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Installation of HM9c Headers

Started by _jklumpp_ , Apr 03 2011 08:22 PM

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27 replies to this topic

#1 _jklumpp_

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Posted 03 April 2011 - 08:22 PM

Got around to attempting to install my HM9c Headers today....
Now I wasn't expecting it to be easy, as they do say you may need to modify the floor & engine mount, but bugger me it was a lot more difficult than I imagined!

So, expecting the problems with the engine mounts, I propped the engine under the sump, and removed the mount altogether.... but the headers still wouldn't go on.
Problem was trying to get the end stud (#6) into the hole in the headers - the headers were hitting the engine mount bracket on the crossmember, and stopping me from aligning the holes....
So I took the die grinder the the crossmember bracket, and removed some meat, but after several trial fits, and removing more meat, I didn't seem to be getting closer.... I also bent the bracket down for more clearance, but still not enough to engage the stud....
OK, so what about removing the stud? well I tried that too, but the bloody thing wouldn't budge!
In the end, I jacked the engine a bit higher, and got the clearance to get the pipes on - all sweet...
Lowered the engine back down, and a few hours & a bit of skin later, I got the engine mounts back on OK too.... but the headers will not come off with the mounts on - Surely I don't have to remove engine mounts every time I want to take the headers on & off?
There's not much clearance to the engine mounts themselves, so they will need to be trimmed, but I don't know that that will be enough to be able to remove the headers with the mounts in place.....

I know I'm not a pioneer with installing these things - what others experiences?
What do I need to trim, and how much?
Do I need to replace the studs/nut with a cap screw or bolt?
Or maybe make the end hold in the headers a slot rather than hole?

Attached is a photo of the mount & modification to the crossmember bracket - am I doing something wrong here?

Advice/ help please anyone?!!?

Attached Files

IMAG0096.jpg 1.11MB 13 downloads

Edited by jklumpp, 03 April 2011 - 08:28 PM.

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#2 _CraigA_

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Posted 03 April 2011 - 08:30 PM

Your engine seems low for some reason. It's like your block is mounted lower than it should be???

My HM9Cs fit in my LC with only a simple floor modification. They are close the the area you cut on the engine mounting but do not hit.

I use bolts on both ends of the headers and studs and 12 point nuts on all others. The headers are sprung together a little but nevertheless easy to fit and remove.

Are your engine mount plates Torana ones?

Edited by CraigA, 03 April 2011 - 08:33 PM.

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#3 _jklumpp_

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Posted 03 April 2011 - 08:40 PM

Your engine seems low for some reason. It's like your block is mounted lower than it should be???

My HM9Cs fit in my LC with only a simple floor modification. They are close the the area you cut on the engine mounting but do not hit.

I use bolts on both ends of the headers and studs and 12 point nuts on all others. The headers are sprung together a little but nevertheless easy to fit and remove.

Are your engine mount plates Torana ones?

Yeah Craig, that's exactly what it seems like - that the engine is too low.
Not sure about the mounts - they are the ones that have been in there as long as I've had the car.... but the engine is from a HR (HP block)??? How do I tell?

I think removing the end stud might help... I have (front to back) Stud, Cap Screw, Stud, Cap Screw, Cap Screw, Stud, Cap Screw, Stud.

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#4 _CraigA_

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Posted 03 April 2011 - 08:51 PM

Maybe someone on here has a way to tell what the engine mount plates are from.

What about the engine mounts themselves? If they are too short then maybe that's it?

I just went down and measured mine - the engine mounts are 65mm from the top of the flat metal plate to the bottom of the mount, below where the bolt joins then to the cross member. It's all pretty hard to get to as it's underneath the carbies

If I can measure anything to help let me know.

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#5 _jklumpp_

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Posted 04 April 2011 - 12:31 PM

Just had a look on Rare Spares, and there are only 2 types of mounts for red motors - Eh-Hr, and HK on, and mine are definitely the Torana Ones...
One difference I did notice though is that (in the pics) the rares ones don't have the end piece that sticks up (that look like 2 hands praying!)
Posted Image

If I cut that off it would no doubt help, & I guess that as long as the tabs would still hit the plate it shouldn't effect the integrity?

Can't find anything on the bracket that connects the mount to the engine block though - so not sure if they changed at all?

Edited by jklumpp, 04 April 2011 - 12:31 PM.

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#6 _CraigA_

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Posted 04 April 2011 - 02:05 PM

I found these pictures of my mounts out of the car. Hope that helps.

