question about mains in LT1

I have been told by a couple of random people that the stock mains will walk or just crap out completely when running a supercharger and I have also been told that there won't be any problem at all. Which is more likely? I'll be running a procharger 9lb P1sc. Thanks.

What are you talking about Eddie? your HE pistons & rings are going to crap out way before the cast crank & mains come apart, & if you still got a stock 94 shortblock in there, you probably got a few miles on it, No?

As far as problems with the crank flopping around and walking, if it's all aligned and the belt tensions are ok, it will live long enough to let you destroy the pistons and join the 'Rebuild Club'.

I'm a little ahead of you there. The motor is already being rebuilt with forged goodies, less mains. I shoulda mentioned that, sorry. The rebuild situation is a little wierd since it all started with a minor cam swap then got way out of hand. Then I jumped on the tyrbne sale last month and bought the blower. So would you still have the same situation or is it a whole new ballgame now. Sorry I didn't mention it earlier.

Well you might want to scratch up the $400 or so for the 4 bolt mains since you are doing a forged engine, but I understand where you are coming from about the build costs spiraling out of control. Still, for a street engine that only sees redline once in a while, the stock caps will hold together. If you end up having to pay for an align hone (at least have it checked as part of your rebuild), then you might consider it. If you bolt it all together and the crank spins nicely, you're mains are probably OK, but sometimes the OEMs put different thickness bearings in there to make up for the mains being different heights from eachother. Some guy not knowing that can just bolt his crank in there with a new set if identical bearings and get caught. Align hone has problems of its own, though, cause then you got a crank up higher which loosens the timing chain and might even misalign the trans.

Align hone has problems of its own, though, cause then you got a crank up higher which loosens the timing chain and might even misalign the trans.

If it's done right and the block was true, you should never remove anything from the block itself. An align hone should put the centerline of the crank in true specifications. Both blocks that I had align honed had to take a significant amount of material off the caps. Timing chain were never even close to being loose.

So you can just convet to a four bolt block from a two bolt? Is there any modifying required to make it work? I really know nothing about that stuff.

So you can just convet to a four bolt block from a two bolt? Is there any modifying required to make it work? I really know nothing about that stuff.

Ditto I want to learn more about this as well.

If it's done right and the block was true, you should never remove anything from the block itself. An align hone should put the centerline of the crank in true specifications. Both blocks that I had align honed had to take a significant amount of material off the caps. Timing chain were never even close to being loose.


And if material is removed from the block we're not even talking about as much as a cylinder hone, maybe a couple of thousanths if that.

So you can just convet to a four bolt block from a two bolt? Is there any modifying required to make it work? I really know nothing about that stuff.


You can indeed. You need to buy the center three caps, and the block must then be drilled for the outer bolts and the crank align honed. This can be an expensive operation to have done.

If it's done right and the block was true, you should never remove anything from the block itself. An align hone should put the centerline of the crank in true specifications. Both blocks that I had align honed had to take a significant amount of material off the caps. Timing chain were never even close to being loose.

Hope mine comes out as good as yours. I only posted that because those things do pop up every now & then. That's why Cloyes makes a slightly larger crank sprocket to tighten up the chain & you can get offset dowels for the trans to keep it aligned. But, yeah, for the typical 3 thou or whatever it takes to true the block, you don't usually need this stuff.

You need to buy the center three caps, and the block must then be drilled for the outer bolts and the crank align honed. This can be an expensive operation to have done.

My align bore was $220. Not that expensive.

Guys,

When you are build a blower motor and have the ability later on to add more boost, intercoolers etc.... building a good foundation to start from is paramount. Getting a good block on something that is going to be abused heavily or rebult many times it's best to start off with a good block. Cup teams use blocks for a long time now and just keep putting new cylinder sleaves in them. They do the block prep right the first time and get tons of use out of them.

In this situation a 4 bolt conversion is key to making the motor live and deal with what you are throwing at it down the road.

Bret

what would it cost to convert a 2 bolt to a four bolt?

