boring out engine block
Anyone here ever bored out a 1600 (1598cc) block?
IF so how much did you go? I have a rebuild ongoing and plan to bore out and FI (10-12psi) an engine i have in the garage. I can source 1mm =(1640cc) ,1.5mm=(1660cc) and 2mm=(1680cc) oversize pistons in comp ratio,s from 8.5;1 to 9.4;1- but i wasnt sure if i really wanted to go out as far as 2mm oversize. Any help/info greatly appreciated |
Most people go .5mm, some push it to 1mm without issue. I wouldn't go any further than that, thing was already bored out from a 1300cc
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Mine is .5... I was originally going to go 1mm, however, if something ever happens to the motor, you want to allow some space.
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If you don't need to do it, then why if you'll run boost? The power gain is insignificant IMO. I've done two 1.6s - one to .040"/1mm and the other to .020/.5mm - but neither were boosted.
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Originally Posted by m2cupcar
(Post 206307)
If you don't need to do it, then why if you'll run boost? The power gain is insignificant IMO. I've done two 1.6s - one to .040"/1mm and the other to .020/.5mm - but neither were boosted.
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Yea it's a hard call to make. Larger bore and pistons adds displacement, which is great. However, it's not much, but it's some. If you had to choose a header that gave you 3hp or 5, which would you choose? Still, larger pistons are heavier, so smaller is lighter and that's a plus. If you punch it out to the max, you won't be able to rebuild that block again without sleeving it.
FWIW, if you do bore it out to the max, you can also open up the combustion chambers on the head to reflect the new bore, and gain some power there as well, as you can unshroud the chambers. If it were me I'd punch it to the max. |
Originally Posted by patsmx5
(Post 206343)
Yea it's a hard call to make. Larger bore and pistons adds displacement, which is great. However, it's not much, but it's some. If you had to choose a header that gave you 3hp or 5, which would you choose? Still, larger pistons are heavier, so smaller is lighter and that's a plus. If you punch it out to the max, you won't be able to rebuild that block again without sleeving it.
FWIW, if you do bore it out to the max, you can also open up the combustion chambers on the head to reflect the new bore, and gain some power there as well, as you can unshroud the chambers. If it were me I'd punch it to the max. Think i,ll stick with 1.5mm oversize 9:1 wiseco,s. |
1.5 is a pretty thin wall...1 should be plenty and allow you the piece of mind.
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My point being for the cost of an overbore that cash could go elsewhere and sure reap more benefits (that and thinning the cylinder walls isn't so desirable for boost).
I've got a 40-50k mile block that I'm using for my next engine build. It's getting a different crank, pistons, rings and rods - so in effect a rebuild. and the cylinder walls look absolutely new, the bores perfectly round - I'm not gonna touch 'em. I'll put that money towards the forged pistons. |
Originally Posted by m2cupcar
(Post 206390)
My point being for the cost of an overbore that cash could go elsewhere and sure reap more benefits (that and thinning the cylinder walls isn't so desirable for boost).
I've got a 40-50k mile block that I'm using for my next engine build. It's getting a different crank, pistons, rings and rods - so in effect a rebuild. and the cylinder walls look absolutely new, the bores perfectly round - I'm not gonna touch 'em. I'll put that money towards the forged pistons. maybes best with the 1mm o/b then. what crank you going for m2cupcar? |
I agree- IF it needs an overbore go minimal. Boost changes everything.
I'm going to run an F2T crank in an FE block = 2200cc with stock FEdohc rods and either venolia or wiseco forged pistons. |
if your just trying to acquire some displacement then bore a 1.8 since it will not be daily driven it is not needed immediately right?
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True on a boosted motor, there is more heat and thicker cylinders would be better suited to handle the additional heat and loads. If it was a NA motor, I'd bore it to the max, but since it's an FI motor, just whatever it takes to punch them square and slaper' back together. Does anyone know how thick the cylinders are or the centerline?
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http://forum.miata.net/vb/showthread.php?t=216610
Have you guys forgoten Motorworx and his 1.6? 1991 1.6 Familia B6T block with oil squirters B6T oil pump Stock crank and rods Arias 81.5 mm pistons for Toyota 4AG TODA 1mm X 81.5mm MLS head gasket HKS 264 hydraulic cams Sheetmetal intake manifold/60mm SR20 throttle HKS cast T2 exhaust manifold Innovative Turbo wastegate Custom built T28 turbo (originally GTiR SR20) Custom down pipe and full 75mm exhaust Custom intercooler using two late-FC3S cores in vertical. Aluminum piping 60mm on hot side and 70mm on cold side OS Giken twin plate clutch with custom discs FD3S RX7 transmission BP differential with Kaaz LSD SDS EFI management with Denso 700cc/min injectors Walbro 255 liter fulel pump 336.6 RWPS (332 RWHP) 272 lb. 1.3 bar
Originally Posted by Scott Hayden
I did not think you could bore a 1.6L that wide. Mine is bored 1.5mm over using 79.5mm wiseco's.
Originally Posted by Motorworx
TODA Racing in Japan doesn't even sell a piston for the B6 under 81mm. I cut several blocks in half, many years ago, to check cylinder wall thickness, and there's a lot there. I go as large as 81.5 and have never has a cylinder wall problem, even through 9,000 rpm.
I seems to have worked fine for him Also i had no issues when i went .40 over. Stock bore is 78 mm |
YAY THERE IS HOPE FOR MY BORKE ASS YET!!!!11!1 :bowdown:
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I think it's a little different when you're a mechanical/fabrication wizard. And when going that extreme in an overbore, you're supposed to sonic test every cylinder for wall thickness. That way you avoid falling victim to any casting defects. What he did is just plain nuts vs. swapping in a 1.8 IMO. All I'm saying is if it's NOT needed to straighten out the bore, it doesn't make sense to put the dough there on a boosted engine.
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Originally Posted by magnamx-5
(Post 206421)
http://forum.miata.net/vb/showthread.php?t=216610
Have you guys forgoten Motorworx and his 1.6? 1991 1. Arias 81.5 mm pistons for Toyota 4AG 336.6 RWPS (332 RWHP) 272 lb. 1.3 bar This setup gives him about 1744.5 cc I seems to have worked fine for him Also i had no issues when i went .40 over. Stock bore is 78 mm |
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