A/f gauge shows lean

[350Z FRENZY]

A friend of mine has a 1983 fox body and the Engine is a 40 over 302 (308) that is running lean and fouling plugs
he said that the air /fuel mixture gauge shows lean and tried another gauge and shows the same. 'COULD THIS BE A VACUUM LEAK' any ideas guys :beer:

 

[LS1PUSSOUT]

how does it run lean and foul plugs? Im pretty sure a fouled plug 99% of the time is from too much fuel. But anyways I would check all the lines coming off the intake manifold. If those are good start checking the fuel system

 

[99MustangGTman]

Is it a wideband or non wideband?

 

[ponygt65]

not alot of info......I presume this is lean at WOT....and with a wideband. What exactly is the A/F ratio from 2-6k. has the car been tuned?.... mods....?

 

[350Z FRENZY]

thanks guys ill get more info :beer:

 

[350Z FRENZY]

this is what he sent me:

I had a bad year with the white car, re-ringed the block and put it back in after checking all the bearing. While it was warming up I noticed I had almost no oil pressure and shut it off. Had to pull the motor again and we ended up almost spinning a bearing. Had the crank check and it just needed to be polished, new bearings and now we are braking it in. Still having a problem fouling out plugs, carb is new and A/F guage is reading the we are lean. Pulled my Digital 6 off to have it check and MSD said it was ok. I am running a 6AL right now and the problem is still there. Just can't figure it out and this has never happened to me with any other car I have owned.

Let me know what's up with you.

I have had 12 carbs on this motor, even had Norm Benard build me a Proform last year. New intake and yes we checked for vac leak. Went to an Accel Hot plug to try to see if it would stay clean and no luck. Again, Dickie is thinking it might be a bad cut cam (split was cut wrong). Just don't know, going to run the ground and then drive it a little bit. Just put in a new high volume oil pump and with the new bearing I am only getting 40 psi at idle, this engine is just one thing after another.

Have checked just about everything. Dickie thinks that it might be a bad cam, maybe cut wrong leaving the exhaust open to long and causing reversion. Plugs are not fouled like fuel, they look like diesel plugs (full of sut).

Engine is a 40 over 302 (308) 11.5:1 pop ups/eagle I beam rods/stock crank/Twisted Wedge heads, stage 3 by Lew's Venton/Comp cams hydraulic roller 600 lift-duration 238/238@50, 110 lobe sep. Single plane torker/BG 650.

Car has been on a dyno many time, I have a regular A/F gauge (not a wide band). I pretty much know what is 12:1 on my guage based on past dyno runs.

Just to satisfy MSD, I am going to run a heavy gauge wire from the battery in the back to the front of the black for ground. All grounds have checked out but I am still going to do it so that there are no other reason to suspect the MSD.

If you have any clue, let me know.

 

[ponygt65]

this is what he sent me:

I had a bad year with the white car, re-ringed the block and put it back in after checking all the bearing. While it was warming up I noticed I had almost no oil pressure and shut it off. Had to pull the motor again and we ended up almost spinning a bearing. Had the crank check and it just needed to be polished, new bearings and now we are braking it in. Still having a problem fouling out plugs, carb is new and A/F guage is reading the we are lean. Pulled my Digital 6 off to have it check and MSD said it was ok. I am running a 6AL right now and the problem is still there. Just can't figure it out and this has never happened to me with any other car I have owned.

Let me know what's up with you.

I have had 12 carbs on this motor, even had Norm Benard build me a Proform last year. New intake and yes we checked for vac leak. Went to an Accel Hot plug to try to see if it would stay clean and no luck. Again, Dickie is thinking it might be a bad cut cam (split was cut wrong). Just don't know, going to run the ground and then drive it a little bit. Just put in a new high volume oil pump and with the new bearing I am only getting 40 psi at idle, this engine is just one thing after another.

Have checked just about everything. Dickie thinks that it might be a bad cam, maybe cut wrong leaving the exhaust open to long and causing reversion. Plugs are not fouled like fuel, they look like diesel plugs (full of sut).

Engine is a 40 over 302 (308) 11.5:1 pop ups/eagle I beam rods/stock crank/Twisted Wedge heads, stage 3 by Lew's Venton/Comp cams hydraulic roller 600 lift-duration 238/238@50, 110 lobe sep. Single plane torker/BG 650.

Car has been on a dyno many time, I have a regular A/F gauge (not a wide band). I pretty much know what is 12:1 on my guage based on past dyno runs.

Just to satisfy MSD, I am going to run a heavy gauge wire from the battery in the back to the front of the black for ground. All grounds have checked out but I am still going to do it so that there are no other reason to suspect the MSD.

If you have any clue, let me know.

