I didn't see any response to your questions, perhaps everybody is on a Facebook page somewhere. I now have 2 302 Miatas, both have the original Ford PS pumps and serpentine belts with no problems. I don't have the fittings documented, but it must have been pretty straightforward.

One of the sections of that blog shows some pics of the fitment of some Ebay tri-y headers, but the fitment is based on the subframe I built, so can't really comment on your chances with a V8R sub. Those Tri-Y headers are a copy of the ones Shelby used on the original GT350 Mustangs, which had a very narrow engine bay, similar to Miatas, so it looks to me to be a good place to start. They are available in painted steel or stainless, the painted ones may be easier to modify if necessary.

My feeling on the offset is that you should put the motor where it best fits. As far back and as far to the pass side as possible. Corvettes since 84 and all Vipers have significant offset toward the passenger side, for the same reason as V8 Miatas, steering clearance. Look closely at the mounts on the V8R subframe for LS motors. And it can only help your side to side weight balance with driver.

Thanks for supporting the forum, there's a ton of info in the archives relating to Ford conversions and now you are part of that.

Mike

 

Hi Mike. Your responses are VERY helpful. Thank you!

I'm now satisfied that I can go with the Ford PS pump and make it work. I've spent time on your (GREAT!) blog; I'll visit it again. My question about the headers is really if the subframe is the only limiting factor, or if the car's frame rails come into play. From what I can tell from pictures, the exhaust side of the cylinder heads exits below the level of the frame rails, but it is hard to tell. If only the subframe comes into play, I think the V8R / tubular one likely frees up pretty good room for a close-fitting header. I've seen at least a couple fabricated long-tube SBF headers on this forum. And of course V8R / Kooks has a long-tube for the LS crowd (I emailed Kooks and they don't have an off-the-shelf SBF application for a Miata).

And yes, I will certainly post any lessons I learn along the way on my build.

Again, thanks.
Bryan

 

Hi Bryan,

Great work thus far well done.

I can attest to the use of a Ford power steering pump on the Miata rack without issues. I use the Ford Explorer GT40P steering pump and accessories brackets on my car. You are correct with the long tube headers and the subframe. The subframe is the limiting factor here. There is ample room for a 1 3/4 inch long tube exhaust setup. It will need to be custom made but there is room to make it work and make it work well. Both V8R and Monster Miata can do a custom subframe. I use the Monster Miata subframe. My setup is trickier than yours because my car is RHD so the starter AND the steering arm are on the same side. Your car will have much more clearance. Not that mine is bad, its actually pretty good (see my build thread) considering the stuff that's packed in there. But the steering on the other side would have made it a breeze.

My advice, get a custom subframe and exhaust if you want it to perform, need it neat and want clearance everywhere.

cheers

 

Thank you much for the additional advice, and for confirming both Ford steering pump and long tube headers. I've spent a lot of time on your build thread!

Cheers,
Bryan

 

I can attest that a tubular subframe definitely make long tubes easier...(if that is such a thing).

Great buld BTW!!

 

awesome work on your build, just wanted to add that the T-bird 5.0's have the E6TE heads. If you are doing any performance upgrades you will have to toss those heads in the scrap metal bin. There is a fin at the intake valve to promote swirling, may work for low RPM stuff but did not work well on the track. I changed to Mustang E7TE heads and gained 1.2 seconds in the 1/8th mile with no other mods.

 

Hi folks,

Thanks much for the additional relies.
"Engineer," I revisited your build page. Those are fantastic Tri-Ys! I don't suppose you have any pictures off of the car??? I was planning dual 2.5" pipes to a merged 3" at the rear (through a Corsa muffler - I used to work there and love the sound). Looks like this will work out fine, particularly since my block is not a stroker.

"Trueblue," I also appreciate the confirmation on the tubular subframe, long-tube headers. I'm running long-tubes on my '83 Mustang and think they are the only way to go. Any dyno comparison suggests this is the case. I'm planning a longer-duration cam, and it seems that's where the scavenging of a long-tube is most beneficial.

