GT40 "Variations"

[Seymour Snerd]

A long long time ago there was a long thread that at one point motivated me to catalog the differences between the SPF GT40 and its predecessors. I realized I haven't updated that list so I thought I'd repost it as a new thread that hopefully those of us obsessed with historical accuracy can use and maintain as a reference. My interest is mostly with Mk IIs so the details at the end are going to reflect that. I will incorporate any verifiable information on Mk Is that anyone wants to contribute. The "significance" tends to but does not always decrease as you go down the list.

1. Wilwood brakes with drum-type parking brake, cables and center lever vs. Dunlop or Kelsey-Hayes on originals
2. AC evaporator box where oil tank or spare tire might be, AC condenser in front of radiator; reciever-dryer, hoses, etc., AC compressor on motor vs no A/C
3. Ventilated seats simulated out of foam vs. webbing-suspended parachute cloth; no brackets to support original-style seats.
4. Cable shift in center-shift cars vs. rod shift. (no deviation for RHD)
5. Fuel tank crossover by flexible hose across engine bay vs. (this seems to vary among originals). Mk IIs I believe used large pipe across interior under driver's knees.
6. SPF has locking gas caps hidden within "Le Mans" caps.
7. "Rear flare" variations. Possibly SPF supplies all the interesting MK I variations. (?)
8. Stainless steel fuel tanks vs. form-fitting bladders
9. Pedal cluster welded steel vs. cast aluminum
10. Sponson ribs slightly different.
11. Bilstein shocks vs. whatever
12. Aluminum wheels (vs. Magnesium)
13. Aluminum uprights (vs. Magnesium)
14. MK II exhaust in carbon steel, vs. stainless
15. Mk II rear-most exhaust pipes slip joint in vertical section.
16. Muffler vs. straight megaphone
17. Engine variations (eg, Windsor). Installer choice.
18. Ford interior mirror vs. Lucas
19. Galvanized frame (I think Mk V's did as well, but then they have their own set of differences some of which are substantial).
20. ZF vs T-44 transaxle in Mk IIs. (installer choice)
21. Racing originals had various number light configurations.
22. Some MK I originals had colored recognition lights.
23. Originals: various quick-lift hook colors (eg white on P1032)
24. Rounder front fender opening profile (Mk I, not sure about Mk II)
25. Mk II SPF has Mk IIB front fender shape.
26. Mk IIB original: wider rear fenders, wider rear wheels (12"?) and tires.
27. Mk IIB original: cut away radiator opening below radiator.
28. Dash profile difference in LHD cars, less so in RHD cars (corner and edge profile)
29. Later Mk II original use "Holman-Moody" dash with SW instruments.
30. Later MK II original have roll cage.
31. Mk IIs have internal chain-driven dry sump oil system with oil tank on one or the other side of rear window.
32. Later Mk II original (?) run plumbing down left side of interior rather than through central tunnel.
33. Later MK II originals(?) use much deeper seat.
34. Later Mk II originals (?) foil covered insulation under rear clip over engine. (eg P1032)
35. Some Mk II originals foil covered insulation on interior firewall. (eg GTX1?)
36. Some Mk II originals (?) gray painted rear clip interior. Don't know about front clip.
37. Some Mk II originals mount rear AR bar off end of upper shock bolt.
38. Mk II orignals vary from SPF and (?) each other as to how upper rear lateral link loads are fed into rear hoop to establish "double shear" for fasteners.
39. Mk II original RHS frame engine mount forward of LHS engine mount.
40. Mk II original sponson cross section different shape from SPF.
41. Mk II original hydraulic reservoirs mounted near center and accessed through opening (i.e. without opening lid or removing clip).
42. Mk II original: some had contrasting fluorescent (?) paint across front.
43. Mk IIB original: some/all (?) had Ford "swash" along side. And then there's the "Mercury" thing....
44. Some Mk IIs had "non-overhead" passenger door.

 

[Kirby Schrader]

Al,

If you recall, the front swaybar mounts are different.

Kirby

 

[Seymour Snerd]

If you recall, the front swaybar mounts are different.

Had forgotten that; were there variations among the originals (eg. Mk I vs Mk II)?

 

[Ron R.]

Alan,

The changes that were made to fit the BB Ford motor in the Mark II chassis...didn't SPF make this change, but use the same chassis for both the Mark I and II versions?


ie, the SPF Mark I chassis could potentially fit an FE?

 

[Seymour Snerd]

The changes that were made to fit the BB Ford motor in the Mark II chassis...didn't SPF make this change, but use the same chassis for both the Mark I and II versions?

