Tilton emailed me back. Their Chevy button flywheel is .700" so I should have plenty of room. They don't make any custom button flywheels and referred me to aascomotorsports. I forwarded my information to them.

Anyone know what the flywheel bore is for a Chevy crank?

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Turbo 3800 E85 F23 5spd spec5
10.91@133.1

I don't remember right off (google probably will...) but there are Chevy and LS engines at my dad's place I can measure.

The 1-piece rear main seal ones are about 2.071" - same as the LS engine family as well, but the bolt patterns are different between the two.

[This message has been edited by fieroguru (edited 09-03-2014).]

For the 7.25" twin disk Cerametallic setup I thinking about the 66-302UGG pressure plate (910 ft/lb). Then i'll need the 64185-8-VV-12 disk pack to fit the F23 input shaft with 25mm x 14 spline.

Summitracing
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Turbo 3800 E85 F23 5spd spec5
10.91@133.1

[This message has been edited by Justinbart (edited 09-04-2014).]

Seen these?


https://www.fiero.nl/forum/F...HTML/129350.html#p17

http://www.j-body.org/forum...php?f=41&t=34558&a=1

Your flywheel failure isn't an isolated incident.

quote Originally posted by Justinbart: Car was making a strange noise last weekend. Took it apart this morning and found that the aluminum flywheel was loose. The bolts were loose and it was crack around the bolt circle so its trashed.

The aluminum creeps under the bolt heads. This happens often. A steel spreader plate might permit you to use an aluminum flywheel. I opted to go back to steel.

quote Originally posted by Steven Snyder: The aluminum creeps under the bolt heads. This happens often. A steel spreader plate might permit you to use an aluminum flywheel. I opted to go back to steel.

AASCO emailed me back and said a button flywheel would be best and they can make me one. Waiting on price... It would be a billet steel unit.

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Turbo 3800 E85 F23 5spd spec5
10.91@133.1

quote Originally posted by Justinbart: AASCO emailed me back and said a button flywheel would be best and they can make me one. Waiting on price... It would be a billet steel unit.

Awesome. A button flywheel will have minimal MOI. I would love to have that setup on my track car.

[This message has been edited by Steven Snyder (edited 09-06-2014).]

Have you asked Tilton about the throwout bearing interface? Reason I ask is Mwhite ran a 7 1/4" quartermaster twin disk clutch setup with his LS4/F40, but the stock HTOB would not fit right with the newer clutch. I think the bearing OD was too large or something.

quote Originally posted by mwhite: Here is the clutch installed on the engine. The geardrive clutch discs and flywheel spacer. The HTOB installed on the transmission The HTOB mount and transmission seal Answers to the the most obvious questions. Is it noisy, yes but not too bad. Is the clutch like an on off switch, no but a lot quicker engagement than a regular clutch, but I think I can get used to it. But at this point I have stalled it a lot trying to get it to creep forward, but that could have a lot to do with the bad tune that I have it currently...

[This message has been edited by fieroguru (edited 09-06-2014).]

I do not want to spend that kind of money on a new HTOB. I have a plan in the works and it involves wastegate parts, lol

Edit: I was just thinking... SPEC makes a spacer that clips onto f23 Htob. I could have them machine down the outside to the required ~44mm OD with a 1/4" step. I need a dimension on where the pressure plate fingers sit to see if I have enough room.
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Turbo 3800 E85 F23 5spd spec5
10.91@133.1

[This message has been edited by Justinbart (edited 09-07-2014).]

The "stack height" from friction surface to throw out fingers is on the drawings.
It's no t just the diameter of the TOB face... the face has to be convex/curved in order not to scrape across the ends of the fingers and wear them prematurely.

Oh yeah, duh. I looked at that number before. I'll have .460" of room at full worn. I'm hoping I can get that shape machined into the bearing cap.

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Turbo 3800 E85 F23 5spd spec5
10.91@133.1

If you have that much room to work with, you might want to weld a smaller diameter spacer to the end of the Spec HTOB spacer, turn it true on a lathe and then round off the edges as needed.

