Max boring an aftermarket BBC cast-iron block?
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Max boring an aftermarket BBC cast-iron block?
Has anybody ever offset bored either a Merlin III or a Dart BBC cast-iron block out to like 4.75" and then rework the crank counterweights to line up the rods??
I guess that I am poorly asking what's the biggest bore these blocks can be bored out to?
And how much trouble is it to install a 4.50" crank in a 9.8" deck BBC block?
Just thinking about max cubes in a standard deck height aftermarket BBC block is all...
pdq67
I guess that I am poorly asking what's the biggest bore these blocks can be bored out to?
And how much trouble is it to install a 4.50" crank in a 9.8" deck BBC block?
Just thinking about max cubes in a standard deck height aftermarket BBC block is all...
pdq67
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Re: Max boring an aftermarket BBC cast-iron block?
There is a guy on here that has 620 inches in his shop truck.
Re: Max boring an aftermarket BBC cast-iron block?
Dart big m says 4.625 still has .300 wall thickness. On a na deal you could go thinner on walls but not sure what that gives you on a standard bore space motor as a max.
Guys have done 4.65 bore on dart big m’s
4.5” crank fits
Guys have done 4.65 bore on dart big m’s
4.5” crank fits
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Re: Max boring an aftermarket BBC cast-iron block?
Hmm
Long stroke...
Pdq was gone for a while.
Maybe abducted by aliens?
Just kidding.
It would probably be most effective to bore it max without having to offset it, and use the time/expense saved on the cylinder heads to net more than that the extra 0.080 or 0.100 would "get" you.
Long stroke...
Pdq was gone for a while.
Maybe abducted by aliens?
Just kidding.
It would probably be most effective to bore it max without having to offset it, and use the time/expense saved on the cylinder heads to net more than that the extra 0.080 or 0.100 would "get" you.
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Re: Max boring an aftermarket BBC cast-iron block?
More important then boring for max cid is that during the process you offset the Bore to both unshroud the Intake valve and ease the thrust loading on cylinder wall, or atleast unshroud the valve to the max!
You can cut a man's tongue from his mouth, but that does not mean he’s a liar, it just shows that you fear the truth he might speak about you!
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Re: Max boring an aftermarket BBC cast-iron block?
Honestly, I don't know why you'd want to go through the trouble of trying to offset bore the block, unless you've encountered bore shift and are trying to correct that. GM has their GMPP racing block with 4.9" bore centers. It was developed for Pro Stock racing, and one of the issues it addressed was bore sizing to unshroud the valves. You can offset bore a standard block, but that's not necessarily going to address that issue, and will likely cause other issues that need to be addressed as well. More hassle than it's worth.....
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Re: Max boring an aftermarket BBC cast-iron block?
I think you could use a larger bore with iron heads than alum. 4.70" bore would leave .140" between cylinders, warm up the engine with external heat source before starting and give it a try, if I wanted to disguise cubic inches from onlookers I would take a tall deck block, cut it down to maybe 10" deck
and relocate the water pump holes, use a billet water pump housing cut to spec
and relocate the water pump holes, use a billet water pump housing cut to spec
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Re: Max boring an aftermarket BBC cast-iron block?
I've moved the outers .100 and inner. 050 on a dart pro. That bore was 4.670pdq67 wrote: ↑Mon Dec 30, 2019 5:07 pm Has anybody ever offset bored either a Merlin III or a Dart BBC cast-iron block out to like 4.75" and then rework the crank counterweights to line up the rods??
I guess that I am poorly asking what's the biggest bore these blocks can be bored out to?
And how much trouble is it to install a 4.50" crank in a 9.8" deck BBC block?
Just thinking about max cubes in a standard deck height aftermarket BBC block is all...
pdq67
I have gone 4.640 std borespace without offsetting the bores for an NA engine call a ring manufacturer first to see what rings are available for your desired bore size. Not a lot of options. And a lot of work for nothing. Might as well for 5.0 bs if you want that large of a bore
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Re: Max boring an aftermarket BBC cast-iron block?
On a Dart Big M block you can go 4.650. There is still plenty of cylinder wall thickness, but there is no more room for the head gasket. I have run customer engines at 4.650 no problem with custom Cometic head gaskets.
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Re: Max boring an aftermarket BBC cast-iron block?
The 4.90" bore Chevy BB block has to have a 4.90" spaced crank, doesn't it?
A 5" B/S block, better look up PackardV8 and see if he will sell me a Packard block. Then also stroke a Packard crank...
I would have to sleeve it to get any sort of big bore out of it though.
pdq67
A 5" B/S block, better look up PackardV8 and see if he will sell me a Packard block. Then also stroke a Packard crank...
I would have to sleeve it to get any sort of big bore out of it though.
pdq67
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Re: Max boring an aftermarket BBC cast-iron block?
No. You can have a 4.84 crank with a 4.9bspdq67 wrote: ↑Sat Jan 04, 2020 3:53 pm The 4.90" bore Chevy BB block has to have a 4.90" spaced crank, doesn't it?
A 5" B/S block, better look up PackardV8 and see if he will sell me a Packard block. Then also stroke a Packard crank...
I would have to sleeve it to get any sort of big bore out of it though.
pdq67
Re: Max boring an aftermarket BBC cast-iron block?
"No. You can have a 4.84 crank with a 4.9bs"
mt,
I have to ask if the 4.84" bore spaced BBC heads will also fit IF CENTERED RIGHT like the crank and also if you know how thick the cylinder walls are before any boring is done so I can see how big a bore to bore to?
Thanks,
pdq67
mt,
I have to ask if the 4.84" bore spaced BBC heads will also fit IF CENTERED RIGHT like the crank and also if you know how thick the cylinder walls are before any boring is done so I can see how big a bore to bore to?
Thanks,
pdq67