9014josh

iTrader: (1)

had my swap going great for a couple months now and about 2 days ago the motor started knocking,im assuming its from the lower end in the crank.

Question is:Whats next? stock rebuild? im definetly NOT made of money so i would have to go the cheaper route...Feedback would be helpful!

84redta

iTrader: (34)

Check oil pressure. If you haven't run it too long, you may be able to get another pump in and give yourself some time to save on rebuild if poor oil pressure is your only issue. 383 kits can be had for $700ish, stock rebuilds are $300 for bearings and such, and i think $500+ for pistons (size desirable) and the whole nine in a rebuild kit.

adamwbennett

Check the KISS stuff first. I once saw someone rebuild a motor that was "knocking" that turned out to be a bad spark plug wire!!!

9014josh

iTrader: (1)

I do believe it is a rod bearing because it is slowly getting worse..i dont believe my factory oil pressure gauge maybe ill hook up my mechanical gauge tomorrow and see what it reads.

What would be involved in a stock rebuild? could i get away with just bearings and an oil pump? im assuming the crank would need to be turned too right?

Pocket

iTrader: (24)

If a bearing is spun it needs machine work to clean up the crank and rod journal. Sometimes the rod is beyond saving and needs to be replaced. Once you drop the pan check out the rod caps. If one is a different color than the other 7 then it's history. Luckily LTx parts are super common and cheap and even better that most SBC stuff interchanges freely

Cheapest option is to find a B-body in a JY and pull the longblock with a warranty. If your original LT1 came from a Fbody then swap the heads over, otherwise run it as-is. Be sure to pop the vave covers before leaving the JY. Sludge means dont buy that engine. Bring a breaker bar to spin it over a few times

9014josh

iTrader: (1)

Good idea..i have seen several roadmasters and caprices in my junk yard,i could prob score a block pretty cheap if it hasnt been ruined by the klunkers program

Falconiroc

More fantastic advise from Pocket.


On the suggestion to Keep it Simple first, I sold my '88 IROC after it fell off of a Jack (Jack slipped, I was doing an emergency plug/Wire swap) (another reason not to work under your car while on a jack)

When I got it down it had a knock. A hard-sounding one. I sold the car for $650, I regret it badly because it ended up being a very simple fix, I thought the engine needed to be rebuilt.

Anyway, you came to the right place for good troubleshooting advise.

9014josh

iTrader: (1)

do you know what the problem turned out to be?

adamwbennett

I just finished doing a stock rebuild just like you are considering. I ENDED up replacing: bearings, cam bearings twice, gaskets throughout the motor of course, ALL sensors, had block cleaned, line bored, and checked by shop, electric fans, thermostat, rod bolts, rod caps, timing set to upgrade to vented opti, opti, water pump, spark plugs, plug wires, computer sent for tune, egr delete plates ( to avoid replacing EGR related items ), starter, transmission cooler lines, radiator hoses, and the serpentine belt. I am sure there is something I missed but that gives you an idea atleast of how quickly it can spiral out of control. Having a second motor here was very helpful. I bought a second motor basically for the updated opti and timing gears and used a lot of odd and end bolts and random odds and ends from it. Plus once you have tore apart two in a row you know how they go together pretty well!

9014josh

iTrader: (1)

Oh im sure lol if i had the cash to do what you did i would be all over it but thats not the case.The knock isnt that bad at all yet in fact it doesnt even make any noise at idle for the first 5-10 minutes then once its warm you can hear it then you hear it again around 1600 RPM but past that you wont hear it, possible lifter? im hoping i can just do crank bearings and an oil pump and be ok.

9014josh

iTrader: (1)

Looking on summit for parts,what should i be looking for? are all the new SBC bearings the same? or are the LT motors different?