Posted Image

Edited by CraigA, 04 April 2011 - 02:06 PM.

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#7 _jklumpp_

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Posted 04 April 2011 - 03:09 PM

yeah, your engine mounts look like the Rare's ones.... So if I trim them to be like that, it might be a good start.
Brackets look the same though, although I imagine if there is any difference it would be small, and hard to tell from photo's....

Thanks again Craig....

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#8 _jklumpp_

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Posted 05 April 2011 - 08:22 PM

So Craig is the only one who has installed HM9C's?
No-one else with experiences to add?

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#9 orangeLJ

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Posted 06 April 2011 - 07:32 AM

Next time ispeak to ray, I'll ask him for you as im sure he has.

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#10 dpz

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Posted 06 April 2011 - 09:52 AM

I remember trimming the engine mounts when i did mine, but had no other issues. Body clearance wasn't an issue either.

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#11 _Agent 34_

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Posted 07 April 2011 - 08:38 AM

JK,

what was the cost of the headers and what make are they.

Also what was the modification of the floor pan area ?

Ive got the trimmed left side engine mount, but need to know if there is other mods that need to be done, prior to the car getting painted.

thanks grant.

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#12 _Agent 34_

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Posted 07 April 2011 - 08:51 AM

don't worry about the headers make and the and the make - sorted. got the cost - $470

still need other info though

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#13 _CraigA_

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Posted 07 April 2011 - 10:28 AM

The floor will need to be modified where is sticks out on the lower passenger side footwell.
Leslie did mine so just speak to him or Glenn when you are out there next. They know what needs to be done.

We took a reasonable amount from mine as I wanted enough clearance to make sure it didn't hit and that the floor didn't get too hot.

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#14 _jklumpp_

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Posted 07 April 2011 - 05:15 PM

Hi Grant,
Assume you worked out they were HM headers HM9C's?.... and I think I paid about 1/2 that price, but was just lucky! (found them in an online repco clearance sale!)
Mine don't actually hit the body, but are probably within about an inch of the area Craig mentions.... I may do some slight modifications to get extra clearance.... but I've also got to add another 6" to the collector, which may change things again....

I'll be having another go this weekend, with engine studs removed and mount trimmed - we'll see how that goes.....

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#15 _Agent 34_

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Posted 08 April 2011 - 08:38 AM

Gents,

This was the engine mount modification that was done to the cross member of the GTR, you can see the cracks in the K frame that have now been repaired.

I was not going to use this cross member and bought another one without the cut off engine mount, but the cracks were worse in the K frame.

Im using this one and have just cleaned up the cutting. It was done with a oxy and it must have still been in the car when it was done as the splatter marks were everywhere.

Just through that I would add this photo to the thread for anyone wanting to know the cutting than can be done.

Not sure how structural it may be, but there was no other signs of distress with the engine mount on the K frame apart from the cracks, which are apparently very normal.

JK, I had to sit down with the price of the extractors and this was striaght off the maker $470 seems high, so I'll be saving up again,

grant.

Attached Files

engine mount mod for extractors.jpg 53.92K 7 downloads

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#16 _jklumpp_

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Posted 13 April 2011 - 08:00 PM

Hey Grant,
Thanks for the pic - If I had an Oxy, that's probably what mine would have looked like! It looked like that in my mind when I started, but using a die grinder instead I found I didn't need to go that far.

I finally got them in on the weekend - had to do a fair amount of work though! Trimmed the end off like the rares ones, bent the pipe side tab around, ground it down, ground down the side of the mount, and put studs in only on right side notches (so the pipes could be slid into position from front to back)... then finally it all went together!
.... not sure why it was so much more difficult than anyone elses, but it wasn't going together without all that work!

So now I've extended the collector, welded the flanges on, & mated the exhaust pipe up.
This weekend will be painting & wrapping the headers, and then getting it all back together.... then on Monday off to the mechanic for a proper tune.
...For all the effort to fit these things, I hope there a noticeable gain!

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#17 biga064

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Posted 13 April 2011 - 08:07 PM

Hey Grant,
Thanks for the pic - If I had an Oxy, that's probably what mine would have looked like! It looked like that in my mind when I started, but using a die grinder instead I found I didn't need to go that far.

I finally got them in on the weekend - had to do a fair amount of work though! Trimmed the end off like the rares ones, bent the pipe side tab around, ground it down, ground down the side of the mount, and put studs in only on right side notches (so the pipes could be slid into position from front to back)... then finally it all went together!
.... not sure why it was so much more difficult than anyone elses, but it wasn't going together without all that work!