Lean conditions will result in a white/greyish Plug, not 'sut'.

12:1 is not lean. He says he knows where that is on his gauge, but is not clear as to if that is what he is running.

Pending what he means by 'sut' he could be running rich and be a tad off running high 11s A/F.

Try to find out what he 'thinks' his A/F is and if he has changed the plugs since the last R/R with the 'almost spun rod bearing'? Also, why has he had 12 carbs on that motor? :??:

Also, where is that A/F reading in the RPM range?

 

[350Z FRENZY]

Lean conditions will result in a white/greyish Plug, not 'sut'.

12:1 is not lean. He says he knows where that is on his gauge, but is not clear as to if that is what he is running.

Pending what he means by 'sut' he could be running rich and be a tad off running high 11s A/F.

Try to find out what he 'thinks' his A/F is and if he has changed the plugs since the last R/R with the 'almost spun rod bearing'? Also, why has he had 12 carbs on that motor? :??:

Also, where is that A/F reading in the RPM range?

thanks ill ask him and get back to ya' :beer:

 

[Maching-U]

Is it possible that may be it's burning oil since the plugs are full of 'sut' and not fuel. AFR of 12:1 is not lean if you're not supercharged.
May be the plug heat range is too cold? What plugs are you running?

Since the car has been on the dyno many times, do you have at least one print out with AFR readings on it?

 

[ponygt65]

Is it possible that may be it's burning oil since the plugs are full of 'sut' and not fuel. AFR of 12:1 is not lean if you're not supercharged.
May be the plug heat range is too cold? What plugs are you running?

Since the car has been on the dyno many times, do you have at least one print out with AFR readings on it?

+1.


Also I want to add that 12:1 A/F read at the tailpipe IS rich. With a wideband he'd be in the upper 11s, most likely and that is virtually FI A/F.

 

[350Z FRENZY]

thanks ill tell him :thumbsup:

 

[thumper_302]

Hi, I am the owner of the 1983 Mustang.

There is no oil getting past the rings, the rings are new and they are working fine. The reason I have had 12 carbs on the engine over the last year is due to the fact that we kept thinking it was running fat and could'nt get any of them to the clean up the plugs, even if we leaned out the jets so bad that the car wouldn't even run.

As for the A/F guage, the guage is marked were 12:1 is and 12.8:1 is based on dyno runs. Currently the guage is read leaner than 12.8:1.

The plugs look like diesel plugs (black sut). This is with an Accel hot plug in it. There are no vacum lines coming off the intake, all blocked off and we have check for vacum leaks and even changed intakes.

Carb is brand new out of the Box BG.

As stated, I am going to run a heavy guage wire from the negative of the battery all the way up to the block even though the grounds check good just to satisfy MSD tech.

Only item that we have not changed and I wish I had when I have the block out is the cam. We had reversion in the intake with the cam set at top dead center, we retarded the cam 4 degree's and got rid of the reversion in the intake (Same black sut the plugs have). We just can't keep the plugs clean.

Thanks for all your input and I will be checking the thread for your thoughts.

 

[350Z FRENZY]

Hi, I am the owner of the 1983 Mustang.

There is no oil getting past the rings, the rings are new and they are working fine. The reason I have had 12 carbs on the engine over the last year is due to the fact that we kept thinking it was running fat and could'nt get any of them to the clean up the plugs, even if we leaned out the jets so bad that the car wouldn't even run.

As for the A/F guage, the guage is marked were 12:1 is and 12.8:1 is based on dyno runs. Currently the guage is read leaner than 12.8:1.

The plugs look like diesel plugs (black sut). This is with an Accel hot plug in it. There are no vacum lines coming off the intake, all blocked off and we have check for vacum leaks and even changed intakes.

Carb is brand new out of the Box BG.

As stated, I am going to run a heavy guage wire from the negative of the battery all the way up to the block even though the grounds check good just to satisfy MSD tech.

Only item that we have not changed and I wish I had when I have the block out is the cam. We had reversion in the intake with the cam set at top dead center, we retarded the cam 4 degree's and got rid of the reversion in the intake (Same black sut the plugs have). We just can't keep the plugs clean.

Thanks for all your input and I will be checking the thread for your thoughts.

great to have you here pete

these guys are great and will help out alot :beer:

 

[ponygt65]

Hi, I am the owner of the 1983 Mustang.

There is no oil getting past the rings, the rings are new and they are working fine. The reason I have had 12 carbs on the engine over the last year is due to the fact that we kept thinking it was running fat and could'nt get any of them to the clean up the plugs, even if we leaned out the jets so bad that the car wouldn't even run.

As for the A/F guage, the guage is marked were 12:1 is and 12.8:1 is based on dyno runs. Currently the guage is read leaner than 12.8:1.

