Andrew's 91GT Engine Thread
11-08-2007, 12:03 PM
#121
Drifting
id say dont worry about pulling the pistons or crank. its unnecessary cost and there isnt any problem with the bottom end. if you replace the rings, will they bed in properly??? you might create a problem with blowby that you dont yet have...
i dont know for sure about this, but i did think a lot about it myself when i was having the GTS engine currently in my car rebuilt.
i dont know for sure about this, but i did think a lot about it myself when i was having the GTS engine currently in my car rebuilt.
11-08-2007, 12:10 PM
#123
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This is kind of what Bill is refereing too with the amout of room you have to work with when you skim the heads...there isnt much room really! You can see it doesnt take much until you get into the combustion chamber and close to the valve seats. Depends how bad/deep the corroasion is. My guess is you will need to get it filled, then taken down. You may not have enough room just to "skim" them?
11-08-2007, 12:30 PM
#124
Captain Obvious
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11-08-2007, 12:38 PM
#126
The corroded material is gouged out, and new material is somehow welded in, and then the head is decked very little.
11-08-2007, 12:39 PM
#127
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Ok... so lets say that the mad scientist looks at my heads and gives me a thumb up on getting it filled and resurfaced. 
If I want to get the block decked, this is going to raise my CR quite a bit potentially, right?
At that point, maybe I should look into dishing the pistons slightly to lower CR into a slightly safer range... Double black diamond... here I come!
If I want to get the block decked, this is going to raise my CR quite a bit potentially, right?At that point, maybe I should look into dishing the pistons slightly to lower CR into a slightly safer range... Double black diamond... here I come!
11-08-2007, 12:43 PM
#128
Swain has a very nice skirt coating and crown coating. The Skirt is PC-9, and the crown is a nice thick thermal coating so the pistons don't get shocked so much at higher combustion temps.
That gives you extra safe guard on the stock rebuild. The cylinder honing with the final stage pads and paste is a good way to make sure the new rings will seat. It takes only a tiny bit away, and really only makes sure the Si is showing proud of the Al.
The skirt coating is a safety mechanism for during the re-break in. Its tough enough that Lindsay racing (951 stuff) is running regular forged aluminum pistons in the alusil bores.
That gives you extra safe guard on the stock rebuild. The cylinder honing with the final stage pads and paste is a good way to make sure the new rings will seat. It takes only a tiny bit away, and really only makes sure the Si is showing proud of the Al.
The skirt coating is a safety mechanism for during the re-break in. Its tough enough that Lindsay racing (951 stuff) is running regular forged aluminum pistons in the alusil bores.
11-08-2007, 12:50 PM
#129
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Ok... so lets say that the mad scientist looks at my heads and gives me a thumb up on getting it filled and resurfaced. If I want to get the block decked, this is going to raise my CR quite a bit potentially, right?
At that point, maybe I should look into dishing the pistons slightly to lower CR into a slightly safer range... Double black diamond... here I come!
If I want to get the block decked, this is going to raise my CR quite a bit potentially, right?At that point, maybe I should look into dishing the pistons slightly to lower CR into a slightly safer range... Double black diamond... here I come!
Skim or fill and skim, either way they will take it down to just below the original height. Less if you have it filled.
From that point go with the thicker gasket like Bill showed.
See if you can CC it before you bolt it back up.
I believe there are folks out there who have CC'd GT pistons. I think they are the same as S4's...anyone?
Clean it up...bolt it up..and go.
Cars out there are running fine on stock pistons..rings...gasket..etc etc. (knock on wood) Just as yours was.
11-08-2007, 12:54 PM
#130
Captain Obvious
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11-08-2007, 12:55 PM
#131
Ok... so lets say that the mad scientist looks at my heads and gives me a thumb up on getting it filled and resurfaced. If I want to get the block decked, this is going to raise my CR quite a bit potentially, right?
At that point, maybe I should look into dishing the pistons slightly to lower CR into a slightly safer range... Double black diamond... here I come!
If I want to get the block decked, this is going to raise my CR quite a bit potentially, right?At that point, maybe I should look into dishing the pistons slightly to lower CR into a slightly safer range... Double black diamond... here I come!
The deck surfacing will not make a huge difference. It is just needed to make sure you don't have sealing issues. The two combined of course (head and block) will make a difference, so a thicker headgasket may be required. But just a bit. Last i checked, scooping those pistons was very pricey in the inevitable comparison to JE pistons and going full bore into this slope.
11-08-2007, 01:01 PM
#132
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You could always run ethanol like I will, and run as much boost as you dare and keep the pistons the way they are.
The deck surfacing will not make a huge difference. It is just needed to make sure you don't have sealing issues. The two combined of course (head and block) will make a difference, so a thicker headgasket may be required. But just a bit. Last i checked, scooping those pistons was very pricey in the inevitable comparison to JE pistons and going full bore into this slope.
The deck surfacing will not make a huge difference. It is just needed to make sure you don't have sealing issues. The two combined of course (head and block) will make a difference, so a thicker headgasket may be required. But just a bit. Last i checked, scooping those pistons was very pricey in the inevitable comparison to JE pistons and going full bore into this slope.
Why not wait and see how it works out for you first?
Tony’s suggestion of keeping it simple is the way to go. This is only a HG replacement project hwy not just keep it at that?
11-08-2007, 01:15 PM
#133
For your second comment the reason to look deeper is Andrew's mileage, the fact that the engine is out and nearly disassembled, and the intended use. Pre-emptive and pro-active work on these engines improve the situation. I know we like to stand our hats on the longevity of these engines and cars, and they do last a long time, but not replacing and resurfacing things that are "out for Work" because we like the idea of longevity is not good practice.
Andrew lives in the upper midwest. He's out for the count anyway until the snow melts in May.
11-08-2007, 01:34 PM
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Ok... so lets say that the mad scientist looks at my heads and gives me a thumb up on getting it filled and resurfaced. If I want to get the block decked, this is going to raise my CR quite a bit potentially, right?
At that point, maybe I should look into dishing the pistons slightly to lower CR into a slightly safer range... Double black diamond... here I come!
If I want to get the block decked, this is going to raise my CR quite a bit potentially, right?At that point, maybe I should look into dishing the pistons slightly to lower CR into a slightly safer range... Double black diamond... here I come!
11-08-2007, 01:46 PM
#135