I'm somewhat unsure about all this, but based on my experience putting an FE into a 351 roller, with the exception of the rear clip I think the answer is yes, you could put an FE into an SPF Mk I and the "tubs" are the same. Again ignoring bodywork, the key difference is that the FE is mounted 1" higher and 1" further back (given the same transaxle, i.e. ZF). The position of the FE engine is dictated basically by the intersection of the bell housing and the rear hoop, and the desire to have reasonable ground clearance. Even with the shallowest wet sump the FE oil pan sits 1" lower than the tub in an SPF.

I've been told the SPF-supplied rear subframe for the FE-bound chassis is different (I think the longitudinal struts are further apart). I've never verified that. And because of the 1" higher position the upper crossmember is more shallow (that is the two big holes from which the transaxle is hung are 1" higher.) However, my 351-roller rear subframe required only a couple mods to take the FE + Quaife: Move the upper rear ~10"-long square tube cross-piece to the far rear and make a jog in the upper right longitudinal strut to clear the Olthoff/Quaife lateral shift arm. This also means that the ~1.5" deep aluminum spacers on those long mounting bolts are now ~2.5" which leads to a pretty fragile looking mount for the transaxle; I suspect any serious vertical load would fracture the transaxle mounting ears. Olthoff deals with this by supporting the transaxle at the far rear on the subframe. (I've always suspected a better solution would be to support the bell-housing-to-block junction at the bottom of the hoop but so far have not done so.) Furthermore, the transaxle and bell housing have only about 1/8" clearance top and bottom with the "hoop" so maybe their contacting the hoop would prevent mounting ear breakage, since the polyurethane bushings in the upper mount are quite flexible (depending on how much you tighten the bolts).

Even with the engine shifted back an inch the removable firewall piece as supplied for SBF is about 1" shy of clearing the water pump pulley. In my case I used a replacement firewall piece in aluminum from Olthoff that essentially pushes the rear seatbacks 1" forward. If you look at the corresponding piece on an original Mk II you'll see a huge ugly ~12" dia. "blister" to clear the water pump, pulley and belt.

The upshot of this is that, as far as I know, the SPF "tub" has Mk I dimensions in all significant respects (except maybe for some "tall driver clearance" mods). However, that statement may be meaningless because other than rear subframe mods and some hoop mods I'm not clear on how the original Mk I and Mk II tubs differ dimensionally. I wish I knew more but short of getting one each of them together I'm not sure I'll ever know with certainty.

So Ron, are you thinking what I think you're thinking (CARB issue?)..:lipsrsealed:

Either way, here's off the top of my head the "parts list" for putting an FE into a 351 roller chassis:

1. FE rear crossmember (Olthoff sells? Get from SPF? Have made by good sheet metal fabricator)
2. FE exhaust headers and collectors. (get from SPF?)
3. Mod to exhaust support bracket on transaxle (widen ~ 1", two cuts two welds of 1" steel strap)
4. Mod or new firewall plate. (Olthoff sells, or cut and cover big hole in center of stock one with sheet steel, or just make a new one like item 1)
5. Brackets to mount compressor and alternator at lower right and left, respectively (Olthoff sells).
6. Spacers, rear crossmenber to transaxle (2" dia aluminum rod, drilled)
7. Mod rear subframe (two cuts, two welds of 1" sq. tubing)
8. Coolant hoses/pipes (corrugated pipe and rubber couplers work ok).
9. Engine mounts (Othoff sells)

Only really difficult or expensive thing in there is the headers. And then there's Mk I body work issue and I'm not sure of it's nature. Do the rear corners of the valve covers hit the rear window? More likely the top header pipe where it loops over. I can measure their height and location if you want. Maybe you could run without a rear window, and or make a plexi one that bulges. One or more of the Mk IIBs with dual quads did that.

 

[Rick Muck- Mark IV]

Alan,

The changes that were made to fit the BB Ford motor in the Mark II chassis...didn't SPF make this change, but use the same chassis for both the Mark I and II versions?


ie, the SPF Mark I chassis could potentially fit an FE?

Yes, but the headers will not clear the MK I rear body panel. Look at the taper of the rear body from the bulkhead to the spoiler MK I vs. MK II and you will see why.

 

[Seymour Snerd]

Yes, but the headers will not clear the MK I rear body panel. Look at the taper of the rear body from the bulkhead to the spoiler MK I vs. MK II and you will see why.

So if you really really wanted to do this you'd have to make a kind of long bulge down the center of the rear clip?

 

[Mike Drew]

So if you really really wanted to do this you'd have to make a kind of long bulge down the center of the rear clip?

No, if ou really wanted to do this, you'd buy a Mk II!!!! :laugh:

 

[Ron R.]

Alan,

Despite my CARB issues, I'm not planning to FE my Mark I.

However, if I were going to do a Mark II, an FE would be the only way to fly.

 

[Seymour Snerd]

No, if ou really wanted to do this, you'd buy a Mk II!!!! :laugh:

Well sure, but that's close to being an issue of buying a Mk II rear clip (or trading with someone that wishes they'd bought a Mk I).