BHG AGAIN within 2 months.

[spunkenhimer]

I just did a BHG REPLACEMENT that took me awhile and finally got the car back on the road and running pretty nice i thought.
anywho about 3 weeks ago i was coming back up from Jacksonville NC (where my girl stays) and started getting white smoke out the back again. "To be sure i don't have another BHG right after i just replaced it." i thought. Well my dad told me that a Bad catalytic converter can cause the car to smoke really bad and even be the root cause of the first BHG well we took it off today and found it was horribly clogged up. I then crancked the car again in hopes that it was just the catalytic converter that was causing the white smoke and all but yet again it started smoking only just a few minutes after starting her up. I got another BHG within 2 months after just replacing the first one. Thing is i'm wanting to prevent anymore issue if possible for awhile cause i'm going to eventually do a 1uzfe swap. But i would like to have the car running in the mean time.
any suggestions on what i should make sure of this go around?

[Sonyps307]

Did u torque to 78lbs or more? Did u have the head shaved? Get some Arp head studs they have more clapping force.

[ksd9000]

Your dad has it backwards...

BHG causes the coolant to dump into the catalytic converter that causes it to fail, get clogged up etc.

Tighten the head to 80 ft lbs. If you are palanning to run the engine for a relatively short time, dont waste you cash on expensive studs/MHG etc.

[MJG]

re torque of the heab bolts / studs, after replacing the head gasket is, in my opinion, always a good pracice.
72 LB FT maximum for stock head bolts.
75 LB FT for ARP bolts.
80 LB FT for ARP studs.

[spunkenhimer]

thanks guys i'll post pics of the tear down and rebuild again. hopefully this time it will be quicker.

[cre]

Torque specs:
http://www.toyota-supra.info/forums/84660-post8.html

Make sure you chase the threads in the block and lubricate the fasteners thoroughly with a GOOD moly lubricant.

Were both the head and the block inspected for cracks, pitting, warpage?

Generally if a HG is already leaking I don't recommend re-torquing as an attempted fix... You're liable to trap moisture and open yourself up to cavitation of head or block (and with an old HG possibly compromise the reinforcement rings around the coolant jackets and cylinder bores). If the block's really expendable then feel free.. if it works, then you've lost nothing as it's only going to be in there for a year or so and if not well, you're still pulling it.

[spunkenhimer]

cre sorry its taken me so long but no they weren't i did my own inspection of them and they seemed fine. I think this time i'll do it right i'll be getting my tax money here soon and I'll be putting towards it getting done.

[cre]

You may come to find that 'seems fine' and 'is fine' are two VERY different things, especially when you're talking about precision machined parts operating under significant force and thermal extremes.

A crack which is not visible to the eye can open up a disastrous amount once the head is torqued in place. As they may be difficult to see with the naked eye, florescent or UV reactive dyes are applied as they will be sucked up via capillary action and thus highlight any cracks under UV.

A warped head or block can have an excellent seal in most areas but one weak spot can blow in a week and ruin all of the efforts you've put in to it.

Pitting is a bit of both of the above in many ways. It acts like a crack as the coolant may be able to just push through under certain conditions due to the HG not having enough pressure in those areas much like warpage causes; If moisture manages to move through it on a regular basis the cavitation will continue to erode the block or head at an ever increasing pace.

If you ignored any significant pitting or didn't check anything for warpage well, it's a bummer, but anyone with shop experience and 90% of hobby mechanics would have told you right away that those are a must (it's covered in the manual too). The same goes for running a thread chase though all of the threaded headbolt holes in the block.