Bnr34 Rb26/30 Conversion

[zebra]

Wouldn't heating only part of the block make is distort more than if the heated the whole thing evenly?

[GTRNUR]

Wouldn't heating only part of the block make is distort more than if the heated the whole thing evenly?

Yes absolutely. Pre-heating allows the weld to take to the steel without the engine block acting as a huge heatsync, pulling heat out of the metal pool as the weld is performed. It also allows less heat to be used to achieve the weld.

Probably the most important thing is that it reduces the thermal differental between the two materials. Consider the length of a block being about 600mm long, and factor in the thermal expansion of iron/steel at 1000 degrees. The block will grow about 7mm in length. Heating allows less thermal variation at the point of the weld between the two materials, and therefore less stresses will be formed in the block when it cools to room temperature again.

Ideally the whole block would be heated in a gas oven, and welded in stages where the block is returned to re-heat and stabilise the block's temperature. It should also be cooled in an oven after the welding is done over 6 hrs or so. One of the engineering shops I work for does this soft of thing all the time. Not with engine blocks, but with other heavy industrial and mining equipment. They also often heat cycle the welded item many times to stress relieve it after welding.

You can liken the induced material stresses to that of a spring or a rubber band stretched to its limit. Or even better, an ARP fastener. Compared to an un-welded item it will take less force exerted to push past the point of elasticity into yield and eventual failure.

Please don't take this as criticism with your project. I take my hat off to anyone willing to have a go but since your posting this publicly expect a few differing opinions.

[zebra]

You lost me after yes absolutely lol

I wasn't thinking the deeply about

More along the lines of stuff warping after an overheat which would be nowhere near the heat that welding would produce nor as quickly

So heating only half the block would do all sorts of weird stuff unless it was heated very slowly

[r32-25t]

I'd still like to know where the oil pick up is going to go, cause so far it looks like he is using the rb30 one in which case the sump won't fit

[destrukshn]

+1

I've not measured a standard block and seen all the mains measure up the same, let alone a welded one. For the extra few hundred dollars its worth the piece of mind. Personally I hate the idea of pulling an engine out of a car to fix something I could have done better if I'd just paid a tiny bit more.

While you might 'get away' with it in a lowish power situation combined with big 2.8+ thou clearences, why would you set an engine up like that if you can do better. Especially in a GTR.

Of course when assembling the block, you would always have to check and see if the block is twisted or sprung on the main bearings. You would make sure that all clearance on the main is right and then go ahead. If its sprung then you would line bore. Every professional engine builder knows that so you guys don't need to worry about if the block is warped or not as we cross that path it will definitely be sorted. But appreciate the comments, warnings and what to look out for, just be aware we already got those covered. All my machining is done free, all my mechanicals is done free so it is not about cost and it is not a dodgy build. The rebuilder just doesn't like the use of a plate and believes that this technique is better and as an engine builder he doesn't want to just buy someone elses product (such as a plate) and assemble even if it may be easier. He has his reasons for not adding 10mm extra for the adaptor plate too. lol.

Regardless, when i started the thread i just want to see if anyone has taken this approach. I was more worried if the strength of the weld would it hold say vibrations from the differential, engine movement etc. Since then, we have drilled the holes and the welds are damn tough, it retains about 12 original holes from and including oil pump so there won't be much pressure on those welded areas anyway and that is why the engine builder builder believes it will work.

Edited April 23, 2012 by destrukshn

[destrukshn]

I'd still like to know where the oil pick up is going to go, cause so far it looks like he is using the rb30 one in which case the sump won't fit

If you look below. The extra piece welded on is going to be the new place of the oil pickup. We are going to drill in to the oil galleries and will be using the same oil pick up place as the RB26. It is pretty much replicating the RB26 block and will operate like a RB26 block. The current RB30 oil-pickup will be blocked off. Hope this makes sense and as I said I will provide pictures of the assembled to show what has been done.

[MYRB30]

What was the end result of this project?

[destrukshn]

http://www.freeimagehosting.net/mwhbz

That was the finish product. Still running in, seems to run fine, no leaks or anything