The plugs look like diesel plugs (black sut). This is with an Accel hot plug in it. There are no vacum lines coming off the intake, all blocked off and we have check for vacum leaks and even changed intakes.

Carb is brand new out of the Box BG.

As stated, I am going to run a heavy guage wire from the negative of the battery all the way up to the block even though the grounds check good just to satisfy MSD tech.

Only item that we have not changed and I wish I had when I have the block out is the cam. We had reversion in the intake with the cam set at top dead center, we retarded the cam 4 degree's and got rid of the reversion in the intake (Same black sut the plugs have). We just can't keep the plugs clean.

Thanks for all your input and I will be checking the thread for your thoughts.

Hey man...glad to see you post in here.

'generally' speaking for a 1320 car 12.8 A/F is fine. It's not too lean. The 'non'-whitened pluges reinforce that. IMO, you have a different problem. Are you certain the rings seated correctly? Black sut is most common with either too rich, or oil issues, which I'm sure you are aware of. It hasn't been mentioned, but I assume you are not getting any smoke out back, even on start up. I'm wondering if it's the rings not seating or the cam issue comebined with the timing you retarded is part of the issue.

to be kind of frank, 12 carbs, sut'd plugs, and 12.8 A/F is enough (I think) to start looking outside of a fuel issue. I had to say it, but pulling the cam and double checking the rings may be in order.

Is the car idling and runnign relatively ok? What's she run/idle like? Have the valves been checked? What octane are you running and what CR? Has a CR test been done? What oil did you use to break in the motor and what break in measures did you take?

Sorry for the gazillion Q's, just trying to narrow down the gap.

 

[thumper_302]

Thanks for the input.

Car seems to be runing fine, idle's fine and there is no smoke coming from the exhaust. Break-in was done by running the car at different rpm for 30 minutes at a time, (2000/3000/1500/2500/etc). Total 30 minute runs were 3 hours total. Oil was a lite grade 10/30 and now the motor has 20/50. Just got done running the ground from the block to the battery, will try driving the car tomorrow. Gas in the tank is 91 octane with one bottle of octane boost. Time is set at 13 static and 32 total right now. I have a manual timing retarder/advancer (whatever you call them) I can put a max of 22 static and 42 total advance with the dial.

Heads were redone during the last rebuild, I only had 12 passes and less than 3000 miles when I decided to pull the motor due to the poor leak down test. We had them check again anyway and they were fine, just covered in sut along with the pistons.

I really am thinking it's the cam. Really, what the F else can it be. Every item on the engine inside and out has been change.

Iam one frustrated MFKR.:shrug:

 

[350Z FRENZY]

Some one please help pete before he shoots his mustang oke:

I would change the cam A.S.A.P...What else is there :beer:

 

[ponygt65]

Thanks for the input.

Car seems to be runing fine, idle's fine and there is no smoke coming from the exhaust. Break-in was done by running the car at different rpm for 30 minutes at a time, (2000/3000/1500/2500/etc). Total 30 minute runs were 3 hours total. Oil was a lite grade 10/30 and now the motor has 20/50. Just got done running the ground from the block to the battery, will try driving the car tomorrow. Gas in the tank is 91 octane with one bottle of octane boost. Time is set at 13 static and 32 total right now. I have a manual timing retarder/advancer (whatever you call them) I can put a max of 22 static and 42 total advance with the dial.

Heads were redone during the last rebuild, I only had 12 passes and less than 3000 miles when I decided to pull the motor due to the poor leak down test. We had them check again anyway and they were fine, just covered in sut along with the pistons.

I really am thinking it's the cam. Really, what the F else can it be. Every item on the engine inside and out has been change.

Iam one frustrated MFKR.:shrug:

I am also leaning towards the cam. IMO, breaking in a motor should be doing it like you normally would drive it (fairly hard in this case), then change the oil at 500 miles, then again at 1.5k. It's still possible that the rings never sat correctly, but never know without looking. ALso, the break in was done with reg. oil, not synthetic correct?

 

[thumper_302]

Yes, you are correct SIR!


About the oil thing.

 

[ponygt65]

Yes, you are correct SIR!


About the oil thing.

Cool.....dont' mean to sound like a pest or act like you dont' know anything, just trying to cover all the basics. (FYI/FWIW)

tear down and ring/cam inspection is what I think should be done.

 

[thumper_302]

Rings are good, no blow-by and compression is way the heck up there. It's going to be a month or so before I can tear out the cam. I have another problem, put in a new high volume oil pump (keep in mind that all the bearings are new) and the best oil pressure I can get with 20/50 when the engine is hot is 30 psi and a max at 6500 of 59 psi. I think I should just sell the pistion/rods/heads/etc in parts and just start the hell over.