AASCO wanted $600 for the button flywheel. LOL.

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Turbo 3800 E85 F23 5spd spec5
10.91@133.1

$600 for a new flywheel? If it will be a strong enough unit that you won't be concerned about breaking it then the price is worth it. How much did the two previous flywheels that broke cost you?

quote Originally posted by Justinbart: I do not want to spend that kind of money on a new HTOB. I have a plan in the works and it involves wastegate parts, lol Edit: I was just thinking... SPEC makes a spacer that clips onto f23 Htob. I could have them machine down the outside to the required ~44mm OD with a 1/4" step. I need a dimension on where the pressure plate fingers sit to see if I have enough room.

Don't try to get SPEC to do any custom work for you. It's either not going to happen or it's going to be wrong. You could get the stocked part from SPEC and machine it yourself.

Now thinking about getting a Ford small block button flywheel and welding a concentric ring to the flex plate ( spun on a lathe to true) then re drilling for the 3800 bolt pattern. I would also have to take .100" or more off the flywheel. It has a total thickness of .870". SBF has a 1.75" crank bore with a 2.75" bolt circle. I think the 3800 is ~2.5". Does anyone have any technical drawings of a 3800 flywheel?

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Turbo 3800 E85 F23 5spd spec5
10.91@133.1

[This message has been edited by Justinbart (edited 09-11-2014).]

I would not recommend using an modified Ford unit. It probably is a 6 bolt pattern vs. the 8 of the 3800 so several of the holes will be significantly elongated. Even if it was an 8 bolt pattern and you could fit the 3800 bolt pattern in between all the existing hole, there would be much, much less material at the hub around the bolt pattern that could lead to the same cracking through all the holes - even with steel.

At your power levels and with the flywheel spinning at 7K right behind your back, I would highly recommend getting one made specifically to your application.

quote Originally posted by Justinbart: Tilton emailed me back. Their Chevy button flywheel is .700" so I should have plenty of room. They don't make any custom button flywheels and referred me to aascomotorsports. I forwarded my information to them. Anyone know what the flywheel bore is for a Chevy crank?

I measured 1.238" 2.475" ID on my SBC button flywhel for the SD4.
*EDITED to correct radius/diameter mixup*

Seen here:



And what I came up with for my app:

[This message has been edited by FastIndyFiero (edited 12-01-2014).]

quote Originally posted by Justinbart: AASCO wanted $600 for the button flywheel. LOL.

Why LOL? How does that compare to off the shelf button flywheels? I don't think it's out of line for a one-off, especially if it meets SFI specs.

quote Originally posted by Will: Why LOL? How does that compare to off the shelf button flywheels? I don't think it's out of line for a one-off, especially if it meets SFI specs.

Off the shelf is $150. I can get a whole flywheel for cheaper.

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Turbo 3800 E85 F23 5spd spec5
10.91@133.1

quote Originally posted by FastIndyFiero: I measured 1.238" ID on my SBC button flywhel for the SD4. Seen here: And what I came up with for my app:

Did you mean 2.238"?
I've emailed quartermaster but no response yet. Is that the part number on the flywheel.
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Turbo 3800 E85 F23 5spd spec5
10.91@133.1

[This message has been edited by Justinbart (edited 09-12-2014).]

quote Originally posted by Justinbart: Did you mean 2.238"? I've emailed quartermaster but no response yet. Is that the part number on the flywheel.

Sorry, 2.475". I was thinking in radius when I retrieved that measurement and forgot to convert it

It is the QM PN. 505170 SC (scalloped).

[This message has been edited by FastIndyFiero (edited 09-12-2014).]

quote Originally posted by Justinbart: Is that the part number on the flywheel.

Shouldn't matter unless you want to run a 5 1/2" clutch instead of the 7 1/4" one.

quote Originally posted by fieroguru: Shouldn't matter unless you want to run a 5 1/2" clutch instead of the 7 1/4" one.

At the time he said it had a small crank bore and I wanted to cross reference it to a particular engine.