I think I paid ~500 for my splayed mains. But I just ruined my block(frozen water = big oll crack!) so I'm out some cash and have to have it done to another block now.... yay!

what would it cost to convert a 2 bolt to a four bolt?
parts+labor you are looking anywhere from 500-800 depends what kind of caps you use and who's dong your labor. If i would guess a job like that with billet caps can run 1k

DAMN! I wish I'd know that before. I am running low on funds to get into something like that. How long would the stock ones hold up? This sucks! That's what I get for getting ahead of myself.:cry: :( :cry: :(

What machine shop is charging you $1000 for a 4 bolt conversion and billet main caps. I live in Phoenix and am having Frontier engine do my block here pretty quick and all of the machine work is going to come to around $1,200
and that is the price with very high quality billet mains (3). I would say no more than around $500 with some caps. If anyone here payed $1,000 you got straight robbed!!! Oh and I speak from experience since two people in my immediate family have been machinists for more than 30 years and I have even mentioned it to them. They laughed. Good luck

I could probably squeeze out 500 if that's the case. Thanks.

500 is what i paid i've heard 750 from Golen.
I have done same mistake as you before, had the short block build and then found out that i needed to get splayed. so had to take it all back apart. I didnt know much about it back then, Golen was Ignorant on the matter i told them from the bigining on what the motor was being build for a D1 with about 15+ psi they said that would be fine. Then a friend of mine told me that i have to have the caps done, i called them back the guy askes me what blower, how much boost? when he heard the answer he said "yeah you def going to need some splayed caps and you can ship it back and we can do it for you for 650 regular price is 750"
i said thanks but no thanks 650+ 200 dollars to ship to them. I went localy and paid 400-500 dont really remember.

also gotta remember that you god labor taking the short block back apart, drilling the block and i had mine rehoned just to be safe.

That's not a problem the motor was just removed today to do the rebuild anyway so i guess 5 should get me by. Thanks.

I absolutley agree that you should go as far as your budget permits. I did not go with the four bolt conversion, as I had heard there were block strength issues that could arise. For my application, I had the block align honed (my crank was fitted with undersize bearings from the factory) and crank ground ten under. I also opted for the ARP main studs. My machinist went through the block completely and even reconditioned the main caps (trued the mating surface and sides). Through my research, if you are under 650 hp, a two bolt with studs would hold up quite nicely in a street application.

I wouldn't hesitate to use a 2 bolts block and ARP studs. Oh wait, I am :)

-Shannon

Well after a lot of thought and discussion I have decided to do th main conversion. I really don't want to replace this motor with the money I've got in it at this point.

Through my research, if you are under 650 hp, a two bolt with studs would hold up quite nicely in a street application.

I have heard the same from a few people. Although 4 bolt will give you sure peace of mind,....I have been told a studded 2 bolt is still very reliable for a street driven car even at 500 HP levels and driving hard, but......I would personally take a 4 bolt if I had the chance, but I think Ill be doing the 2 bolt stud setup myself because I know I wont be over 500 HP with the PD unit Im going to be using.

I am also using ARP studded stock mains. Studding the mains adds a lot of strength without being so much $$$. I've heard this should be good up to my ~600 flywheel hp goal (later on with 9 PSI Vortech), and some even say they prefer a studded 2 bolt over a 4 bolt design. The guys at my local machine shop aren't experts IMO but they say they've seen more cases of 4 bolt mains walking than 2 bolt mains, of course the 4 bolt designs probably took more abuse from the users.

Whether you go with 2-bolt or splayed 4-bolt I suggest good quality hardened bearings clearanced at .0025. My engine designer recommended this for many many reasons and you'll find it's a common clearance target for a high hp engine by many people like Lingenfelter, Yunick, etc. Use +/- .005 bearings to achieve the ~.0023 - .0027 clearance goal. I use hardened Federal Mogul bearings, so far so good.

4-bolt splayed caps or Corvette 4-bolt block?

I looked into the splayed cap option and it was around $1000 over/above
the price of a used 2-bolt block. Instead, I opted for a Corvette 4-bolt
block...$300.

Emil:93Z,383,Corvette block,Vortech 13psi,NOS,Snow water/methanol

It might be more money up front, but that 2-4-bolt conversion is alot stronger than your vette block which you know, although at his power level I wouldnt even mess with the vette block, just stud it and call it a day. And where dd you get a quote for your coversion??? Machine shops must be ripping people off where you live. There is no way in hell that a conversion is going to cost $1000, thats just stupid. Maybe if the caps were gold plated.

but that 2-4-bolt conversion is alot stronger than your vette block which you know


Alot stronger? Not hardly. Maybe a bit stronger at best, but not alot. If anything the billet caps are stronger, and that's it. There are some who suggest that the vette block is stronger due to the web design and the location of the outer support bolts.

