I just finished the last minor things for my hotcam and long tube headers upgrade and took it for a test drive. I warmed the car up for a good 10 mins. then drove at low rmps never above (3000) for another ten mins. Everything seemed fine so i decided to open in up. I took it up to 5500-6000 rmps in second gear. I let off the gas and the car died... I pulled over to the side of the road and then tried starting it again, It started, but hardly. I gave it some gas to keep it running and drove it home. I pulled into the garage and let it run. it had a hard time staying running at idle and finaly stalled. the engine is knocking but only at about 1500-2500 is when u can hear it clearly. does this sound like a spun bearing? how can I tell. what else could it be? do the rockers ever come loose? i wouldnt think it would only knock at cetain rmps either way..
also no engine codes were thrown at the time it happened untill after it idled for a while.
oil presure is way low. but car is full of oil.
car is a 96 lt4

 

To check to see if rod bearing rev engine till you hear it then take off 1 plug wire at a time until it goes away.

 

For oil pressure you only need a minimum of 10 psi per 1,000 RPM. If the "knock" noise is that loud it should have triggered a knock code.

Pull the valve covers and take a close look for shavings, busted springs or loose rockers, nuts or studs.....hopefully this will be where your problem lies.

 

The "way low" oil pressure doesn't sound good. I would drain the oil and see what you find.

 

its at about 5-10 lbs at idle. would loose rockers mke a knock only noticable at certain rmps? also makes a squeking noise? i cant tell if ins te top of the motor or bottum though. I will drain the oil and listen from underneath the car tommorow. lets just hope its no e bearing

 

Well, first to define "knock". If it is a low tone, firm sound, kind of like knocking on a hard wood table of piece of solid metal, this is probably a bottom end situation.

I had my hotcam installed about two weeks ago. Drove her ginglerly for about 200 miles. Then opened it up. As I pulled of from the next stop light (easily) when she hit about 2500, there was that sickening, gawd awful sound. I know it well from a previous vehicle.

I just got her back today, new crank, bearings and #8 rod. That money was supposed to go to an ecm tune and new front tires. The odd thing was that you could only hear the knock at 22-2500. We were really hoping that a bearing would be all it needed. Hard to believe that it spun and didn't make a cr@p ton of noise. Only way to know for sure is to drop the pan and check it out.

The really weird thing is that the hotcam caused a random misfire code and triggered the SES light. Eventually the light went out and didn't come back on even after the bearing had spun. I too get the low pressure at idle, pretty common but no issues when gas was applied. Even with the new crank, I think she's seen her last 6000 rpm romp. It's wax and show time if you know what I mean.

 

Sorry man, but looks like you´ve spun a bearing. The squeeking sound often comes up when you get metal to metal contact. Do like this. Drain the car on oil, and remove the oilpan ( It´s doable but a little tricky ). If you see metal shavings on the bottom of the pan you know a bearing is spun. Feel/look at the rods, if there´s any slight different in color or if you feel a large clearance on any of the rods you know what to do

Hope everything looks ok.

/Johan.

 

lots of great info/advice posted already. First,like the man said,find out which cylinder is knocking BEFORE you pull the pan.Rod bearing are easily replaced with engine in car. My encounters with spun bearing have always resulted in fixable damage,but having to pull the motor.

 

Once the bearing has spun, the crank is ruined. You still have to tear the engine apart and grind the crank, measure all the rods, check the bearing gap. Oversize bearings and so on. A lot of work :/

You can lift down the pan and check it properly, doesnt even need a new pan gasket, these rubber gaskets are reusable. You can do it in a couple of hours. Ask a friend for help taking the pan down. You also have a nice view on everything else down there.

Best of luck.

/Johan.

 

well I'm pretty sure she spun a rod bearing. the engine has 120,000 on it. I guess I can be optimstic about this situation. 377 or 383? Im thinking 377 is the way I want to go. it would save money on the bore and I dont need the extra couple horsepower. Or should I just do a stock rebuild. What should I do with the heads? Im thinking regrind valves and new springs is all. maybe a light port job done by myself. I dont want to spend a ton of money. what can a guy expect to spend on this project? can it be done for 1000-1500 if I do all the work myself?

