I am a new member. i have been collecting 5.0 parts to put into my 1993 miata. My miata is still a daily driver and i do not want to hack it apart prematurely. I have front and rear subframes from a 1995 miata and would like to complete the differential and motor mount fabrication before the 4 cylinder is removed. this is a problem in the fact that i cannot mock up the motor in the car to find a good spot to weld motor mounts in. i was hoping some one could give me the dementions where the 5.o motor mounts should be located.

 

Welcome to the forum.

Somewhere in this bunch of pics you may find enough info for you to make an educated guess as to where to put the mounts. Basically, the motor mount biscuits from a 70's Dodge truck are attached to plates that are bolted to the block at the original motor mount points. So that establishes the width. What ever the width of the block mounting points is, that's what the width of the subframe mounts need to be. Minor adjustments can be made at the block plates (slotted holes), as well as the top plates of the subframe mounts (more slotted holes or just revised plates). You might want to use the two-piece scheme that I used for the subframe mounts, as it allows some vertical adjustment, as well as making for easy changes to the absolute position of the subframe mounts, i.e. just make a new piece with the holes in the right place.

I would suggest offsetting the motor more toward the passenger side than I did originally. There's really no reason not to, and it would make more clearance at the steering shaft.

MiataV8 Conversion: Modified stock subframe

Mike

 

But wait, there's more...

MiataV8 Conversion: Tubular Subframe with Ford 302

I put up a few more pics that may show the relationships a little better. Note how the mounts appear to be almost in line with the steering rack mounts. The angled mount was necessary to clear the power steering connections on this particular car. Yours may vary.

Also be aware that the oil pan should be modified for best location. A stock pan can be used, but the motor won't be as far back as possible and will sit somewhat higher.

Mike

 

I was planning to make a Martin style subframe like the one in tony laboy's build.
http://www.cardomain.com/ride/530924...photo-gallery/
One of the pictures on this page gives a good illistration of where to install the mounts.
I am trying to avoid a total subframe overhaul like the one in your first link or Stein's build.
Stein's DIY 5.0 build thread - Page 2 - MX-5 Miata Forum
In the end i wanted to modify some shorty headers to come out in the wheel well like the martin kit. If i am unable to modify the headers then i will ask Martin nicely to sell me his headers. I have heard people saying they are $650. I will try to avoid that seeing as my core drive train cost less. But i digress...
How much should i offset to the passenger side? What is the approximate hight of the mounts from a stock miata K member? And after moding the oil pan will i have enough room for a high volume double sump oil pump?

Edit: it is odvious to me now that the motor needs to be as low as possible. I will remove the oil pan from the short block and mock it up to the K member to establish the hight of the mounts and then modify the pan as needed. I still need to know how far to offset to the passenger side.

 

Thanks for asking this question, rowen... And your replies, Mike. This helps me and even convinced me to join the forums (which I should have done anyways)!

 

If you're planning on minimal mods to the subframe there's not much you can do to maximize header clearance by moving the motor over. And really not much need to, either, if you're going to imitate or use Martin's headers. My inclination from the start was to use off the shelf headers and make them work, which led me to the Hedman mismatched setup, and ultimately to offsetting the motor.

Maybe someone with Martin's subframe will come up with the numbers.

Mike

 

The Hedman mismatched setup does sound like a good idea compared to a hack job Martin imitation. i bought some 11 gauge steel plates and am going to start chopping up a sub frame this weekend.
New question: how far from the fire wall are you 5.0 guys mounting your motors? As i said before i am trying to fabricate a sub frame without an engine bay to mock it up in. without some basic measurements i am just shooting in the dark. ANYONE who has a 5.0 Miata, PLEASE snap a pick of your engine bay and post a few dimensions!

 

If you make your oil pan fit the sub-frame, your engine placement should be about 1" from the firewall as measured from the rear of the left cylinder head.

 

are you referring to a stock 1993 5.0 oil pan ( what I am working with ) or a modified marlin pan?

 

Modified pan. All that is basically done to modify the pan is to flatten out the area between the 2 humps & square off the back side of the front hump & the front side of the rear hump so the pan will sit lower over the cross member. It can only sit so low before it will hit the rack & pinion. You will most likely need the engine/trans assembly installed in the car with trans cross member in place to set the height of the motor mount attaching points at the frame.

 

I managed to get my last two builds about 1/4 inch from the firewall on the driver's side with that area of the firewall "massaged" back about the same 1/4 inch and the air diverter (Smog) tube removed from the heads (that alone buys you 3/4 of an inch). All together this added inch helped out greatly when I went to move my fans behind the radiator with a full fox-style accessory setup (other than the power steering pump).

-Jason

 

This subframe is very nice. If they do offer it for sale like they planned to do it's a very viable option if you want to avoid the pretzel exhaust of the Monster Miata kit. Depending on the price of those off the shelf headers he lists, how much you'd save by not shipping your subframe out to San Marcos, and how much Martin would take off the kit price if he did not have to mod the front sub and oilpan it may actually be a break even on a new build. If I do another build or my headers on this car ever need replacement I'll look into it closer.

-Jason

-Jason

 

You mean when (not if) you do another build...

 

I basically did the same thing. There is a limit to the benefit obtained by firewall massaging because the real limiting factor is the interference between the oil pan and steering rack. When the front sump of the oil pan is cut back vertically to the point that it is just slightly clearing the oil pump, that defines the practical limit to how far back you can place the motor. Same with the horizontal cut, it can only go to the point of interference with the rotating assembly, then add some for running clearance. That's assuming you don't move the steering rack, the location of which is generally considered to be sacred and many bad things will happen if its location is violated.

But there's a limit to all this anyway, even the LS motors, with their rear sump, cause issues if you try to get them too far back, things like interfering with the A/C, heater, gas pedal, footroom, etc.

Mike

 

Awesome blog, Mike.
I had to pretty much download the whole thing because it is chock full of great and needed info!
KUDOS!!!!!

 

If you all don't mind I'm going to flip this thread out of emissions into the Ford build section. It's great info and would probably be missed here.