Boring out the mains???

[Fierobsessed]

Just curious, If I have an "old" 2.8 block with the small (2.48"?)mains, is it safe and advisable to bore out the mains to the modern 2.65" mains? I'ts only about .100" of metal off. Im only asking if its possible, and perhaps If the mains themselves are swappable (bolt hole wise) The location of the bolt holes is of consern because I know they are pretty close to the saddle for the main bearings.

Thanks all!

[Doubt_Incarnate]

you'd have to check the bolt spacing as you mentioned. if they dont match up for the newer caps, i wouldn't try it, you might be doing more harm than good. iv'e thought about this just last night, and then concluded that since i've never seen mention of it before or in the gm power book it's probly not a good idea. or maybe, just never tried.

[sharkey]

id get another block. the biggest pain would be the rear main seal.

[Fierobsessed]

They didn't make too many aluminum blocks. oops did I just slip that out?

[donk_316]

They didn't make too many aluminum blocks. oops did I just slip that out?

What Aluminum block came with small main journals?

[Guest]

I would like to know that one too. I have never ehard of that. Is this the one on ebay? DId the guy mic it for you?

[Fierobsessed]

yes and "yes" he said it mic'd out to 2.66" or so WITHOUT the bearings. So I can only assume this means its an "early" design block, Or its just rough machined. From the pic's I can pretty much see that the block does not have grooved main saddles, witch indicates "early" design as well. And finally it looks like it is not set up to accept a 1 piece rear main. Probably a rope seal type, and again a characteristic of a "early" design block. Not exactly what I call great. But I am holding hope that its just a rough machined piece. It just looks like something I would enjoy toying around with.

[bszopi]

It makes sense since it also has only 2-bolt mains...

[geoffinbc]

This must be one of thoes prototype aluminum blocks that was floating around and nobody ever did anything with and said it should be left alone. It is not a bowtie block.

Meh it might be fun to do something with it. The only advantage is weight. But it seems to have several dis advantages versus a modern iron block.

[Guest]

That is not a prototype block. That is a a Bow tie block.

The proto looks nothing like that one. Ask me how I know.

the iron blocks have 2 bolt mains. so does that mean all are small journal? WTF man you think because it has two bolt mains its a small journal crank? How did you make that jump?

Ever think it is possible that maybe gm decided to go with the 4 bolt later on after some were already made?

FYi the mains can be made larger if it really needs to be done which it won't

2.66 is spec if thats what he mic'd them at althought I am guessing it was a quick measurement and not exact. Either way thats correct for a large main.

I have a 4 bolt block and those numbers are correct.

Hell dont' bid on it. I dont' care. I am in. Just means its cheaper for me. Yes I already have one but thats ok. One more never hurt esp at that price.

And fieroobsessed are you basing your guess on teh rear main seal from the ebay pics? Because if so you can't tell sqaut if its a one or a two peice seal. And even so, I can't beleive you would make such a big deal about a 2 peice seal being so horrible.

Are you also basing your assumption on the grooves from the ebay pics? Because if so you can't tell from that pic either. AS a matter of fact I think I can see them. Unless he sent you close up pics of the block and the mains then you can't make an educated guess. If he did send you pics then post them up. Just because the grooves arent' 8 inches deep and arent' visible in crappy handheld phone pics, doens't mean they arent' there. If I took a pic of my block from 10 feet away with a phone camera you could tell on my block either if the grooves were there.

Like I said I could care less if you think this block is a prototype or a first gen with a 2 peice seal and small mains and all this other mumbo jumbo. just means its cheaper for me and another lost opportunity for everyone else.

Just stick to wanting to put a inefficient M90 on a 3.4 dohc and claim it will make huge power. that project has gone nowhere and prob a good thing too. The M90 would suck on that motor. Can you say 350 degree intake temps? Yea thats efficient alright

[geoffinbc]

Whatever I was just going by the description he gave. I never saw pics or the auction.

And where did I say 2 bolts means small journals?

[Guest]

Guess I didnt' get it. The douchebag retracted my bid at the last second.

Reason? "don't believe Ebayer will follow through from past history"

Umm yea ok dont' know how he came to that conclusion based on that fact that we havent' done business before ever, and I also have 100% positive feedback.

I am guessing he wasnt' going to get what he was hoping the bidding was going to go to.

Phucking turdball.

Oh well, I didnt' need it anyways, but still it pisses me off he retracted my bid for that reason.

[donk_316]

Yeah and he cancelled my bid also ... I guess im hard to satisfy

[Fierobsessed]

That is not a prototype block. That is a a Bow tie block.