 

I´m suffering with you :/ it´s so damn sad when stuff like this happen. I´ll go with the standard stroke, it may be enough to hone the cylinders, if there no turn edge from the piston rings. Or else just go with .30 overbore and new pistons. Do a full balance of the engine, change the rods and crank, or grind it and get the parts measured. Clevite 77 bearings, change the rod bolts to ARP, ARP the mains to. A new High volume oilpump with Arp driveshaft is not to bad.
About the price. It depends how expencive the company is that have the machines to grind a crank, balance the internals, measure the rods, hone or bore the block and clean it afterwards. ( Make sure to remove all the oilplugs and freeseplugs in the block ) The cleaner the better.
You can get away with $1200. If you do the build yourself. Maybe someone here knows a good guy that can help you with the work on the engineparts? I live in Sweden so i can´t help you there =)

As for the heads.
I would try out the 200cc kit from Advanced Induction. That would be enough to punch out 500rwhp for you. They cnc port the factory heads for you. www.advancedinduction.com

Here´s a Camaro running 10.8 with that upgrade.
http://www.youtube.com/watch?v=2g1cq...eature=related


Post some pictures as you go!

/Johan.

 

Could someone comment on how a hotcam install and spun bearings might be related? It seems to be an odd coincidence. Is it just because the engine was rev'd higher than had been the case before the install?

 

 

My 1990 Vette engine went 6 weeks after I bought it. I am very tight on funds, working a second job just to make ends meet (especially with the with the new car payment and extra insurance).

I figured if I was going to have a ton of machine work done, I might as well have it done on a 400ci block. So after spending a few weeks checking local listings, I found one.

Machine shop cleaned it and checked it out and told me what it would need. All told, between the machine work and parts, the machine shop told me it would cost about 1000.00. The machine shop would give me a crank if I paid for the machine work on it, they had rods from a new model engine that would be good for 500HP easily they would give me. I would need to buy pistons, rings and the bearings and cam. It comes out to be about 500.00 for machine work and 500.00 for parts.

I am planning on porting my stock heads myself if they are still good, and using my stock TPI intake. I figured that was the cheapest way to get the most bang for the buck. Luckily I know someone who has put together a lot of engines and will help me with the engine rebuild. I know new parts like water pump, thermostat, hoses, wires, ect... are going to nickel and dime me to death. I plan on putting in a heater core too as long as the car is all torn apart (working on the interior at the same time while the car is down).

 

A 383 is a 350 block with a 400 crank. A 377 is a 400 block with a 350 crank. You would need a different block for the 377.

 

I think if he doesn't bore it .030, he can stroke his shortblock to 377 C.I., providing the correct parts are used to put the piston where it belongs.

 

If you think you're getting 500hp stroker engine that's durable for $1000 or even $2000, you need to put down the crack pipe.

For starters, the 400 block uses a 2 piece rear main seal. 2pc rms cranks do not have the same bolt pattern as the one piece design your '90 came with. That means you have to switch the flexplate (if it's an auto) or flywheel (if it's a manual). If it's a manual, the 2pc rms flywheel won't work with the ZF6 transmission.

Misc parts will easily set you back $700. What pistons did you buy? You'll need them as well. Stock style rods...late model or not...will not last long in a 500hp application.

Stock 113 heads with all the porting in the world are not going to get you to 500hp. Then there's the TPI intake that won't support that kind of hp.

 

I thought we still talked about the car that brought this thread up =) a 96 ( LT4 ) no 400 gen 1 block will fit this car. He have to go aftermarket to go destroked 400.

I´m also curious why the bearings spinns after camchanges, it´s happened once awhile over here to.. Does´nt really makes any sense.


/Johan.

 

a 377 is the same set up as a 383 except standard bore. with a 400 crank, 377 = std bore, 379= 10 over, 381= 20 over, and 383 is 30 over with is the most commom bore for a 350 thats why you here bout 383s the most.

Anyways I drained the oil and pulled the oil filter and cut it open... lots of metal particals, time to decide what to do. Im thinking just doing a 355 and use my stock crank and rods so save money. I dont need 450 hose. I just want a reliable 350-400 horse engine.

 

If you're on a budget, you may find the cylinders will be sufficient with a light hone and new rings vs boring and going to a 355. This will also allow you to retain the stock pistons.

For what it'll cost to have the rods checked and resized, you can pick up a set of new SCAT or Eagle I-beam forged rods for the same price at CNC Motorsports.