How to prevent Spun bearings...

[ar0ck]

Someone please tell me!

My motor combo is pretty simple yet some may consider kind of dumb since I am playing Russian Roulette on a stock bottom end but it was all I could afford at the time.

Engine:
-Comp Cams CC306 (230/244 .544/.576 112 lsa)
-Comp Magnum 1.52RR
-Comp .0072 Chromemoly Push-Rods
-Stock Lifters
-Comp 977 spring
-Comp Ti +.050 retainers/seats/locks
-ARP 7/16 studs
-561 casting heads flowed @ 255cfm @ .500 lift
*54cc Chambers
-ARP Head Bolts
-Racetronix 255lbhr Fuel Pump & Hot-Wire kit
-Lunati Double Roller Timing Chain
-Port Matched LT1 Intake with Ported Runners
-GMPP EGR Block-Off plates
-Enlarged Throttle Body Opening (sized for 58mm throttle body)
-Stock ported Throttle Body
-Meizer Electric Water Pump
-!AIR/EGR
-Throttle Body ByPass

What should I look for to build into a competent bottom end that can handle 350-450 crank horse?

[97ws6]

Most aftermarket balanced rotating assemblies can handle that, you are talking 700.00 to 1700.00 if you want a forged one.

[johnjzjz]

Most assume that buying a set of bearing inserts and installing them is what you do -- WRONG -- a real shop mikes every journal comes up with the numbers than installs a set of susposetoo fit bearings and uses a bore gague to measure that - the number between them is the ( rod - main ) clearence -- the import stuff is at best all over the place the reason cranks are $200 / $3000 -- inserts can be bought in an over size = undersize .001 .002 like that and mixing gives you .0005 more or less clearence BUT you have to have good tools for this and know what your doing -- and in my shop we almost all the time send new cranks back out to a crank shop and have them finesse the journals to the spec we send them so clearences are correct -- most think expensive shops are stuffing their pockets with money when on real side it is all the extra time and effort it takes to make it right the first time you only get what it is you pay for -- jz

[Savage_Messiah]

change your oil

[ar0ck]

Originally Posted by Savage_Messiah

change your oil

Doesn't mean s***. I changed my oil and it still happened. The car does not get driven often but I do turn it on regularly. LT1's are notorious for spinning bearings with "big" cams.

[GrandmasterCow]

just build another motor or this one but redo your bottom end. when i had all top end on my ls6 it threw the bottom end badly, now i have built a new setup but all aftermarket bottom end and we'll see what happens

[Slow Z]

Originally Posted by TransAm4Life

Doesn't mean s***. I changed my oil and it still happened. The car does not get driven often but I do turn it on regularly. LT1's are notorious for spinning bearings with "big" cams.

really? I've never heard that, is there a particular reasoning behind LT1's being notorious for spinning bearings? I would think it's safe to say that most bearings spin because they are either starved of oil or they were simply installed incorrectly / improper clearances?

[johnjzjz]

from what i understand its after tweeking the top end if the bottom is not gone through as well at the same time -- they rattel out the bearings i could be incorrect but its what i have been seeing -- jz

[deadtrend1]

Originally Posted by TransAm4Life

LT1's are notorious for spinning bearings with "big" cams.

thats a new one

[NJSPEEDER]

big cam = more cyl pressure, more cyl pressure = more pressure against old stock bearings, more pressure against old stock bearings = boom.
it is actualy a truth of all gen 1 and 2 small block bottom ends as far as i have heard.

[bubba428]

well if you beef up one part of an engine your just exposing any weak spots...i don't want to tear into the botom end on mine but at 180,000 original miles...no choice

[The Fixer]

Originally Posted by NJSPEEDER

big cam = more cyl pressure, more cyl pressure = more pressure against old stock bearings, more pressure against old stock bearings = boom.
it is actualy a truth of all gen 1 and 2 small block bottom ends as far as i have heard.

Come to think of it, I know a guy that did a cam swap on his good-running, high-mileage 305, and it wiped the bottom end within a few weeks. I guess there is some truth to it, but I thought the shortblock Alex started with was low-mileage, and taken apart/checked for clearances and such?

[NJSPEEDER]

the safest things you can do are always installing fresh bearing whenever you take it apart for any reason or plan a major upgrade and to install the highest volume pump available for your application.
having a ton of oil pressure is not the most important thing since it is the volume that floats the bearing and keeps the bottom end happy. as long as you have 10+psi at idle and 50-60 at peak RPM everything shoudl live a nice happy life.

