How is it possible to run lean on #7 and #8

MustangPunk302

Founding Member

Sep 11, 2002

1,051

0

36

West Michigan

Jun 25, 2004

#21

• Jun 25, 2004

• #21

IndyBlk5.0 said:

the motor has 350 miles on it. blew head gaskets on those two cylinders for the past 3 times. headgaskets put on by different people including me. something is really weird.

Click to expand...

You used new bolts everytime, right? This is really strange... Really weird is right..

 

IndyBlk5.0

New Member

Nov 24, 2003

1,122

1

0

New Whiteland, IN

Jun 25, 2004

#22

• Jun 25, 2004

• #22

Yes, new bolts each time, heads were milled, block was decked.

 

dastang2

Active Member

Dec 11, 2003

2,020

0

46

tx

Jun 25, 2004

#23

• Jun 25, 2004

• #23

have the heads checked for cracks. something is wrong between 8 and 7 if you have good psi when #7 plug is in and when both 7 and 8 plugs are out you only get 80

 

93 teal terror

Founding Member

Jul 13, 2001

971

62

69

Durham N.C.

Jun 25, 2004

#24

• Jun 25, 2004

• #24

just a thought....but if 7&8 typically run a little leaner than the rest, is it possible that you could be on the verge of running lean and just those two cylinders were affected?

 

B

blownfordtech92

Founding Member

Oct 20, 2001

247

0

0

Iowa

Jun 25, 2004

#25

• Jun 25, 2004

• #25

I realize my setup is not quite the same as yours but i know your pain. ever since i put my procharger on i have blown head gaskets every time i get on it. i have now blown three sets in around 300 miles and every time it has been on #'s 6 and 7 and at least once i think it was eight. in between the first and second set i went to 24lb injectors from 19lbs. and installed a 255lph fuel pump. didn't make a bit of difference. at WOT my fuel pressure never drops below 90psi (still using FMU, flame me at will). oh, and this was also with two different engines. i put a 96 explorer long block in after the second time. i just got done putting on another set and i have driven it maybe 50 miles but i haven't got on it yet. i know that i'm going to have to go to 42lb injectors and a custom program, and i'm also wondering about going to a larger fuel rail. my theory is that under WOT those two injectors are furthest from the supply and therefore may be getting starved through those tiny stock fuel rails. once again, just my theory. oh, and one more thing to tantalize you-i'm a ford mechanic and almost every time high mileage 5.0's come in the shop (usually grand marquis and town cars) and they are missing, it's because #7 or 8 spark plug is oil fouled. seems they are always the first cylinders to wear out. go figure.

 

S

SmockDoiley

New Member

Jun 14, 2003

1,591

2

0

San Diego, CA

Jun 26, 2004

#26

• Jun 26, 2004

• #26

I dont care what anyone says, but running too rich will never blow a head gasket, and having too low compression will not create a lean condition. Secondly, like I said before, are you sure your running lean because all you keep saying is that you are blowing head gaskets. Running lean isnt the only thing that blows head gaskets. Lastly, how do you know its the head gasket. I dont see how on Earth you keep blowing gaskets if you keep using new bolts, and everything is decked and true and your torquw specs are right. Obviously, you dont have all the answers needed, and furthermore with gasket blown like symptoms and low compression shared in 2 adjacent cylinders, it sounds more like a cracked head or block. Face the facts. You need to find out if they are really running lean because it sounds like you just guess they are. Have you ever thought, that after assuming something and trying to fix it 3 times, that maybe your original assumptions are wrong. If the engine was just rebuild, and everything is decked and straight and you followed all correct procedures to installing a head,and your electrical is good and your injectors were just rebuilt, your not running lean. I'm going to go with a major crack somewhere.

 

Rick 91GT

Mustang Master

Nov 29, 1999

9,692

95

99

PA

Jun 26, 2004

#27

• Jun 26, 2004

• #27

If oil is getting into the cylinder it significantly decrease the octane on the fuel, hence the lean condition and this will cause head gasket to blow.

#7 on most 5.0EFI motors is the lean cylinder due the to way the intake design is, the GT40 isn't the best for fuel distribution, the TFS and Holley are better but you still see most guys checking the EGT on #7, and #3.

Make sure you PCV valve is good and you have proper venting, if not this may cause your oil problem. What does the gasket look like when it blows? Do you have a pic? What gasket are you running? What head? The 3 time sthing blows my mind, something is obviously wrong with something. We found the STOCK GT40 cast iron heads on our 93 Cobra had 1/2" holes (not 7/16" like stock) after blowing the gaskets twice once the blower was on the head would lift.

