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3800SC Modified Flywheel Approach by Dennis LaGrua
Started on: 07-19-2007 10:15 AM
Replies: 24
Last post by: 86GT3.4DOHC on 07-01-2008 07:56 PM
Dennis LaGrua
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Report this Post07-19-2007 10:15 AM Click Here to See the Profile for Dennis LaGruaClick Here to Email Dennis LaGruaSend a Private Message to Dennis LaGruaDirect Link to This Post
On a 3800SC / Getrag swap a modifed flywheel must be used. The two approaches seem to be modifcation to the original flywheel or using a mid 90's 3800 F body flywheel and machining to .840" final thickness that requires removing about 1/4"off the face. ( about 5 lbs of material) The later appraoch makes the most sense to me, but the worrysome part is the amount of machining needed to get the F-Body cast flywheel down to the necessary thickness. It seems to amount to a machine shop charge of $200 or more. Anyone found a more cost effective solution?

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Report this Post07-19-2007 10:26 AM Click Here to See the Profile for neverendingprojectClick Here to Email neverendingprojectSend a Private Message to neverendingprojectDirect Link to This Post
I've found a non automotive machine shop with a lathe big enough to turn it down for about $100 but after that I still have to take it to an automotive machine shop for balancing. It's not ideal but it's better than being charged $90/hr to let the flywheel sit on a resurfacer until it gets to the proper thickness.

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darkhorizon
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Report this Post07-19-2007 11:08 AM Click Here to See the Profile for darkhorizonSend a Private Message to darkhorizonDirect Link to This Post
our machine shop is a well known v8 builder, and he did it fairly cheap. I really dont know what he did specifically, other than spend a decent amount of time balancing it.

IIRC it was about $130 in machine work.
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Dennis LaGrua
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Report this Post07-19-2007 04:49 PM Click Here to See the Profile for Dennis LaGruaClick Here to Email Dennis LaGruaSend a Private Message to Dennis LaGruaDirect Link to This Post
The 3800 flywheel is cast steel and not the easier to machine billet steel. Machine shop work around these parts is very expensive plus Autozone wants $258 for an F body 3800 flywheel. As for balancing, it shouldn't be a real big problem as the 3800 uses a neutrally balanced flywheel. If you add up the total cost of making a 3800 swap flywheel it can amount to one expensive proposition. Going out to the boneyards today to see what I can find.

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Fie Ro
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Report this Post07-19-2007 05:03 PM Click Here to See the Profile for Fie RoClick Here to visit Fie Ro's HomePageClick Here to Email Fie RoSend a Private Message to Fie RoDirect Link to This Post
I have looked for pictures of these "balanced" flywheels forever but didnt found em, found one but it appeared machined wrong later. I also sent that pic to the machinist and he came back to me saying it didnt make sense...
I sent a 99 camaro flywheel and the flexplate of the 98 GTP donor engine as a guide for balancing.
Turned down to 0.840 and two holes were drilled for balancing, hope this is done right..
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neverendingproject
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Report this Post07-19-2007 05:42 PM Click Here to See the Profile for neverendingprojectClick Here to Email neverendingprojectSend a Private Message to neverendingprojectDirect Link to This Post
 
quote
Originally posted by Dennis LaGrua:

As for balancing, it shouldn't be a real big problem as the 3800 uses a neutrally balanced flywheel. If you add up the total cost of making a 3800 swap flywheel it can amount to one expensive proposition.




My 3800 SC series 2 is externally balanced and I assume the rest of them are as well. Check this out for reference http://dtcc.cz28.com/tech.htm

It took me a while to find a machine shop to turn down the flywheel for a reasonable price. The trick is to try regular machine shops that don't usually deal with automotive parts, they won't make a big deal of it. If all else fails Loyd can sell you one for a good price.
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darkhorizon
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Report this Post07-20-2007 12:06 AM Click Here to See the Profile for darkhorizonSend a Private Message to darkhorizonDirect Link to This Post
www.rockauto.com has them dirt cheap.

At autozone, you can buy a 3800 flywheel and use any random flywheel for a core charge usually because they have highschool kids working there most the time.
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goatnipples2002
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Report this Post07-20-2007 02:11 AM Click Here to See the Profile for goatnipples2002Click Here to visit goatnipples2002's HomePageClick Here to Email goatnipples2002Send a Private Message to goatnipples2002Direct Link to This Post
Go to Advance Autos site ( www.partsamerica.com ) they offer the flywheel for $50.99 w/ $40 core.

[This message has been edited by goatnipples2002 (edited 07-21-2007).]

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fieroguru
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Report this Post07-20-2007 07:09 PM Click Here to See the Profile for fieroguruSend a Private Message to fieroguruDirect Link to This Post
I know nothing about 3800 swaps, but have you thought about using a 1/4" spacer between the block and tranny and keeping the camaro flywheel unmodified?

Should only require longer dowel pins and a simple spacer.

