I finally got the heads and cam into my car, and I can feel it pulling all the way to rpm cutoff in the PCM. I kind of want to freshen up the bearings in the bottom end, and do some better rod bolts so I can spin it higher and hang out above 6k without fear. I would like to save downtime on this, so I am getting a core set of rods and a crank to get them machined before I pull the engine. Would it be safe to use a different set of rods and a different crank without tearing the whole bottom end apart? I would be replacing all bearings, but I won't be replacing the pistons or the rings. Thank you!

 

So, you want to replace the crank and rods without tearing apart the bottom end? That's your question, yes?

 

Basically. I will be pulling the engine and putting it on a stand, flipping it over, and disassembling it from the bottom.

 

If you got a stock LT1 crank and rods from a donor motor that was known good you could have that crank polished and rods resized (big end) and ARP rod bolts installed. New Bearings

...But you would need to pull the pistons off your rods to put on the donor rods....at that point why not also hone and re-ring....and then there is the cam bearings (worth at least a look)

LT1 is rear external balance motor so IDK if donor crank/rods=your crank/rods in terms of balance.

 

My issue is price and downtime. I'm trying to keep the costs as low as possible, and I was hoping to just change out the bolts and bearings so I wouldn't have to do new rings and a hone. My local machine shop won't touch any parts still in the block unless they're doing the entire engine, and they want around $2400 for a basic rebuild, as opposed to around $150-200 for resizing rods with new bearings.

 

The pistons are going to come out of the engine with the rods, and the heads will need to be removed to do so. The pistons are pressed onto the rods, so they will need to be pressed off.

My advice? Leave it alone. You are going to waste more time and money trying to take shortcuts than you will doing it correctly the first time. You aren't allowing any room for incidentals that may pop up, and when no room is allowed, Murphy's Law will be in full effect. Leave the engine alone, save up to have things done correctly, and enjoy what you currently have.

 

If you install rod bolts you need to have the rods resized, if it were me I would but some Scat I beam rods and speed pro forged pistons and if you have another crank have it checked/polished the have the rotating assembly balanced. Install new rings and bearings bore/hone the block and now you have a fresh 0 mile engine and you can beat on it all you want.

 

I know that the rods will need resized, which is why i'm gonna pull them in the first place. And as an aside, I want to enjoy what I have, only my car spun a bearing(I think) this past evening. I'm looking for the cheapest way to have a 6500 capable engine.

What if I just take a new bottom end, pop out the pistons and ball hone it lightly to clean out the ring ridge? I found a high mileage sbe that runs, but this will be my first time screwing with anything below the deck. Is it safe to just clean up the bores and put everything back after resizing the rods? Assuming all the bearings and other surfaces check out.

 

Without inspecting and measuring the actual engine, it is anyone's guess. You may be fine, or you may be back to square one.

I would recommend that this book be your first investment before going any further:

 

94..

Using a "high mileage" donor motor of unknown condition other than it "runs" to then push 6500 rpm....high mileage bearings (cam, rod, crank) all should be replaced. That means a complete engine tear down with minimally polishing crank and resizing rods with ARP fasteners. Would you be able to just hone and re-ring the cyl.."maybe" but very likely you need a .030 over bore which requires new pistons

Consider buying a short block from ERE or Golen (383 4 bolt forged). I did the later and now have over 40k mi on that motor

 

I guess I'll just be tossing a completely factory bottom end back in, then. It's kind of ridiculous to even consider a $4k bottom end when I could get my stock one rebuilt for under $2500.

I'm just looking for experience from people who have done a cheap refresh, on the off chance that the bottom end I have is still clean.

 

I already have it. It's got nothing but recommendations for a complete rebuild.

 

not on a LT1 but I did put new rod bearings into a 350 in a truck I had while motor was still in. Got another 100k mi on it...but it was just a work truck that never saw rpm's above 5200

Unless you know you have a spun rod bearing or something just leave your motor alone until it does present a problem.

pulling the "bottom end" out because you want rods re-sized with ARP fasteners means the pistons need to come out and those need to go in/out through the top. At that point the motor is completely apart Sure you could just throw the pistons on the re-sized rods keeping the rings and not touching the cyl walls or cam bearings...if you want. IMHO though you may find during this process those untouched items need attention to the point it voids wtf you would just re-size rods and new crank & rod bearings

its your motor & $, do what you want.

 

I'm pretty sure that I have a spun bearing, because the other day when I was driving, I made a trip to 6500 and about 5 minutes later the car would stall any time I hit the clutch without gas. The last few drops of oil came out almost as a paste with a bit of a shimmer to it, and the filter has what looks like small(.1-.2mm) chips of non magnetic material in it. The top end had some of these as well, and I could be mistaken but I don't think I should have any of that after 200 miles on new heads and a cam.

 

well 6500 rpm is really pushing a stock bottom end. Sparkles in the oil are a sure sign bearing material is in it. Oil pressure is also likely low now

Once you spin a bearing you would need to get the crank ground .010 under to clean it up

The metal flakes are now throughout your oil system and will and have started to scratch all the other bearings

You need a new short block rebuild

cheapest path is just slap in a junkyard LT1 so you could drive the car if $ are tight now. Still some $ and time just to do that

Given hw you really want to drive the car, get a 4 bolt forged short block and put your H/C in it

 

Well, that's the long term plan. But for the meantime, I was hoping I could get by with a freshened up bottom end. I guess it's unlikely to work out the way I hope it will, so I'll just be careful until I rebuild the stocker I have.