defrag010

I'm gradually piecing together a 5.3-based budget street engine that will eventually find it's way into my '91 RX7. I say eventually because I've had the shell since like 2005 but something always comes up right when I'm about to dump money into it.
I already have the top end of the build completed with milled 64cc 317's that I ported while @ SAM (301cfm), a LS1 "hot cam" copy, and a LS6 intake. I'm trying to spend as little money as possible, so I'm just using un-wanted junk and doing everything myself and waiting on deals.

Anyways, I figured some LS1-people would enjoy pictures of the welding and offset grinding process. They are cell phone pictures, though. Goal is 3.8" stroke, and I thought about using a honda journal and nascar rods.. but decided to weld and get 3.8" with a standard 2.0" chevy rod. Figuring out what size journals and stroke you can do isn't hard, but I'm not gonna explain how in here.. so read about it somewhere else.





I started out with a #216 crank straight out of the scrap pile.



It was scrapped because the #1 rod had spun enough that it needed to be welded, and whoever worked here before TRIED to weld it but failed miserably. Horrible reason to junk a crank, but it's fixable.



The correct process for welding and offset grinding a crank is to grind the rods first, THEN weld, then finish grind the rods, THEN grind the mains. Reason being, the mains will move around alot during both welding and grinding of the rods.
I indexed the grinder to 3.8" and offset ground all the rods until they cleaned up. Another reason to do it this way is because there will not be any residual oil/contaminants on the journal right out of the grinder. No matter what else you do to a crank (vat, polish, etc) it will still have a very very light film over everything that WILL affect the weld. Fresh out of the grinder will yield a journal that is clean enough to immediately start welding on without any prep.

IIRC, this was around 1.91"~ish diameter.


Then, once all of the rods were offset ground to my stroke, I brought it over to the welder and welded all of the rods. There are many important steps to properly welding a crank, but I'm also not going to go through them in this post. Some people only weld one side of the journal, but I welded all around the journal because I am putting an outside radius on the journals instead of having one side be outside radius and the other side being rolled fillet.




Then, it's off to the straightening press to get straightened. Usually every crank needs to be straightened after a weld, but this one was only out about .003", and that's good to go for grinding.


look closely at the gauge, you can see it's about .003" off in the next pic with the crank rotated 180 degrees.



Finally, it comes back to the grinder to get the rods finish ground.




Voila!




The oil holes will be a little rough around the edges because of the weld.



A little love with a narrow carbide burr, and we're done with this journal!




... and that's it! Pretty simple. Then, just repeat 3x for the other rods and then grind the mains and you're done.

sjsingle1

iTrader: (1)

did you flux core or stick on those welds?

KCS

iTrader: (20)

That's pretty cool. I've been tossing around the idea of offset grinding a stock crank ~.030" but instead of welding it up, just running it like that and using .030" under bearings. With a 3.905" bore, I'd end up with a true 350ci LS1.

It's squirrely I know, but it's really not too much more effort when rebuilding an engine anyways.

lifeisgood

iTrader: (4)

that has to be flux. i would hope so.
and ive never seen or heard of anything like this. is it even worth it time wise to do all that work?
wouldnt it be cheaper to just buy a crank?

KCS

iTrader: (20)

This is how the old school guys did stroker cranks before all of these aftermarket companies started making stroker cranks. It's very cost effective if you do all of the work yourself.

defrag010

It's a submerged arc welder, a dedicated crankshaft welding machine. you can see the tip and flux spout hanging down in the first welding picture.

It would not be cheaper to buy a new crank (unless you use a machine shop that severely overprices everything), the cheapest one I have found is a scat and it's still 600 bucks on ebay. Plus, since I do everything myself I don't have any labor costs in doing this to my crank. Even if someone walked into the shop and had me do an identical crank to this, it wouldn't even come close to 600 bucks.

joecar

Thanks for sharing... diy is good...

I see work environment is kept clean...

jman54002

iTrader: (11)

I'm from the old school and yes we did this a lot on stock cranks!!
It worked well and was the only way to get a different stroke. And we did it with a mig welder by hand so He is doing a much better job. Cool to still see it happening

KCS

iTrader: (20)

When did you go to SAM?

1989GTA

We still do this on the SBC. Instead of zero decking the block we increase the stroke length as shown above to bring the piston up close to the deck height.

defrag010

left houston on 6/21/09

lifeisgood

iTrader: (4)

nice work. its pretty cool too see. and i went to wyotech, wish i would have done a lil more research and gone to s.a.m. instead. oh well.lol

1CAMWNDR

iTrader: (21)

Very cool. A 3.85" crank with 1.88" or 2.0" rod journals sounds interesting....

DCC!!

iTrader: (8)

that is great! i have read bout it in books and mags but never seen it done thank you!

btw u should make a real budget build thread!

ssinister550

iTrader: (8)

Thats cool man. So what did you do about the rolled fillets which are one of the main reasons these stock cranks are so strong? It looks like you replaced it with a radius fillet?

bww3588

iTrader: (49)

did you learn to run the crank grinder at SAM? thats the only machining process we dont learn at UNOH, because only 1 or 2 instructors know how to do it, and apparently its a "try it and learn" process insted of something that can be taught. (so im told)