Big block attack 4.50 vs 4.60 bore
Thread Starter
Le Mans Master
Joined: Apr 2006
Posts: 5,403
Likes: 95
Big block attack 4.50 vs 4.60 bore
Yr ago I sold a .030 over four bolt 454 block and two new forged
427 cranks, wish I had kept at least the block. If I buy a new
aftermaket block the 4.60 block is tempting but i'm assuming at
that bore size theres not much left for an overbore and the 4.50
bore block would have thicker cylinder walls. Any thoughts on
what brand block to buy Dart, World products, GM bowtie ??
427 cranks, wish I had kept at least the block. If I buy a new
aftermaket block the 4.60 block is tempting but i'm assuming at
that bore size theres not much left for an overbore and the 4.50
bore block would have thicker cylinder walls. Any thoughts on
what brand block to buy Dart, World products, GM bowtie ??
Race Director
Joined: Jan 2000
Posts: 13,018
Likes: 2,262
From: Corsicana, Tx
2020 C2 of the Year - Modified Winner
2020 Corvette of the Year (performance mods)
C2 of Year Winner (performance mods) 2019
2017 C2 of Year Finalist
I have a Merlin in mine and it's been great.....they weren't making much else at the time. The Bowties were backordered for about a year it seems and the Darts weren't out yet.
The Merlins have been upgraded even more these days...and the newest Bowties CNC blocks are also great. But unless I got a good deal on one of those, I'd probably buy a Dart today. I've dealt with a couple of them and they are real nice.
Just make sure you have a good machinist that measures things. Lifter bores need to be sized and stuff like that on most of them. They don't have any idea what parts you will use...so they size things on tight side.
The 4.500 deal is fine...4.560 is also very common. I probably wouldn't punch to 4.600 first time around on a motor that wasn't a pure race deal. Bad things happen sometimes.
JIM
The Merlins have been upgraded even more these days...and the newest Bowties CNC blocks are also great. But unless I got a good deal on one of those, I'd probably buy a Dart today. I've dealt with a couple of them and they are real nice.
Just make sure you have a good machinist that measures things. Lifter bores need to be sized and stuff like that on most of them. They don't have any idea what parts you will use...so they size things on tight side.
The 4.500 deal is fine...4.560 is also very common. I probably wouldn't punch to 4.600 first time around on a motor that wasn't a pure race deal. Bad things happen sometimes.
JIM
Racer
Joined: Jul 2000
Posts: 385
Likes: 0
From: Garden City KS
I'm pretty sure the majority of World's blocks max bore is 4.625, including the Al with sleeves. Of course, big bores equal great squish/quench. A nice compromise would be one of those blocks (eg Merlin III) with a 4.560 bore. That'd give you at least 2 more rebuilds.
Drifting
Joined: Aug 2004
Posts: 1,883
Likes: 124
From: Lubbock TX
Go to Reher-Morrison's site and look up the tech article "No Replacement for Displacement". There's not really any reason not to go 4.600 first bore. The cast iron they use is much, much harder than production. Unless you have a catastrophe, you'll probably never wear a 4.600 block to the point where it needs to be overbored. Why waste the potential cubes - how many of us have ever rebuilt an engine for a particular car more than once? If you screw up one hole, have it sleeved and go. If you tear it down due to scuffed pistons, etc., you can have it honed .005 or .010 over, get the pistons - it's not that much more for custom bore size pistons than shelf stuff. My Bowtie came with a factory sonic sheet. At 4.600, my thinnest thrust surface is still at .270, that means at max bore of 4.626 (there are shelf pistons made at this size), I'll still have cylinder walls over 1/4" thick. Get all the cubes you can, the heads will breathe better and you'll make more power. The world is full of 540's any more, go 565 and be different AND outrun 'em!
Race Director
Joined: Jan 2000
Posts: 13,018
Likes: 2,262
From: Corsicana, Tx
2020 C2 of the Year - Modified Winner
2020 Corvette of the Year (performance mods)
C2 of Year Winner (performance mods) 2019
2017 C2 of Year Finalist
While I agree with all you just said......I keep having visions of poor 'ole Nicks brand spanking new 632" at a 4.600 bore that dropped a valve on the dyno (note...no matter how much you pay *professionals" most suck!) and how we had to go 4.625 this time around. It wouldn't clean up at 4.610 or so....sleeving works of course..but you sure hate to do it if you don't have to.
But 565's DO run!!!
JIM
But 565's DO run!!!
JIM
Pro
Joined: Jul 2002
Posts: 723
Likes: 0
From: North Port, FL
I recently went through the same arguments myself. I am in the process of building another BB for my 71. I started down the path of a 4.5 bore but the added cubes and added flow of the 4.6 bore made it very tempting. I ended up with a Brodix Aluminum block with 4.6 bore. It will be a simple job to re-sleeve it if neccecary and it will go to 4.62 before requiring sleeves. I got over 100,000 miles on a Gen V block before it required cleaning up the bores. My GM ZL1 block has over 40,000 miles on it and the last time I had it apart there was no detectable wear in the bores. Unless I have a catistafic event (like L88PLUS said) I don't think mine will ever require a rebore.