Ok I see your point that I may have mis-used ALOT, more like quite a bit stronger than the vette block. Cosidering the vetter block has bolts and not studs. But , the converted block will still be stronger from the splayed caps and the fact that they are billet. Im sure a vette block would do just fine in most applications, but for all out, everyone is pretty much doing the conversion and its not because they arent as strong. If I remember correclty the fastest LT-1 in the coutry has a 2-4 bolt conversion using milodon caps. I guess we can just agree to disagree;)

Ok I see your point that I may have mis-used ALOT, more like quite a bit stronger than the vette block. Cosidering the vetter block has bolts and not studs. But , the converted block will still be stronger from the splayed caps and the fact that they are billet. Im sure a vette block would do just fine in most applications, but for all out, everyone is pretty much doing the conversion and its not because they arent as strong. If I remember correclty the fastest LT-1 in the coutry has a 2-4 bolt conversion using milodon caps. I guess we can just agree to disagree;)


Yeah, and it's still not QUITE A BIT stronger either. I think there is very little if any additional strength to be had from having outer splayed bolts as opposed to standard 4 bolt mains. Having bolts or studs doesnt matter, you could use studs in either. You could use billet caps in either.

Yeah, and it's still not QUITE A BIT stronger either. I think there is very little if any additional strength to be had from having outer splayed bolts as opposed to standard 4 bolt mains. Having bolts or studs doesnt matter, you could use studs in either. You could use billet caps in either.

I disagree with that. If 4 bolt blocks were so strong, the guys at the track would just go to the dealer & get the 4 bolt blocks instead of going thru all the trouble & expense of splaying a 2 bolt block. The angled bolts for the steel caps go into a stronger part of the block to secure the caps. You can believe what you want to believe, but you are going to find a lot of builders who disagree with you.

I disagree with that. If 4 bolt blocks were so strong, the guys at the track would just go to the dealer & get the 4 bolt blocks instead of going thru all the trouble & expense of splaying a 2 bolt block. The angled bolts for the steel caps go into a stronger part of the block to secure the caps. You can believe what you want to believe, but you are going to find a lot of builders who disagree with you.


Do they go into a stronger part of the block? hmm... GM designed the block for the outer bolts to go straight down, parallel to the inner bolts, not out towards the pan rails. You really think if two blocks (one splayed, one standard) both used billet caps and studs on all four bolts there would really be a big difference in failure rates? I doubt it.

I am using Milodons caps and just to clear up the cost issue, the labor for install and align hone is 350. Total with mains is 550. Here anyways.

The machine shop that I used to work at charged ~$600 for a splayed conversion and that included the cost of the caps/studs which is around half of that figure.

Every engine builder has a different opinion on the splayed vs. strait 4 bolt strength issue. In my opinion, the splayed caps are nice but I have never seen any real world tests between the two. Most opinions on the two are based on engineering theory. It would be great to speak to someone with real racing experience on high hp cap failures.

I think that most of the f-body community goes with splayed caps because 2-bolt blocks are alot easier to find than factory 4-bolt LT1 blocks.

Jason

Do they go into a stronger part of the block? hmm... GM designed the block for the outer bolts to go straight down, parallel to the inner bolts, not out towards the pan rails. You really think if two blocks (one splayed, one standard) both used billet caps and studs on all four bolts there would really be a big difference in failure rates? I doubt it.

Yeah, but they designed the optispark too :D Like the other guy mentioned, we really don't have enough empirical data to go off of and two bolt blocks are more plentiful, so that's what most of us end up with. I try to limit my destructive testing to head gaskets & pistons :D

Do they go into a stronger part of the block? hmm... GM designed the block for the outer bolts to go straight down, parallel to the inner bolts, not out towards the pan rails. You really think if two blocks (one splayed, one standard) both used billet caps and studs on all four bolts there would really be a big difference in failure rates? I doubt it.

Just because they "designed" it that way doesn't mean its stronger dude. They engineer things to handle the power limits the vehicle is going to see, no more! They make thier decisions believe it or not on cost effectiveness, thats how they make money. The vette block is engineered for the purpose it was built for, not for aftermarket modifications to withstand a higher HP combination. To think they would engineer a block to withstand 750 HP when it comes from the factory with say 400 or so is just silly. I believe splayed would be the way to go for any serious high HP/stress application.

I run a standard GM 4bolt (vette)block with no block fill! Have never had any problems with bearings or crank. 4 years of 20 +lbs of boost.