Engine Bay Seam welding: Pro's & cons

[808wish]

Hi all, back again still researching the best way to do my engine bay for a clean smooth look for show car type detailing.

I would like to ask all the basics on Seam welding.

Firstly, What are the advantages of seam welding?

I imagine the seam welding would be much along the same lines as say putting a larger sway bar in, it would create a stiffer front end etc,am I right in assuming this?

Is it better to weld the full seam or do staggered inch long welds along the seam?

When the seam is welded in either fashion (above) will it strengthen the jiont strong enough to use body filler (bondo) to smooth it out and reduce the risk of cracking?

Once welded will there still be flex to cause cracking in Body filler(bondo)?

Most area in my bay will have body filler(bondo) only a couple millimteres think but in 2 small areas approx 5cm square will be roughly an inch think as long as it is done in stages it would be fine to fill?

I have an ARC welder basic set up will that do ok for the seams?

Apoligies for any questions that are general basic stuff but I want to know as much as possible before starting the project.

Thanks for any help
Cheers

 

[piman]

Hello 808,

seam welding was done for rally cars to stiffen and strengthen the shell. I believe they used to be brazed, but I don't think that an arc welder will be suitable unless you are extremely skilled.

If you can get the seams fully welded I think you will have a reasonable chance of using a good quality filler without it cracking?

Alec

 

[cumbriasteve]

I can only comment on the actual welding really and that is the fact you are considering an arc welder, this will be so difficult, they are not really suitable for car work and you will either have to be very very experienced or very lucky to get any decent welds without blowing through.
I have arc welded for over 30 years and would not consider it for car work, especially when visual appearance is important.

 

[cumbriasteve]

pieman beat me lol..but we agree

 

[808wish]

What is the best type of welding for the Seams, Would MIG be better. I am a general Welder so obviously ARC will be a challenge to get right for me.

So if the welding is done correctly using a decent body filler will with stand cracking as the seam welding will create a lot more stable base for support.

 

[piman]

Hello 808,

"So if the welding is done correctly using a decent body filler will with stand cracking as the seam welding will create a lot more stable base for support. "

I would say so, as long as you don't go rallying :-)

Alec

 

[cumbriasteve]

What is the best type of welding for the Seams, Would MIG be better. I am a general Welder so obviously ARC will be a challenge to get right for me.

So if the welding is done correctly using a decent body filler will with stand cracking as the seam welding will create a lot more stable base for support.

Yes I would say a Mig, although it used to be gas and brazing, you get a good 'weld' with no build up, you also get lots of heat which could distort the large flat seams if not careful.

 

[pleej]

i did my bay , welded all the holes up , got all the sealer off ,did abit of spot welding on the seams, then used fiberglass sheats and body filler.

i hate sanding so it took me a long time

befor

after

 

[808wish]

pleej: wow that came up a treat, so the fibreglass worked all good on the seams, and did you just spot allong the seams to give extra strength.

Yep I hear ya on the sanding part, but once it gets to the finishing ending I start liking it again.
At this piont I am using filler for the non stress pionts to fill and smooth out but as you can see by my post is my main worry with filler cracking when used over seams, so looking at all the alternatives

 

[Weldinator]

All i can advise you on is fully seam welding the chassis/engine bay can cause too much stiffness which in turn wont work well. Stitch welding the seams means the car still has a little flexibility which is needed else the car may crack in places for being too stiff and put too much strain.

 

[mjrally]

Im currently seam welding my rally car, the best practice i have been told is to weld an inch every 3 inch, so as mentioned by weldinator it doesnt become to stiff. That's why im doing, in terms of seam sealer its been an apsolute b*****d for me, been strugling as it bubbles out even if the end of the seam are clean. so ive just been removing as much as i can. Ive been using a mig and would say that its probably the easiest way of doing it.

 

[pleej]

i just stitch/spot welded along the seams first

 

[Justme]

Wont it screw up the crumple zones?

 

[808wish]

Thanks guys, great info and advice.

I think I have a plan now on how to tackle the job.

Will do the tack/spot weld 1 inch long every 3 inches along the seam. As I dont want the chassis to be too rigid and risk tehe cracking in other areas
I will also seam fill any exposed areas that havent been welded.
Hopefully that will give enough strength so I can use a good quality metal style filler to smooth it all out as planned. Without the risk of cracking.
I am lucky as compared to some cars I have seen, the seams are fairly limited(not many).
My car will not be a daily driver, its plan is a weekender, with a little bit of drag racing action. More show and cruise though. And the occasional out for a quick fun fix when the feeling arises.