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Topic Review (Newest First)
02-07-2013 08:03 AM
jeepers creepers hey guys, i set the timing about 15* and engine seems to like it, great throttle response and quick revving, problem at WOT still but i would say it's minor so, i went further and installed an A/F ratio with analogic gauge, it's made by Fuelairspark or something like that, anyway, it says 14:1 at WOT wich is too lean i guess and even leaner at idle, it's usually close to 15, the richer value i've seen is 13ish but very rarely.

I spoke with the tech guys at Howell EFI , and he agreed with me to increase fuel pressure to achieve a richer mixture in the all RPM range, i don't know if is a good idea try to modify the TB internal pressure regulator or just put an external one with a gauge, anyone who worked on the Throttle body?
02-01-2013 02:58 PM
jeepers creepers I'm going to do some work tomorrow and try to advance timing, today i took of a spark plug, of the new set , engine ran for about 3 hours, there's a light black powder on ring and electrode even if it's not really "coated" with that because plugs are fairly new, i'll post picture tomorrow ,said that, engine did run pretty good generally speaking, i tried today to put a stock chip that i have instead the custom one Howell made for my TBI and engine runs just horrible, shakes, black smoke and was idleing at 200 rpm, the chip came from an ECM i got years ago from a junkyard so i'm not even sure if is ok, i was just curios to try.
A buddy of mine has an air/fuel mixture gauge, i need to put the sensor in the exhaust pipe e see how is the ratio, i think is a pretty good way to to see what's going on.
I'm looking for infos about TBI chip burners, i'd like to try reprogramming chip and find the best one, i have seen also new ECM without chip that you can tune up while the engine i running with the laptop and a specific software, any suggestion about them?
Thank you.
01-29-2013 04:32 AM
cobalt327
Quote:
Originally Posted by jeepers creepers View Post
Thank you, i have Edelbrock performer alu heads on so i believe it's better a little more advanced, are 36* ok? Because the total timing with vacuum plugged in is way more of that, i think was close to 45*.
What a 45* or too much total advance would cause to the engine?
Total advance is initial plus mechanical, without vacuum advance added in. This should be around 36 degrees. Too much total advance causes detonation, and detonation will kill an engine- no two ways about it.

You want another 10-12 degrees to come from the vacuum advance. That means under light throttle cruise/low engine load conditions you'll see upwards of 46-48 degrees of advance.

A common problem we have is the cam wants a lot of initial timing, but if you give it enough initial timing, the total timing is now too high. The way around this is to limit the mechanical advance to an amount that, when combined w/the initial timing, equals the 36 degrees total timing target. An example would be 18 degrees initial timing, plus 18 degrees mechanical timing. Or any combination of the two that equals 36 degrees. Remember- this is w/o vacuum advance added in. It will be disconnected and the hose to the carb plugged. Only reconnect the vacuum advance after the initial and mechanical is set.

The exact way to go about limiting the mechanical advance depends on what distributor you're using. The following link covers GM-type HEI and MSD distributors: Ignition advance
01-29-2013 03:46 AM
jeepers creepers
Quote:
Originally Posted by cobalt327 View Post
If you add initial, be sure to recheck the total timing (w/o vacuum advance, vacuum line plugged). Keep the total under 36 degrees for non fast burn chamber heads, 30-32 degrees for fast burn.

If you have no change when the vacuum advance is disconnected, you're either using ported vacuum or the vacuum advance unit is bad or the advance plate is hanging up. Try hooking it up to a vacuum port that has vacuum at idle (manifold vacuum).
Thank you, i have Edelbrock performer alu heads on so i believe it's better a little more advanced, are 36* ok? Because the total timing with vacuum plugged in is way more of that, i think was close to 45*.
What a 45* or too much total advance would cause to the engine?
01-28-2013 01:53 PM
cobalt327
Quote:
Originally Posted by jeepers creepers View Post
Timing is now set about 12* (initial), but i will try to get it more advance like you said, tried to disconnect the vacuum hose and there was no difference at all at idle, any suggestion?
thank you.
If you add initial, be sure to recheck the total timing (w/o vacuum advance, vacuum line plugged). Keep the total under 36 degrees for non fast burn chamber heads, 30-32 degrees for fast burn.