[johnjzjz]

just a side note -- some high volumn oil pumps require a cam button or end plate to keep them in the block ( the camshaft that is ) - also they are real hard on the dist gear if it has one and the high vol pumps need a hardened drive shaft as well -- the roller motors have end plates because - the way the cam is ground ( flat across the lobe ) - with out it the cam can walk out if not held in place -- flat tappet cams are angle ground so the lifter turns and the cam is than driven to the rear so gear thrust against block is used -- jz

[ar0ck]

Well it looks like I am going to be ordering a new LT4 short block through Scoggin Dickey. They come pre-assembled, 4-bolt mains, 0-deck, with Clevite bearings. I'm also having them install a new CC306 cam w/ lifters. Now all I need is to pick a good oil pump that can handle it.

[97ws6]

How much did S+D get you for there lt-4 shortblock?

[Pampered-Z]

Sorry Ladies and germs,,,I know,,, I've written another novel!

Originally Posted by johnjzjz

most think expensive shops are stuffing their pockets with money when on real side it is all the extra time and effort it takes to make it right the first time you only get what it is you pay for -- jz

Excellent point!

That's exactly why when I'm getting machine work and the inital assembly done I leave it to the true engine builders. I'll freshen a bottom end, but when everything is new I think you’re better off having a builder that will spec everything out and make sure it's perfect!

You might be amazed at the differences it makes when a good shop does the work, making sure the cam is true and indexed, deburring the block, pinning freeze plugs and cam bearings etc. Most companies don't list this type of work, it's somewhat hidden in the cost. But it can be the reason you do pay that little more! This is where doing your research and talking to the builder you'll learn about their knowledge and how their work is done.

As far an LT1 spinning bearings, beside the fact these engines have low oil pressure to start with, I see a few things thT I think people do wrong with the install:

1) Not keeping everything clean, getting dirt and debris in the engine. From reading on other boards it appears scotch brite pads seem to be a common problem, pieces getting into the oil system.
2) Using a BFH to install parts like the crank hub! Do not beat the crank timing chain gear and crank hub on!
3) Using high volume oil pumps with stock pans, yes you can suck the stock pan dry and starve the engine of oil.
4) And the big problem I see!!!, people spinning stock bottom ends too high. The big cams people install need RPMs that the stock bottom end can't support. 6400 RPMs should be the limit.

There are allot of LT1 out there with 70,000+ miles on them making 400HP, BUT with RPMs limited! I built a few using 306, GM847 and custom grinds and they all run fine but I tell everyone to limit RPMs to 6400. Yes, there are guys out there spinning the motor higher, but they are the exceptions and not the standard. Remember you using an assembly line motor, not something that was carefully balanced and assembled.

Upgrading the oil pump is good, but you're going to have to make a call on this. There is currently allot of talk about problems with the melling stock replacements (Melling makes GMs), so you would need to go up to a HD the "M: series. But that's too much for a stock pan's capacity. I don't know of which other brands to use, some are using GM's white spring to add a little pressure and still run a stock pan. Again, people say the aftermarket HD pumps won't sucking the pan dry, but go look around on boards like CZ28 and see how many people burned up motors with high volumes pumps and stock pans! And here again, during assembly check the clearance between the pick up and the pan. You never want to assume anything, like the clearance between the pick up and pan is right, check it.


Alex, ( Here is where I go and start spending other peoples money again )

This is one of those areas where I suggest doing it right the first time and be done with it. Spend the extra dollars and get a bigger pan with windage trays and control flaps and a HD pump.

Before you buy the LT4 block you need to do some more homework. You might be better off just having your block rebuilt with better parts!

The LT4 is out of production, you are most likely buying a remanufactured engine. The LT4 block is nothing more then a Corvette 4 bolt main LT1 with a few upgrades. The LT4 was designed to be spun higher then an LT1 by way of a different machine process to the crank that made it stronger. But is the same material, upgraded bearing caps and the HD timing chain, and differently cut piston valve reliefs ( for higher compression). But you still using stock material rods and pistons and bearings. I would not consider an LT4 block a high HP unit, it's fine for 400-425HP, but if you're really shooting for 450HP or more then I would not buy an LT4, Just build a block with better internals then the LT4.

Now, I'm not trying to scare you or tell you this will happen, just that it COULD happen! So this is something else to try to research. The LT4 had a .4 higher compression then the LT1, by way of a smaller valve reliefs in the pistons. Since your looking at a block that has zero deck and I assume your heads were milled and with 570 lift of the 306 cam you need to be very careful to check every cylinder for your piston to valve clearance! You may need to either go to a smaller cam, pull the piston and get them cut, or go with thicker head gaskets. Only thicker gaskets I know of for the LTx motors are the Cometics and you will pay a premium for them. Comectic gaskets cost $125ish each and require the block and heads to have a special finish in order for them to seal. So if you have problem you'll need to tear the block apart to have it and the heads refinished.

