BHG jOb

[cuel]

Why are you taking the head apart? Let the machine shop do it. They have the experience to get it done right.

To answer your question, I just pulled them off with pliers. Since I'll be installing new ones, I wasn't worried about tearing them up. You are talking about the rubber seal, and not the steel guide, correct?

 

[Figit090]

WOW why are there so many people saying not to reuse the stock head bolts? the TSRM specifically does NOT list them as a part to replace in this ordeal. I went through this SAME debate when I did my BHG fix and ended up reusing them. This is the second time they've been reused if they were reused when the original owner blew the headgasket, and i have about 2k miles on the engine since then. Plus I was a beginner learning as I went with help from people on these boards (thanks again guys).

I can show you my thread later if i can find it. its pretty long though and i dunno if you feel like reading it...if you do let me know.

A good machine shop will put your (engine) head in a hot bath or chemical bath to remove ALL the carbon and oil. you can then have it checked to see if you have leaks and need a valve job, and they can do all that for you. Then they can check it for warping and refinish it. If i remember right, my head cleaning and re-surfacing didn't go above 60 dollars. A quick pressure check was free on the valves. hopefully you checked to notice if you were burning oil before this, but if you have a lot of miles on the clock new valve stem seals isn't a bad idea. i wish i put them in but i don't really burn oil with 111k miles on my engine so at least that's a bit on the bright side.

I used a toyota OEM gasket set on my engine, scraped the block with a razor, got the head done, did misc. cleaning and such, stuck it back together, and it seems to be OK! I see my temp guage go up a little now and again but i'm not consuming coolant and i think i have a little air bubble right now. in combination with absolutely NO OEM shrouds...i dont think its a BHG. i need shrouds....

but yeah dont take the head apart unless you know what you're doing. and if you haven't already - keep your lifter pucks and cam bearings are removed and replaced IN ORDER or you will have to double check that they all fit properly within spec when the head is reassembled. I think the cam bearings are numbered but of course the pucks are not. machine shops should take the head with this stuff removed, maybe even less. if you've removed more just take it how it is i guess.... dont bust your ass when a tech can pop those out in seconds.

I didn't bother - but one thing you can check upon reassembly is cam bearing clearance. I did however check my lifters to make sure they were not too tight. they were a bit on the loose end of spec, and they tick now, but they are still fine. but if you want to avoid a little ticking, you can spend a few dollars and get new pucks that will stick you within spec. you'll have to do measuring or pay the machinist to do that though.

best of luck with all this.

OH and another thing - PLEASE consider heli-coiling your exaust studs. If they are not done I can almost guarantee you will strip at least one out, most likely in the back by #5 and 6 exaust ports. this is in my BHG thread too i think. I didn't do them (as per my machinist's suggestion) and ended up buying a new angle drill and helicoil kit for doing it IN-CAR once the head was on. one of the worst feelings i had while doing this was getting it all on and then feeling that exaust stud begin to pull out as i got the exaust on...

Best,
Andrew

 

[Frank Rizzo]

the worst feelings i had while doing this was getting it all on and then feeling that exaust stud begin to pull out as i got the exaust on...

My thoughts exactly.

I had to helicoil 4. All 3 surrounding cylinders 6 and 5, and 1 near cylinder 3. Had to do all 3 around cyl 6 with the head installed on vehicle. Worst labor day weekend of my life.

Do them ALL with head off the car!! Or better yet, have a machine shop do them!

 

[cuel]

I think you may be over tightening the exhaust nuts a bit if you're pulling the studs out. When I installed my OBX header, it had a slight bow in the flange. Following the correct tightening sequence(center out, ALWAYS, EVERYTHING), I was able to pull the flange straight, and didn't strip a single hole. Either you're trying to get the nuts to tight, or the head has been severely over-heated, and the metal has become to soft. I believe this would be called "annealing," although I'm no expert in the field. More than likely, its a combination of the 2....

According to the TSRM, the exhaust manifold flange nuts only take 29 ft. lbs.

 

[Figit090]

I think you may be over tightening the exhaust nuts a bit if you're pulling the studs out. When I installed my OBX header, it had a slight bow in the flange. Following the correct tightening sequence(center out, ALWAYS, EVERYTHING), I was able to pull the flange straight, and didn't strip a single hole. Either you're trying to get the nuts to tight, or the head has been severely over-heated, and the metal has become to soft. I believe this would be called "annealing," although I'm no expert in the field. More than likely, its a combination of the 2....

According to the TSRM, the exhaust manifold flange nuts only take 29 ft. lbs.

your correct on the cause, that is exactly what happens, but you're incorrect at the rate at which 7mge's have this problem.