If you have no change when the vacuum advance is disconnected, you're either using ported vacuum or the vacuum advance unit is bad or the advance plate is hanging up. Try hooking it up to a vacuum port that has vacuum at idle (manifold vacuum).
01-28-2013 12:54 PM
jeepers creepers Thank you for the answer, i spoke with the tech support of the EFI kit and i 've been told to try a little thing to see if is a rich mixture problem related or not just by reducing fuel flow using a clamp or vise grip on the pressure hose.

I noticed the 3 bolts of the exhaust flange in between to pipe and headers a little loose, i guess that air can go in and mess up the o2 sensor wich is 2inches above, i guess that is air go in the o2 sensor would make mixture richer by sending a lean signal to the ECM, i need to test the car better.

Timing is now set about 12* (initial), but i will try to get it more advance like you said, tried to disconnect the vacuum hose and there was no difference at all at idle, any suggestion?
thank you.
01-25-2013 08:34 PM
cdminter59
lean mixture?

Where do you pull these spark plug numbers from? Anyway Edelbrock recommends Champion RC12YC plugs for their heads. Now if you want to crossreference that to a NKG plug it is BKR5E. Another thing about the timing. Always unplug the vacuum line from the distributor while checking or adjusting timing. Loosen the distributor lockdown and set the knob on the back of the timing light to zero. Adjust the initial timing to 10*-12* BTDC. Have someone rev the engine to 3000 rpms and point the light at the scale. If the line on the balancer is past the 0 mark on the scale adjust the knob on the back of the timing until the line aligns with 0 on the scale. What is the reading? Do this again at 3500 rpms to see if it changes or stays the same as for 3000 rpms. The reading should have been close to 35*-37*. This is your total (initial + mechanical advance). Now unplug the vacuum hose and connect it to the distributor. That's it, you can check to see how much vaccum is added by revving the engine to 3500 rpms, zero the timing light and check it by turning the knob on the light until the balancer line aligns with 0. What is the reading? 49*-51*. Good. Take the foam out of the tank. If you have enough fuel in it the pickup will stay wet.
01-25-2013 09:44 AM
jeepers creepers No way, it's better but problem still...
01-25-2013 08:11 AM
jeepers creepers
Quote:
Originally Posted by cobalt327 View Post
I'd give it 16-18 degrees of initial and use a vacuum advance limited to 10 degrees, or use the vacuum advance you have now and if you're getting too much timing at idle w/it hooked to manifold vacuum, just hook it to ported vacuum.

Use a lighter spring on one side to see if you can get the timing all in by about 3000 rpm.
Thank you Cobalt, i already put a lighter spring on one side and the curve is ok but i have definately good news...
Did you know that i'm an idiot? I checked today the lenght of the spark plugs hole in the cylinder heads (Edelbrock alu) and it's about double compared to the stock cast iron so the plugs i put on before were reaching just half of that!!!
poor engine...i just put the new NGK BRP6EFS plugs on and i will try them very soon, can't wait to...
01-25-2013 04:38 AM
cobalt327
Quote:
Originally Posted by jeepers creepers View Post
i printed out the article yesterday night! thank you.
I checked timing again and did some work on it, by setting the initial advance to 10-12 degrees i get a total of 44 with bith mechanical and vacuum,i thought was too much so i tried to disconnect the vacuum one...result is that mechanical only advances 16-18 degrees so i'm reaching 30ish at 4000 RPM wich is too much.

Reading the article on cranckshaft coalition, they say advance can go up to 45-50 during light throttle cruise with no problem getting a better fuel mileage and a cooler engine, i'm not considering mileage like the goal, i just want to solve this problem and a healthy engine, fuel mileage is a bonus.
I' ve got new spark plugs 10 minutes ago, they're colder than the previous Accel, i hope will help.

Another thing i noticed driving the car is the misfiring happens just if i push down the pedal all the way suddenly but not if i rev up the engine gently, guessing is a good clue for you, i'm thinking about too much fuel and a denser mixture in the combustion chamber coupled with a too hot plug that cause preignition?
Just wondering...
I'd give it 16-18 degrees of initial and use a vacuum advance limited to 10 degrees, or use the vacuum advance you have now and if you're getting too much timing at idle w/it hooked to manifold vacuum, just hook it to ported vacuum.

