MG Sports Cars

engine swaps and other performance upgrades, plus "factory" and Costello V8s

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mgb260
Jim Nichols
Sequim,WA
(2013 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: LS4 Into an MGB
Posted by: mgb260
Date: December 22, 2013 02:21PM

Scott,Looking Good!


Scott68B
Scott Costanzo
Columbus, Ohio
(542 posts)

Registered:
10/25/2007 11:30AM

Main British Car:
1968 MGB GM 5.3 LS4 V8

authors avatar
Re: LS4 Into an MGB
Posted by: Scott68B
Date: December 29, 2013 09:57AM

Not quite there yet with the motor mounts but getting dangerously close. This first picture shows the drivers side engine mount tacked together. I'm pretty pleased with the way things are turning out.

LS4DrivMount.jpg

The next shot shows the same side with the engine in the car.

LS4DrivSideMount.jpg

Except for permanently welding the engine side of the mount, adding a couple of gussets and drilling a hole for the rubber mount this side is done. Oh, I will need to make sure the steering shaft has clearance on the mount as well. Still a few tweaks needed on the passenger side and then the transmission mount needs to be completed. Hope to get it there in the next day or two. It will be nice to have the motor permanently installed in the car.

While I was working on the car, this came.

LS4HeaderPipe.jpg

I used Ken Hiebert's suggestion and went with Columbia River Mandrel Bending. Of course, I only ordered one pair of exhaust flanges instead of two and forgot the O2 bungs so they will be getting another order. :(

I'll have more detailed descriptions and pictures once the mounts are completed.


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5833 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: LS4 Into an MGB
Posted by: BlownMGB-V8
Date: December 29, 2013 10:59AM

Scott, the mounts look strong but there is a weakness that you might want to consider while there is still plenty of time to address it. I've been thinking about whether or not to say anything and have decided I should.

The attachment to the frame rails in itself is strong enough and well designed, but it is welded to thin material, and I'm not sure it will hold up. Over time I can see the frame rail developing stress cracks around the mount welds because the stresses are concentrated in a relatively small area. You might want to think about what you could do to spread out the loading, and there may be some fairly easy way to go about it. I'd guess the torsional loads are going to be the biggest factor.

If you hadn't welded them on yet it'd be a fairly simple matter to plate the rail with some 12 or 14 gage under the mount. If you do that (meaning cutting the tabs off and rewelding) do not run your front and rear edges of the plate vertical. Best practice in frame repair is to spread the load by using round, diamond shaped, or diagonal front and rear edges to spread the load out on the frame. If I was doing it I think I'd also drill some holes in the plate under the tab and use those to spot weld the plate to the frame before welding the tab on. That will let you get by with thinner and lighter plates.

I know I just made more work for you, but hey, I'm only here to help! ;)

Jim



Edited 1 time(s). Last edit at 12/29/2013 11:02AM by BlownMGB-V8.


Charles
Charles Long
McDonald, TN
(177 posts)

Registered:
09/15/2013 08:54AM

Main British Car:
1966 MGB V6 1994 Camaro 3.4L 60V6

authors avatar
Re: LS4 Into an MGB
Posted by: Charles
Date: December 29, 2013 04:48PM

Scott, Nice shoes, I had a pair like them once. Dog carried one off, someone threw the other away. I was lost till I found a new brokein pair.
I agree with Jim B, I don't know why, is there room to add a plate from the rear cross member bolt to the welded engine mount? The metal of the frame is light weight and now it is brittle due to welding, with no way to relieve stress. I am enjoying your post and efforts. I am just starting my 60v6 swap.
charles


Scott68B
Scott Costanzo
Columbus, Ohio
(542 posts)

Registered:
10/25/2007 11:30AM

Main British Car:
1968 MGB GM 5.3 LS4 V8

authors avatar
Re: LS4 Into an MGB
Posted by: Scott68B
Date: December 29, 2013 08:04PM

Quote:
The attachment to the frame rails in itself is strong enough and well designed, but it is welded to thin material, and I'm not sure it will hold up. Over time I can see the frame rail developing stress cracks around the mount welds because the stresses are concentrated in a relatively small area. You might want to think about what you could do to spread out the loading, and there may be some fairly easy way to go about it. I'd guess the torsional loads are going to be the biggest factor.

Jim, thanks for the feedback, sounds like a good idea. Not sure I'd cut the mounts off but I think I can strengthen them anyway. I've welded the mounts directly over a supporting tab for the rear crossmember bolt so it isn't quite as weak as it might appear.....still needs something more. I'll get it done before I put the car back on the road.

