BritishV8 Forum

I got my car soda blasted and put a light corrosion inhibitor on it. I was wondering while looking at my spot welder if it was worth adding a few spot welds and if so were.  Any comments gentlemen.

Dave

Well... you might get some ideas from this article which shows what areas British Motor Heritage beefs up when they seam weld their Competition Bodyshells:
http://www.britishv8.org/Articles/BritishMotorHeritage-Competition.htm

Ahhh Yes that is very helpful thank Mr Jacobson

Dave

Dave, if you're paying for the work, consider there are quite a few cars without those extra welds that have been driven very "spiritedly" for years without issues.  Unless you are planning a very high HP track car, you'd probably be better off spending your money elsewhere.  Maybe check with Perry.  If any car would find the weak points in the unibody, I'd think his would have.

Oh no I have a full personal automotive shop and machine shop at my disposal. Tig and mig in hand Sir. I traded the soda blasting work for some mill and lathe work, I love bartering.  I am just looking for hints and direction.

I don't know if it's worth it but I've gone ahead and done it. I read the article Curtis mentioned and checked the pics. To my somewhat simple mind it seemed a reasonable idea.

FWIW, I added sub frame connectors to the rear, they noticeably stiffened the rear suspension.  there is an article in the "How it was done"  part of the Board.  They were welded from the spring hangers to the center X-member.  I submit this would be a very positive addition to your project.  
SAFETY FASTER!

I had a 2.8 Ford V6 in my GT which it was a full race car for a few years. The engine develop 275 hp 240 lb of torque
The first2 years the cars started to show cracks between the firewall and inner panels and also where the top gets attached to the body in the rear panels. The Gt had a full SCCA spec cage attached as per SCCA.

I fix the problem by adding frame extensions and following the the LBC recommendations.
If you are going to use a V8 I would say follow those points in the article. Just keep in mind that the rear section of the MGB is not really completed, it is a if the factory got rush to finish the project.

From the seat back is the weakest section of the RD.

Here's my version of what Kelly did.  Plug welded to the floor and MIG welded to the spring hanger and the cross member by the jacking point.  I used paintable seam sealer on the seams that weren't welded closed.

Great job, Phill  mine were very Basic, but made a noticable difference.   MERRY CHRISTEMAS ALL!

I would just add a diagonal between the two extensions.

YES 1 Merry Christmas to you all and a safe 12

Now would you bolt the cross brace or would you weld it ,classic conversions ?

Dave

I would welded to each end and about every other 1" to the floor boards.
The brace would have to just in front of the rear sheet metal brace to clear the drive shaft.

BTW you can make your own bracing out of 20 or 22 gauge sheet metal. Once bent in to a box it becomes rigid and light.

Is there anywhere I can buy the bracing "pre bent" ?

Many steel places have steel channel of different sizes in this case a 2" or 3" is plenty.

By the thin one channel.

Also a sheet metal shop can make you some.

Isnt it dimesionally different at either end so standard channel wont work?

This old article might help... <a href="http://www.britishv8.org/Articles/MGB-Chassis-Reinforcement.htm">How to Give Your MGB 6-Pack Abs</a>

Mine are probably heavier than needed, but I used 1x3 rectangular tube - 3/16" wall if I recall.  You can get it at Metal Supermarkets if there's one by you.  They"ll cut it to the length you want (vs having to buy an 8 or 10' piece).  I just butted it up to the cross member and welded the three exposed sides.  At the spring perches I used a cut-off wheel to trim it so that it saddled the perch and again seem welded.  I don't recall why, but I plug welded it to the floor from inside the car every few inches instead of along the edges as Bill suggests.  I think I may have had dillusions of it being easier to replace the floor pans if that's ever needed.  I did have the body shop use seam sealer along the length when the car was painted.

Anything thicker than 20 ga. really is overkill but it doesn't add much weight so whatever you can find is going to be OK. Thicker metal also makes for a good jacking point. I've seen claims that it stiffens the car, maybe it does. Even if not it isn't hard to add, and in any case reinforces the mounting holes for the spring bushing which are prone to wallowing out. I added a reinforcing rib out to the sill on my RD instead, by forming some sheet metal to leave room for access to the bolt, but I only did that on the right hand side. Basically, within reason, anything you do to triangulate in any of the three dimensions is going to add strength. The idea is to add it where it is most needed. The theory on adding this rib is that it will spread out the forces from acceleration and deceleration and cause less flex. It's good theory but the body of the MGB doesn't flex much anyway. Despite that, reinforcement of those particular mounts can't be a bad thing when you double or triple the power. It's sort of like welding the seams. Is it necessary? No. Can it help? Probably. So if you want to do it, there's no real reason not to.

JB

I do use them as a jacking point.  And for jack stands when I need them away from the spring perches.

One important issue is to make sure the body is relaxed. If you jack one side an then weld one of  the stiffeners, it will not work very well. One way to prove this and to find weak areas, is to place a string and pace it really tight from inside to the outside of the the floor board. Jack one side of the car, now take a look at the string, is either tighter or relax, would mean that you need to a stiffener.
The all fashion way of finding weak areas on a chassis.

Twisting of the chassis is possible even with the extensions welded to the front spring eye. Reason why I suggest welding a stiffener between the extensions across to triangulate the space.

The best way and perhaps the correct way to do, is to have the car on all 4 wheels high enough to give you space to weld the stiffeners on the car.

Tack weld  both sides and alternate the welding when running a full bead.
Not a bad idea to check the car for squareness at this point, but not really needed for the street.

The best way to stiffen the chassis is by stiffening the center trans tunnel, fire wall and rear wall of any chassis.


This two pictures are of two chassis, one for the street one for racing. We are trying to form a racing series base on a light chassis and low cost engine such as the ECOTEC 2.4 liter.
Yes when I finish all of my MGB projects.

Notice both chassis and look at the front of chassis #3 compared to chassis #2.