I re adjusted the timing to about 35 total advance then checked at idle it was about 20 which seems high. Is there possibly a problem with this distributor? The vac advance is capped off. Its an HEI off a smogger and not re curved.

It seems to be making better power now though!

Thanks for any sugestions.

 

Considering you have a 262H Comp Cam 20 inches of vacuum is great. Usually bigger cams give lower vacuum. Not that your cam is that big but good vacuum is a good thing for brakes, accessories, etc.

 

I tried the timing again heres where I'm at:
34 degrees timing at 3200rpm and 21 degrees timing at 750rpm.

Something doesn't seem right here timing at idle is too high, what might be the problem?
TIA

 

If I were you I'd go get the advance curve kit and change the bushing...If I remember correctly the HEI has the mechanical advance bushing in it that changes how much the distributor will advance with the weights all the way out. If you get it to have more mechanical advance then the initial won't be quite so high. It'll give you the same upper end performance without sacrificing the low end as much. Good luck, keep me posted and I will help as much as I can from far away

Trip - he was saying his initial was 20 degrees, not 20 lbs vacuum

 

That is NORMAL for an Oldsmobile HEI, don't sweat it.

 

That's why I always use the ° symbol — makes it easier for readers to understand .

And, just to be a ____buster, it's inches of vacuum, as in inches of mercury ("in. hg.") in a glass column .

- Eric

 

Yeah but most people don't know how to make that symbol appear. °

For those of you not in the know press and hold the ALT key and then hit 0176 and then release the alt key and the temperature symbol will appear.

 

On my computer, I press Shift Option and 8 at the same time.
On my phone, I hold my finger over the 0 and a ° choice pops up.
You guys with Win-DOS machines have it hard - that's like some hard core ASCII shinizzle.

- Eric

 

Ok today I picked up a new 750 edelbrock carb and installed it. I also got an HEI re curve kit from morosso, any one have one of these? its a set of weights and plastic bushings with a bunch of different springs. Don't know if this is a good kit or a waist of money. Thanks for all the responces!

 

That is a decent kit. How many pairs of springs are in the set? And the bushings go inside the weights where they would rest on the pivot point.

 

Put the lightest pair of springs on it.

 

Thanks guys, the car runs pretty good, just need some tweaking and tuning

 

Heres a couple pics

 

Saw that on a Pontiac engine i installed (but didn't build) wasted all the bearings. I should have caught it, it was my cousins car. I feel for you.......

 

Well since I got the car running, I have driven it a bit probably put 7 or 800 miles on it and everything seems normal, motor seems fine so far. Only thing is sometimes the temp gauge will spike up to 220 even 240 degrees and come right back down again in a second or 2. Otherwise will run at 192 all day long. I think there must be air in the system that hasn't worked its way out yet!

 

With the cam you said you was running, Those 2.73's aren't that bad, as long as you still got a stock converter or no more than 2000 stall. With all that low end tourqe the 455 don't really need that much gear to put you in the seat! I would just get a posi carrier for your Type "O" (i'm assuming it's the original rear?) and keep the existing gears, you'll thank your self in the long run.

 

After a rear end swap (3:55 posi) and front disk brake conversion, I'm back to tunning... Put in the morosso re curve kit. Total timming is set at 35 degrees and its running 23 degrees at idle. Under hard acceleration there is some pingging I'm running the lightest springs in the kit, might try the medium spring or maybe go to 34 degrees total timing? Any sugestions? Thanks in advance!

 

You have too little mechanical advance. Remove the bushing, you should have about 18-20 or so in the distributor. That will allow you to have 16 or so at idle to achieve 36 total faily easily. You don't need that much initial (23) with that small cam. That's most probably causing your pinging. Remember everytime you hear that, it's beating the pistons back the other way, not good.
Make sure your carb isn't too lean as well, that will make things worse.

 

X2

I have a lot more cam than you and I run 14 initial 35 total. I would put in a 21 degree bushing and step down to the medium springs.

 

I'm not sure what your talking about when you say to change or remove the bushing? This is an Hei distributor and I don't have much experience with them. Rookie questions I know!

 

Normally, the bushings affect how far out the arms can travel, and therefore affect the maximum amount of advance that the distributor can furnish.

Looking at your instructions, without actually having the kit in my hand, I wonder whether the bushings supplied are the ones that affect the travel of the arms - it looks like they are designed to slip over the pivots and reduce play in the arm pivot points. You may have a kit that doesn't have the advance-limiting bushings in it.
Someone more familiar with this specific kit can tell us more.

