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Discussion Starter #1
Hey everyone.
Wanted to get an opinion on this.
I am about to mate my TKO 600 to my rebuilt 350 on the stand in prep for getting my car back from paint soon.

I purchased a flywheel and clutch set from the local parts store(supporting the local guy) months ago. Way passed returning now. I have sense decided to upgrade to a hydraulic throw out.
Turns out the mechanical clutch flywheel is about 1/4" thicker than ones that come with the hydraulic TO (which I didnt get, not knowing there was a difference).
This is causing a major problem with the TO clearance. I'm in the negative. So I have ordered a 1/4" spacer to go between the trans and the flywheel. This will give me enough clearance for the TO.

My concern comes with the input shaft engagement in the pilot bearing/bushing. Right now, my math says I'll have 0.367" engagement. So a hair over 1/3rd the depth of the input shaft. Seems borderline to me. Using an extended pilot would increase that engagement to about 0.617", much more in comfort range.

So I called up American Powertrain and the gentleman I talked to made it sound like it would be jerry rigging to use the spacer and an extended pilot. Suggested a new flywheel to the tune of over $250 :oops:
Spacer and new pilot puts me back $75.
Not like $250 is a crazy amount to spend, but is it really necessary?

Will the drivetrain be weaker with the space/pilot?
Would I need a different clutch disk and pressure plate if I changed flywheels, Adding more expense?

I can't imagine this being all too uncommon (using a spacer) What do people do if they're just wanting to upgrade to hydraulic??

I'm not opposed to spending to make it right. But I am opposed to spending when it's not wrong.

This is a mild build. 325ish hp, nothing crazy.

Any input appreciated!!
 

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I feel your pain and understand what you are going through. I have dealt with American powertrain a few times on my last two builds and trust them without question. I had close to the same issue when I switched from a gen 2 small block to an LS in the middle of the build. Got through this with their advice on a flywheel also. BTW, my trans is a TKO 600 trans upgraded by American.
 

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I would get the right parts instead of trying to make the wrong parts fit. Using the wrong parts may cost you more than using the right parts if something goes wrong down the line. Sell the wrong parts on eBay to recoup some money. If you ask enough people for the answer you want to hear, someone will eventually give it to you. Doing it right while the engine is out of the car is the way to go.
 

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Discussion Starter #4
I feel your pain and understand what you are going through. I have dealt with American powertrain a few times on my last two builds and trust them without question. I had close to the same issue when I switched from a gen 2 small block to an LS in the middle of the build. Got through this with their advice on a flywheel also. BTW, my trans is a TKO 600 trans upgraded by American.
Thanks for your input, glad I'm not the only one that has experienced this. I have no doubt that his recommendation(and yours) is best practice.

jd128,
I feel ya and I'm leaning the same way after hearing there are different flywheels. I learned long ago that the easy path is most certainly laced with landmines.

I ordered the spacer not knowing. Called AP after measuring for pilot depth, and....

The flywheel part number that AP gave me doesnt exist. Found one close on their website however no parts that I have been able to find anywhere give a dimension for thickness or denotes it as being specific to a hydraulic T/O:unsure::unsure:


Anyone need a standard flywheel????
 

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I had the same problem when I converted my 350 sbc with a Tremec 5 speed over from manual clutch to hydraulic. My solution was to use a steel spacer .250" thick installed between the transmission and the bell housing. My motor makes 425 hp to the crank and has been rode hard for 3 years since switching to hydraulic. I too was concerned about the pilot bushing engagement but so far there has not been an issue. Your mileage may vary:)
 

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Discussion Starter #6
I had the same problem when I converted my 350 sbc with a Tremec 5 speed over from manual clutch to hydraulic. My solution was to use a steel spacer .250" thick installed between the transmission and the bell housing. My motor makes 425 hp to the crank and has been rode hard for 3 years since switching to hydraulic. I too was concerned about the pilot bushing engagement but so far there has not been an issue. Your mileage may vary:)
Great, thanks for stiring the pot!! 😄
Have you had the trans out the see the condition of the input shaft by chance??
 

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No, I haven't had the trans out since the install of the hydraulic TOB. I will be needing a new clutch soon and when I do, I will look into a thinner pressure plate or a shorter tob if either are available.
 

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Discussion Starter #8
Thanks, I already have the spacer and extended pilot on the way. Ordered before I thought to ask.

I cant get a straight answer on the thickness of the flywheel. Nor can I find any mention on any description of any flywheel of it being designed for a hyd TO bearing.
I'm half tempted to feel that these companies have indeed produced a thinner flywheel, but as a way to make $$$$.
No evidence to back that up, however. Just a gut feeling.
Besides a factory replacement that's thicker is half the price of the new one. Not quite sure how that makes sense.
But I also dont like that I pay the same amount for my M shirts as the guy that wears a XXL ;)

I guess I'll bolt it all up and see how I feel about it.
 

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Thanks, I already have the spacer and extended pilot on the way. Ordered before I thought to ask.

I cant get a straight answer on the thickness of the flywheel. Nor can I find any mention on any description of any flywheel of it being designed for a hyd TO bearing.
I'm half tempted to feel that these companies have indeed produced a thinner flywheel, but as a way to make $$$$.
No evidence to back that up, however. Just a gut feeling.
Besides a factory replacement that's thicker is half the price of the new one. Not quite sure how that makes sense.
But I also dont like that I pay the same amount for my M shirts as the guy that wears a XXL ;)

I guess I'll bolt it all up and see how I feel about it.
Take the advice above and go with the correct parts. i went through a ton of misery dealing with a clutch issue and it was all due to a flywheel that had been installed by a previous owner. Once i purchased and installed the correct thickness flywheel all of my problems went away.



Dennis
 

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