This is another example of where an engine builder knows to check and can adjust it during the assembly. Because I talked with the engine builder and he knew all the specs of the cam and heads I was using, he was able to determine the clearance was going to be tight. So he modified the reliefs in the pistons and finished the block to the smoothness required for cometic gaskets before he assembled it and shipped it to me. And he was right, I need .055 gaskets to get the clearance I wanted,

JB

[NJLT1SS]

Go check out a few engine builders, get some pricing on what it will take to build a 355 with some good parts, and most importantly good machine work. Have them assemble it with your cam and heads. If you throw your cam heads on this SD LT4 crate, you will be working on kaboom #3.

[procamaroz28]

http://store.summitracing.com/partde...5&autoview=sku

that short block sounds nice how much do they go for??

[ar0ck]

John, I got the heads from Brian. They were ported by Jason Short in NY. they were completely broken down by my machine shop. They flowed right around 255cfm at .500 lift. Chambers are 54cc's, valve springs are comp 977's with Ti retainers and locks ARP studs and Comp 4084 guide plates. Before they were put back together the valves were lapped and seats cleaned up. I don't know what the installed height of the springs are off hand. I belive they were set up at 1.800 so they should be good for .600 lift. I'm using Mr. Gasket .026" gaskets. The intake was also ported by Jason Short. Nothing real fancy just a basic port job on the runners and the TB was opened up to 58MM. Finally the cam is a Comp Cams "306" LT1 Camshaft, 230 / 244, .510 / .540 112 LSA

I don't know of any Engine Builders in the area unfortunately. The good thing is I have two spun LT1's so I can get my original rebuilt and leave the car alone until one is finished. What kind of money am I looking at for a basic 355 fully assembled, and a time frame?

[NJLT1SS]

Alex, if you want, I can give my buddy John down at Ceralli's a call, he is located in Paterson. He built my 396. I can ask him what he wants to do a budget 355, with you supplying the cam and heads. Let me know.

[ar0ck]

If you could that would be awesome! I'm trying to sway my parents on helping me out as a graduation gift since they aren't to keen on the motorcycle idea.

[johnjzjz]

hey pampered Z ------ you need to be very careful to check every cylinder for your piston to valve clearance

when we have a motor with issues and we need to get more we do a simple trick with a degree wheel and the valve timing - @ between 5* / 15* is the spot that the valves on over lap are at their closest -- if you use checker springs and rotate the motor you can actually measure the total distance between the valve and the piston in its cycle and adjust the cam deg if you want more bottom advance it and use the exhaust valve as your guide to how much you can with knowing .100 is the ruel -- don't know if you follow if not i can go into more detail its not for a novis to try but you sound as if you have done this sort of work and this trick is a value to those in the know about getting the most of what you have to work with -- jz

[GP99GT]

alex did you degree the cam when you did it? degreeing the cam is a big factor, if you dont do it, you could be off by many degrees of timing

[Pampered-Z]

Originally Posted by johnjzjz

hey pampered Z ------ you need to be very careful to check every cylinder for your piston to valve clearance

when we have a motor with issues and we need to get more we do a simple trick with a degree wheel and the valve timing - @ between 5* / 15* is the spot that the valves on over lap are at their closest -- if you use checker springs and rotate the motor you can actually measure the total distance between the valve and the piston in its cycle and adjust the cam deg if you want more bottom advance it and use the exhaust valve as your guide to how much you can with knowing .100 is the ruel -- don't know if you follow if not i can go into more detail its not for a novis to try but you sound as if you have done this sort of work and this trick is a value to those in the know about getting the most of what you have to work with -- jz

Thank you for the offer, that is exactly how I was taught to do it. I didn't want to go into full detail with Alex until I actually have an idea of things he may not think of. I've posted on a LT1 board to have the engine builders tell me if it might be an issue. the 306 cam on a stock LT1 block, even with milled heads have plenty of clearance, but the LT4 piston and zero deck I haven't played with. I hate to have Alex put the engine together and have it go bad! A zero desk LT4 block should be a -4 flat top, so if I do the calculations right with 54cc heads and the felpro should be real ner 11,8:1 that's high for pump gas. With the drop in desk and those gaskets the intake will probably also need to be milled to match the ports back up.

This is why I'm thinking it might be cheaper to take one of his blocks and build it with something like a scat forged 355 kit would be better in the long run and be more reliable and maybe less money then the LT4.