Here are your instructions:

"INSTALLATION INSTRUCTIONS
ADVANCE CURVE KIT*
For all G.M. HEI distributors with an internal coil in the cap
1. Remove the distributor cap and rotor. Note the position of the weights and center plate
before removing them. Be sure to install the Moroso kit the same way.
By flipping the center plate over the kit will work in either clockwise or counter
clockwise rotation distributors.
2. Now remove the original springs, E-clips, weights, and center plate and install the
Moroso components in the original position for proper rotation. Then select the springs
from the chart below, which outlines the curve desired. (Heaviest springs
are closest to stock).
NOTE: Three sets of weight bushings are supplied with this kit: Use the bushings
that just slip on the weight pins without too much slop or are too tight (if the
bushings bind, it can affect the weight’s movement).
3. After the springs and E-clips are in place. Replace the rotor and cap. Set the timing
in the following manner: remove the vacuum line from the distributor and cap it off,
if your distributor is equipped with a vacuum advance. Set the idle at 750 RPM.
Now set the timing to the stock setting (Usually 8° B.T.D.C.). Replace the vacuum
line, if necessary, and readjust the idle to factory specs.
If it is desirable to modify the vacuum advance curve you can purchase the Moroso
Performance Products Vacuum Advance Module (Part # 72315). So, you can fine-tune
your ignition curve under all conditions.
*NOTE: THIS KIT IS INTENDED FOR OFF ROAD USE, AS IT MAY AFFECT
EMISSION LEVELS
RPM 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500
6000 6500 7000 7500 8000
Spring
LIGHT (Copper) 0º 10º 20º 22.5º 23º 23º 23º 23º 23º
23º 23º 23º 23º 23º 23º 23º
MEDIUM (Silver) 0º 0º 6º 13º 19º 23º 23º 23º 23º
23º 23º 23º 23º 23º 23º 23º
HEAVY (Gray) 0º 0º 0º 6º 10º 16º 21º 23º 23º
23º 23º 23º 23º 23º 23º 23º
In Crankshaft Degrees**
**NOTE: This chart is FOR REFERENCE ONLY. Actual advance can vary greatly
due to differences between the location of the
weight pins, the weight’s drag, magnetic pickup, Ignition module and other variables. "



- Eric

 

On a side note, before my timing chain skipped, i bought a 5 dollar Mr. Gasket HEI curve kit, worked great. I had my initial set at 12 BTDC and total either 30 or 35 i can't remember. She ran like stink.

I plan on trying to give it a bit more initial once the paint dries and i seal up my engine.

 

Did your engine ping with the original setup of 20* initial and 34-35 total? Because Imho that sounds almost perfect. The only thing that I believe you need to set is how fast the total would come in. Most people have found that 1 light and 1 medium spring worked for them.

 

I have the moroso kit in my HEI. I arrived at 1 light 1 mid spring the 2 lite springs had me advancing at idle speed w 1 lite and 1 mid I am all in by ~3200 +- rpms and no advance at idle

I agree w oldcutlass ~20° initial and mid 30s total. (note i use alt 248 for the ° symbol )

The supplied bushings are indeed as eric pointed out for reducing slop where the weights are on the pins not for limiting travel

If the HEI condition is a used 30 yo item I would suggest rebuilding it or at a minimum ensureing that the mechanical and vacuum advance mechanisms work smoothly and fully travel

 

Exactly, i used one light and one medium spring as suggested by some corvette forum thing that eric posted about a year ago.

I never ran the engine at 20* initial that the HEI has, should i be trying that out? I assumed to try to keep it as close to OEM spec as possible.

 

Thanks guys, I'm going to try a heavier spring and see if that helps drop the initial timing. I'll keep you posted

 

An HEI has a different timing curve than the stock points distributor. So basically I set my total around 34-35 deg's BTDC at around 3500 RPM with vacuum advance disconnected. With vacuum advance it should be somewhere around 50. All sttings with no detonation or surging at moderate or WOT. This where most engines like to run. Then I see where my initial winds up.

 

I might need to use a timing tape because my own timing light is from '79 and doesnt have the adjustible setting...

In other news, speaking of WOT, i really need to fix my bloody detent cable. My car doesn't downshift if i bury the gas. I assume that's the problem.

The cable is stuck in the fully extended position on my gas pedal and won't retract into the housing...

 

Why not just go buy or borrow a set back timing light? The tape is kind of a pita. The cable thing is its probably dry and gunked up. It may be easier to just replace it.

 

The previous owner put a hurst "hot shift 2" kit in the car.

I'm sure he screwed something up when he was doing it as he did with everything else, i'm worried the internal linkage was lost somewhere along the way...

 

I went a different direction with the distributor. I put the factory weights and center plate back in with the medium springs from the moroso kit. intial timing is 22* at idle and full advance is 34* I have too much other stuff to do so this will have to do for now. I am wondering if 92 octane is enough for this motor compression is around 9.5- 9.7:1 Thanks for all your help guys, I appreciate it. Now I need to drive this thing

 

I found a deal on some hooker competion headers new in the box, before I get into this can anyone tell me if these hreaders are going to fit into the car with out taking things apart? Anything I need to be aware of? I hate taking things apart only to get a surprize half way through!!

 

This is on the 68 cutlass in my avatar 455 with a turbo 400, thanks in advance!

 

Hello ah64pilot, when a camshaft is advanced or retarded with a multiple keyway timing gear, how does that affect ignition timing? what do you have to keep in mind in those scenarios as far as initial and total ignition advance?

kind regards

 

I've been learning all about making an HEI work with a high compression cammed Olds motor lately:

http://www.realoldspower.com/phpBB2/...83080&start=30

Note the easy to read chart of advance springs vs how much advance vs RPM- they specify that it is in Crank Degrees, but we have to assume that the chart RPM is CRANK RPM, for otherwise the top end of the chart [8000] would be 16,000 crank RPM.

