Issue with Head / Ex Man mounting

[gottadiesel]

As some reading this already know, I am doing a partial re-build on my 7mgte starting this weekend. Well I did a little work on this motor last spring just after buying it and just enough to get it on the road. It included but not limited to replacing the turbo with a used one off of a JDM motor and while doing that, replaced EMG, as it was leaking. Of course I discovered while putting it all back together that the issues of it leaking, I think came from a missing support for the turbo - goes from top of turbo to head, so I constructed a replacement one.

Ok enough of background, when re-installing EM, 3 head bolts would not go to Spec'd tourqe (I think it was like 26lbs or so) so I put heli-coils in all of them, but 1 would still not catch, it went to like 18lbs and started to slip, so I have to go to a 7/16" heli-coil, as the next MM size would not fit through EM hole.

Does anyone have experience with having a machine shop fill and re-build these so I can go back to stnd size EM bolts... avoiding having to find a new head and I am not certain the the 3rd one will go through another remove and re-install to torque.

Thanks for your time in reading and offering your experiences...

 

[mkIIIman089]

7/16 isn't a problem, I think driftmotion actually sells a kit so you can helicoil them all with the larger studs. With the thought being that they will hold up better.

 

[grimreaper]

Enlarge the holes on the exhaust mani. to fit the stud. Dm's kit works great! (do them all or do it again later < speaks from experience)

 

[gaboonviper85]

7/16 isn't a problem, I think driftmotion actually sells a kit so you can helicoil them all with the larger studs. With the thought being that they will hold up better.

It's a thought that wasn't thought of very well...bigger doesn't mean better.

 

[Weeves]

I helicoil'd all my exhaust holes to 7/16. Works great!

 

[gaboonviper85]

I helicoil'd all my exhaust holes to 7/16. Works great!

So you say.

 

[lewis15498]

Having the exhaust stud holes strip out is usually a sign of annealing. Did you have your head tested for hardness?

 

[gottadiesel]

OK, did not mean to start an argument lol... So gaboonviper, you do not agree with being ok to go larger, what is your recommendation and/or experience?

To enlarge holes, I would assume that I need to have machine shop do that, being cast material, but if I do them all 7/16" I do not need to enlarge holes, it is a perfect fit...

Anyway I appreciate everyone's input

 

[gaboonviper85]

Going to 7/16ths means you'll have to drill out the holes even larger for the helicoils...this is bad!

This is bad because there isn't much aluminum around each hole as it is...this means less meat...the aluminum is already soft from annealing so now you'll be removing more material....this can promote cracking, further striping, coils too just pull out over time (you'll notice the nuts won't stay tight after you put some miles on)...it's just bad!

I recently rebuilt my head...my head wasn't annealed (or atleast not as bad as I've seen)...but what "I" did was, helicoiled for a smaller stud than stock "3/8-16"....this meant I didn't have too drill out much aluminum at all!

I'm not arguing as the only people who would argue this simply aren't that smart when it comes to this type stuff....I machine for a living so I just kinda see this stuff as basic...although I consulted ij about doing this first he too agreed with my idea and it wasn't new info to him either as he is a machinist also with years more experience than I!

 

[gottadiesel]

Yes I can see why that would make sense, which is why I wanted to take them back to stock. So I am assuming there is no physical way to convert the one that I have @ 7/16 back to the stock (I think they were 10x1.25 - right?) Anyway so right now I have 1 at 7/16", two @ 11x1.25 and the remaining being stock... so what to do, what to do...

I appreciate your insight from your experience with supras and as a machinist...

 

[gaboonviper85]

Were they helicoiled? If it wasn't helicoiled then maybe (I'll have too look up the drill size for a 10x1.25 helicoil tap). If it was helicoiled then probably not unless timecert makes a custom insert....

 

[gaboonviper85]

Just reread your info....you already fucked a stock size helicoil correct? If so then your only option is too drill it out and go bigger or fill with weld and start over...both suck

You may be able too have an insert made too keep stock bolts but you'll still be removing more aluminum from the head which is the real problem here...

 

[gaboonviper85]

Your honest best bet is to timecert them all to 7/16....timecert is a better more solid design unlike helicoils...a cert will distribute the load much better...this is in my opinion the only logical thing to do at this point...short of gettin a good head.

 

[gottadiesel]

Thanks for all of your insight, I will watch for a head between now and when it is time to take the head and block to machinist, if nothing reasonable is found I will take the route of time-sert, I had heard of them, but have had no experience with them, so I appreciate the info - for anyone else reading, here is their web-site -

http://www.timesert.com/index.html

Thanks to all of you for your time and advise based on your different opinions and experiences...

 

[mkIIIman089]

It's a thought that wasn't thought of very well...bigger doesn't mean better.

I worded it in that specific way for a reason.

 

[bigaaron]

The 7/16" helicoil kit is an inexpensive way to fix the exhaust stud issues for most people. If the head is really in bad shape, it may need timeserts, or to be replaced with another head. IMHO, tapping it with 3/8" would be a complete waste of time and money. If a 10mm stud pulls out, 7/16" is the way to go. Many hundreds of heads have been saved with our exhaust stud kit. Most 7M heads have a small amount of soft annealed aluminum around each stud, but it doesn't go very deep, drilling it and tapping it to 7/16" gets into harder aluminum, and the helicoil helps protect the aluminum around the stud from further damage.

 

[gottadiesel]

I think once I have head off, I will post pics of the condition of the holes now and see if the helps determine best route... Again thanks for the input and advise based on your experiences...

 

[IJ.]

Might also consider 2d Helicoils if trying to save soft heads.

 

[gaboonviper85]

The 7/16" helicoil kit is an inexpensive way to fix the exhaust stud issues for most people. If the head is really in bad shape, it may need timeserts, or to be replaced with another head. IMHO, tapping it with 3/8" would be a complete waste of time and money. If a 10mm stud pulls out, 7/16" is the way to go. Many hundreds of heads have been saved with our exhaust stud kit. Most 7M heads have a small amount of soft annealed aluminum around each stud, but it doesn't go very deep, drilling it and tapping it to 7/16" gets into harder aluminum, and the helicoil helps protect the aluminum around the stud from further damage.

It does not get further into the harder aluminum...the more you open the hole the closer you get to the exhaust port=softer

 

[nick88]

Did you torque the studs or nuts?