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couple of lt1 questions

This is a discussion on couple of lt1 questions within the LT1 forums, part of the Vehicle Specific category; Is the lt1 internal or external balanced? And what is stock compression on a 93 lt1? also while im getting ...

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    couple of lt1 questions

    Is the lt1 internal or external balanced?

    And what is stock compression on a 93 lt1?
    also while im getting motor rebuilt, if i go with flatops can I deck the block or heads without messing up knock sensors or computer? or should I just leave compression alone?

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    Senior Member JaycenK's Avatar
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    The lt1 is internally balanced with a weighted flex plate or flywheel. If you replace these items you need a stock weighted one to replace them but the balancer should be neutral or zero balanced. There have been some cases were people say they have run across a weighted balancer but I have never seen it. As for the compression, the stock ratio is already higher than normal at 10.25 to 10.50 to 1. If you increase it you are going to increase the chances of detonation with out a tune. As for the piston that is a question for the engine builder as you need to know what cam, rocker ratio, deck height, head and the thickness of the head being used. Basically you need to calculate out the distance between the piston and the valve through the valves duration from open to close. There are all types of lifts and durrations so this can change based on the cam and type of piston used. Tons of guys have used preformance cams on stock heads and bottom ends so it is usually not a problem untill you get in to changing the pistons to 0cc flat top or +cc or dome piston.

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    Quote Originally Posted by JaycenK View Post
    The lt1 is internally balanced with a weighted flex plate or flywheel. If you replace these items you need a stock weighted one to replace them but the balancer should be neutral or zero balanced. There have been some cases were people say they have run across a weighted balancer but I have never seen it. As for the compression, the stock ratio is already higher than normal at 10.25 to 10.50 to 1. If you increase it you are going to increase the chances of detonation with out a tune. As for the piston that is a question for the engine builder as you need to know what cam, rocker ratio, deck height, head and the thickness of the head being used. Basically you need to calculate out the distance between the piston and the valve through the valves duration from open to close. There are all types of lifts and durrations so this can change based on the cam and type of piston used. Tons of guys have used preformance cams on stock heads and bottom ends so it is usually not a problem untill you get in to changing the pistons to 0cc flat top or +cc or dome piston.
    Ok sounds like I will leave compression where it is. But now Im confused on the balance, If it internal balance why have a weighted flywheel? I guess im just thinking of older style, like the 400 thats externally balanced with weights. not debating you just trying to learn something from you, thanks alot.

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    Senior Member JaycenK's Avatar
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    I don't know man I know they call it internally ballanced but it has weights lol.

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    Quote Originally Posted by JaycenK View Post
    I don't know man I know they call it internally ballanced but it has weights lol.
    k, thanks

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    The flywheel has wieghts because the LT1 is actually a split balance. The front portion of the engine is a neutral balance but the back half is balanced, this is why there is a weight on the flywheel. At least that is what I was told.

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    Quote Originally Posted by 97bluebird View Post
    The flywheel has wieghts because the LT1 is actually a split balance. The front portion of the engine is a neutral balance but the back half is balanced, this is why there is a weight on the flywheel. At least that is what I was told.
    Well I think after looking that all one peice rear main seal engines have a weighted flywheel, do you know if I can take a 90 model m5 flywheel and use it on the lt1? know it will bolt just not sure of weight

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    Quote Originally Posted by dirttrax View Post
    Well I think after looking that all one peice rear main seal engines have a weighted flywheel, do you know if I can take a 90 model m5 flywheel and use it on the lt1? know it will bolt just not sure of weight
    I'm gonna take a wild guess and say that a BMW M5 flywheel wont work.

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    Quote Originally Posted by 5.0THIS View Post
    I'm gonna take a wild guess and say that a BMW M5 flywheel wont work.
    lol I think he means a 90 f-body with a 5 speed. But your right he didn't say for sure lol.

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    Quote Originally Posted by JaycenK View Post
    lol I think he means a 90 f-body with a 5 speed. But your right he didn't say for sure lol.
    Yeah thats what I meant, lol

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    Still need an answer if anyone knows, thanks

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    Quote Originally Posted by dirttrax View Post
    Still need an answer if anyone knows, thanks


    Did it come off a 305 or a 350? Is it the same weight? Is it the same diameter, same number of teeth? Is the counterweight exactly the same weight and in exactly the same position? Just use the correct one if you dont know the answers to those questions.

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    Quote Originally Posted by 5.0THIS View Post
    Did it come off a 305 or a 350? Is it the same weight? Is it the same diameter, same number of teeth? Is the counterweight exactly the same weight and in exactly the same position? Just use the correct one if you dont know the answers to those questions.
    None of the others matter, I was just wondering bout the counter weight, dont know if it got one or not. Guess I will just pull it and see.

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    Quote Originally Posted by dirttrax View Post
    None of the others matter, I was just wondering bout the counter weight, dont know if it got one or not. Guess I will just pull it and see.
    It has to be weighted in the exact same manner as the lt1 flywheel. if it is not you are going to wipe out bearings.

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    Quote Originally Posted by JaycenK View Post
    It has to be weighted in the exact same manner as the lt1 flywheel. if it is not you are going to wipe out bearings.
    I understand that, but some where I know somebody has bolted a t-5 to a lt1, but I cant find an after market flywheel or a answer telling me wich one to use.

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    Senior Member JaycenK's Avatar
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    I don't know about that but I did read somewhere long ago about the LT1 and that the crank was more like a 305 crank because the 305 was supposed to be internally ballanced while the 350 was externally balanced. I think it was just to compare but I would go to a parts store and see if they have them in stock and set a 305 5 speed fly wheel next to a 350 5 speed fly wheel and an lt1 6speed flywheel and see if the either of them look to be close to the lt1 6 speed. Thats what I would do, and then you can see if they are weighted the same. or you might just find someone to wieght the 5 speed flywheel to the lt1 flywheel specs.

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    Or just save a bunch of headache and find an LT1 flywheel.

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    well finally found the answer, 86 and up chevrolet does have a counter weighted flywheel.
    I fyou click the link and look at page four it tells the answer.

    http://www.s-series.org/htm/tech/GMP...ts/076-081.pdf

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    Quote Originally Posted by JaycenK View Post
    I don't know about that but I did read somewhere long ago about the LT1 and that the crank was more like a 305 crank because the 305 was supposed to be internally ballanced while the 350 was externally balanced. I think it was just to compare but I would go to a parts store and see if they have them in stock and set a 305 5 speed fly wheel next to a 350 5 speed fly wheel and an lt1 6speed flywheel and see if the either of them look to be close to the lt1 6 speed. Thats what I would do, and then you can see if they are weighted the same. or you might just find someone to wieght the 5 speed flywheel to the lt1 flywheel specs.
    Thanks maybe now I have my answer, but just to let you know the 350 and 305 are the same. And thanks again for always replying to my post.

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    Senior Member JaycenK's Avatar
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    Are all gm flex and flywheels weighted the same? is that what this link says? it sounds like all of the one piece rear seal cranks use the same wieghted flex or fly. Just diff sizes.

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