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Turbo 3800 E85 F23 5spd spec5
10.91@133.1

Another idea: Get a flywheel insert for the 7.25 clutches. Machine mystery flywheel so the insert sits 0.100" above. Then get flywheel balanced matched. Weight would probably have to be added. Only problem is the insert will overhang about 0.25 on the inner diameter.

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Turbo 3800 E85 F23 5spd spec5
10.91@133.1

quote Originally posted by Justinbart: Another idea: Get a flywheel insert for the 7.25 clutches. Machine mystery flywheel so the insert sits 0.100" above. Then get flywheel balanced matched. Weight would probably have to be added. Only problem is the insert will overhang about 0.25 on the inner diameter.

Kinda similar to what you are thinking, this is the setup for my SBC. Insert is trapped by clutch housing (titianium QM) in compression, and also holes in insert at clutch mounting studs - anti rotation. Flywheel is steel, and you notice it is not much thicker than starter ring gear. Purpose of this design was to maximize surface contact with clutch disk, ie., no fastener pockets in insert face.

Where would I get that insert? I can find some similar pictures with image search but can't find any details or part numbers.

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Turbo 3800 E85 F23 5spd spec5
10.91@133.1

quote Originally posted by Justinbart: Where would I get that insert? I can find some similar pictures with image search but can't find any details or part numbers.

It's custom made original with no part number ( I suspect QM may have made it ). I could never find out any details on it, Replaced mine about 4 years back, had a local machine shop make it using original as template, as well as getting critical dimensions off flywheel.

edit to add: you aren't going to like the price I paid, which was $160.00 for the insert. Also note mating surfaces of flywheel and insert must flush as close as possible to 0.0000 inch.

[This message has been edited by California Kid (edited 09-13-2014).]

quote Originally posted by Justinbart: Another idea: Get a flywheel insert for the 7.25 clutches. Machine mystery flywheel so the insert sits 0.100" above. Then get flywheel balanced matched. Weight would probably have to be added. Only problem is the insert will overhang about 0.25 on the inner diameter.

As I've mentioned on CalKid's setup previously, having the friction surface be a separate piece from the flywheel means that it's hard to conduct heat away from the friction surface... the insert runs hotter and makes the entire clutch more susceptible to heat damage... which is already a big concern when driving a multi-disk clutch on the street.

blaaahhh. I didn't want it to cost this much. If only I had an SBC...

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Turbo 3800 E85 F23 5spd spec5
10.91@133.1

any updates here?

Have you called SPEC? They made me a one off Flywheel for a 03 Kia Spectra back in '03 (it later went into production) all I had to do was send them my stock flywheel I did the same thing in '11 on a On a Boss 302. Give them a call and don't bother with sales get a hold of someone in Tech.

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1986 SE 3800SC/4t65eHD (12.871@104.96)
HX-40, FrozenBoost I/C, 80lb injectors & E85 Coming soon.....

https://www.fiero.nl/forum/Forum4/HTML/070765.html

FINALLY back on the road! The time frame on getting a flywheel was a total ***** . Longest my car has ever been down, 6 months. Looking back I wish I would have just threw money at that shop online to make one. (still wasn't a guarantee on the timeframe.) Ended up missing a few ice races and taking the car to a really fun spectator rally event called Sno*drift up north. Anyways, enough whining. Here is what I came up with.

I did get the Tilton Cerametallic twin with 66-302UGG pressure plate (910 ft/lb) and 64185-8-VV-12 disk pack

I had an extra neutral balanced spec aluminum flywheel on the shelf but it obviously wasn't going to work with the twin disk.




I decided to make a new insert for that aluminum flywheel to work with the twin disk. I wanted something as thick as possible but simple. The twin disk has very small tolerances and any warping of the insert would be bad. I drew up a plan to take to a machine shop. The machine shop I go to doesn't do this kind of work so he sent me to this guy who does it on the side. He works for the big three as a machinist and can do small projects like this in his free time. He had it for several months but when I got it back I was totally impressed. Everything was perfect.
I bought a piece of 1/2" ASTM A514 T1 steel for the insert.















