Langdon HEI Dizzy SPECS???

[Powerhouse]

Howdy all,

I am still waiting for a reply from Langdon on what the advance specs are on the HEI he sells. I need to know what the centrifugal and vacuum advance operation rpms/degress are . When they start to function and when they stop in degrees. I know how they work, just not when. I cannot get a clear reading on mine. The timing light jumps around a little at higher rpms.

The dizzy is from a 1983 GMC S15 Pickup - 173 V6 2.8 L

ANYONE have a spec sheet on this thing. I am trying to find out when the advances function.

[martybose]

I don't have a spec sheet, but I can tell you what mine does. All references are to engine RPM and crankshaft degrees.

The centrifugal advance starts at 1300 RPM and adds 13 degrees by the time it is all in at 2800 RPM.

My vacuum advance adds 19 degrees at full advance.

Unlike most, I run manifold vacuum as a source, with 3 degrees static timing, so I have 22 degrees at idle and 16 degrees at full throttle above 2800 RPM.

Marty

[BeBop138]

This was one of the reasons I didn`t use his unit--it worked but I didn`t like how it was hard to time. The timing marks jumped around on the wheel---there were other reasons I don`t like his Hei. That being said the specs I remember were very close to what they were in---2.8V6. I think my 265 original specs are close to what the Hei is. That and changing the shaft makes it a quick conversion---I hope you work it out.......Lee

[Powerhouse]

Thanks much for that info! I didn't get a chance to check it out again last night.

Marty, what engine are those specs for? I just went back to an old post and see that you had a 230 with 9 to 1 compression, a mild cam, dual Carter-Webers and cast iron headers to full 2" dual exhausts. I pretty much have the same in my 218 but with a stock cam. I ma unsure as to what my compression is. I did take off .050 from my 47ply head.

Edited January 9, 2013 by Powerhouse

[martybose]

Thanks much for that info! I didn't get a chance to check it out again last night.

Marty, what engine are those specs for? I just went back to an old post and see that you had a 230 with 9 to 1 compression, a mild cam, dual Carter-Webers and cast iron headers to full 2" dual exhausts. I pretty much have the same in my 218 but with a stock cam. I ma unsure as to what my compression is. I did take off .050 from my 47ply head.

Yeah, that's my engine. I have a good timing light that lets me dial in an offset with a digital readout, so I just ran the motor under various conditions to get the numbers I listed.

Marty

[Powerhouse]

nice...Mine is kind of crappy. But it works I guess. Better than the ancient one I gave to a friend...but it still worked.

[Powerhouse]

One more question...

Vacuum advance and Centrifugal advance...do they work together or against each other?

What I found out is when centrifugal is in operation, vacuum isn't.

Does the vacuum advance...advance or retard timing? I am guessing it advances. SO it adds to the advance of the centrifugal...which would occur at cruising speeds if ported and also at idle if manifold.

Is that correct?

as I found here:

http://www.setyourtiming.com/Timing_Settings.html

Vacuum advance is primarily used in an effort to improve economy, therefore you won’t hear much about vacuum advance when discussing performance and racing. There is little to no vacuum during wide open throttle which means no vacuum advance any way!

A vacuum advance canister provides a way to advance the ignition timing during moderate and part throttle conditions. This is when the load on the engine is less and vacuum is higher. There is a diaphragm inside the canister which is connected to a linkage connected to the pickup plate in the distributor. When vacuum is applied, the plate is pulled which advances when the trigger signal is created. When the engine accelerates, vacuum drops so the advance returns to the original position.

When connecting the vacuum advance, most applications connect to a port above the throttle plates. This is called ported vacuum compared to manifold vacuum which comes straight from the intake manifold. The difference here is that manifold vacuum is there constantly while the ported source provides vacuum only when the throttle blades are open. The amount of advance that occurs varies by application but generally ranges from 10°-15°. Some companies even offer an adjustable vacuum advance canister. This lets you set the exact amount of vacuum advance that your engine requires.

Edited January 9, 2013 by Powerhouse

[Plymouthy Adams]

vacuum advance is that amount of advancement that is beyond the mechanical limits..it is not necessary needed to make the car run or perform but is an added amount of advance timing so to take advantage of the low load and ability to lean the engine..it provides added fuel economy

the vacuum does fall off with WOT throttle conditions but the mechanical is still doing its job..so you have three factors in timing, inital setting, mech advance and vacuum advance..a good timing light with dial advance will allow you to read all three and verify if you are close to specs....

[greg g]

Then there is that old concern about which vacuum signal is being used, ported vacuum from the carb, or manifold vacuum. Ported signal vacuum increases as the throttle is opened andair flow through the carb increases. Manifold vacuum decreases when the throttle is opened. It seems to me that ported vacuum would keep the advance increased during acceleration until engine rpms and there for centrifugal advance caught up with it.

[Powerhouse]

well, I hooked up the ported vacuum. Engine nocked like crazy when accelarating. So I backed it down to 5 deg from 10. Still nocked. So it's back to no vacuum for me and st at 5 instead of the 15 deg I had it at. Freakin ridiculous.