And the handy Excel chart of how to convert readily measured VA or MA unit motion into Crankshaft Degrees of advance. [I think that discussing advance is terms of DIST degrees is "retarded" [pardon the pun], unless you own a distributor machine... we always read, work with, and measure advance AT THE CRANKSHAFT]

Kit does not tell how to ID one spring from another. Durr. Light is obvious. Med vs strong, not so much.

Note that the stock HEI weights and center allowed THIRTY crank degrees of advance. I ended up with about 20. Have yet to install/ test drive the distributor. I was waiting for the NOS GM 1973511 VA canister to arrive. It provides up to 15 crank degrees of VA, starting above 12" Hg. First however I shall try the VA can that was on the HEI, as it is adjustable for travel and is now set to 10-11 Crank Degrees max travel. It does start low, like 6" Hg, and is all in by about 10" Hg.

I too do not see any place to put a "bushing" to limit travel of the MA system- I see that the shape of the weights and the center piece limit the amount of MA that can be provided. The only "bushings" in the MA kit obviously go in the weights' pivot holes.

This is the best summary I have yet seen:
"Set the total at 36° without the vacuum advance. Make it idle down to 700 and see what it reads . Almost every single engine I've worked on with increased duration of the camshaft , has responded positively to advancing the timing at idle. The best setup I've come up with for engines like the 403 mentioned here, is 24-26 degrees initial, 36-38 total, max of 10° added vacuum advance, hooked to ported vacuum , with the adjustable can set as loose as it will go. The determining factor of max vacuum advance is the fluttery miss that occurs at sustained light throttle and low load. You can stiffen the mechanical springs to make it come in slower, or decrease the amount of advance in the vacuum advance and accomplish the same thing, if the fluttery miss occurs. The determining factor for max initial timing is starter kickback. and total (of course). Most engines with increased duration cams, idle very cleanly with 36° advance at idle."

More great words of wisdom:
"If you choose to run straight manifold vacuum to your vacuum advance in order to gain the additional timing advance at idle, you must select a vacuum advance control unit that pulls in all of the advance at a vacuum level 2" below (numerically less than) the manifold vacuum present at idle. If the vacuum advance control unit is not fully pulled in at idle, it will be somewhere in its mid-range, and it will fluctuate and vary the timing while the engine is idling. This will cause erratic timing with associated unstable idle rpm. A second tuning note on this: Advancing the timing at idle can assist in lowering engine temperatures. If you have an overheating problem at idle, and you have verified proper operation of your cooling system components, you can try running manifold vacuum to an appropriately selected vacuum advance unit as noted above. This will lower engine temps, but it will also increase hydrocarbon emissions on emission-controlled vehicles."

Be SURE to read this
http://www.corvette-restoration.com/...c_Adv_Spec.pdf

if the above fails, try a shorter version:
http://www.corvette-restoration.com/...hnical_papers/

and while you are there, look around for stuff like THIS:
http://www.corvette-restoration.com/.../Timing101.pdf

 

Officially hijacked...

Camshaft timing is different than ignition timing. When you advance or retard a cam, you are changing at what point the valves open and close in relation to the position of the piston in the cylinder.

When you advance or retard ignition timing, you are changing at what point the spark plug fires in relation to the position of the piston in the cylinder.

In any case, you should time the car to where it runs best. There are numerous ways to do that for various levels of performance. For a stock motor, most guys say wherever it makes the most vacuum at idle is where it is running best. For a performance engine that doesn't make much vacuum, then changing the timing can be checked at the track to see where the car runs best. Just a couple of the many ways guys tune their engines.

 

Decided to do some more tweaking to the olds. Put on a new 2 1/4" dual exhaust with magnaflow mufflers dumped before the diff, still using factory 442 manifolds. Sounds much better! Then I dropped in a new distributor from ebay (for $50) wasn't sure if it would be very good for $50 but the car ran better and sounded much better. fattened up the jetting, pings less now. Then I put in the moroso re curve kit, weights and springs. running better, went to the lightest springs (copper) now it is 15 degrees at idle 32 degrees full advance all in at 2900 rpm. Running strong. Will boil both tires through 1st gear and pulls strong throughout. I may try bump full advance to 34 degrees. Otherwise I might also try a 1" spacer open adapter (spread bore to square bore). Right now I have a 750 edelbrock (square bore) on a performer manifold (spread bore) with just a steel plate between so it will seal.

 

2 questions, do you think the 1" open spacer (adapter) will make more power? And what plugs and plug gap should I be running? Does an NGK XR45 sound right?

455, 9.5 compression, comp282h camshaft, C heads, HEI, 3000' above sea level

Thanks in advance

 

I just read this whole thread. You went from having a grenade situation to a tire frier! If that isn't cool, I don't know what is. That car is the first one I've seen that I like the look of the bigger rims on. Very nice.

 

Thanks z11375, the old school guys don't seem to like the big rims, but they can be changed in 20 minutes so not a big deal. Looks like you've got a nice 68 there too!