So now I've extended the collector, welded the flanges on, & mated the exhaust pipe up.
This weekend will be painting & wrapping the headers, and then getting it all back together.... then on Monday off to the mechanic for a proper tune.
...For all the effort to fit these things, I hope there a noticeable gain!

Hi can you give us a honest opinion on any performance gains ? Thanks

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#18 _jklumpp_

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Posted 18 April 2011 - 09:02 AM

Well didn't quite get there this weekend...
Was all going well, go the headers wrapped & painted, and services the car in between, but when I went to fit them up, of course it wasn't that straight forward....
Had to shave some of the sides of the inlet manifold to fit, and then of course the studs, screws & bolt are in different places, and have to be made to fit, and the inlet manifold has a 12mm mounting face, and the headers a 10mm! Grrr
Ran out of time then, so will have to get back to it next weekend....

Does anyone have any suggestions for the difference in thickness between header mount & inlet so that bolt applies same pressure to both?
I don't know whether to weld a 2mm plate to the headers, or just make a 1/2 washer that fits on the headers side, or grind/weld the factory washers/spacer to have a 2mm difference 1 side....?????
...arrrgghh - remind me why we love working on cars?

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IMAG0122.jpg 894.81K 4 downloads

Edited by jklumpp, 18 April 2011 - 09:07 AM.

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#19 orangeLJ

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Posted 18 April 2011 - 03:09 PM

I've got the same issue with my extractors and inlet, I was running washers with a small weld down one side, ground flat so it seated properly.

Helped fix the issue but was a bit shitty looking.

Ive got some alloy washers machined up and the sides of them ground to the right height.

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#20 _Agent 34_

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Posted 18 April 2011 - 04:07 PM

Any photos of the engine mount mod ?

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#21 _jklumpp_

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Posted 18 April 2011 - 06:18 PM

Best I could find, but still hard to see....
Tab closest to headers bent back toward block & material removed from end of tab, & material also removed from base plate adjacent headers.... & NO, I aint pulling it all back out to get a better photo!!

Attached Files

mount.jpg 207.78K 1 downloads

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#22 _Bomber Watson_

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Posted 18 April 2011 - 07:07 PM

I ground the Holden washer things to suit on one of my motors, made custom ones on one of the others...

Ground Holden was neater.

Cheers.

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#23 warrenm

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Posted 19 April 2011 - 09:19 AM

Here's a few pics of some washers that I've used in the past.
Another method is to weld a spacer to the header flange, but you have the pipes fitted & you don't sound to keen to take them out again.

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P1010673.JPG 75.33K 5 downloads
P1010674.JPG 70.48K 2 downloads

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#24 biga064

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Posted 19 April 2011 - 04:46 PM

Here's a few pics of some washers that I've used in the past.
Another method is to weld a spacer to the header flange, but you have the pipes fitted & you don't sound to keen to take them out again.

Do one at a time !!!! No need to take headers back out .

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#25 _jklumpp_

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Posted 22 April 2011 - 10:43 PM

Well they're finally IN!!
Started at 9am this morning - welded some 2.5mm spacers on the headers, and then re-assembled... at 11am, I had 1 bolt to do - at 4.30pm, I still had that same one bolt to do!!! (manifolds had been taken on & off several time in between!)
After getting all the bolts/nuts in place, and nipped up, I found that I could only get 2 of the nuts on the studs finger tight - the spanner wouldn't fit between the manifolds & nut!... pulled it all back off again, decided there wasn't enough meat on the manifold to remove any for clearance, so had to remove those 2 studs and replace with cap screws...leaving only 1 stud because I could only have studs on the right side of the headers so they can be slid into place from front to back....
So now there is only 1 stud, and the rest are bolts & caps screws.
Then checked the bolts for clearance before re-assembling, and found some were too long & would bottom out in the head, so had to trim them down....
Re-assembled again, and then that same 1 bolt wouldn't tighten right up because the washer was binding on the side of the manifold....
Undo the bolt & washer again, trim the washer a little more, and re-assemble....
Finally at 5.30pm, everything was in place and time to give it a check start......and......IT WORKED!!! (and sounded AWESOME with an open exhaust because I hadn't bolted the exhaust back up yet!)
6pm, she was back on her wheels, and took her for a test drive.... now I may be imagining it, ut it definitely felt gruntier.... and had a different sound.
Pipes are knocking somewhere though when the engine lopes at idle, so I need to look at that...

Looking forward to the results following a tune