S14 SR20 Trans Mount Height

[brianstj]

Hiya,

After several extended delays, I am finally back to working on my S14 SR20DE conversion on my '68 1600. I have the frame all stripped down and I'm working on the mods to get the new drivetrain mounted. I have all of the SPRISO components offered for the conversion, as well as the huge library of pictures (which are enourmously helpful), but I have a couple positioning questions to throw out there.

I am setting the front/back position by the shifter - centering up the new shifter in the stock body hole by measuring off of the mounts on the frame - looks to be about where most of the other conversions are sitting. The left/right positioning is a no-brainer - just get everything centered up. What I am not sure about is the height placement. I have a good idea of how to do the plate for the rear transmission mount based on the pictures I've seen, but I have no info on the optimal height to place it. If I can get a good reference dimesion for that rear mounting plate, then I can level things from there and stick the front in place. Anyone have a recommendation?

Also, my engine/trans came without a rear transmission mount. Any ideas on sourcing one?

Thanks!

[SR311DET]

Brian,

My name is Eric and I help out Michael at Spriso when ever I have time and currently working on my own conversion. When setting up this it is common for us to use a 2x4 dug fur piece set on the short side at the end of the snout where the drive line goes. You will also notice that the bolts for the trans mounts are going to be close to the x member. You also can use a angle finder and match the pinion angle.

When it comes time to use a trans mount we always use a Energy suspension GM trans mount. It is cheap, new and most auto stores even stock this part. It also is a direct bolt in and is very low profile. The part number is 31108G and ebay has good reference photos.

One thing to remember is to make sure the trans is level side to side on the top of the shifter plate and not the valve cover as the engine sits at a angle.

Hope this helps

Eric Straw

[ppeters914]

Just in case anyone wondered, dug fur = Douglas Fir.

[brianstj]

OK...so about 1-3/4" between the frame X and the ottom of the end of the transmission case? Cool!

Thanks for the info on the trans mount as well!

[JFBrink]

Brian,

The Spriso folks obviously know what they're doing, but let me offer a nerd-based method to double check the stud-based method.

You ultimately want the centerline of the tranny output shaft on the swap to be at the same height as the centerline of the output shaft on the stock tranny. Otherwise, you're creating a different pinion angle than stock, which is not desirable.

I don't know about the '68, but on my '66, that gave me a height from the top of the x-frame plate to the tranny output shaft center of 2-1/2".

Hope this helps.

Jesse.

[spriso]

Jesse,

Don't forget that your Miata transmission is a different length than the SR gearbox, which will put the centerline of the output spline on the rear of the transmission at a different height than it does for our applications. As it turns out, a 2x4 placed under the rear of the transmission at the end of the case puts the gearbox at the right angle (when using our JIG anyway!)

Michael
spriso motorsports

[JFBrink]

Ah, I should have thought of that. So, to double check the 2x4 method mathematically, you'd need to do a little trig. But, why bother with math when you've clearly determined its accuracy empirically!

Best,

Jesse.

[brianstj]

So is this where we are talking about throwing in a 2x4 to set the tail shaft height?

SR20TailSpacing.jpg

[spriso]

So is this where we are talking about throwing in a 2x4 to set the tail shaft height?

Yep. Looks good from here!

Michael

[brianstj]

So at this height for the tail shaft, it does not look like there will be much clearancing needed for the speed sensor module. Some of the pictures I have seen show a pretty significant dish out of the X - anything I am missing?

It also looks like the notch for the trans mount plate does not have to go too deep in to the X - but again I have seen pics that show this notch going all the way from top to bottom. Is this just for easy access to the trans mount bolts once the plate is welded in?

One more question....any recommendations on the height of the front of the engine? Any tricks like the 2x4 under the tranny, or do you level it off the shifter plate?

Once I am solid on these questions I think I will be about ready to permanently mount the SR20! Thanks for all of the help and input so far!

[spriso]

Brian wrote:

So at this height for the tail shaft, it does not look like there will be much clearancing needed for the speed sensor module. Some of the pictures I have seen show a pretty significant dish out of the X - anything I am missing?

The more of a notch you can give the speed sensor, the more room you will have if you ever need to remove it. Also, if you are planning on leaving your speedo stock, then you are going to want more room for the 1600 90-degree adapter. We find it is easier to make more room now so you don't complain later.

It also looks like the notch for the trans mount plate does not have to go too deep in to the X - but again I have seen pics that show this notch going all the way from top to bottom. Is this just for easy access to the trans mount bolts once the plate is welded in?

Every swap is different. We find that it is easier to notch the crossmember all the way through and then build a plate for the trans mount to sit on... And yes, it does make access to the transmission bolts much easier if there is a 'shelf' for the trans mount to sit on.

Any recommendations on the height of the front of the engine? Any tricks like the 2x4 under the tranny, or do you level it off the shifter plate?

We have a JIG that we use to set the height of the engine which also centers it in the engine compartment. If you read the "Bob" thread (S13 SR20DE swap into a 1969 Roadster) you will see how we determine center line and height.

Remember, you want the BOTTOM of the pan to be level. Use the photos that are on the DVD and on this website to give you a good reference for setting the height.

Good luck and keep us updated with your progress!

Michael