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MG MGB GT V8 Factory Originals Technical - Crossmember dilemma
|Okay, I have spent almost 3 days digging through the archives concerning modifying the crossmember. I can't find enough information that I would feel confident beginning to lay out the mod. I am looking at putting in a 302 with a T5 (Mustang sourced) and am almost ready to begin layout of the modifications (though I don't have an engine/tranny yet). Can anyone help me out with what measurements / amounts of the crossmember I am going to have to remove and drop to fit the engine as low and far back as possible? Also, anyone do anything specific to brace the newly modded crossmember? Any information on this part of the mod is greatly appreciated, I feel confident in modding the engine bay, just not the crossmember and engine mounts. Might end up going with a custom built front end...|
|D. T. Barnes|
|Just how far and low back you want to go is what will determine how much, if any, crossmember cutting is required. On a chrome bumpered car like mine, I initially started out cutting out about 1" across the entire lenghth of mine and left it "open" while I trial fit the engine several times. I had cut away both the driver's and passenger side bulkheads and the opening to the transmission tunnel at this point to allow easier initial placement of the engine. My thought was it would be easier to try and build the engine compartment around the engine once the mount locations were established and welded in. I then fabricated out of 1/4" a plate to weld back in to the top of the crossmember that I had just cut out. Then I quickly discovered how tight the engine bay is on a chrome car and decided to go with the "radical" setback approach and redesigned the firewall and steering setup to allow the engine to set behind the crossmember altogether. With this approach, no crossmember mod is needed if a rear sump oil pan is used. In the end I ended up having to make new steering rack mounts to "rotate" the rack back a few degrees to allow my u-joints to work smoothly and in the process welded another 1/4" plate across the front of the crossmember to add strenghth. I then notched out the top of this plate to allow my crank pulley to clear. I'll have to send you a picture, it makes things much clearer.|
The trouble with trying to mod your car before getting your engine is that no 2 people do these swaps the same way. If you follow someone else's example, you need to follow EVERYTHING they did to the letter sometimes to get it to work. This is one of the reasons I decided to go the route I did. When I started my conversion the advice was "Make your engine bay look exactly like a rubber bumper car and then swap in a steering rack, column and crossmember from a rubber bumper car and go from there... Trouble was I already had a perfect chrome bumper car, column, crossmember, etc.
My advice is to see as many examples as you can and go with the one that looks like it will work for your situation. And don't be afraid to experiment a little. The book has not yet been written on the 302 engine swap, although many of these transplants have been successfuly done. Good luck, and let me know if you want any pictures. My car is still in process, but it might scare you into doing things a different way!
|It is my understanding that the third edition of Roger Williams book, How To Give Your MG V8 Power, will have information on the SBF transplant, including pictures with arrows and a detailed account on the back of how it was done. |
(oops, sorry, I broke into a little Arlo Guthrie there for a minute)...
Several listers have done this work including Pete Mantell and Steve Carrick (both of whom now have Ted Lathrop's crossmembers in their MGBs)
I'm sure they will chime in when they read this thread.
I second all Scott's advice... (re: multiple trial fits & doing your own thing.) His experience pretty much matches my own, except I was fitting a 215/T5 in a '71 GT. I put it far enough back that I didn't have to modify the crossmember at all, but I did replace the front sixteen inches-or-so of tranny tunnel with my own fabrication. (I had already decided to omit the heater and I used the cowl inlet for engine air intake.) This was all done back around '91, when there weren't so many examples to look at.
IMHO, the stock front crossmember is plenty strong without bracing, but I did choose to replace the stock radiator mounting and slam panel with my own fabrications. Amoung them, I welded in a piece of 1x2 box tubing just in front of the top tank of the rad, so it functions sortof like a Monte Carlo bar, plus anchors the new radiator and fan mounts.
I would welcome any pics of your conversion. It sounds like you are creating one of the more radical conversions out there as far as the 302 swap is concerned. e-mail peter_plouf at sympatico.ca (replace the word "at" with @)
| My experience with doing both BOP/Rover and Ford 302 conversions on a RB chassis suggests that the engine will seek its own location relative to major components like steering rack, steering shaft, suspension crossmember, bulkhead sheetmetal . Both can be installed with no hood modifications or major engine bay rework (other than some minor tunnel messaging and inner fender cutouts for RV8 type exhaust headers). |
For the Ford installation, the front crossmember needs to be notched about 1-3/8 suggest that the cutout take the shape of the front sump profile rather than a sharp U to preclude stress risers and retain as much material in the crossmember weld in a 1/8 thk plate over the cutout.
Clearances: After notching the top of the xmbr and allowing 1/2" vertical clearance to the oilpan, the closest point for the engine oilpan is about 5/16" behind the steering rack where the strg shaft enters the cast 'T' portion of the rack assembly. Relative to the firewall, the left rear cylinder head is about 5/16" from the sheet metal. There is about 1/8" clearance for the harmonic balancer (which comes to the front/upper edge of the rack) and about 1/8 clearance for the oil pan front seal lip above the rack.
If early small block Ford engine mounts are used, the left mount will have to be modified (partially removed) to allow clearance for the steering shaft.
All the above clearances assume that correct engine components, (short front accessory drive, oil pan, etc) have been used and that the overall length of the engine from bellhousing mounting face to water pump flange is 27.5.
Notes: I believe that Steve Carrick's 74 CB car has the firewall modified and the engine moved back about 1-1/2 from my position. Pete's '69 CB engine positioning is the same as mine (ie 5/16" rack to pan clearance).
|Thank you for all of the replies, I am sure this is a subject that has been beaten to death, and I truly appreciate everyone responding. |
Scott - awesome information, that was my gameplan all along, I just wanted to gather some more information to get a feel for all of the options out there. I love the idea of not modifying the crossmember and dropping the engine down and as far back as possible (without having to heavily modify the firewall bulkhead, i.e. cut the whole firewall out and shift it back). I am currently junkyard diving trying to find a decent set of donor parts in order to trial fit while I rebuild the engine. PLEASE feel free to email all of your pics, I won't be scared off from any avenue once I decide I like the results (I am pretty competent with metal and fire, so I should be ok, hahahaha).
Rick - thank you for the information, I contacted Ted a while back and got the information on replacing the entire front end. I also looked into Classic Conversions for the reworked front suspension (with stock crossmember) and their soon-to-be-released rear suspension.
Curtis - thank you for the information, I like the idea of the modification you did on the radiator mounts, especially the Monte bar..nice touch.
Graham - Thanks for the numbers and explanation, duly noted.
Anymore ideas or recommendations are appreciated, right now information is my biggest tool in order to get some ideas and then meld them together to best suit me and the 73 GT napping in the driveway. Thanks to all.
|D. T. Barnes|
This thread was discussed between 03/01/2006 and 04/01/2006
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