"Movieboy," thanks. The heads will be ditched in favor of AFRs. On my '83 Mustang build I hand-ported a set of E7TEs. It was a major budget compromise at the time; one I don't plan to repeat on the Miata 5.0L. :-)

My sons are raising a major "save the Mustang" campaign. So my latest thought is to go back to my original plan - pull the 2k mile 306 from the Mustang and put on a new clutch / new rear main seal and designate that the Miata engine. Then do a re-hone / re-ring and drop that back in the Mustang (with the hand-ported E7TEs). With the Miata in the garage, the Mustang will never see track or autocross again, just ice cream runs, so it should fare okay with a mild rebuild. The plan evolves....

 

Hey Brian,

So sorry but I dont have any pics of the Tri Y's off the car. But I can tell you that they are 3 separate pieces per bank and they do NOT have a common flange at the head. Each cylinder has its own little flange, which makes it possible to remove them and put them in in sections, as a full 4 cyl; wide solid flange just wont fit in.. The setup is 1 3/4 tubes from 2 cylinder pairs into a common 2 inch pipe. Then its 2 x 2 inch pipes into a 3.5 collector then to a 2.5 inch outlet. Then its two by 2.5 in pipes until before the diff. Then it merges into a single 3 inch pipe. Sounds great, not noisy at all and packaging is neat.

cheers

 

Very helpful! Thank you much for sharing all of the details. If I can't get that replicated, I'm not working with the right fabricator. :-)

Again, if this is working for you on a stroker, I know it will keep up with my 302.

Cheers back (I always liked that greeting),
Bryan

 

Well, after a summer of autocross and track lapping (I do love this Miata!), the Miata developed a bad vibration around 70 mpg. My shop re-balanced all 4 wheels and indicated some play in the bearings where the driveshafts enter the differential. So, they think it is driveline vibration. That means, IT'S TIME TO DROP THE DRIVELINE AND PUT IN A V8!. I'm working on the 8.8 differential mount with an additional rear subframe I have. I also just ordered the V8 Roadsters mountless tubular front subframe. Does anyone know the tubing size on the V8 Roadster subframe? Looks like most everyone uses the front "up" bars to attach their frame mounts. I'm buying some steel for other reasons (door bars) and would like to go ahead and get some stock for the motor mounts as well. Thanks.

 

If you keep the Tbird front drive the Alt.sits slightly lower than the SN95 Alt. just a FYI tidbit.

 

Thanks, Trueblue! When I bought the salvage motor it was missing the alternator and bracket (the power steering pump was on there, which I plan to retain), so I think I will be going with custom / fabricated accessory drive brackets. I appreciate the tip though.

 

I got a response from V8 Roadsters, in case anyone needs this in the future. The side rails are 2"X1" rectangle (I thought they looked square), and the main hoop is 1.5" I can only assume that the uprights are 1.5" as well. I'll likely attach the motor mounts to these, as that appears common. I should have a subframe in 4 weeks!!

As an aside, I am a frequent reader of the MotoIQ site, mostly folks from Sport Compact Car that I read avidly back in the 90s. They built a motorcycle-engined NA Miata and used a V8R subframe and ran some interesting cross-bracing. There may not be room for that with the 5.0L oil pan, but I am considering the advantages of a subframe cross-brace.

Cheers,
Bryan

 

Hi Mike,

Thanks again for providing the drawings. They have been INVALUABLE the last couple of weeks as I have finally been working on the differential mount.

Bryan

 

Looks like I missed several steps in my updates. I rebuilt the Ford 8.8 last October on my workbench - new friction plates, seals, and a coat of paint.


I tore down the 5.0L and polished the crank journals.

I sent the block out and had it machined 0.030" over, and had new pistons mounted on cleaned rods. I've painted the block and put main bearings, the crank, and the cam in. I will focus on that once I get the differential mounted.
I'm benefitting from a LOT of people going before me. I'm taking a slightly different approach to the differential mounts. I'll explain and post more when I have a complete set of pictures, but I at least got the front mounts welded on last evening. After all of the cutting and drilling, it's nice to be able to start welding things together!!

