MG Engine Swaps Forum

We've kicked around the idea that an LS4 swap might be feasible without cutting the firewall. I honestly do not know if it is or not, but I have a '74-1/2 RB car out in the shed that we've been prepping as a Chump car, and everyone on the crew seems to be in agreement that at this point it is more interesting to see if the LS4 will fit. So we've decided to take a little detour. One that apparently will take us out of contention in Chump car, but nevertheless here we are.

As we all know, Scott Costanza blazed this trail and has a good result to show for it, but our approach is just a bit different. We are more concerned with minimizing body modifications than with positioning the engine lower and further back, as has been the case with all LS swaps to date. So to that end, our next LBC weekend at Blackwood Labs is faced with the task of finding and acquiring an inexpensive low mileage LS4 engine. Luckily for us, we are within 1-1/2 hr of six major metropolitan areas so hopefully we can accomplish that goal. Assuming we do, the rest of the weekend will be spent playing "fit the square peg into the round hole".

It has been suggested that we cut the crossmember to do this, but I wonder if perhaps we can avoid that. The stock crank sits above the crossmember and has a 3.5" stroke. The LS has 1/8" more stroke but that's only 1/16" on the bottom side. The steering rack is more likely the issue of course but I have a ready answer for that one, an easy method to re-position the rack. But perhaps that large diameter damper is not really needed? Or maybe the pulley can go in front of the rack as on the other LS series engines. After all, electric water pumps are becoming ever more popular so perhaps all it really needs to drive is the alternator.

Also, we have already fitted a CB crossmember to the car so the steering system isn't exactly cherry. It wouldn't hurt us to have another look.

So these are just a few preliminary thoughts, and from someone who hasn't attempted this at that. I'm sure any number of you would like to comment on one aspect or another of this project. At any rate, having proven a number of challenging conversions to date, I have little doubt that we can pull this one off successfully, the only real question being, "Just how simple can we make it?", and for the benefit of all MGB owners my perspective is that we make it just as simple and easy as we can, given the constraints of reliability and such. If we do succeed, it would not surprise me to see Carl as the next victim of the LS4 scare but let's not get ahead of ourselves.

Jim

Jim B, You are giving up an inch of hood room with the chrome bumper crossmember. To lower car use drop spindles. The truck damper sticks out farther and could be turned down and drilled and tapped for SBC v belt pulley. Here is adapters for BBC electric water pump:



http://www.ebay.com/itm/LS-Electric-Water-Pump-Adapter-Plate-Converts-BBC-to-LS1-LSX-Engine-/142207069577

Radical idea.... move the crossmember forward. You can disguise the added wheelbase by adjusting the front wheel arches. Done well, it would take a sharp eye to detect.



Edited 1 time(s). Last edit at 2016-12-27 09:34 PM by Mustangsix.

While an intriguing idea, I think you just moved to the advanced side of the class with this proposal. Trying to mentally step through the task required to do this properly.

An interesting idea to be sure, and perhaps no more difficult than moving the holes in the crossmember. (Some cutting, welding and drilling probably.) But the issue would then be clearance between the tires and the headlight buckets. We seldom think of that but they are actually quite close and I know of a couple of instances where that has caused trouble. With oversized tires of course, but it could limit you. I know there is a bit of an issue with the Roadmaster which has oversized buckets and oversized tires. In fact those should go down one size because of this problem. I've heard of one more owner who had a problem but do not remember the circumstances. With the sizes that will fit inside stock bodywork it may not be a problem, so worth looking into if space is that tight.

From what I've learned so far, it seems likely that with the RB crossmember there may be enough room to clear the rack and the firewall and have enough room to change the belt on the front. That strikes me as a rather important consideration.

What are the issues with 1" dropped spindles? I remember seeing one post somewhere that said there was something. Might have been camber gain or something like that. Anybody know for sure? I'm not really willing to swap back to the RB crossmember without a compelling reason to do so, and the CB rack can easily be re-positioned to duplicate the RB location if we deem it necessary. With better mounts in the bargain. Right now we have a great deal of flexibility.

Anybody know if the RB rack was positioned further forward for clearance with the Rover engine? I understand the distance was significant.

Jim

Scott measured that the RB rack is right at one inch farther forward than the CB rack position. I don't believe it had anything to do with the OEM Rover V8 engine, though.

Jim B, The drop spindles will lower the car in front while the RB crossmember allows 1" more hood room. The drop spindles help turn in and usually you exchange with the steering arms so they can be bent to eliminate bump steer. The RB rack is at least an inch further forward. Bill Gaulin on BritishV8 has the 4.8 with truck damper straddling the steering rack. His engine sits high so he has a large hood scoop.

That's helpful info. I also checked the rack positions and can confirm that 1". Did Scott use the RB crossmember?

Jim

No, Scott retained his CB crossmember & rack.

I'm most interested to see how cheap you can find an LS4!

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Ryan

I thought that might be what you were suggesting. I have actually done this with a Miata, extending the wheelbase 7" and I can tell you that it is a significant amount of work. The first thing you need to do is have the car jigged on a platform with a separate jig built to ensure the front of the car goes back on straight.



It gets a bit scary in the middle of the job



And then you have to make up the bits to re-connect the two halves.





None of it is particularly difficult, but probably more work than most people want to do.

I agree with the jig. I built a fixture to hold both halves of my roadster body when I cut it longitudinally. The fixture allowed me to move the two halves apart while retaining the relationship between the two so I could fill the gap with metal.

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Jim

"If you want me to agree with you then we would both be wrong"

'66 MGB widened 11" with supercharged LT1 Chevy and 6 speed, C4 Corvette suspension
Pictures here Part 1 http://forum.britishv8.org/read.php?13,7581
Continued in Part 2 http://forum.britishv8.org/read.php?13,22422
Continued in Part 3 http://forum.britishv8.org/read.php?13,33108
Continued in Part 4 http://forum.britishv8.org/read.php?13,40751
Continued in Part 5 http://forum.britishv8.org/read.php?13,48698,48698#msg-48698
Continued in Part 6 http://forum.britishv8.org/read.php?13,61672

Shooting for an economical, bolt-in swap into a RB MG.

That's why I mentioned the RB crossmember and steering, to simulate a real world 74 1/2 - 80 swap.