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Quote:
Originally Posted by v2rocket_aka944 View Post
if you can find someone who can properly over-bore and re-condition the Alusil cylinders you could put 2.7L pistons in your 2.5 block/crank/rods. you'd get a 10.9 2.7L, the only real difference would be that you'd be using a standard (smaller ports) 2.5 head but i doubt it'd make a lot of difference.

you can get a suitable head gasket for this bore/block combination from Lindsey Racing/Cometic.

if you were interested in doing that, i've got a set of 2.7 pistons i'd trade for the nice condition 944S pistons.
Ok Thank you for the offer. I don't have any one local. I
Would probably have to ship the block to Lindsay.
Old 09-10-2018, 12:35 AM
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Where are you located?
Plenty of places around the US that can do it.
Old 09-10-2018, 08:08 AM
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Doesn't boring the 2.5 block to take the 2.7 104mm piston involve using sleeves? The 2.7 block is the same bore as the 3 liter, both with Siamesed cylinders. Pardon me if I'm wrong.
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Old 09-10-2018, 03:10 PM
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Doesn't NEED sleeves. There's plenty of meat for 104+ mm bores in a 2.5 block, it's been done for 20+ years. Even the 928 guys put 104mm 944 pistons in their "100mm bore" stroker blocks.
Old 09-10-2018, 03:56 PM
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If that's the case why does everyone need a 2.7 head to build the 3 liter Turbo when if you could just bore out your 2.5 Turbo to 104mm and add the 3 liter crank for a full 3 liters. Just asking.
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Old 09-10-2018, 08:44 PM
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Quote:
Originally Posted by jhowell371 View Post
If that's the case why does everyone need a 2.7 head to build the 3 liter Turbo when if you could just bore out your 2.5 Turbo to 104mm and add the 3 liter crank for a full 3 liters. Just asking.
They could modify a 2.5L head to fit a 3.0L block by modifying the coolant casting in the head and fitting larger intake valves, it’s been done. The attraction of the 2.7 head to the 3.0L turbo builds is the stock larger intake valves and the ability of it to simply bolt up to a 3.0L block without modification. Also a siamesed 3.0L block is inherently stronger than a 2.5L, stronger is good when you up the boost. There are also other advantages to a 3.0L block for the turbo builds but this thread is about increasing capacity and compression in an na engine.
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Old 09-11-2018, 03:32 AM
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Quote:
Originally Posted by jhowell371 View Post
If that's the case why does everyone need a 2.7 head to build the 3 liter Turbo when if you could just bore out your 2.5 Turbo to 104mm and add the 3 liter crank for a full 3 liters. Just asking.
Because those 3.0 cranks usually come with a block attached

Really though, there's a guy over on RL who had his 2.5 turbo block sleeved and bored to 106mm (so the cylinder barrel was taken to 109-110mm to fit the sleeve) about 15 years ago who has done over 100,000 miles on that build.
The 928 guys regularly dry-sleeve their 100mm blocks to a finished bore of 4.125" (104.78 mm).

Last edited by v2rocket_aka944; 09-11-2018 at 07:42 AM..
Old 09-11-2018, 07:38 AM
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Originally Posted by v2rocket_aka944 View Post
Where are you located?
Plenty of places around the US that can do it.
I am in Gulf Shores, Alabama. What tolerance group are the 2.7 pistons you have?
My NA block is tolerance group 0.

What will be the HP increase of having the crankshaft
Cross drilled? I have the 944S crankshaft in my garage out
Of the engine block. I see Lindsay and Albert Broadfoot offer
this service, along with knife edging the
Crankshaft. Just wondering if the cost yields
an equal increase in horsepower?
Old 09-12-2018, 11:10 AM
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I take it the 2.7 pistons are 104 mm and my
my NA pistons are 100 mm, so overboring the cylinder walls is necessary. So
I would be better off to just buy a 2.7 engine from an
89 944.
Old 09-12-2018, 11:15 AM
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If you wanted to bore to 104mm for the 2.7 pistons I could refer you to a guy in Baton Rouge who "has the technology" 8-)

Guess the question is, do you want a freshly rebuilt engine or a running used 2.7 if you go that route?

Either way, you have a 944S engine complete or in parts? I am still interested in those pistons if you won't be using them.
Old 09-12-2018, 02:00 PM
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Quote:
Originally Posted by v2rocket_aka944 View Post
If you wanted to bore to 104mm for the 2.7 pistons I could refer you to a guy in Baton Rouge who "has the technology" 8-)

Guess the question is, do you want a freshly rebuilt engine or a running used 2.7 if you go that route?

Either way, you have a 944S engine complete or in parts? I am still interested in those pistons if you won't be using them.
My plan is to buy a 2.7 engine and rebuild it.
The one I am looking at has 155,000 miles. I want to get it replace the head gasket, Rod bearings, water pump, belts, etc. New
clutch. While I have the engine out, make it
As close to new as I can.

I have the 944S in pieces. I sold the head
and cams. I have three of the pistons out.
The number one cylinder wall is galled,
so not sure How that is going to come out.
I have poured ATF in the cylinder wall to
hopefully help get the pistón unstuck.

The pistons are tolerance group 1.

Any idea on cost to overbore the cylinder walls
On the 944 NA block?
Old 09-12-2018, 05:49 PM
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I know here in southern California it's less than $300 to bore and "paste hone" an Alusil block.
Don't know about where you are.
Old 09-12-2018, 09:01 PM
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Quote:
Originally Posted by v2rocket_aka944 View Post
I know here in southern California it's less than $300 to bore and "paste hone" an Alusil block.
Don't know about where you are.
Okay Thank you. I can buy the 2.7 engine for $700.
I think I will come out better buying the engine.
Old 09-12-2018, 09:56 PM
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