BHG. But why?

[MDCmotorsports]

Well this is a new one to me.

Never actually had to deal with this monster, and now here it sits in my lap.

The car over heated on me last night. It had puked all the water out the over flow bottle.

I did a compression test. 160 accross the board. Ok.

Checked all the plugs. No water or coolant deposits. Ok.

I did a leak down test. #6 cyl has 3-4% leak down and is comming out of the radiator filler neck. Icky. :nono:

I understand that this is indeed a BHG. :cry: I also understand that detonation and poor engine building practices kill head gaskets.

This engine was built by an ex indy car engine builder. I personally saw the engine machined, prepped and assembled. No worries there.

Now...

What baffles me is how?

-Ive always been a little on the rich side of the engine's entire life (30k miles)
-The engine when built, had all new parts in it. The only thing that was left over from toyota was the block, head, crank, and oil pan.
-I have arp hardware through out the engine
-Im running a commetic 2.0mm head gasket
-Timing is and has always been 12 deg btdc
-The 440's that were on the car and the 550's that are on the car have been inspected by R/C
-Walbro pump, new.
-Aeromotive AFPR
-New fuel filter, Toyota
-Stock cpu
-Always been turbo timed
-NEVER AND I MEAN NEVER have I ran any thing less than 93 in this car
-Autolight 3923 plugs for the life of the engine
-Mobil one 15w50
-EGR is plugged at the back of the head, no cooler
-All head bolts were at 75lbs of torque (and yes I checked them)
-Ive never ran more than 14psi on a 57 trim ct26, and now with the monster on here Ive never ran more than 10psi.
-Ive never encountered a boost spike

Im off to put on the new gasket here this week.

If any one has some light to shed on how this could have happend, please discuss.

 

[Allan_MA70]

1uz AFM?

 

[MDCmotorsports]

550 lex combo yes.

 

[hottscennessey]

has it been 30k miles since you assembled the motor, or was that accumulative?

 

[MDCmotorsports]

Nope its been 30k since the engine was reborn. I do believe the block and head have a total of 250k on them.

I know both were precision ground (not machined) flat when rebuilt and I know both of them were x-rayed and magnafluxed before assembly.

 

[Allan_MA70]

its possable the head was soft! secondly theres a good chance the shitty ignition and fuel maps you end up with runing the 1uz afm helped it along!

that being said I did about 50,000km on a toyota head gasket and ARP bolts runing 440's, afpr and the lexus afm!

where the arp's torqued to 75 with arp moly or engine oil as lube?

 

[MDCmotorsports]

its possable the head was soft! secondly theres a good chance the shitty ignition and fuel maps you end up with runing the 1uz afm helped it along!

that being said I did about 50,000km on a toyota head gasket and ARP bolts runing 440's, afpr and the lexus afm!

where the arp's torqued to 75 with arp moly or engine oil as lube?

So you believe that the lex afm gives a crappy air, ignition and fuel map?

Explain?

The arps were lubed....

 

[Nick M]

Perhaps he means how the signal is lower that what it should be, so timing is incorrect.

I dont see anything in your report about cooling. As you partially indicated, a BHG isnt something that just happens, it is a side effect of something else wrong. The soft head, or overheating, even if it doesnt show on the gauge, will do it. Obviously the dissimilar metals dont expand and contract at the same temps, so overheating is disasterous to an iron block/aluminum head engine. Just a possibility. Your teardown will reveal more. Think of it as a learning curve when you take it apart.

 

[hottscennessey]

I know you're very knowledgeable, I doubt I could think of anything that you havnt already thought of. The best i can do is agree with what Alan stated about the head possibly being soft?

 

[Allan_MA70]

your shifting the fuel and ignition maps about 25% from the afm signal where it was tuned by toyota!

as the ecu see's it thats 25% less load to the engine so it dosent back off the advance as much or drown it with as much fuel under some load conditions!

its far from ideal! I personaly would not use it on a car with anything other then a stock ct-26 to about 12psi

 

[IJ.]

Wonder if it scales the KS threshold as well?

 

[siman]

There is your problem Jon, your headBOLTS were torqued to 75ft/lbs. You need about 15-25 more ft/lbs to torque

You probably ran too much boost to constant and the bolts threads/head of the bolts streched upwards causing a gap and a BHG. I see it all the time on turbo B series hondas.
I actually just took apart a Full Race turbo'd B16 for a friend to find that the bolt threads were stretched .009" and caused the ENTIRE head to lift off the block. He only torqed his ARP head bolts to 80lbs fearing any more would cause the threads in the aluminum block to stretch or strip under his 30lbs of boost.

Either way, ARP STUDS are the only way to go and the only way to prevent the bolt heads from stretching off the bolt shaft itself. Its a proven fact.

Also that compression of 160psi across all six does sound minimally (but nonetheless) BAD. Even with a 2mm headgasket ( about 1mm over stock) the increased space of 1mm or so should not decrease the compression by 10-20psi (given that good 8.5:1 compression should put us in the realm of 180psi). Hence my theory of the head lifting under boost loads due to the streched bolts.

Give those bolts a check. Were they OEM bolts or ARP?

-Jonathan Mann

 

[siman]

On the same note, I had a friend run over 500whp on his rebuilt 7m with a SP67 when it first came out about 3 years ago. The first dyno he did, the head gasket blew and, no joke, coolant spewed from the sandwhich area between the block and head. He was trying to run in excess of 25lbs of boost.

His longblock was completely rebuilt and all, though he used OEM head BOLTS and torqued them to 55ft/lbs. I have the video somewhere of the coolant spewing from the block.

I think you have a MILD head stud thread elongation failure/happening/occurance.

Also you can check this video and documentary of the phenomenon out:
Second video of head stud failure:

http://exvitermini.com/mr33.htm

-Jonathan Mann

 

[bigal0043]

in his first post he said arp hardware so im assuming it was arp studs... im surprised that with you not running alot of boost and really covering everything that you blew a hg...

maybe you will design a new head for all of us that flows better and wont get a bhg so often.. just something to think about

other than that i dont have any advice


*edit* on the post above that was his problem only 55ft/lbs

 

[Allan_MA70]

umm he said ARP hardware :nono:

*switchs lights off*

 

[siman]

ARP or no ARP, either way torquing to only 75ft/lbs is still LACKING when your running a boosted motor.

I stand by my theory, again a THEORY.

 

[Disced]

^^

You mean hypothesis; not theory...

A hypothesis is something you have come up with and a theory is something which has stood the test of time being proven countless amounts of times.

Just sell your car and leave bro.

Thanks

 

[Dirgle]

So you believe that the lex afm gives a crappy air, ignition and fuel map?

Explain?

The arps were lubed....

If you could clarify what you used as lube, that would help. moly or engine oil?

The reason I ask is because ARP recommends 86 ft/lbs with moly lube, however that number goes up to a 106 ft/lbs recommendation if your using 30 wt. engine oil.

 

[shaeff]

There is your problem Jon, your headBOLTS were torqued to 75ft/lbs. You need about 15-25 more ft/lbs to torque

i'm going to go with a... NO. 75ft lbs is fine! i'd have gone higher, personally, but i doubt the headbolts being torqued to "only" 75ft lbs caused his BHG.

many people run 75ft lbs.

-shaeff

 

[bigaaron]

This is why a wideband in-car is so nice. You could have been running lean under boost for a long period of time. Did your plugs show any signs of detonation? Reguardless, I know it is a sucky situation and sometimes it is hard to pinpoint the actual cause.