Scott


Scott68B
Scott Costanzo
Columbus, Ohio
(542 posts)

Registered:
10/25/2007 11:30AM

Main British Car:
1968 MGB GM 5.3 LS4 V8

authors avatar
Re: LS4 Into an MGB
Posted by: Scott68B
Date: December 30, 2013 10:02AM

Ok, I know what I'm going to do about strengthening the mounts. I'll run a couple of gussets on top of the current mounts to the very top of the "frame rail". For good measure, I'll weld the seam at the top of the rail as well. That should address Jim's concern about stressing the thin metal on the side of the rail and will be fairly easy to accomplish at this stage of the fabrication. I'll have to get creative around the steering shaft.


mgb260
Jim Nichols
Sequim,WA
(2013 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: LS4 Into an MGB
Posted by: mgb260
Date: December 30, 2013 08:33PM

Scott, Just a suggestion but, an easier way is to use a plate like on your motor about 3" wider than the mount on each side and same height as frame, notched to go over lower mount. Grind and weld in frame seam. Matching top frame plate and little square piece under mount. Weld all together. No steering issues. Hey, did you get your clutch stuff yet?



Edited 1 time(s). Last edit at 12/30/2013 08:42PM by mgb260.



DiDueColpi
Fred Key
West coast - Canada
(1259 posts)

Registered:
05/14/2010 03:06AM

Main British Car:
What if the Hokey Pokey really is what it's all about?

authors avatar
Re: LS4 Into an MGB
Posted by: DiDueColpi
Date: December 31, 2013 04:10AM

Ditch the rubber X frame mounts and build a tab down to the X member.
Stronger body, stronger mount, better suspension but more noise.
Good trade off.
Cheers
Fred


Scott68B
Scott Costanzo
Columbus, Ohio
(542 posts)

Registered:
10/25/2007 11:30AM

Main British Car:
1968 MGB GM 5.3 LS4 V8

authors avatar
Re: LS4 Into an MGB
Posted by: Scott68B
Date: December 31, 2013 11:38AM

Quote:
Just a suggestion but, an easier way is to use a plate like on your motor about 3" wider than the mount on each side and same height as frame, notched to go over lower mount.

Jim, I appreciate the suggestion. I considered that approach earlier but I think adding an upper gusset to each side will be just as strong and will be easier/quicker to complete.
Quote:
Ditch the rubber X frame mounts and build a tab down to the X member. Stronger body, stronger mount, better suspension but more noise.

Fred, thank you! Interesting suggestion. The cross member pads you see there are brand new, never used urethane pads I just put in last month. I know they aren't like a solid mount but they will do for now. They should be much better than the 46 year old, flattened rubber pads I pulled out of there. I'll file this suggestion away for when I get to the suspension. I have a pair of GAZ coil over shocks I want to use on the front end...had them for over a year but just can't seem to find the time to put them on. How would you implement the solid mounts, steel replacements for the pads?

I think this might be good time to say a few things that have been on my mind lately. I REALLY do appreciate the feedback I'm getting from everyone. I would have done a journal if I didn't want feedback. It seems like I'm always ignoring some of the advice I'm getting but as "Project Manager" for this project I have to keep in mind the overall plan/timeline I'm working toward. When I get a suggestion that affects the overall plan in some way, even though it might address the current task, I have to look at the effects of implementing that suggestion. So far the plan is working out really well so I'm not inclined to make any changes to it unless a huge issue comes up. I trying to not let this become a multi-year project and constantly changing the plan is a sure way to get there.

Anyway, what I'm trying to say is although it might not seem like it at times, your comments are very welcome. One of the main reasons I'm doing this is to learn and I guarantee you I will be making mistakes.

Happy New year!


MGBV8
Carl Floyd
Kingsport, TN
(3791 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
1979 MGB, Buick 215

authors avatar
Re: LS4 Into an MGB
Posted by: MGBV8
Date: December 31, 2013 04:24PM

Don't forget, someday, someone doing a similar swap, will do a search & find this thread. The additional ideas presented here may be fuel for thought for them. Thank you, Scott, for the non-journal approach.