The proto looks nothing like that one. Ask me how I know.

I'm going to take a guess that you are referring to p8ntman442's All aluminum open deck block. I dont know, otherwise.

the iron blocks have 2 bolt mains. so does that mean all are small journal? WTF man you think because it has two bolt mains its a small journal crank? How did you make that jump?

Well, seeing as how he sent me the specs of the mains WITHOUT bearings even being in place It would be impossible for this engine to be a Large journal. The 2.65" is the measurement at the crank, not the mains saddles.

Ever think it is possible that maybe gm decided to go with the 4 bolt later on after some were already made?

Absolutly.

FYi the mains can be made larger if it really needs to be done which it won't

The only reason I asked The question in the first place was to get an answer to that question. I just feel much more comfortable using the later design cranks witch are all large journal, so if it can be safley punched out, then why not?

2.66 is spec if thats what he mic'd them at althought I am guessing it was a quick measurement and not exact. Either way thats correct for a large main.

Well, perhaps if there were bearings in the motor.

And fieroobsessed are you basing your guess on teh rear main seal from the ebay pics? Because if so you can't tell sqaut if its a one or a two peice seal. And even so, I can't beleive you would make such a big deal about a 2 peice seal being so horrible.

OH MY GOD, 2 piece rear main seals are HORRIBLE... Right, sure I actually said that. But I think It went more like this:

And finally it looks like it is not set up to accept a 1 piece rear main. Probably a rope seal type, and again a characteristic of a "early" design block. Not exactly what I call great.

Yep, really made a big stink about that. How can you NOT tell that its a 2 piece? Either there is a machined step in the rear of the block to press the seal into it, or not. And it sure as hell don't look like it is machined for it. And looking back at the auction, It actually says it too.

Are you also basing your assumption on the grooves from the ebay pics? Because if so you can't tell from that pic either. AS a matter of fact I think I can see them. Unless he sent you close up pics of the block and the mains then you can't make an educated guess. If he did send you pics then post them up. Just because the grooves arent' 8 inches deep and arent' visible in crappy handheld phone pics, doens't mean they arent' there. If I took a pic of my block from 10 feet away with a phone camera you could tell on my block either if the grooves were there.

It still doesn't look like it has them. You can clearly see the oil inlet holes in the main bearings so why is it so wrong to say you cannot see the grooves. Shit, look at how I said it, Im not 100% sure it doesn't either, but It doesn't APPEAR to have them.

Like I said I could care less if you think this block is a prototype or a first gen with a 2 peice seal and small mains and all this other mumbo jumbo. just means its cheaper for me and another lost opportunity for everyone else.

Ok cool. All I asked is if the mains could be safley bored out for the modern crank. Check the tittle of the topic, and the question asked.

Just stick to wanting to put a inefficient M90 on a 3.4 dohc and claim it will make huge power. that project has gone nowhere and prob a good thing too. The M90 would suck on that motor. Can you say 350 degree intake temps? Yea thats efficient alright

You seem to know alot about my project. So, why don't you tell me where my engine is now? What blower am I really using? (If your going to play that card at least get it right, hint: The pictures are on this site) What have I put into it and give me any good reason it won't perform to my expectations? You don't know me and you certainly don't know what I know and don't, and what I am and am not capable of building. And you are definatly in no position to point and say, "thats going to suck" When you are not looking at ALL the details of the design AND the execution especially when I havn't given out all that info anyway. So how do you know that its going to suck? How the hell would you know weather or not my project has gone somewhere if you are over 1000 miles away?
Assume I assume?

The reason I am building a supercharged 3.4 DOHC is because I am looking to make a "modern hotrod" of sorts, and that is what it is in most respects. And as far as performance is concerned; Sure I'm expecting a lot from it. I sometimes say that I expect "X" amount of power from it. Or that my target or goal is "X". Im not going to say "It's going to make "X" because I did so and so to it." Thats not how I work, and thats not what I am all about.

I am building the bottom end to withstand anything I can throw at it. Stock they can handle some pretty decent power anyway. Custom forged pistons and boost on a relativly large DOHC engine that has huge ports? Sounds like a combination one can only dream of. I chose a blower as the means of boost for its extended lower range to complement the DOHC's natural upper range. I also happen to like how it sounds and want that brute torque down low for any driving condition.

On a personal note: I used to have at least a shred of respect for you. And I really dislike the critisizm coming from someone who doesn't even know me.

By the way. I didn't bid on it. I was too busy at work. Gotta support the hobby somehow. Also the fact that it was a private auction made it seem more like a scam anyway. Too bad the seller was so picky, he only got $550 for it anyway.