 

IndyBlk5.0

New Member

Nov 24, 2003

1,122

1

0

New Whiteland, IN

Jun 26, 2004

#28

• Jun 26, 2004

• #28

Interesting. Well I know the running lean on the 2 cylinders is a long shot. The heads and block have been checked for cracks and came out fine according to the machine shop. The heads have been milled several times. I don't know if that makes a difference.

I would hate to buy new heads and that not be my problem.

 

dastang2

Active Member

Dec 11, 2003

2,020

0

46

tx

Jun 26, 2004

#29

• Jun 26, 2004

• #29

did they shve the heads enough that you had to get shorter pushrods, this is surely not the answer to your problem since more than just those cylinders would have no compression too.

 

IndyBlk5.0

New Member

Nov 24, 2003

1,122

1

0

New Whiteland, IN

Jun 26, 2004

#30

• Jun 26, 2004

• #30

stock pushrods. The guy is good. But I don't think he payed that much attention to my motor, when it needed it.

 

IndyBlk5.0

New Member

Nov 24, 2003

1,122

1

0

New Whiteland, IN

Jun 26, 2004

#31

• Jun 26, 2004

• #31

Any other reasons ? maybe heads milled too many times?

 

B

blownfordtech92

Founding Member

Oct 20, 2001

247

0

0

Iowa

Jun 26, 2004

#32

• Jun 26, 2004

• #32

i forgot to add earlier that i agree, a rich condition will NEVER blow a head gasket. lean conditions cause extremely hot cylinder temps and rich is the opposite. also, the low compression causing a lean condition thing is a long stretch. all i can say is, if i spend all the money to get 42lb injectors and a custom program and it still blows head gaskets, i'm gonna be mega-torqued.

 

IndyBlk5.0

New Member

Nov 24, 2003

1,122

1

0

New Whiteland, IN

Jun 27, 2004

#33

• Jun 27, 2004

• #33

I think it might be that my fuel pump isnt keeping up? I think it is stock. 7 & 8 are the last to get fuel on the fuel rail....

 

C

chevyeater

Founding Member

Sep 17, 2002

438

0

0

Jun 27, 2004

#34

• Jun 27, 2004

• #34

Have seen same problem om 351's between cylinders 5&6. the conclusion was that the two adjacent cylinders fired in consecutive order but both cylinders were firing at the same time due to cross arcing of the plug wires. may also be due to cracked distributor cap.this causes detonation on one cylinder causing blown gasket.gasket failure will usually be between the cylinders. Not saying this is your case but check the cap and the wires. is some suspicion since cylinders 7&8 are in consecutive firing order.
Later,
Dave

 

RacerRick

20+ Year Stangneter

Jun 26, 2004

90

0

7

Ponchatoula, La.

Jun 27, 2004

#35

• Jun 27, 2004

• #35

sounds like a intake leak at the head/intake gasket. spray ether (starting fluid) around the intake while idling, if it sucks it in the rpm's will rise.

 

IndyBlk5.0

New Member

Nov 24, 2003

1,122

1

0

New Whiteland, IN

Jun 28, 2004

#36

• Jun 28, 2004

• #36

My wires are bunched together and not in seperators, just zip tied. Makes sense. Also, I will have to rig up a fuel gauge to make sure my psi is actually 40 psi @ WOT, its set to that, but who knows when im driving down the road if my fuel pump is keeping up. 7 and 8 and the farthest away. The shop also said that i was running rich at idle but lean at other rpms.

 

r6bullet

New Member

Jul 25, 2003

112

0

0

Jun 28, 2004

#37

• Jun 28, 2004

• #37

Just get new heads, if you can't afford them then wait and get new heads

 

IndyBlk5.0

New Member

Nov 24, 2003

1,122

1

0

New Whiteland, IN

Jun 29, 2004

#38

• Jun 29, 2004

• #38

I dont think they are the problem, they have been rebuilt and checked for cracks

 

shttygtstang

New Member

Jun 2, 2004

978

0

0

Jun 29, 2004

#39

• Jun 29, 2004

• #39

im not the best tech but could it have any thing to do with a piston ring being installed improperly or screwed up smell your oil does it smell like gas that could cause you to run lean.....or get a fel prohead gasket and arp head bolts youll find out what it is when you brake it

 

shttygtstang

New Member

Jun 2, 2004

978

0

0

Jun 29, 2004

#40

• Jun 29, 2004

• #40

ttt