Another P1800 build - All NB Miata from radiator to rear axle

After 74 trips around the sun I decided to do yet another build.

This new part of the forum seems appropriate for this type of build.

My car restoring/ building spans 50+ years with most activity in the last 40 years.

I personally do 99% of all the work (for my cars only, to do it for others would steal the fun). The only tasks I can't do is the actual engine machine work since I don't have the equipment.

This project fell in my lap indirectly due to me by buying 2 cars from one of older friends that is aging out (even though I had 5 other antique/ vintage cars).

First I bought his 50 Chevy Styline Deluxe sport coupe from him


Then his 1933 Chevrolet Master a few years later

He knew I had some interest in early Volvo's PV's (shrunken 46 Ford sedan styling) (influenced by my son. Next is my 63 PV544 I just gave to my son.


During the restoration of a 1 owner 544 and trying to chose a color, I ran across a fenderless PV544 build.

I thought at my age (70 at the time) I really would enjoy not having to bend over the fenders to work on it. After studying the image I realized it was a Photoshop Car only. Undeterred I found a ragged 1958 Volvo PV 444 on Facebook and this happened. With a 93 Chevy s10 2.8L v6/ 5 spd as the parts donor from the radiator fan to the rear axle and a mustang II front suspension the game was on.

 

Well my good friend that I bought the 50 and 33 chevy from told me about a buildable 1958 Volvo Duett 2dr wagon near him and also 3 P1800 parts cars. Being addicted to the 4 wheel types I couldn't resist looking. By the time I got around to visiting the cars, I had already ruled out the wagon. Good thing because when I got there the wagon was sold but there were 3 homely looking P1800's.



I've never been one to walk away from a challenge.

I knew from my PV544 and 444 builds I did not want the original suspension (almost no caster) or the original drivetrain (low performance 1800cc by today's standards. From the 444 I knew I didn't want the aftermarket MII type suapension iwth 4 bar rear suspension with low travel coilovers.

This led me to a Pontiac Solstice GXP - 260 hp turbo 2.0 L (I have always held the GM Ecotec 4 cylinders in high regard). Dimensions were very comparable with the P1800. So I found a 1 owner and bought it (I got it at a bargain because even though it was a 1 owner, it had been left out doors for years and had some sun damage).


After much study of dimensions in AutoCad of the P1800 overlayed on the Solstice I realized everything did indeed fit well except the width would have required ~ 3" fender flares (if I was 30 yeas younger I would have loved the wide body look, but I now want something a little more subdued)

I then stumbled on NOHOME's P1800 Kinda grassrootsmotorsports build thread. The Miata NA and NB are narrow enough but do require moving the front axle forward 6-7".

Being and old fart I opted for a a 2 owner 2002 Miata Automatic instead of a stick.

It runs and drives great but after digging deeper I learned about the dreaded IMMOBILZER security system and Mazda no longer sells the IMMOBILZER module (it reads the computer chip key and sends a code to the PCM ) which leads to a dependency on used junk yard parts and when those run out you are left with a BRICK. I looked into aftermarket ECM/PCM's like Megasquirt but quickly learned that these were all only compatible with manual transmissions (the Automatic trans TCM could not talk to the aftermarket ECM's).
Well this led to a 1999 3 owner Miata 5 spd which apparently doesn't need the computer key and it''s associated paraphernalia and being a 5 spd it has terrific after market ECM support due to the high demand by Miata enthusiasts (younger than me).

 

From the A pillar back the 1964 was the better body so I proceeded to cut the entire undercarriage from front to rear in prepartion for the Miata splice.

 

A few days later the 99 Miata comes apart - I mean REALLY apart - Plasma cutting party !

 

Split the Miata for the wheel base stretch. The P1800 wheel base is 96.5, the Miata is 89.2 so the stretch will be 7.3", all in the front because the firewall to centerline of rear wheel is 74.875 for both cars.
I will use some 11 ga for the splice with plug welds 3/4" back from the cut and seam weld at the cut.

 

Many steps to get to the first attempt to marry the P1800 body to the 99 Miata chassis. [/ATTACH]

 

This is awesome

 

Hell yeah!!