I'm with Fred, though. I looked over your pics & I kept thinking subframe mounts. Hey, they are available for Ford. Maybe time for some Chevy subframe mounts. :)


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5833 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: LS4 Into an MGB
Posted by: BlownMGB-V8
Date: December 31, 2013 05:31PM

I'm not a fan of subframe mounts. I used those on my original conversion and the stancheons were plenty strong but the (215) motor mounts needed a through bolt to counter mount separation from torque and even then they weren't good at torque resistance due to being close together. They also weren't all that easy to get the bolt in and out when changing the engine. But the worst thing was that the torque caused the frame rails to crack around the subframe mounting tubes. All four of them. Now granted I was also running stiff lowered springs and competition shock valves and I drove it hard so it was undoubtedly the combination that did it, but I had less torque than an LS4 I think. I just don't see running engine torque through the subframe to frame mount as being a great idea. It seemed like it until I tried it, but also consider if you will, the subframe attachment is designed to move. Consider if you will, the massively larger and greatly more widely spaced mounts of the cradle used on the TR7 and all modern cars by comparison. The MGB attachments are not really designed for it.

We're transferring a lot of torque to a small vehicle with thin structure and all that torque goes directly through the motor mounts. You have a factor of about 10:1 between what is seen at the axle and what is seen at the engine in 1st gear but the axle mounts are spread out over a considerably greater distance. In the case of the MGB, the length of the spring leaves and doubled, yet some still feel the need to add channels to support the front spring hangers, and doublers spread the load out into the body.

At the front, the stock mount brackets are fine for the 1800 and the later mounts are OK for the 3.5 and arguably for the 3.9 but more powerful engines require more substance. (Even the stock mounts sometimes crack so that part of the car definitely is not overbuilt.) The first consideration is distance between the mounts, since this directly affects the amount of torque that can be absorbed. Shorter distances require larger cushions, stronger brackets, and more load spreading.

This is a big part of the thinking that went behind the head-to-frame mount design I created for the MG-Roadmaster and my blown 340. It gains at least a couple of inches on the lever arm length, allowing smaller cushions to do the same job. It uses a reinforcing plate on the rail to spread the load out. And it uses a vertical tube to simplify install/removal. But everything is a compromise so it requires realignment of the pulleys and leaves scant space for the wiring to sneak past.

Scott, I think the gussets you have in mind should do pretty well, though they won't do much for ease of installing/removing the main bolt. A gusset of some type to the front and rear might also be helpful. The larger of an area of the frame rail that you can tie into the better.

Jim



Edited 2 time(s). Last edit at 12/31/2013 05:37PM by BlownMGB-V8.


mgbreis
Ryan Reis
Beatrice, NE
(202 posts)

Registered:
07/16/2008 11:07AM

Main British Car:


Re: LS4 Into an MGB
Posted by: mgbreis
Date: January 01, 2014 03:05PM

I think Jim makes a good point, I was concerned about welding my mounts to the frame rail so I bent a sheet metal cap over the rail to weld the mount to. On the other hand, it's not like you're going to experience a catastrophic failure. More likely cracks as Jim said. You do have quite a bit of surface area where it welds to the frame, a lot more than mine. I'd do the same as you, add the gussets and move on to the next hurdle! You're going to have a lot of hp and torque, but it's not like you're going to hook up hard and transfer all of it to the mounts.

Good luck with the headers, I sure wish mine had turned out a little nicer.


classic conversions
bill guzman

(294 posts)

Registered:
01/09/2008 01:58AM

Main British Car:


Re: LS4 Into an MGB
Posted by: classic conversions
Date: January 01, 2014 10:49PM

First weld a flat piece of steel to the frame rail, this gives a foundation, then weld the motor mount pads to the lat steel that is welded to the frame. This should be key to fit on top of the rail and welded for added support.
similar to the original MGB mount.


Scott68B
Scott Costanzo
Columbus, Ohio
(542 posts)

Registered:
10/25/2007 11:30AM

Main British Car:
1968 MGB GM 5.3 LS4 V8

authors avatar
Re: LS4 Into an MGB
Posted by: Scott68B
Date: January 02, 2014 11:02AM

Everyone,
Thanks again for the great feedback! I hope to have a few hours this evening to devote to the mounts.

Carl, if someone wanted to go with subframe mounts (despite Jim's concerns) it would be very doable. With the setback I'm using the stock LS motor mount location lines up quite well.

Hope everyone had a good new year.


