Custom sierra engine mounts

[GRPABT1]

Hey guys, I'm sure at least a few of you have come across engine mount dramas in your 1.3L screamers before, well so have I. 4 of them in 6 months of owning it actually. The under engineered mounts just cannot handle the torqueing of the motor at high revs and with a GTi motor like in mine that's compounded a little more. The problem seems to only be with the passenger side mount which seems to tear from being stretched to much when revved hard. I have tried a chain bolted to the block and chassis to no avail, (it just stretches the chain).

So here is my plan, custom engine mounts! Probably just the passenger side unless I am thoroughly impressed with the final result so as to want to bother replacing the drivers side which is good.

Below is a quick paint drawing of what I intend to make, using a 3 inch offcut of 1 inch X 4inch (or there abouts) RHS with a thread welded to the one side. Inside there will be a plate with a thick pole piece welded to it and then a threaded piece welded to that which will protrude out the other side of the RHS. This plate will be suspended in either 3M window weld or devcon 80 shore urethane (depending on cost and availability).

The blue in the pic represents the urethane, the yellow is the suspended plate with pole piece and thread and the grey is the RHS surround and attatched thread. The red arrows represent the movement of the inner plate/pole piece/thread.

So... what do you guys think? I will post pics and measurements as I go and it should be easily replicated. Please feel free to offer any opinions as many minds are better than one and I would like to do this right the first time.

[wattyzuk]

If you put the cup shaped metal cap back over the mount when it's replaced you will most likely solve problem. Wattyzuk

[GRPABT1]

I've tried it with and without the metal cap on there, why do you say that?

[wattyzuk]

The metal cap is there to limit the flex in the mount and therefore reduce the likely hood of the mount tearing it's self apart

[GRPABT1]

I don't think it is doing a good job then! Mine seems to tear straight out and only when I rev it to 7000rpm+, not really flexing sideways at all. If I didn't rev it it would vertually last forever but I can't help myself :D

[rustyzook]

whats next? rev it to hard it might show some leg :):):):):) like my old subie!!!

[GRPABT1]

Well it is a GTi motor and the factory rev limit is 7500rpm and it's still there. You can actually get a chip to bump it up to 8300rpm and apparently they love it. The Gti's come with forged crank and conrods and to tell you the truth I think it is running a little rich if anything so I doubt it would have a shit with the factory rev limit still in place.

[GRPABT1]

All the welding and cutting is done, just have to buy the window weld and apply it. I will probably end up using sikaflex's version of the 3M stuff as I can't find 3M window weld yet.

[Aerenandmel]

Well it is a GTi motor and the factory rev limit is 7500rpm and it's still there. You can actually get a chip to bump it up to 8300rpm and apparently they love it. The Gti's come with forged crank and conrods and to tell you the truth I think it is running a little rich if anything so I doubt it would have a shit with the factory rev limit still in place.
you can buy a 10,000rpm chip too...............old bud at tamworth takes his there regulary! must be tuff donks ah

[GRPABT1]

10k seems a little high for a stock motor for me, I would assume they would need a set of bd14 or custom cams to get that kind of RPM not to mention upgraded valve springs. They will do 8300 stock quite easily.

[rustyzook]

what are they like offroad with that motor in cause that one in tamworth dosent seam to belong to the one person for long!

[DieselJack]

Gidday GRPABT1, back in the late 70's when I was playing with big Ford V8's we used to tear engine mounts fairly often as well. We fixed it by drilling a hole through the engine mount and putting a bolt through it with a nylock nut to limit the amount of stretch on the mount. We'd leave the nut 1 turn loose so the mount could flex a little.

Cheers,
John.

[GRPABT1]

Yeah I thought of that but there isn't alot of room to fit a bolt through the standard mount. I had a chain limiting stretch but it just stretched the bloody chain! This custom one hasn't cost me anything so far and will only cost the amount that the urethane costs (around $17 from memory) so ends up cheaper than a factory mount anyway :D

And rustyzook, they go alright offroad. Still no low down torque monster but with the right gearing and some revs they are great in a lightweight package like a sierra. On the road it's nowhere near as quick as my Worked V8 commodore but still just as much fun with it's high revving nature. I guess they would be alot like the stock 1.3L but better, eventually I would like to rebuild mine with a sc12 toyota blower for more low down torque.

[rustyzook]

nice nice, iam thinking a 1.3 swift but it sounds hard and alot of money!

[GRPABT1]

I have finished applying the urethane and I think it will work great. I ended up using the Sikaflex 11FC which has a shore hardness of about 45 so isn't very harse but should hold up nicely. My only concern is that it can stand the heat being close to the header as it's recommended max temp is 80 deg C. I have a metal heat shield that should help with that but I will have to wait and see. I'll give it a few days to fully set then wack it in and give it some redline action to test it out.

[GRPABT1]

Ok the mount has been there for a few days now and seems to do the job well. It's a little stiff but idles normal, cruises and revs fine but makes a slight vibration for a second when you let the revs drop to low like under 2000rpm which it doesn't like anyway.