This could cause issues with tranny mount to engine mount spacing vs. the non-spacer setup.
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goatnipples2002
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Report this Post07-21-2007 02:26 AM Click Here to See the Profile for goatnipples2002Click Here to visit goatnipples2002's HomePageClick Here to Email goatnipples2002Send a Private Message to goatnipples2002Direct Link to This Post
 
quote
Originally posted by fieroguru:

I know nothing about 3800 swaps, but have you thought about using a 1/4" spacer between the block and tranny and keeping the camaro flywheel unmodified?

Should only require longer dowel pins and a simple spacer.

This could cause issues with tranny mount to engine mount spacing vs. the non-spacer setup.


I for one would rather simplify the swap not make it more complex.
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fieroluv
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Report this Post07-21-2007 08:14 AM Click Here to See the Profile for fieroluvClick Here to Email fieroluvSend a Private Message to fieroluvDirect Link to This Post
 
quote
Originally posted by fieroguru:

I know nothing about 3800 swaps, but have you thought about using a 1/4" spacer between the block and tranny and keeping the camaro flywheel unmodified?

Should only require longer dowel pins and a simple spacer.

This could cause issues with tranny mount to engine mount spacing vs. the non-spacer setup.


To me this actually sounds logical. How is this any different that a small block chevy swap? Don't they use at least a 1/4 inch spacer?
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Report this Post07-21-2007 02:05 PM Click Here to See the Profile for MstangsBwareClick Here to Email MstangsBwareSend a Private Message to MstangsBwareDirect Link to This Post
 
quote
Originally posted by fieroguru:

I know nothing about 3800 swaps, but have you thought about using a 1/4" spacer between the block and tranny and keeping the camaro flywheel unmodified?

Should only require longer dowel pins and a simple spacer.

This could cause issues with tranny mount to engine mount spacing vs. the non-spacer setup.



There was a guy locally that was using this approach on a S1 swap but I think he sold it before it was done. I done see why it wouldnt work just the same and be alot cheaper.

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Riceburner98
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Report this Post07-21-2007 09:19 PM Click Here to See the Profile for Riceburner98Click Here to Email Riceburner98Send a Private Message to Riceburner98Direct Link to This Post
Cost of machining flywheel vs. cost of custom-making a 1/4" transmission-sized spacer though?? Somethin tells me that's not going to be cheap unless you DIY, but even the 1/4" aluminum plate stock in that big a size will be a few $$..
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darkhorizon
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Report this Post07-21-2007 09:27 PM Click Here to See the Profile for darkhorizonSend a Private Message to darkhorizonDirect Link to This Post
The flywheel approch is really easy, its just a shame shops are trying to rip you off. I honestly spent next to nothing on my flywheel, It was so low I dont even remember the price excatly.
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fieroguru
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Report this Post07-22-2007 08:59 AM Click Here to See the Profile for fieroguruSend a Private Message to fieroguruDirect Link to This Post
 
quote
Originally posted by Riceburner98:

Cost of machining flywheel vs. cost of custom-making a 1/4" transmission-sized spacer though?? Somethin tells me that's not going to be cheap unless you DIY, but even the 1/4" aluminum plate stock in that big a size will be a few $$..


Since this would merely be a spacer (no bolt pattern change) with the dowel pins providing the needed precision there are 3 ways to go about making this spacer.
1 - just use machined washers at the bolt locations. This will leave a gap in between washers, but this is super simple. You could then fill the gap with silicone
2 - use a multi part spacer with 3 to 4 pieces of 1/4 x 2" aluminum and drill the needed holes
3 - go full bore with a larger 1 piece spacer - requires the most cutting and largest investment in material.

[This message has been edited by fieroguru (edited 07-22-2007).]

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Report this Post07-22-2007 10:01 AM Click Here to See the Profile for vortecfieroClick Here to visit vortecfiero's HomePageClick Here to Email vortecfieroSend a Private Message to vortecfieroDirect Link to This Post
another approach is have an aluminum one made up. Ive driven a few 3800SC with one and it makes a big difference.
Joe formally of Racetec can still get them made up

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Report this Post07-22-2007 11:07 AM Click Here to See the Profile for darkhorizonSend a Private Message to darkhorizonDirect Link to This Post
 
quote
Originally posted by vortecfiero:

another approach is have an aluminum one made up. Ive driven a few 3800SC with one and it makes a big difference.
Joe formally of Racetec can still get them made up



On paper, the alum flywheel would be worth the money. Might help save the transmission by reducing rotating shockload.
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Dennis LaGrua
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Report this Post07-22-2007 03:53 PM Click Here to See the Profile for Dennis LaGruaClick Here to Email Dennis LaGruaSend a Private Message to Dennis LaGruaDirect Link to This Post
Priced used 96-02 Camaro 3800 Flywheels at my local junkyard and they can be had for around $50.00. So far the best machine shop cost that I can get is $150 -$200 for the milling and the balancing. That's $200-$250 which seems high so we are still looking around for a more cost effective solution. Has anyone tried using a Fiero flywheel and redrilling for the 3800 bolt pattern? Probably not the way to go but it has been done before.

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darkhorizon
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Report this Post07-23-2007 02:09 AM Click Here to See the Profile for darkhorizonSend a Private Message to darkhorizonDirect Link to This Post
 
quote
Originally posted by Dennis LaGrua:

Priced used 96-02 Camaro 3800 Flywheels at my local junkyard and they can be had for around $50.00. So far the best machine shop cost that I can get is $150 -$200 for the milling and the balancing. That's $200-$250 which seems high so we are still looking around for a more cost effective solution. Has anyone tried using a Fiero flywheel and redrilling for the 3800 bolt pattern? Probably not the way to go but it has been done before.



I saw a thread on redoing the 2.8 flywheel and it seemed to be a real catastrophe.
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Report this Post07-23-2007 12:15 PM Click Here to See the Profile for jerry455Click Here to Email jerry455Send a Private Message to jerry455Direct Link to This Post
i am not sure if it is a good idea to machine those flywheels thinner. what about the strength of it after? that is sitting right behind you, what happens if it comes apart ? i think a custom made flywheel might be safer.
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Report this Post07-23-2007 12:23 PM Click Here to See the Profile for JncomuttClick Here to Email JncomuttSend a Private Message to JncomuttDirect Link to This Post
 
quote
Originally posted by vortecfiero:

another approach is have an aluminum one made up. Ive driven a few 3800SC with one and it makes a big difference.
Joe formally of Racetec can still get them made up



I looked into this. Last I heard from James (3800sc cavi) and talked to the shop in NS, they were eating the bottom end out of the motors. The flywheels were mis-balanced by about 247grams or so. They thought it was the mounts but turned out to be the flywheel. If you know someone who still makes a PROPER aluminum flywheel, I'd like to know. I didn't know how to get ahold of the guy from RaceTech since they're out of business.

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Report this Post07-01-2008 05:59 PM Click Here to See the Profile for JumpStartClick Here to Email JumpStartSend a Private Message to JumpStartDirect Link to This Post
 
quote
Originally posted by Jncomutt:


I didn't know how to get ahold of the guy from RaceTech since they're out of business.



Not out of bussiness. Hes in this thread... http://www.fiero.nl/forum/Forum2/HTML/088881.html
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Report this Post07-01-2008 07:33 PM Click Here to See the Profile for MOBILEClick Here to Email MOBILESend a Private Message to MOBILEDirect Link to This Post
I was wondering why a few of you guys worried about the strength of the flywheel after machining? I have never heard about a fiero flywheel cracking or breaking, and we are machining the new one to match. Wouldn't that mean it's just as strong as the fiero flywheel? I know we are putting more power to it, but I've never heard of anyone breaking them. There is a ton of SC3800 fieros out there now and quite a few have manuals.

Just my $.02

Dennis: Definitely don't skip the balancing. They are for sure counterbalancing the engine. Look at how much material is punched out of the auto flexplate on the one side...
I believe I was charged $50 or $75 to balance mine. My machinist/engine builder said they mandrel balance them all the time. Hopefully you can find someone cheaper!

MOBILE

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Dennis LaGrua
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Report this Post07-01-2008 07:42 PM Click Here to See the Profile for Dennis LaGruaClick Here to Email Dennis LaGruaSend a Private Message to Dennis LaGruaDirect Link to This Post
The problem was solved. Found a shop who did the machining for $130 and the balance was maintained. The machined 3800SC flywheel ends up to be the same thickness as the Fiero flywheel so in theory no loss of strength is experienced. While I did work on a stick swap, I much prefer my auto swap. The stick swap is easier to do but IMO the auto gives an extra measure of strength over the Getrag. .Also the Spec 3 clutch that was used is still chattering after 300 miles. Just wonder if it will ever break in and be completely quiet. .

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Report this Post07-01-2008 07:56 PM Click Here to See the Profile for 86GT3.4DOHCSend a Private Message to 86GT3.4DOHCDirect Link to This Post
There is absolutely nothing wrong with machining the flywheel, its no weaker than a normal Fiero flywheel, not to mention if it came apart, it would have to blow through the tranny case and two to three layers of metal in the firewall. To beable to make it through the tranny case, the piece would have to be rather small, and theres no way a piece that small is going to carry enough momentum to break the tranny case, much less carry enough energy afterwards to go through a couple more layers of metal.

As for the spacing idea, you still have to balance the flywheel even if you shim the tranny out. Also, you are loosing a lot of strength. The bolts arent the only thing that hold the tranny to the engine, there is a LOT of sheer force from the tranny face touching the engine, and the force of the bolts on the tranny case is spread across the face of the tranny, if you had washers in there, all that force would be focused on the area the washer is touching, making it very likely to crack the case. IMO it would be a VERY bad idea. Using an adapter plate is a diffrence situation, as you still have the surface area to clamp to and dissipate the pressure.
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