Tech Contributor
Joined: Jun 2004
Posts: 20,910
Likes: 962
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
I recently went through the same arguments myself. I am in the process of building another BB for my 71. I started down the path of a 4.5 bore but the added cubes and added flow of the 4.6 bore made it very tempting. I ended up with a Brodix Aluminum block with 4.6 bore. It will be a simple job to re-sleeve it if neccecary and it will go to 4.62 before requiring sleeves. I got over 100,000 miles on a Gen V block before it required cleaning up the bores. My GM ZL1 block has over 40,000 miles on it and the last time I had it apart there was no detectable wear in the bores. Unless I have a catistafic event (like L88PLUS said) I don't think mine will ever require a rebore.
thanks,
Mike
Race Director
Joined: May 2005
Posts: 10,674
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From: Millington Illinois
St. Jude Donor '08-'09
Yr ago I sold a .030 over four bolt 454 block and two new forged
427 cranks, wish I had kept at least the block. If I buy a new
aftermaket block the 4.60 block is tempting but i'm assuming at
that bore size theres not much left for an overbore and the 4.50
bore block would have thicker cylinder walls. Any thoughts on
what brand block to buy Dart, World products, GM bowtie ??
427 cranks, wish I had kept at least the block. If I buy a new
aftermaket block the 4.60 block is tempting but i'm assuming at
that bore size theres not much left for an overbore and the 4.50
bore block would have thicker cylinder walls. Any thoughts on
what brand block to buy Dart, World products, GM bowtie ??
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Thread Starter
Le Mans Master
Joined: Apr 2006
Posts: 5,403
Likes: 95
Thanks for all the replies, I was just looking at the dart catalog and
they have both a 4.50 bore and 4.60 iron block, the price tag is the same and they claim at 4.625 the minimum wall thickness is .300.
There is a lot of width on factory blocks between cylinders for head
gasket seal, the only down side to having 4.60 cylinder bore I would
think might be width between cylinders for head gasket seal.
probably not a problem for me I will want comp low enough to run
on pump gas.
63mako I have three good 4 bolt main factory small blocks lying
around and some other new parts. I could build a 383 or 396
with one of them, but I have made up my mind if I were to build
another small block it would have to be a raised runner and no
23 degree heads. At the power level I would want with one I do
not feel comfortable using a factory block so that kind of puts me
starting from total scratch on parts. The cost to build a big block
when you consider what you have to have to run raised runner
heads on a small block and just the cost of of the raised runner
head is about the same as most standard layout big block heads.
I can build a 509, 540, 555 standard layout head big block for
around the same money as a raised runner head small block if
I start from a new block on up.
they have both a 4.50 bore and 4.60 iron block, the price tag is the same and they claim at 4.625 the minimum wall thickness is .300.
There is a lot of width on factory blocks between cylinders for head
gasket seal, the only down side to having 4.60 cylinder bore I would
think might be width between cylinders for head gasket seal.
probably not a problem for me I will want comp low enough to run
on pump gas.
63mako I have three good 4 bolt main factory small blocks lying
around and some other new parts. I could build a 383 or 396
with one of them, but I have made up my mind if I were to build
another small block it would have to be a raised runner and no
23 degree heads. At the power level I would want with one I do
not feel comfortable using a factory block so that kind of puts me
starting from total scratch on parts. The cost to build a big block
when you consider what you have to have to run raised runner
heads on a small block and just the cost of of the raised runner
head is about the same as most standard layout big block heads.
I can build a 509, 540, 555 standard layout head big block for
around the same money as a raised runner head small block if
I start from a new block on up.
Last edited by Little Mouse; Mar 3, 2007 at 03:00 AM.
Safety Car
Joined: Aug 2001
Posts: 3,892
Likes: 13
From: Pettis Performance 565 with two stages of Nitrous Supply nitrous 1.082, 4.61 at 155, 7.17 at 192
The Dart blocks are very nice. GM recently lowered the prices on their GM CNC Pro-stock blocks from close to 3,000.00 (when I bought mine
) to less than 2,000.00 now. I would check one out, very nice block.
) to less than 2,000.00 now. I would check one out, very nice block.
Thread Starter
Le Mans Master
Joined: Apr 2006
Posts: 5,403
Likes: 95
The sportsman blocks I have looked up so far are $1795. the
pro stock blocks I have found so far are special low deck blocks??
Safety Car
Joined: Aug 2001
Posts: 3,892
Likes: 13
From: Pettis Performance 565 with two stages of Nitrous Supply nitrous 1.082, 4.61 at 155, 7.17 at 192
http://www.gilbertchevy.com/frame.ht...Blocks/gm.html
P/N 24502500
Go to this page and look under bare blocks. If you look around a little you can find it, with pics.
P/N 24502500
Go to this page and look under bare blocks. If you look around a little you can find it, with pics.