DiDueColpi
Fred Key
West coast - Canada
(1259 posts)

Registered:
05/14/2010 03:06AM

Main British Car:
What if the Hokey Pokey really is what it's all about?

authors avatar
Re: LS4 Into an MGB
Posted by: DiDueColpi
Date: January 02, 2014 08:37PM

I guess that I should have elaborated a little more on the tab idea.
I would do a 3/4 wrap around the frame rail with 0.250" material
It's overkill for the purpose but it lets you wrap it under the subframe mounts and eliminate the bushings.
Drill it with lightening holes and trim it out as Jim described before welding it in place.
A tab down from this plate would then tie into the subframe making it a solid structure.
The motor mount would be welded to the plate on the vehicle frame much as it is now.
I'm in total agreement with Jim regarding mounting the engine from the subframe.
The loading and severe angles required would cause a failure sooner or later.
My intention is to make the subframe and vehicle frame one solid structure.
With so much material removed from the firewall you need to buy back some structural support.
And this is an easy place to start.
A nice solid trans X member. Yes an actual X shape. Tied in well to the vehicle frame.
With forward facing struts that would bolt up to the lower portion of the front subframe.
And rearward struts that would tie into the rear spring mounts.
Would give you a pretty solid base.
A well designed roll bar or cage (better) would add even more stiffness to the structure.
Anything that can be done to improve the body rigidity should be contemplated.
Because that thing is going to want to pretzel up bad.
Hope that's useful.
Cheers
Fred



TXS67BGT
jay musgrove
low country
(15 posts)

Registered:
11/16/2008 10:12AM

Main British Car:
1967 MGB GT 1998 LS1

authors avatar
Re: LS4 Into an MGB
Posted by: TXS67BGT
Date: January 03, 2014 08:31AM

for your reference, a removable trans mount, pretty stable after I put the tunnel back in. angle the tops of the plates toward the center a couple of degrees to ease installation and put 2-3 sheets of paper between the plates when fitting, leaves a tiny gap
TRANS MOUNT 011.jpg



Edited 1 time(s). Last edit at 01/03/2014 08:39AM by TXS67BGT.


302GT
Larry Shimp

(203 posts)

Registered:
11/17/2007 01:13PM

Main British Car:
1968 MGB GT Ford 302 crate engine

Re: LS4 Into an MGB
Posted by: 302GT
Date: January 04, 2014 07:22PM

I originally mounted my 302 on the frame the same way. The frame rails cracked in under 1000 miles. The cure was to make braces from the top of the frame rail down to the mounting pads. On the left side the front brace had to have a hole for the steering shaft to pass through. The cracking problem was worse on the right side because that gets a downward force during acceleration.

I have just puled the engine and transferred the mounting pads to the front subframe because I like the idea of another set of rubber (urethane) pads between the engine and the car. Certainly, the subfrane metal is much thicker than the body frame rails so I do not expect problems with it.

In terms of the engine torque cracking the frame rail tubes holding the subframe attaching studs; I am not convinced that engine torque is the problem. I would think that side forces from cornering would stress the frame more, and Jim's car has by far the widest tires (and hence the largest expected cornering forces) of any of the converted MGBs I am familiar with. But if Jim never exploited the cornering capabilities of the car, then maybe it is engine torque...


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5833 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: LS4 Into an MGB
Posted by: BlownMGB-V8
Date: January 04, 2014 07:32PM

Oh, I exploited it Larry. I exploited the H*ll out of it. ;)

Jim


classic conversions
bill guzman

(294 posts)

Registered:
01/09/2008 01:58AM

Main British Car:


Re: LS4 Into an MGB
Posted by: classic conversions
Date: January 04, 2014 10:47PM

I did not know that Jim's car ever run................................Just kidding Jim LOL

Forces do have an effect on cracking material, but vibration is the biggest culprit on stress, does not matter how smooth the engine is or how good the mount are.

Take a look at the CB B frame mounts and how they were welded, that is how any mount that is welded to the sheet metal frame rail should be fabricated. for any engine that is going to have the mounts welded to the rail.


TXS67BGT
jay musgrove
low country
(15 posts)

Registered:
11/16/2008 10:12AM

Main British Car:
1967 MGB GT 1998 LS1

authors avatar
Re: LS4 Into an MGB
Posted by: TXS67BGT
Date: January 05, 2014 08:15AM

agree with bill, vibration is the major factor in stress cracks, continual back and forth working of the metal. the bigger area you spread the load onto, the less likely a crack, no abrupt or straightline ends to the reinforcement plate the better, hence diamond shaped plates, round the corners and stop the edges of the backing plate where the base structure has a change in material direction
FIREWALL AND FRAME 001.JPG
FIREWALL AND FRAME 006.JPG
struct1.JPG
1st pic shows what was removed, 2nd general idea of material added back and 3rd is some doodling I did to get an idea of tying the structure together. hope this may help
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