rockhq

Hi everyone,

I'm rebuilding a 1979 K5 Blazer which came from the factory with a 350sbc+SM465+NP205 setup. Now i'm transplanting a 5.3 L33 2005 motor in it.
I've spent many, many hours searching the internet to get a good idea on what's necessary to mate the Gen3 engine with the transmission, and how to make the clutch work.

Based on that research, i ordered the NFW1050 flywheel from the interwebs, knowing it has a few issues which need addressing before it could work. After seeing it personally, and being able to compare it with a stock (SBC style) 12 inch diaphram style clutch set i had bought before i decided to swap to the LS motor, several issues have surfaced:

I know that:
1. The clutch disc inner 1/4 half will not contact the flywheel's friction surface
2. Measuring the distance of the stock flywheel clutch disc mounting depth from the bellhousing in a sbc motor is approximately 45mm

3. Measuring the distance of the NFW1050 LS-motor flywheel clutch disc mounting depth from the bellhousing in a 2005 L33 5.3 liter motor is approximately 38mm. This should be the standard "short crank" LS engine, which should be identical to most other LS motors except the 1999-2000 6.0 and 4.8's?

4. The NFW1050 clutch cover bolt pattern is indeed identical to the Gen1 SBC "12 inch" clutch bolt pattern

5. The NFW1050 flywheel has something like 11,90mm diameter recessed holes for centering the LS-style clutch (along with the dual non-concentric centering pins pressed in), with the bolt threads 10x1.5mm, and googling for the stock GM LS clutch bolts, they have nothing going on that would locate the clutch cover.

So, to use a SBC style clutch, one needs to ream out the clutch cover holes to 10mm instead of 3/8", right?

Wrong. While you can ream or drill out the SBC clutch cover mounting holes to 10mm, the clutch cover bolts will not center the clutch cover with anything substancial, relying nothing more than the bolt threads being drilled properly, and you being able to some how center the clutch cover. Another issue i found was that half of the clutch cover bolt holes in my replacement SBC clutch set were way oversized and thus would not locate anything.

So, it seems if one needs to mate a short crank LS motor into a vintage GM transmission, one needs to either buy a really expensive conversion flywheel, or use a clutch kit from an LS-motor equipped car or truck.

Having spent way too many hours on the interwebs trying to find out a reason why it's not possible to use a clutch kit for an LS-engine (something along the lines of a 2001-2006 Silverado 6.0 HD manual) along with the 1050 flywheel, to mate the LS engine properly with an older GM manual transmission, in my case the SM465 out of my 1979 K5 Blazer?), with the stock mechanical clutch setup, what's the biggest problem? I tried contacting a few of the better known clutch manufacturers for dimensions of their clutch kits but none have replied at this point.

P.S,

It's not like i can just go to any auto parts store to get a clutch kit for comparison, i have to buy it& then wait for a week or two to compare it, and i'll own it regardless.

Thanks,
Will R,

Finland, Europe.

cobra30689

Watching this one too. In theory I see no issue with using the stock 99-02 clutch for *your* application, as you have a 10-spline input shaft like the newer trannys do. It gets more complicated for those using car transmissions with a 26-spline shaft. With that said, I think it has to do with $$$$. Old school BBC truck clutches are dirt cheap compared to the 99-02 clutch (using Rockauto as a reference), but you are back to all the pitfalls you mentioned in your original post.

garys 68

iTrader: (1)

Although not ideal, I did ream the 3 undersized BBC pressure plate holes and ran that for years with no issues. If you're concerned, simply have the flywheel/pressure plate balanced together.

rockhq

Yes, i've read of many people just reaming the bolt holes on the clutch cover to fit it with standard LS clutch cover bolts with success. However, atleast on my replacement SBC/BBC clutch, the three bolt holes (out of the six) used to center the clutch cover had so little material around the clutch disc side of the bolt holes (something like 0.125" or less) that reaming them didn't strike me as a good idea. And, while i could have the flywheel and clutch cover balanced together, nothing will guarantee the clutch cover will run true to the crank centerline after i install it. It's not going to be off by a lot, but since it's a ~10lbs piece i'd like it to be centered by something other than just a few bolts with their threads.

jeffs55chevy

to hook up my muncie to the nfw1050 i also drilled out the three holes on my original pressure plate (nice write up from garys68) that was on the sbc. it works fine for me as well.

i havent looked into it much, but i also believe the reason of not using the newer truck 10 spline clutch, is the extra cost of the newer clutch. but then you wouldnt have to remove the flywheel dowel pins. the spline size/diameter is supposed to be the same for the newer and older 10 spline clutch disc.

garys 68

iTrader: (1)

What bellhousing do you have? And does your trans have the larger truck bearing retainer.
I suspect an 05 6.0 truck flywheel (Sachs 1050)/pressure plate/disk would fit in the large old school truck bellhousing.

rockhq

I can't remember the bellhousing part number, but it is the big aluminium truck type (with a ball stud hole for z-bar) which fits the truck 12" clutch kits, and the transmission has the large truck bearing retainer.

I guess what i'm really asking is: Using the NFW1050 flywheel, do the truck LS-style clutch kits have the correct depth from the flywheel surface to the diaphram fingers, and the diaphram fingers have correct contact surface OD and ID to use the stock SBC release bearing with the mechanical linkage and fork?