 

Wow, we watch “The Saint” where the Volvo P1800 is Roger Moores personal car and one of the stars of the show. You are a brave man!

 

I set the engine in and bolted the rear axle to transmission brace in. The engine is still in the OEM location relative to the firewall back but of course the front suspension/ crossmember is 7.3" forward.

As expected moving the suspension forward has created space conflict. The steering U-joint is in the way of of the A-C Compressor (using an old antenna as a pointer ). I will have to make new A/C brackets to raise the compressor about 3" and to do that I will also have to make a new bracket to raise the power steering accordingly.

I hope i don't have to lose the Power Steering since the A/C is an absolute must have.


I am considering several options for my space conflict with the front crossmember and A/C compressor.

1. Modify the crossmember with an extensive relief pocket so that I can rotate the rack so that the steering input shaft is almost horizontal so the U-joint at the rack (with rubber bellows) clears the A/C compressor. This method will require an additional U-joint and support bearing. A lot of work but lets me leave the A/C and PS pump in OEM position. There is a small risk when modifying the 2 rack attachment brackets that the rack is not exactly in the same position which could cause some bumpsteer or other complications.

2. Leave the rack in it's original position and make new A/C and PS brackets to move up about 2-3". This will end up crowding out the engine intake filter. There is always a small chance that my new brackets have a small alignment error which could cause premature belt failure. Also there is a small chance that the Miata 4 rib style belt doesn't come in the length I need.

3. Move the A/C up but delete the PS Pump. This would require a manual rack which for NB's is made from rare Unobtanium. Other option is to depower the rack either by simply draining the fluid and looping the rack left and right tubes together. For me to be satisfied with steering effort I would want to change to a 16" diameter steering wheel (that is what the P1800 uses, but unluckily the splines for the wheels don't match.)

 

Some very serious surgery is required to get the steering rack under the air conditioner compressor OEM location.

Establishing horizontal and vertical center line of OEM rack location so that the rack mounting brackets can be positioned correctly after rolling rack back to clear A/C compressor.


This huge cut will require internal stiffeners and some external stiffeners to restore crossmember structural integrity.


Crossmember surgery in progress

Steering rack rotated backwards to clear OEM compressor location, lower U-joint is at an acceptable 30°. I am adding a 1x1x1/8" steel tubing under the rack to help stiffen the crossmember after cutting so deeply. More internal stiffeners to come and then 11 ga to line the the new recessed area.

 

Man
You just used the words internal stiffeners
That means more Viagra adds on the off topic forum.

 

More progress

A/C Compressor bracket in progress using Vintage Air Slotted parts


Working on crossmember mounting brackets due to frame stretch


Working on Motor mount brackets, I trimmed the bottom ~ 1/2 of the engine side motor mounts and tacked 11 ga horizontal for the mounts to sit under . I am using Transdapt 9314 biscuit mounts - much easier to deal with than OEM mounts that are angled and if I need to raise the engine a little, shims can be added at anytime. I have used these mounts on about 10 engine transplants over the years. They have good vibration isolation and hold up well.

 

I added a 1x1x1/8" steel tube at the bottom after removing so much from the top of crossmember and then flipped the crossmember over and welded a 1x2x1/8" steel tube behind that. I also gusseted the reinforcement to the lower control arm attachment points. I am satisfied that the crossmember is as strong as it was originally.

 

Rusty rocker repair, 16 gauge inner flat plate, 18 gauge inner rocker formed on my old Harbor Freight brake.

Outer rocker will be 18 or 20 gauge depending on what I have on the shelf formed on my old Harbor Freight brake

 

Separated the factory welded together (monocoque) front clip - a royal pain - surface rust in the gutter around the fenders made finding factory spot weld centers impossible for some. Finally had to air chisel to finish separating. I will weld fresh metal on the inner fender structure where all the spot welds were drilled and stretched from the air chisel.

The front clip on this 1964 P1800 is too rough. I will use the front clip from the 1970 P1800 parts car when reassembling, I sure hope that it matches the 1964 car dimensions really close . I made a cardboard template of the fender cut point so I can transfer this to the new fender cuts.

