much more flexibility in setting up my timing curve with EFI.
A couple notes about the different types of advance used for an engine.
TIMING
Choosing a vacuum advance port is like choosing IH or chevy.
They both accomplish the same thing just a little different.
First you need to make sure your distr is working correctly
Read this entire thread before just setting the timing.
Vacuum adv does not add power. It is designed to add part throttle drivability. When you are at full throttle there is no vacuum, so there is no vacuum advance so it can't affect full power. Large trucks and boats do not run vacuum adv due to the nature of how they run. They are either at idle or under a heavy load where there is no vacuum.
Ported vs manifold vacuum
Ported vacuum is applied above the throttle plate in the carb so it only has vacuum as you start to add rpm. Then as you go wide open throttle it decreases again to nothing.
Manifold vacuum is applied below the throttle plate so max adv is applied at idle and then it decreases to 0 as you increase throttle.
So the only real difference between the 2 is the amount of timing applied at idle and just off idle. After that, the lines meet and the timing applied is the same.
So any difference at all that may be noticed would be the just off idle pick up on very light throttle. Stab the throttle and you have no vacuum with either.
If all is good in your distributor then you can move on to the timing.
Timing is set with the vacuum line disconnected. So it makes no difference which vacuum port you use.
If your engine runs fine with 10* additional timing from what the factory manual states, then that's fine.
1. Disconnect vacuum line and plug.
2. start engine
3. make sure engine rpm is low so no mech adv is working yet. If the timing lowers as you lower the rpm then there is mech timing being applied.
4. set timing to your preferred setting or start with the factory setting.
5. chose your vacuum port.
If you chose manifold the your timing is going to jump by the amount of advance in the vacuum canister.
This will now raise your idle speed so you will now need to lower it back to the factory spec.
Ported will not affect idle speed.0 -
Bill,
You are correct that the timing marks on the flywheel represent ~2.5 degrees each. See attached.
F
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Thanks for the confirmation Frank.
To me it's all subjective when you can't even get a good line of sight with the timing light.
You can change your view angle and change the timing 10*!
I think that's why the manual says to just perform the old power time method by doing a slow roll in 3rd gear and press the gas. Advance timing till it just pings.
Sort of takes all reference to the marks completely out of the picture.
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Problem with that method is the vastly higher Octane rating from when these cars were made. I still use the "ear-ometer" for tuning, particularly the vintage years. Essex ignition states to advance until engine knocks at 10 m.p.h. at wide open throttle - not very exact with modern fuel!0
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This extremely useful Discussion should really be highlighted in the "Skills, mechanical, and other wise" category.
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