Floader

iTrader: (32)

You could always tram the clutch cover with a indicator, like you would a bell housing. I have done a few of these SM465 swaps in jeeps and they seem to have no problems. They are not max effort 7000rpm deals tho. If you are looking for perfection, the billet flywheels are the way to go.

garys 68

iTrader: (1)

Guessing you have the truck bellhousing. It also has a fifth bolt connecting the trans.
Like I said, guessing an 05 truck clutch will fit.
Since the old school clutch, car LS clutches, etc all work ok with the SBC mechanical throwout bearing, the truck should as well. Just check the fork geometry, throwout bearing depth. That can easily be adjusted by an adjustable ball stud, different bearing.

rockhq

5th connecting bolt? Not sure what you mean by that...The bellhousing is bolted to the transmission with just 4 large bolts (something like 9/16" or close to it). But anyway, it does have enough space in my opinion to fit very large clutch kits, in fact my truck had a Borg&Beck 3-finger 12" clutch, probably from the factory, installed in it when i tore it apart.

You said that all of the common LS clutch kits work with the stock SBC/BBC throwout bearing, so that's atleast comforting to know.

I guess i now have to decide whether i'll take a chance and order a truck LS clutch kit and the adjustable ball stud+throwout bearing, or dig deep into my pockets and order a billet conversion flywheel, which i'd really like since it's less prone to catastrophic failure if abused....it's just that at around $700 shipped and taxed it'll be a f*cking expensive disc of steel.

And thanks everyone for taking the time to discuss this.

garys 68

iTrader: (1)

Why not just go to the auto parts store and measure.
Even if you buy and cant use, you can return it.
BTW, the old school truck bellhousing I've seen have a 5th bolt hole above the Muncie pattern. See bottom pic in post 161 here:
https://ls1tech.com/forums/conversio...s-motor-9.html

rockhq

There isn't an auto parts store in the whole country that would have a clutch kit for a 2005 Silverado 6.0 manual on the shelf....in fact most couldn't order one because those trucks were never sold here, and the major parts importers/distributors do not stock parts for vehicles not sold in the country. There are specialty US parts stores that can get me whatever i want, but if i order a part not in stock, i have to pay for it in advance and i'll own it anyway. So that's out of the question.

The bellhousing you have posted a picture of (with the 5th hole) is from a newer truck (my guess is 1985+), which either came with some other transmission than the SM465 or it was just made to fit several different transmissions, but the SM465 is the only thing available when my truck was made (1979). I can post a picture of mine tomorrow if need be.

garys 68

iTrader: (1)

I give up, what country are you from?
Yeah, I've seen 4 bolt truck bellhousings, wasn't sure what transmission bolted to which.

rockhq

I'm from Finland, Europe

So rare are older Chevy trucks here that mine could very likely be the only 1979 K5 blazer with a manual in it, most likely the only -79 manual with an LS -motor in it, and i'm almost 100% certain that it'll be the only -79 L33 5.3 manual truck in the whole country once done.

Likewise for the newer trucks (2001--->), there are some (probably less than a hundred) with automatics but very likely none with a manual and all are "grey" imports.

Where i live it ain't easy trying to be different, that's for damn sure.

garys 68

iTrader: (1)

Well, good luck with the swap.
In cases like your, I typically go to rock auto. They have pics of the actual part and often dimensions.
It also gives cross references. ie. the 05 truck throwout bear was also used earlier gen SBC trucks. Those clutches will function with the mechanical throwout bearing. So the mechanical TOB should work on a clutch intended for the 05 hydraulic TOB.

rockhq

Gary, thanks for taking the time to search, but you're ultimately wrong in saying that the 05 throwout bearing would absolutely work with a vintage GM clutch kit. You see, the "modern" throwout bearing was used starting from 1996 like you must know, up to 2006/2007, with the NV4500 manual transmission. What you may not know is that in 1996, GM redesigned the NV4500 5 speed manual transmission input shaft bearing retainer, which after 1996 had no snout at all to guide a release bearing, but used a concentric hydraulic unit instead bolted to the bearing retainer through which the input shaft ran. That alone is enough of a difference for me to question the compatibility of the vintage release bearing with the newer clutch cover, and the overall dimensions of the parts.

Here's a link to the 1996- NV4500 input bearing retainer:
https://cobratransmission.com/index....2ac269fa2be69e

And i'm sorry if i'm beating a dead horse here, but at this point i'm ready to pay someone just to go to an auto parts store and measure a 2005 6.0 NV4500 clutch kit, preferrably non SAC, for me.

Now the reason i'm trying to use a newer clutch and flywheel is that they're much lighter than the vintage stuff, have better dampening characteristics, are probably more precise in their dimensions and were designed for the genIII motor i'm using. That said, since this clutch issues has become way more frustrating than i thought, i may just order a conversion flywheel, pay dearly for it, and move on with my project.

garys 68

iTrader: (1)

You might try some of the truck forums, might be someone with a similar setup there. Or google the throwout bearing specs by part number/manufacturers.
When I checked the rockauto crossreference, I did notice the truck 05 throwout bearing was used in Camaros and blazers, probably on a T5 behind a 3.8, 4.3, 5.0, etc, so pretty good chance gm kept dimensions of clutch the same.

BadGoatOR

Check with either Advanced Adapters or Novak Conversions. I'm currently mating a SM465 to an LS motor for a Jeep project using the AA clutch conversion kit. This is a common swap for the offload crowd.

Mike