Use a lighter spring on one side to see if you can get the timing all in by about 3000 rpm.
01-25-2013 04:15 AM
jeepers creepers
Quote:
Originally Posted by cdminter59 View Post
What is the name brand of your aluminum heads? Also what is the name brand of your distributor? Here are some of the wiki articles from this website to use for information on finding TDC. http://www.crankshaftcoalition.com/w..._TDC_lines_SBC. Here is another article to help with tuning the advance curve and timing. http://www.crankshaftcoalition.com/w...EI_distributor. Be sure to check out wiki for more useful info.

i printed out the article yesterday night! thank you.
I checked timing again and did some work on it, by setting the initial advance to 10-12 degrees i get a total of 44 with bith mechanical and vacuum,i thought was too much so i tried to disconnect the vacuum one...result is that mechanical only advances 16-18 degrees so i'm reaching 30ish at 4000 RPM wich is too much.

Reading the article on cranckshaft coalition, they say advance can go up to 45-50 during light throttle cruise with no problem getting a better fuel mileage and a cooler engine, i'm not considering mileage like the goal, i just want to solve this problem and a healthy engine, fuel mileage is a bonus.
I' ve got new spark plugs 10 minutes ago, they're colder than the previous Accel, i hope will help.

Another thing i noticed driving the car is the misfiring happens just if i push down the pedal all the way suddenly but not if i rev up the engine gently, guessing is a good clue for you, i'm thinking about too much fuel and a denser mixture in the combustion chamber coupled with a too hot plug that cause preignition?
Just wondering...
01-24-2013 04:30 PM
cdminter59
lean mixture?

What is the name brand of your aluminum heads? Also what is the name brand of your distributor? Here are some of the wiki articles from this website to use for information on finding TDC. http://www.crankshaftcoalition.com/w..._TDC_lines_SBC. Here is another article to help with tuning the advance curve and timing. http://www.crankshaftcoalition.com/w...EI_distributor. Be sure to check out wiki for more useful info.
01-24-2013 03:58 PM
71nova355 its lean or it wouldnt be white like that. sensors are prone to be inaccurate, especially if its not a high dollar piece.(guage). either way, just was trying to throw some ideas to help get you headed in the right direction.

maybe if you just red line it for 20 minuts itl fix itself?
01-24-2013 02:16 AM
jeepers creepers
Quote:
Originally Posted by 64nailhead View Post
Curious as to why you changed only 3 plugs?

If you put in heavier springs, then the centrifugal advance will come in later, which is not what your after. As cdminter said, your want all of the advance in by 3000.

In terms of the timing, IMO, I'd change the remaining plugs and clean off the 3 you already changed, then unhook the vacuum advance and plug the line. Set the total timing between 34 & 36 and find out exactly what rpm it is all in by, and then drive a WOT throttle session and recheck the plugs immediately and see what they look like.

It will not hurt the motor to run it with no vacuum advance. And, oh yes, MAKE sure your balancer is marked accurately for #1 TDC.

I didn't see where you checked you vacuum, where is it at idle? Did you check for leaks?

Good luck.
i didn't change any spark plug but just 3 caps of the wires because on of them was cracked by the heat and the others were going to, i put heavier spring because advance was all in just over 2000 RPM, today i will try to disconnect the vacuum advance and see what happens.

As i said before the mark on the balancer wasn't matching the tab on the timing cover so i fixed the damper by machining a new groove in the right position, i didn't degree the cam, i thought was an overkill for a mild motor like mine but now i realize it's a smart thing, i will for sure next time.
I can take off valve cover and check the TDC.

By measuring the voltage coming out from the O2 sensor shouldn't be lean , 800 to 850 MV should be the ball park and mine is going from 800 to 900 MV with peaks of 1000, picture of the spark plug doesn't make justice to me.
01-23-2013 05:46 PM
71nova355
You must fix the timing!

You said you built the motor? DId you degree the cam properly? did you use the correct balancer and timing marks? You also need to gap your plugs all around .40. The mixture is way way lean and this is not good at all! If its not fixed pronto, you will be re building very soon. Your plugs should never be that white at all. Just make sure when checking your timing you take all the necessary steps because it will determine whether or not you can calibrate your set up correctly or not. as stated earlier 36 total is a good place to start. unless you have a kit to calibrate your distributor then you wont be able to set initial but if you have a gm distributor with stock settings, then where ever 36 total leaves you will work. At least untill you get everything dialed in a lot closer and then you can experiment with a couple degrees or so one way or another. If you bump up your initial you will have to stop your total exceeding the 36.

I hope you can get her figured out before you melt a piston.
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