Hi All

Rebuilding my 5.3L pre HE and have the opportunity to use a 6.0L crankshaft.
Anybody know what modifications to connecting rods or pistons are necessary and opinions if it is worth the trouble.

Thanks
Ken

 

Is there a problem with the 5.3 litre crankshaft?

Have you checked the journal specifications for the 6.0 litre as the journals may be different along with the length of the connecting rods.

 

The 5.3 crank is fine. While I have it apart just looking for ways to improve performance. I'm changing the cams and increasing compression. Thought I would look at increasing the displacement as well

 

I think the journals and rods (look different but same dimensions) are the same between the 5.3 and 6, but there are alot of component differences. The 6l uses a different sprocket to drive the oil pump, i believe it switches over but am unsure. The Flat head 5.3 has a rope seal rear main seal while the 6l has a 1 piece, you block would need machining to accommodate the 1 piece. The 6l has a relocated piston wrist pin to accommodate (i believe) the same rod length they would leave you with some ungodly compression ratio with flat heads (neighborhood of 15 to 1) so a set of custom pistons would be required. Shorter cylinder liners are used in the 6l to clear the crank throw. lots of articles around on punching out the v12's but its definitely not cheap if your not equipped to do the work yourself. Everything comes is 12X multiples so math is not your friend.

 

Thanks for the great info. I figured that either the wrist pin would have to be relocated or the connecting rod would have to be shorter. I was unaware of the difference in the rear seal so that is big consideration. I was planning to use forged Pistons with higher compression so that's not an issue. I haven't seen the liners in awhile (I replaced one years ago) so I guess they are held at the top of the bore with the bottoms extending down to the oil pan? That would make shortening them a bit easier. If I go thru all of these mods I might as well go to the 96mm liners that would already be cut to the right length? I realize the cost of these mods is over the top, but I will explore them ahead of time with the machine shop. My alternative is to just keep the existing crank and go to stage 2 cams and higher compression Pistons. I really appreciate the info. Anything else you can think of will be greatly appreciated.

 

i think 96mm liners require some extra mods to accommodate+ custom head gaskets 92-93mm? might be the max bore with stock spacing + gaskets. modifying your current liners or getting a donor 6l might be less then buying custom 96mm ones & gaskets. Yes, the liners slip in from the top. The 5.3 already has a not so great bore vs valve area and large bore's play more into this weakness. Its true there is no replacement for displacement, but the 5.3 is already a very lazy engine (45-55 hp per liter). Personally i would try and make the engine breathe alot better with around stock bore, aiming for 60-70 hp per liter.

I have always wanted to make a nice street v12 but never got around to it. we have a few 5.3's and a 6l laying around at the shop. Many years ago i mocked up a 48 valve'er with AJ6 heads, but felt the idea was impractical to proceed with.

 

You are correct. I've read that 93.5mm is the max bore with stock liners. To use there 96mm liners you have to get the block bored out to accept them. THe only 96mm liners I've seen is from rob beere, which makes them expensive. I'm sure I could get them made here. I agree with you on making it breath better. My current heads are stock so I can have them ported which will help. Right now I'm leaning towards porting the heads, 11:1 Pistons stage 2 cams. I'd like to do he weber conversion but might do the exhaust first. Im pretty sure I can run 11:1 on 93 octane gas. I think I'm going to stay away from the 6L crank and the only thing I'm unsure of right now is whether or not to stick with the stock liners or go the the 96mm. That would give me 6.1L and I have to do he Pistons anyway.

 

I found reasonable 96mm liners. Does anyone know the length of a std liner in the 5.3L? Can't find it in any of the shop manuals that I have.

Thanks
Ken