Front differential mounts on subframe

 

I had some productive garage time this weekend. My thanks to everyone on this forum and on YouTube that have posted about mounting a Ford 8.8 someplace new. I've gathered pictures, drawings, and videos to borrow a lot of great ideas. I don't trust the strength of my welds, so I redesigned to run a bolt all the way thorugh the subframe, front and rear (7.5" front, 6.0" rear). I have reinforcement plates on the "top side" front and rear as well. I also ran steel tube through the subframe rails front and rear and welded / covered them up, to ensure that I couldn't crush them later. I cut up and studied the Thunderbird subframe before I scrapped it and found that the differential was mounted THROUGH the subframe rails, rather than ON them. I thought I should do the same. The extra long carriage bolts are there to help me line everything up. I found it was not easy to drill successive holes and keep them in line (not having a boring machine). I have Grade 8 bolts for the front on the way. I'll wait for some warmer weather to paint it, and its done. Now I can focus on building the engine!

 

Hand lay-out and tools

Front mounts

Extra holes do not go all the way through - measuring for inserts.

I cut this plate in half. More surface to weld to, and shimmed up the 1/8" gap.

Rear mount complete. Added extra brace to seam of rail. You can just make out the bolt heads on the back side, welded in place so they function as studs.

Completed mounts.

Top reinforcement plates.

 

I was surprised to find a 1/8" gap between the rear plate and most the length of the subframe rail. I didn't trust my welding that much of a gap. Maybe this is why this part of the mount has failed a few people? Anyway, I cut the plate in half to give myself more to weld to, and shimmed the gap with 1/8" steel strip. Along with the gusset to the rail seam, I expect this to be pretty strong. Most of the force will be transferred through the pass-through bolts anyway.
As I noted above, grade 8 bolts 7.5" long are on their way for the front mount. The overly-long carriage bolts were very helpful to line all of my holes up.

 

ARP main studs in
Now that the rear subframe is complete, I can work on the engine! I had laid the main bearings and crank in before, but just used the original bolts temporarily. I installed the ARP studs and torqued them properly. The crank still spins freely - a good sign. I need to press new ARP bolts into the connecting rods and I'll install the pistons.

 

Long overdue for an update.

I pulled a Thunderbird 5.0L for the "SN95-like" accessory drive. I'm finding that there are a few notable differences between the Thunderbird and true 94/95 SN95 Mustangs. Most prominent so far has been the water pump. I bought a nice, Stewart 94/95 water pump. It matched up fine to the timing chain cover, but the hub had a different bolt circle. My previously painted Thunderbird pulley didn't match up. Fortunately I found this before installing the water pump, so back to Summit it went, and I bought a dedicated '92 Thunderbird pump. Impeller was the same design, so I'm hoping it will function as well. It was that or buy a 94/95 Mustang water pump pulley, and I decided to go this route. I had to chase the threads in the water pump pulley hub to get the bolts in all the way (they are 5/16-24 threads).
I also got the power steering pump off and replaced it (Thunderbird non-variable-effort pump). In case you want to replace the goofy 6-point-head mounting bolts (E-Torx socket to remove them), they are M10-1.5 by 30mm. I got some button head stainless bolts because there is not much clearance to the pulley.
I'm currently wrestling with the Summit-sourced harmonic balancer (SUM-163302). I have the original Thunderbird balancer and one off my Fox Mustang side by side and they are identical. When I assemble the "maximum depth" setup on the Summit balancer, the crank pulley is not in line with the water pump pulley. Looks to be about 5/8" too close to the engine. Odd, since I would think this is replacing a very common balancer size (4.19" deep, measuring from bottom to top of bore, top being the lip that aligns the crank pulley).

 

There is a spacer needed to position the crank pulley correctly... Give me a few and Ill post the number.

 

Here you go

Spacer

 

Hi TrueBlue,

Sounds like you had this problem, too! Thanks much for the response!!

Bryan

 

The other thing I meant to post for future users of the SN95 accessories is that the inside edge of the accessory belt appears to be close to 4.5" from the plane that the timing chain cover bolts to. Same plane formed by the front face of the cylinder head on the passenger side, at least with my AFR heads. That should help get all of the accessories aligned. I'm using the stock power steering / AC bracket (minus the AC), but will fabricate something to hold the alternator. I'll post a more exact / confirmed measurement when I have the full accessory drive assembled.

 

Finally getting the swap started!!
To quote Rafiki from The Lion King, “It is Time!” The original driveline is distressed enough that I don’t want to tempt something exploding. Time for the V8 transplant! Hopefully I will be updating with progress regularly this winter.