Pocket

iTrader: (24)

The rotating assy for GEN II engines is interchangeable with 1 pc RMS SBCs. Simply put, if it fits the late SBC, it fits the LT1

9014josh

iTrader: (1)

ok good just what i wanted to hear..this is what im looking at for it:

http://www.summitracing.com/parts/FEM-MK6394A-000/

ericjon262

No, that will have the wrong gaskets, this is what you need.

http://www.summitracing.com/parts/FEM-205-6383-00/

if it spun a rod you'll need a kit with undersize bearings to compensate for the machined journals.

ericjon262

I know you said you aren't made of money, but there's no time like the present.

http://www.summitracing.com/parts/SCA-1-91050BIE/

if you know someone who will balance you motor cheap...

http://www.summitracing.com/parts/SCA-1-91050-1/

9014josh

iTrader: (1)

i would love to go 383 but like i said its not gonna happen this year just a stock rebuild i would be happy with,Thanks for the useful info tho im gonna prob end up going with what you listed above for a strock freshen up..how will i know if its a spun rod bearing?

ericjon262

The only way to really know is to drop the pan and look, I spun one once and ended up slapping the piston into the head, which means more than just a basic rebuild, if I was you, I would try to find another LT1 in a yard, or one in a wreck roadmaster/ impala, and put that motor in your car, and use your motor for a performance build.

9014josh

iTrader: (1)

what exactly happpens when you spin a rod bearing tho? ive never had to tear a bottom end apart i usually just replace them but i would like to know how to fix it rather than just junking it and getting another one..

ericjon262

The bearings are supposed to remain stationary inside the rod, usually if one spins, it's because the space between the bearing and the crank is to big, either from wear, or poor blueprinting, which allows the bearing to get hammered by the rod's up and down motion, which makes the bearing thinner allowing it to turn inside of the big end of the rod. the one I spun was paper thin when all was said and done, mind you, I drove it for 2 weeks with the piston slapping the head.

five7kid

iTrader: (14)

If the bearing has spun in the rod, you need to have the rod resized, or put in a new rod.

If it is just worn between the bearing and crank, meaning the bearing halves have not spun in the cap/rod, you can get by with crank and bearings.

9014josh

iTrader: (1)

crank and bearings meaning having the crank turned and new bearings?

five7kid

iTrader: (14)

Yes.

9014josh

iTrader: (1)

Think i may end up pulling the intake off this weekend coming up and checking it out it really sounds like its coming from the top end and only makes the noise at about 2k RPM...

five7kid

iTrader: (14)

Might be the piston smacking the head. My 396 with spun rod bearing only made noise under light or no load.

Klortho

Here you go, this is the sound of a spun bearing

actually, 2 spun mains, 3 spun rod bearings

http://s41.photobucket.com/albums/e2...ent=Itruns.flv

and here's the aftermath

five7kid

iTrader: (14)

All from the front of the engine?

From the looks of the crankcase deposits, that engine didn't get very good maintenance. Looks like you've got a full rebuild ahead of you, including crank turning or replacement (assuming it's scored based on the bearing pictures), rod resizing (good time for ARP rod bolts) or replacement, and align bore of the mains. And new oil pump.

Klortho

Oh, that motor was toast, hopefully his isn't as bad as that one. Only thing we can determine is the motor was out of a theft vehicle and it got ragged on pretty hard and the auction company put gear oil in the motor before auctioning off the car. I heard the motor run and it didn't knock at all. The place I bought it drains the oil out of the car before the motor comes out and I picked it up the day they pulled it, put the 5w30 in it and it started that noise. The block was good for a core and 3 of the rods were shot. That motor only had 100k miles on it and they swapped it out for another one which is the one in the GTA now.

The motor in the GTA dropped oil pressure to 0 for just a split second and I noticed a rattle in it around 2000-2200 RPM so I didn't want to take a chance and pulled it, that quick to de-tin the bearing and take it to the copper quick, so it went for a rebuild and I think for a stock rebuild was around 600 bucks (that included new valve guides). The bearings and oil pump is the exact same ones that are used in the L98s, rings are a little different due to the placement of the wrist pin, but it went back together with Clevite bearings and Hastings rings, had the rods checked and cleaned up, crank turned 10/10, cylinders honed out and it runs like a top now.

9014josh

iTrader: (1)

i may have to do the rebuild..is it possible that i bent a valve from bouncing it off rev limiter? some people have told me that i could have floated the valves into the cylinder..

NAASBC355

compression test would tell you that real quick. I dought it did that though. There would be other problems like a "back firing sound" and a bad misfire.

~Couch