The design of the 7m engines give them inherent heat issues, especially near the EGR recirculation - back by cylinders #5 and #6. Pulling exaust studs out of the aluminum head in a 7m is common and when i came across this during my repair, i was told by several people on here to do it. One person I remember had to do it to numerous 7m engines, not just one. I didn't do it because my machinist said he didn't think it was needed and he was an honest good guy. i took his word for it, but he was wrong. they pulled right out, and i think one stud even pulled out when i took the old nut off - the rust made it a bolt and the soft aluminum hadn't a chance. those studs have a short bite for such soft aluminum - and with an older head that's softened as you said - there is a high chance they will strip.

its not that expensive and if you're careful you can do it yourself without much trouble, especially with the head off. ask how much it would be to have all the studs helicoiled and re-installed at the shop, if its reasonable (look at the price of helicoils in your parts store before hand) go for it.

plus, engine builders recommend it because it makes the studs virtually bulletproof, never to strip the threads again. :icon_bigg

 

[Frank Rizzo]

As far as over tightening them, yeah doubt it! You won't get anywhere near 29ft/lbs before you start to strip them. One of my 4 started to strip at 12ft/lbs. I used a snap-on digi torque wrench (like I do on EVERYTHING) and only torqued to 26.4ft/lbs (yeah, thats right, .4), TSRM says 29 which, I personally think, is too liberal. As far as the heat causing the problem, BINGO!! We have a wiener. My head gasket was fucked right in line with my manifold studs, go figure......

Too much on the exhaust studs and not enough on the head bolts, good ol' yoda. They probably thought it would even out....... <------ Joke

It's also a good idea to replace the studs and nuts from the dealer, they are pocket change and with all 7 helicoiled, you will NEVER have an exhaust leak at the manifold ever again in your entire life, which is a very good thing.

 

[cuel]

lol, aye, I can do it myself, easily....

With installing electric fans, and having an adjustable temp. switch(the probe type), I've taken temperature readings across the head(top, exhaust side, and intake side) with an infrared thermometer, so that I could set the fans to run at the correct temps. Under normal idle, at operating temp., I got around a 10 degree difference(190 at cyl.1, 201 at cyl.6, with the t.stat open[that's where I set my fans to come on at]). After running hard(1 mi. loop, on a rarely used access road, after letting the car reach operating temp.) for around 10 min.'s, I got around 195 at cyl.1, and around 210 at cyl.6 I fully expect a motor this long to be hotter at the back then the front. 210 is a good temp., still within normal operating parameters. Now if it was 125 or higher, I'd be worried. This is with the header installed, and egr system intact. I don't know if that would make much difference vs. the stock manifold.

As far as the egr, it seems it only works through cyl.6. I'm not sure if this would have a cooling or heating effect, or if it is just there to comply with U.S. emissions crap. I examined it carefully on a head and intake I have apart, and can't see it working with any other cylinders, do to the design. I've seen in other threads where people have stated that without it, the back of the motor was hotter. It could be that if the egr system is working correctly, you could expect cooler temperatures back there. I don't know this as fact, as I have yet to experiment with it.

 

[Frank Rizzo]

You bet your ass it only uses cyl 6. Next time you have the manifold off, look in cyl 6's port, you see that hole facing the firewall?

Yea infrared thermo's are good but not entirely accurate as you are measuring surface temp only. My valve covers never really get hotter than 200 at the rear, if you want to compare. Of course ambient temp, and other factors create variables in this comparison, so it is not quite accurate. And yes EGR helps COOL exhaust temps. Over and out.

 

[cuel]

I measured the temps across the top of the head at the coolant passage, not the valve covers. No, infrared thermometers aren't entirely accurate, but its much more accurate than the stock temp. gauge. Couldn't get used to the feel of that digi. tq. wrench(or its constant need of batteries). Happy with my Matco clickers.

Egr would only cool the exhaust on cyl.6. If it was plugged on the intake side, you'd have hot exhaust gases trapped at the back of the head.

 

[Frank Rizzo]

That's right. And since every 7M with over 100K will have their passages (either in the EGR valve itself or the passages in the EGR cooler) clogged, it would actually hinder not help. And that is why cyl 6 gets so hot. My EGR passages are nice and clean thank you very much. Mine had a hole the size of a pencil tip for a passage into the EGR at 120K.

And who still uses the stock temp gauge? LOL! Might as well have a sticker that says $2000+ instead of a red mark.

 

[iwannadie]

I think you may be over tightening the exhaust nuts a bit if you're pulling the studs out. When I installed my OBX header, it had a slight bow in the flange. Following the correct tightening sequence(center out, ALWAYS, EVERYTHING), I was able to pull the flange straight, and didn't strip a single hole. Either you're trying to get the nuts to tight, or the head has been severely over-heated, and the metal has become to soft. I believe this would be called "annealing," although I'm no expert in the field. More than likely, its a combination of the 2....

According to the TSRM, the exhaust manifold flange nuts only take 29 ft. lbs.

When I did my bhg I was putting it back together doing the exhaust studs, using my torque wrench. I got to the last stud and never even put alot of pressure. 29ft is no thing and it stripped out at maybe 25ft the stud just turns.

 

[wchico15]

well guys, i just read all of the replies. alot of great info.
i already dissembled the valve spring assembly,etc. but i still just cant get the valve stem seals off. im going to take the head to get it cleaned,milled and see if they can take out those stem seals.im also going to look in to the exhaust studs and get that checked out.

figit090-it would be great if you could find that thread on your BHG job. ive been looking for one but none are good. hopefully you could shine some motivation. the info you gave was really great too. appreciate it.