Drill and tapped the crank for a larger bolt. 3/8-16 I used 3 drill bit sizes to open the hole up so it would stay straight then I used a really good tap and it cut new threads easily. This bolt might be an even better solution.





So I planned on using this piece from a flexplate as a washer but there ened up only being .010" between the bolt head and rivet on the clutch disk. Too close for comfort and would probably hit when the disk wore down. I didn't want to make that area of the flywheel any thinner so I didn't end up using it. Maybe it would have been better to use it, idk. Fingers crossed.




For the hydraulic throwout bearing I bought a spacer from Spec that some people use for F23 swaps then turned it on the lathe at a friend's house. 44mm ID 50mm OD on the contact surface.







So now I needed it balanced matched to the flexplate. I dropped it off to one guy explained how to balance it with the flexplate 180* off. He said that was stupid and that he would spin the flexplate on a crank balance machine, zero it out then spin and balance the flywheel until it read zero. I said ok. 3 weeks later said he couldn't get it right. I took the weight off the broken flywheel and put it on the new one in the same spot. Took it to another place and they said the 180* off method was the way they always do those. Get it back a few weeks later. They put a big ass bolt on the back side of it....whatever I need to get this thing done. Found clearence issue with the starter. Attacked starter with a grinder and now its all good. Engine spins up really smooth and appears to be right thankfully.






Clutch pedal is very heavy. I may have overdone it with pressure plate spring selection. I didn't have to adjust the pedal stop at all from where I had it set before. I am thinking about changing the geometry of the clutch pedal so I can get more rang of motion when disengaging/engaging.

Total cost
Pressure plate 66-302UGG $505.75
Disks 64185-8-VV12 $229.50
Insert material ASTM A514 T1 $61.52
Clutch bolts ARP 651-2000 (10) $14.48
Flywheel bolts ARP 644 1000 (10) $22.52
Bottom Tap 3/8"-16 $19.21
Flywheel Machine labor $200
Flywheel $0
Balancing $160

Total $1,212.98
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Turbo 3800 E85 F23 5spd spec5
10.91@133.1

[This message has been edited by Justinbart (edited 01-27-2016).]

damn man, looking intense! ready for 9's? :P

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"I am not what you so glibly call to be a civilized man. I have broken with society for reasons which I alone am able to appreciate. I am therefore not subject to it's stupid laws, and I ask you to never allude to them in my presence again."

"The day I tried to live, I stole a thousand beggars' change and gave it to the rich."
https://www.fiero.nl/forum/Forum2/HTML/119122.html

Your whole throw out mechanism is weird. Tilton recommends a ROUND faced through out bearing. This maintains the contact point at the same radius from the input shaft and the leverage on the pressure plate fingers the same throughout the pedal travel.

A large flat-faced contact surface like that will push on the throw out fingers closer to the pivot (at a larger radius from the input shaft) than the round faced TOB does. This will reduce your leverage on the PP spring and increase pedal effort. It may also booger up the throw out fingers or cause them to wear strangely.

If possible, go to a smaller master cylinder. That's probably the most straightforward way to reduce pedal effort and increase pedal travel.

It looks like the purpose of the raised portion of the throwout bearing spacer is so only it makes contact with the fingers.
If it is tall enough, the fingers should not make contact with the larger diameter of the main throw out bearing spacer.

quote Originally posted by fieroguru: It looks like the purpose of the raised portion of the throwout bearing spacer is so only it makes contact with the fingers. If it is tall enough, the fingers should not make contact with the larger diameter of the main throw out bearing spacer.

Correct. It would have to move in over 3/4" before it would contact the outer edge, which is impossible.

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Turbo 3800 E85 F23 5spd spec5
10.91@133.1

Have you put an aftermarket balanced on to try and eliminate the flywheel cracking?

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10.263 @ 134.44MPH - 1.49 60'
Billet 6262 Precision turbo, PT1001 intercooler, ST1 cam, 130lb springs, comp pushrods, HV3, ARP Rod bolts, otherwise stock L36.


Old M90 XP Cam time -
11.425 @115.60
1.543 60'