[Plymouthy Adams]

as stated earlier..have you verified the damper and pointer as valid..these do slip and if not a damper and just a pulley there is still the odd chance of a couple degrees of error....another thing is...verifying your initial timing..then verifying the total mechanical advacne then add the vacuum for the total overall advance at X rpm/vacuum combined..if the inital is too high so will all the rest be high..AND yet another thing..have you done a compression test..if your base compression is high could well be a sign of carbon buildup and that will also cause a pinging...you will need to get back to basics and prove what is right before finding what is wrong sometimes..

as this is not the stock distributor you could be anywhere..and the distributor is curved to match the engine and its build..you will want to mimic the curve of the stock with the upgraded GM unit you have elected to use..it is not hard to do and the specs for the original are what you need to set the distributor by..well let me say when I use the Mopar later model for retrofitting they are not hard to mimic and set to specs...I really do not ever mess with GM products..so I do not know if their diaphrams are adjustable or not like the Mopar units are..

maybe a friend has a timing light you can use just to rule out a possible error reading with yours..got to start with known good before you can find the bad..

[Andydodge]

My Langdons HEI is connected to what I understand to be ported vaccum, ie, it is connected above the throttle shaft level on the carby......I have an Australian Stromberg single barrel carby off a OZ GMH Holden straight six of 202 cubes............bolted the HEI dizzy on and connected up the vaccum line which was connected to the stock 41 Plymouth dizzy........runs fine......best thing I've done..........andyd

[Powerhouse]

I didn't see this earlier anywhere??? How does one verify the damper and pointer as valid? Would I remove the small threaded bolt on the rear top of the head and see where TDC is? I hope the Damper didn't delaminate...how does one get that repaired? My 53 truck engine didn't have one. Maybe I could run without it if the crank doesn't need it for balancing?

Also how does one curve to match the engine and its build? Is that done by changing the weights/springs and such? I have no idea what the specs are in that regard, my books don't say.

I will see if anyone has a timing light to borrow.

THANKS much for the great advice. Somethings gotta give.

[james curl]

The damper will delaminate in time from the elements. I had mine redone by the Damper Doc in California. Since I had not installed the head it was easy to find TDC, on mine the key way in the crank was straight up at TDC and the pointer was on 0 degrees when the damper was installed. You can find several people who redo dampers in the Hemmings big monthly magazine under services offered.

[Don Coatney]

Also how does one curve to match the engine and its build?

Below are the distributor specification sheets for a stock engine scaned from a 1953 MoTors Manual. This may or may not help you. I set up my distributor (my engine has dual carbs, dual point distributor, dual exhaust, lumpy cam, etc.) to the stock specifications and my engine runs great.

I increased the size of these pictures so they should be readable.

[Powerhouse]

THANKS MUCH!

I will be checking to make sure my tdc is correct. The dampener might have shifted I am told.

I am thinking of going back to stock dizzy..or maybe stock with petronix if I can't get this figured out.

This car is a daily driver so I want it to be right as rain already. too much time and money to still have a clunker.

Edited January 11, 2013 by Powerhouse

[martybose]

well, I hooked up the ported vacuum. Engine nocked like crazy when accelarating. So I backed it down to 5 deg from 10. Still nocked. So it's back to no vacuum for me and st at 5 instead of the 15 deg I had it at. Freakin ridiculous.

That's why I switched from ported to manifold vacuum, as the more throttle you use the less vacuum advance you get. I found that the car ran smoother at low RPM with the manifold vacuum. It theory you should get better gas mileage at cruising speed with more advance, but I've never bothered to try and prove it.

Marty

[Powerhouse]

I thought I could use the following method to find TDC:( which doesn't work since the valves are under the spark plugs...not the pistons.)

I turned the engine over by hand(in opposite direction) twice to get to the piston stop after hitting the stop the first time. The factory marks on the dampener are about 7 inches advanced!!!! Could this be true? I checked the rotor location where the "new" TDC is and the rotor was at #2 wire...not #1?

OK...I had a major brain fart with that one. What a waste of time. The spark plug hole is over the valves on an L6, NOT over the piston. DOH!

Edited January 11, 2013 by Powerhouse

[james curl]

Yes but the pipe plug in the center of number 6 cylinder is removed and a long wire or rod inserted into the hole which is above the piston on that cylinder will find TDC on #6 and #1. One will be on compression and the other on exhaust.

[Powerhouse]

thanks. I just got done with that and all is well with my dampener. So I know my timing is correct...initially.

[greg g]

pull the plugs and bump the engine by hand or with the starter till you fell compression build up against your thumb placed tightly down on the # 1 spark plug hole. When you feel it start, turn the engine over by hand till the timing marks allign. Shold be close enough to #1 TDC to get you started.

[Powerhouse]

Just to keep you all updated I got a response from Mr. Langdon. Asked me to call him to discuss, but it sounds like no springs are present to him. I checked, they are present. I haven't had a chance to call him yet. But I bit the bullet and bought a pertronix kit. Can't really afford it, but I'll make some sacrifices to make sure this dang thing, which is my daily driver, is running as it's supposed to. Maybe I can borrow some money from Washington D.C....or maybe i'll finally get my tax return that was stolen last year. STILL no word.

[Guest bewillie]

Pertronix in your stock dis is a good choice.

[Powerhouse]

got it all done. pertronix is nice.  correct advances and a stock look.  Until a way to convert the langdon HEI to the correct advances ...I aint putting it back in.  I have heard of premature engine wear being caused by incorrect timing curves...I HOPE my newly rebuilt engine hasn't suffered from this.  

[Powerhouse]

what's a good plug gap to go with?  I had it at 60 for the HEI.