PICS***

vavle springs,keepers in order.

cams,bearings,cam gears, in order

chico just kickin it.

 

[Figit090]

looks like you did a good job keeping things in order! you'll thank yourself for that later on

Here is my beginning "what the hell am I doing" thread;

http://www.supramania.com/forums/showthread.php?t=19541

Here is my "I got it apart, cleaned, and organized, what the hell do I do NOW" thread;

http://www.supramania.com/forums/showthread.php?t=24017

When you're done and start contimplating a re-torque here is my... "do I HAVE TO retourque?" thread... not an issue unless you want info on head studs.

http://www.supramania.com/forums/showthread.php?t=34166

there are other threads relating to my BHG but these are the main 1,2, & 3 that ultimately led to completion.

If you're worried and don't think the TSRM is correct by saying the studs dont need to be replaced, or you think yours could use replacing, get some new OEM studs. Better safe than sorry i guess. I feel the thought on this is 50/50 and i'd hate to tell you not to get them and have them go bad. but you read the discussion on this already.... have you seen the TSRM on BHG repair? seeing it for yourself could help. if you haven't decided.

This is kinda dumb i just looked at my overflow bottle today and it's 1/4-1/2 inch below full.... that better be normal. I'm hoping it was just an air pocket that never worked itself out.... :nono: thats why i reconsidered what i said about the bolts. however if it was a BHG i'd bet its because i didn't clean the block well enough or i overheated it because i have no shrouds. I doubt a BHG but right now i'm not seeing any other reason to loose that coolant other than the air pocket i heard last week. then again maybe thats it. :biglaugh: I think i went over 68ft/lbs and since my bolts were already stretched (from the factory when installed) i doubt its a retorque problem. oh well. i'm rambling. I bet it's an air pocket i never burped properly....
:icon_mad:

 

[cuel]

When I did my bhg I was putting it back together doing the exhaust studs, using my torque wrench. I got to the last stud and never even put alot of pressure. 29ft is no thing and it stripped out at maybe 25ft the stud just turns.

As far as over tightening them, yeah doubt it! You won't get anywhere near 29ft/lbs before you start to strip them. One of my 4 started to strip at 12ft/lbs.

I see. So the high temperatures in that particular area are causing the aluminum to become so soft or brittle that 20 ft. lbs(more or less) can pull the threads out. If it got hot enough to effect the threaded holes for the studs, wouldn't you be concerned with the integrity of that entire section of the head(from deck to cam journals), and the ability of the head to keep a seal in those particular areas? Seems it would be easy to contort/crack the head there, especially when using head studs, and a much higher torque spec. There are probably other problems that could arise, as well.

Please, correct me if I'm wrong as, for me, this is just speculation. I know that if you heat any metal beyond a certain point, it will remove any tempering it previously had, and wonder what that point may be here. I'm sure there is someone here who has a much better understanding of what actually happens to the head under these conditions, and can give a good answer to my question.

 

[wchico15]

suh-weet info. sounds like me and you started just the same "complete newb" "step by step" lol. reading up on them as i type.


p.s. JUNIOR MEMBER!! WOOT

 

[IJ.]

Localised annealing.
(and why a lot of 7M heads banana when unbolted)

 

[Frank Rizzo]

cuel: Put it this way, every 7M will have stripped exhaust stud threads, but not every 7M will have a warped head.

figit090: was it the coldest morning since your last coolant flush when it went 1/4 inch below the full mark? If so, don't worry about it, that is normal. If you have no idea then keep an eye on it.

 

[Figit090]

Hey thanks Frank...actually yeah I had it parked a few nights outside and I haven't done that in a LONG time... and it was a few clear cold nights where the car was pretty freaking cold - and it was on a slant. that is/was the only time recently i've heard the 'waterfall' since before and just after the BHG before the burping....

i'll keep an eye on it and maybe try to burp it again (i probably won't but...maybe)

 

[wchico15]

ok so i take the head to a local cylinder head machine shop and i let the guy look at the head.at first i wanted to know if he could just mill it and clean it and how much it would be. he then tells me that the some of the coolant passages are rotting and that it'll need welding. he said that just milling it and cleaning it will only last 6 months before it starts messing up. so i asked how much. he said $200. he then starts tellin me that the head is in really bad shape. and that im better getting a valve job too. he said in total it would be $400. i was surprised. he said he could get me a completely brand new head ready to bolt on(cams,vavles,etc) for $525. now im just an amatuer and i dont know exactly how much things should really be, but i think this guy is trying to play me for a fool. i figure $60 bucks to clean it and mill it so that leaves $140 just to weld 2 maybe 3 of the coolant passages?

 

[cuel]

If you don't trust him, get a second opinion. If it really needs that much work, I'd say $400 is a good price. I'm paying $300 to have my 7m head cleaned, vacuum tested, valve job, reassembled, and some machining done on the cams. Cleaning usually cost right around $50, and milling should be right in there as well. It does look like the coolant passages in the exhaust side of the 2nd(right at the bottom, it looks like its right up against the ring) and 3rd cylinders from the top are getting a little close to the cylinder seal marks from the old head gasket. I'd say it sounds like a good price.