Merging the P1800 to the Miata since I have the inner rockers rebuilt and stabilized - - - finally

 

Second day progress after a lot of trimming interference. The rear is down within an inch or so of final height. Front needs to go down 2- 3" but I am studying my options before proceeding.

I hope to have the ride height about 1 1/2" lower than a stock P1800 (which has 165/80R15, 25.4" diameter).

I plan on running 195/65R15 (25" diameter) on Konig Rewind Silver Wheels with Machined Lip (15"x 7") RW7510040S = + 40 mm offset. The big positive offset matches the original Miata wheels to avoid excessive fender flares (or maybe no flare). I prefer running 205/65R15 (25.5" diameter) because the sidewall would be closer to the same height as the original tire size but I think fender flares would be a must and would crowd the Miata lower A arm on full lock.
Presently the tires and wheels in the pic are standard 195/50R15 (22.7" diameter) on factory wheels. To me the low profile small tires look lost in the big wheel wells and don't look proper for a P1800.

 

I am vacillating between using the P1800 dash with aftermarket gauges and underdash HVAC and using the Miata dash.

The big upside using the Miata is it greatly simplifies wiring.

However, that ties me to future availability of parts (such as the instrument cluster, HVAC controls and HVAC evaporator, heater core and blower). For my piece of mind I would buy spares of each so that down the road a few years I don't brick the car because major alterations are required due to lack of available parts and I am no longer physically or mentally capable of the tasks (I will be already 75 this summer).

The big upside of the P1800 dash (modified as req'd ) is the universal aftermarket gauges and underdash HVAC which will be available longer than i will live. Also I like that a casual observer would not realize the car is really a Miata.

A potential really big electrical obstacle could be that the OEM instrument cluster receives the raw speed signal on the Y and O wires but the OEM instrument cluster sends the speed signal to the ECM and OEM Cruise Control on a Wht/ Blk wire - does it alter the raw speed signal before sending to the ECM and OEM Cruise Control ? I don't know who can answer the question.

The cowl is sitting at final height which lowers the car about 1 1/2 to 2" lower than Nohomes Molvo.

The Miata Dash is about 1' above windshield opening when the dash bolted to the transmission tunnel brackets only but sitting level.

I'm going to have to create a ~ 1" deep gutter to transition from the dash to the windsheild opening.

I am thinking I may install my front and rear glass in a bed of urethane or butyl windshield tape and then install the bright trim by gluing with weatherstrip adhesive or RTV or something that could easily be removed when replacing a windshield. I would have to close the gap around the glass with maybe a 1/4" of body filler so that the trim fits flush. I did this on a 1961 Rambler convertible in the 1990's because there was no windshield gaskets being reproduced at the time.

 

The Miata NB chassis fits inside the Volvo A pillar without cutting the corner brace (still need to lower body another 1")

 

I am looking to get it lower about like this Volvo P1800 Cyan Racing.
I am still finalizing the ride height considerations.

However, I am not opposed to modifying the Miata dash to slope properly towards the windshield, although I would likely loose the defrost vents (no big beal to me, I don't intentionally drive my old cars in the rain anyway).

I plan on epoxy primering the dash so I can skim coat body filler so that I have a smooth painted dash that appears metal.

 

Floor to inner rocker 18 ga angle temporarily screwed in place. The bottom of the inner rocker to the Miata floor is 3".


Inner quarter splice left side with .75 in emt conduit split for wires to rear of car along the floor to inner rocker interface.

 

Lookin good

 

Very cool I like!

 

That was in car and driver last year it's like 300k to buy one I believe!

 

This is a very ambitious project! Awesome.

 

I am digging this thread, and your skill set. But may I ask, how long has this taken so far to get it to this point?

I am looking forward to more installments.

 

I bought the parts cars and donor cars late September 2023. I got sidetracked on a 8 week project on one of my other cars which has delayed recent progress but I started back on this yesterday.

 

It's ambitious. I will be following along. Get er done!

 

This is fantastic! I love old Volvos. My old 1967 122s may have been the best car I ever owned.

 

Or what we call them in Sweden,,,,,,,Amazon!