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cast iron bellhousing chop-chop
sebastiaan - 25/4/10 at 02:47 PM

Right,

After buying an MK four-into-one exhaust manifold yesterday, it seems it would fit a whole lot better if I manage to get the engine back by a further 25-30mm or so.

There is (just!) enough room in the tunnel to do so without the rear of the gearbox hitting the foremost transverse link in the tranny tunnel (MK indy chassis). The only trouble is that the bellhousing I'm running has two sticky-outy bits that'll hit the firewall if I want to put the engine further back. I don't want to modify the firewalls (it's tight enough as it is already down there with size 46 feet!). That leaves modifying (ahem) the bellhousing.

Whilst I'm sure it won't matter strength-wise if I just chop bits off, I'm not too sure on if it'll be OK to tack (using MIG) a few 1mm pieces of plate over the holes I will be making. What do you think?

ps. Gearbox is Ye olde type 9 with a LHD cast iron bellhousing.


sebastiaan - 25/4/10 at 02:48 PM

Well, someone thinks I'm doomed. Who and why? ;-)


omega 24 v6 - 25/4/10 at 02:53 PM

2 of us think you are doomed now.
it's cast Iron you can't weld it with MIG. if you cut it it will remove a lot of the strength and in effect create areas of possible stress cracking ( maybe ).
I doubt an alloy one would be much different but you could possibly weld it.


sebastiaan - 25/4/10 at 02:58 PM

Let me clarify: In the picture below I've tried to highlight what needs chopping back by some 25mm. I could also just sikaflex some 1mm plate on, as I'm sure the bellhousing should be OK strength-wise.

bellhousing proposed chop
bellhousing proposed chop


[Edited on 25/4/10 by sebastiaan]


big_wasa - 25/4/10 at 03:04 PM

If you weld it with a mig as the weld cools you will hear a ting ting sound as the weld cracks.

get it welded by some one who does cast iron on a regular bassis, you will want dissimlar rods and MMA (stick) welder if you want a go yourself.


iank - 25/4/10 at 03:17 PM

Yes, cast iron is a job for stick welders.
If you don't have one, or the experience then getting it done by someone experienced in cast iron would be good.
Looks like it will be strong enough.


andylancaster3000 - 25/4/10 at 03:23 PM

Probably going to cause some flack here but I wouldn't think twice about going ahead. I guess you want to cover them after just to keep things in/out? Personally, I wouldn't bother.

We modified our bellhousing so we didn't have to remove the tube on the locost chassis under the box that is usually cut out (no one seems to think twice about this). Cut a chunk out, made sure all the corners were nice big radii. Season of racing, year and a bit on the road and a few trackdays and all is well still with no signs of distress or cracks. My vote is, go for it.





[Edited on 25/4/10 by andylancaster3000]


sebastiaan - 25/4/10 at 03:42 PM

H*oly cr*p...

If that has been OK during a year of on-track abuse than my small cuts should be fine. You were correct in thinking I just want to cover the holes to stop crap getting at the clutch.


andrew - 25/4/10 at 04:10 PM

just cut it with angle grinder wont hurt it left open but if you realy want to cover it in just self tap or pop rivet a bit of thin ally plate over


britishtrident - 25/4/10 at 04:36 PM

Just make sure the cuts don't have sharp corners


sebastiaan - 25/4/10 at 04:49 PM

I was planning on drilling 8mm-ish holes at the corners and angle-grinding between them to avoid stress-raisers. I'll go for it and see what happens this winter.


James - 25/4/10 at 05:28 PM

quote:
Originally posted by andrew
just cut it with angle grinder wont hurt it left open but if you realy want to cover it in just self tap or pop rivet a bit of thin ally plate over


That's exaclty what I was going to suggest. Although I be tempted to sikaflex the plate over it.

HTH,
James


mark chandler - 25/4/10 at 06:04 PM

If you want to mig its not impossible as it will not carry any load, you need to heat the area up with a decent blow torch before starting and the metal will stick okay.

Easier to just silkaflex a bit of ali


MikeRJ - 25/4/10 at 08:28 PM

quote:
Originally posted by mark chandler
If you want to mig its not impossible as it will not carry any load, you need to heat the area up with a decent blow torch before starting and the metal will stick okay.


I'll second this, I've repaired a few cast iron exhaust manifolds by cooking them in the oven (wife got a bit angry about that) and then having a blowlamp directed into the port with the crack in it to keep it hot whilst I MIG'd it up. One manifold was off my Fiat Coupe 20V Turbo which are renown for cracking, but it's survived 2 years on that repair.

It welds very nicely as well: