for the LS4 that I am using in the Fiat with an AR5 transmission and a Jeep 2.5 liter AX15 bellhousing, with a solstice AR5 HTOB I can mate all these parts together without any headaches. simple bolts and the parts are cheap. It also gives me the smaller bellhousing needed to lower the motor and transmission in the car and give me the foot well space I need. so please do not suggest a standard LS block and 168 tooth flywheel.

the two headaches come in mounting the starter and the clutch

ditching the 142 tooth ring gear of the LS4 and going with a 148 tooth ring gear of an S-10/F-body 60 degree V6 motor will allow a mini starter to fit and clear most of the block, only the machining register tab at the pan rail will need to be "adjusted" with a grinder

mounting the starter then is just a laser cut plate sandwiched between the block and the bell housing with the starter bolted to the plate. minor headache resolved

Here is the major headache.

If I run a 7-1/4" twin-disc Quarter Master clutch, there are button flywheels available, but I still need a flex plate that fits........

I believe that a S-10 or F-body 2.8/3.1/3.4 flex plate could be made to work, but I am having difficulty finding crank register information and bolt pattern information, and I no longer have any of the 3.1/3.4 flywheels around to measure. The other issue is a street car running on a twin 7-1/4" racing clutch means that starts are actually launches, and that gets tiresome in stop and go traffic. so I would rather have an organic clutch on the street.

I believe that a 1-piece RMS SBC flywheel fits the LS register, however the bolt pattern is off slightly. I am finding difficulty with web sleuthing to verify this. even searching this site did not confirm anything.

if I can use an SBC flywheel, I believe that I can turn down the flywheel from 153 tooth to a 149 tooth flywheel. this would allow me to run a 10.4" clutch. there are also aluminum flywheels and billet steel flywheels that are in the 12 # range for dirt cheap. run this with a ford pressure plate (smaller than GM by a bit) and I should be good

lastly, I believe that a billet steel 148 tooth flywheel for a 9-1/8" clutch will fit better as the flywheel housing gets narrow near the transmission. It would also allow me to run a floater and second clutch disc.. however would need to have the pilot opened up and the bolt hole changed. that is back to needing the 60 degree V6 crank flange information.. And after 3 days of internet searching, I have not found an SFI rated steel billet 148 tooth flywheel for the 60 degree V6 or a billet aluminum one either. a few companies make the 142 tooth for fieros, just not for the S-10 or F-body with the 148 tooth flywheel

I would rather modify a purchased flywheel than have custom machined.

either way, need to know the actual register size and bolt circle dimensions of the 60 degree V6 crank flange and if or if not the 1986 and later SBC flywheel will fit the LS crank

Any help is appreciated.

 

I don't see you mention the thickness of flywheel that is needed.

I have taken billet LS1/2/3 flywheels and turned them down to accept the 142 ring gear. These are typically about 0.8x" thick. Here is one before adding the pressure plate bolt pattern.
The trick is to find one that matches the clutch disk fricture area of your clutch. This one only works with larger clutch setups.


Also I can confirm the 86+ SBC/LT flywheel pilot is the same as the LS4. The hole pattern needs some slight modification. These can also be found thicker with the dual mass LT1 replacements being some of the thickest. The downside it the 86+ SBC/LT1 flywheels are externally balanced, which will not work with the LS4. This one below was an aluminum one that I modified to fit, but ultimately decided to just design and build a custom flywheel.




You can also discuss your project with LSC Performance Flywheels in Murrieta CA. They have made quite a few custom fiero swap flwyheels at decent prices. They can likely get you hooked up with what you needing.

Also, the Ford 4.0L Ranger clutch is 9 7/8" and the pressure plate bolt pattern is about as tight to the cluch disk as you can get it.

 

Can't use the 142 tooth without putting the starter under the oil pan. That means I have to raise the motor up about an inch

Will be using the 148 tooth ring gear

 

I didnt specify a thickness as I have a few options there because I am using a plate between the flywheel housing and block to mount the starter.

Thanks for the confirmation on the SBC pilot. do you know the difference in BC dimensions?

all SBC's except most of the 383 or 400 are INTERNALLY BALANCED or "0" balanced. Been that way for decades.

thanks for the info on the ranger flywheel. even the ford 10.5 is smaller than the GM 10.5 pattern. Im looking at some of the 10.4 and 240mm clutches

 

86+ SBCs with the one piece rear main seal are externally balanced on the flywheel.

 

Will agree to disagree. Won't argue with you, but you should look into that. I have been building SBCs and BBCs for 40 years. Most motors from GM from 1988 on are internally balanced except the 454/502

Even the 4.3 V6 uses the same flywheel as the 305/350

 

I looked into it because I was curious. 1996 S10 4.3 flywheel had a weight on it, as well as the 1987 Blazer 350.

 

1987 Camaro SBC Flywheels:
https://www.summitracing.com/search/...leK3-AhGa_n-5g

Clearly you don't need or want my help, so I will move on...

 

spend better part of a few hours corresponding with Mike. working on a custom variation of the 1514-10, however with the SBC bolt pattern changed to the LS. will be verifying if I need to add a bit back to the hub area to bring the ring gear out vs a flywheel spacer. still vacillating between 148 teeth and 153 teeth, or going to something like 150 teeth. also, looking at the ford 10.5" pressure plate as its 1/4" smaller in diameter than the GM plate and uses a 11.375 bolt circle vs the 11.625 bolt circle.

Note, that the billet SFI rated SBC flywheels are "0" balanced. yes stock cast flywheels have a slight bit of weight from GM because the 1-piece RMS crank no longer has the slight bit of flange.on the end of the stock cast crank. So yes, I stand corrected that stock cranks and stock cast flywheels do have a slight amount of weight. however I havent used stock bottom ends on an SBC/BBC build since 1984. So @fieroguru I apologize for being argumentative.

going to 153 teeth nearly eliminates the interference with the starter and pan rail machining register.

it does require my spacer mounting the flywheel to be slightly thicker and have a slightly larger opening. 150 tooth does not. now down the rabbit hole of locating an off-the-shelf 150 tooth ring gear.

 

anyone have dimensions on a GM 10.5 pressure plate? like the ram 401 or 801?

looking for the OD just above the flange on the stamped cover, and the overall height of the cover as rough numbers. Checking clearances with my bell housing later today. Mike from Ram is out of town for a bit and cant get me info for at least a week.

looking at pictures, my rough-*** guestimate is 10.88 to 11 in diameter and 2.2 to 2.4" at the edge and 2.5-2.7" around the center just outside the fingers on the diaphragm. would like to be a bit more accurate than a guess from a picture

 

Received the dimensions from Mike at Ram for the 401 pressure plate

took a tracing of teh bell housing flange and had a bud that works at a sister company scan the tracing direct to a DXF. that is until I can get time with our 3D scanner to scan the flywheel housing and trans




Took the DXF and laid it over my initial sketch. SBC 153 ring gear (blue) will nearly almost clear




updated my initial CAD sketch to match, and with a bit of die grinding, it looks like I can get a stock 153 tooth ring gear on a variant of the Ram 1514-10 flywheel and a Ram 801 pressure plate to fit.





Next is to make a check fixture to run the profile sweep inside the bellhousing bolted to the motor.

 

Check tool printed

Now to see what hits and adjust

 

Wahoo..... Looks like a nearly stock SBC circle track flywheel and 10.4" clutch will fit the jeep bellhousing