348 mated to LT1 T56

J

Jim123

Member
Greetings,
Brand new here with a question or two for you 348-409 guys. I own a 1958 Impala with a 348 backed by a super T10 4 speed. I'm about to have a LT1 T56 installed and I know challenges are abound. Bob Weir made a bell housing that would be perfect for the application but he is having production problems. The 168 tooth flywheel is problematic and I am searching for workarounds or a bellhousing that would work. The LS T56 has an available adaptor plate but my LT1 has zip. Changing to a 153 tooth flywheel with associated starter challenges seems like a train wreck waiting to happen. Thanks for the help guys!
Jim
 
J

Jim123

Member
You are correct. The LS is a better T56 and it has a longer shaft that works with an adaptor plate. The shorter shaft on the LT1 T56 prevents the adaptor and requires a bell housing or a 153 tooth flywheel conversion so as to use the doner T56 bell housing.
I think I have found a 168 tooth capable bell housing that will work but it will not have pre drilled holes for the starter.
Has anyone on the blog purchased a starter for their 348 that is a block mount application? If memory serves the 58 Impalas (maybe all 348 blocks) had a bell housing mounted starter on the automatics with the manuals using the offset pattern block mounts.
Don't be shy boys. I need some direction here be it 153 tooth conversion or starter suggestions.
Thanks
Jim
 
D

Don Jacks

Well Seasoned Member
Supporting Member 3
Check your block,Jim.Most,if not all,W blocks come drilled for a starter that bolts to the block when using the 168 tooth flywheel.I have both a 59 and 60 5011 block and both are drilled.The only tme that an extra hole is required is when going to the smaller 153 tooth wheel.The starter that can be used is a gear reduction type from a 90's Chevy truck.D-B electrics sells them for about 50 bucks.
 
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J

Jim123

Member
Hi Don,
Car is in the shop so I will check it this week. If memory serves the block is drilled for a starter with an offset pattern for the 168 tooth flywheel. They came from the factory that way to be used with whatever transmission was placed on individual vehicle. Mine has the starter mounted on the bell housing with the manual 4 speed. Unfortunately, I purchased a LT1 T56 that has a small bell housing that will not bolt up to the 168 tooth flywheel if my research is correct. My choices are to buy a QuickTime bell housing and have it modified to accept the starter or if it is small enough to use the block mount type starter. Lastly, I could go with a 153 tooth flywheel and use the entire doner T56 to include bell housing. Don, you mention gear reduction at the end of your post. Do you know anyone who has gone to the 153 tooth set-up and made that work with a drill and tap for an additional starter hole or were you referring to a 153 set up using the existing hole pattern? Sorry I'm a bit confused.
Many Thanks
Jim
 
La Hot Rods

La Hot Rods

Well Seasoned Member
Supporting Member 15
I did a swap in a 67 GTO and I used the factory clutch set up other than the clutch disc.
I use an adapter for the transmission to bell and had to change the input shaft.
For the life of me I can't remember what the transmission came from.
I also had to add a electronic speedometer drive to make the factory gauge work.
 
D

Don Jacks

Well Seasoned Member
Supporting Member 3
Jim,you will have to drill the block for the extra hole only if you use the small[153 tooth]flywheel.One of our members,Dan[tripower] put a 6 speed in his 61,and I believe he went with the 153 toothflywheel,but I'm not sure.The starter that I mentioned was for a block mounted starter and a 168 tooth flywheel.The reason that I mentioned it was that your post said that you thought you'd found a bell that would work with the transmission and a 168 tooth flywheel.Sorry for any confusion.
 
J

Jim123

Member
Don,
The confusion is completely with me. I'm swamped on this and keep running into road blocks. Do you have any advice on switching over to a 153 tooth flywheel? If I am forced to go that direction because the bell (RM9023) will not work out are there any domino affects with the 153 other than the starter?
Thanks again.
Jim
 
D

Don Jacks

Well Seasoned Member
Supporting Member 3
No sir,I'm sorry,I don't.I do know that the factory bellhousing will bolt to a W motor,and the 153 tooth flywheel bolts up to the crank ok.I read that of some members that have drilled the necessary hole in the block,and they indicated that it wasn't a big deal to do.I'm an automatic trans guy my self and have only used the 168 tooth wheel for simplicity sake.
 
DonSSDD

DonSSDD

Well Known Member
Supporting Member 2
No difference in bolting a flexplate or a flywheel to the block Don. As long as the bolt patterns are the same.

Jim, Tripower (screen name) did an excellent posting under Builds forum on his 1961 that Don mentions. Likely some helpful stuff there on what Tripower did if he used a 153 tooth flywheel. He was good with descriptions and with pictures.

I know nothing about the new bellhousings, but there were some later trucks (80's or 90's) that had a 168 tooth flywheel with a block mounted starters. Not sure if one of them would have used a T56 type bellhousing.
 
J

Jim123

Member
Thanks guys,
I will search for Tripower and give it a read. I have talked with a few gents in the field and to a man I am being directed to go KISS with the 153 tooth flywheel. That way we keep all the doner LT1 T56 components to include the bell housing. A tap and drill for a new starter hole is not a show stopper. No such thing as a block mount offset hole (168 type) 153 tooth starter from what I hear correct?
Many thanks gentlemen!
Jim
 
D

Don Jacks

Well Seasoned Member
Supporting Member 3
No,the listing says LS1 spec.trans.,The LT1 small block trans.that he has is different,as in shorter input shaft.
 
J

Jim123

Member
Hi Gents,
We are going with a 153 tooth flywheel and as many components from the LT1 T56 as we can to make this conversion as easy as possible. I do have a guy that I would recommend as a great source of knowledge on this type of application.
Billy at McLeod Racing in SOCAL took his time with me on the phone and briefed me on what was needed, what he recommended and gave me part numbers to pass along to my mechanic for purchase. A real pleasure to talk with!
Jim
 
brushwolf

brushwolf

Well Known Member
I also have a 348 and an LT1 T56 rebuilt with a relocated shifter to clear the bench seat. Already had the transmission and it still cost a small fortune due to mainshaft teeth for 5-6 gears being toast.

Have purchased a new adapter 153t flywheel that uses the LT1 clutch and figured on using the stock LT1 external slave, but have been bogged down in life changes. Retired, bought another house, smattering of health problems. Recovering from shoulder surgery right now, so trying to utilize the down-time to get plans organized again.

Before I got sidetracked I was trying to figure out the starter issue and had concluded I would need to drill the block to mount the starter. Since it has been awhile, any chance a starter has become available that will work without drilling the block or have there been others still on the board that have posted any "how-to" threads on mating the T56 from an LT1 to the 348-409 engine?

Thanks, Mike
 
brushwolf

brushwolf

Well Known Member
Also noticed reading up on it when my son's (formerly mine) LT1 TA broke the clutch fork, that the cast clutch forks seem to be prone to breakage. It was a stock diaphragm clutch too, not a real heavy clutch. Now wondering if I should replace the used LT1 fork I have for mine before installing it. Or is the replacement available probably an import and just as likely to break as the stock clutch fork? Yeah, I worry too much..
 
J

Jim123

Member
Hi Mike,
Sorry for the late reply. I have had problems with my T56 and I wanted to share so as to possibly help you. It has been rebuilt twice because of shifting issues. Very “toothy” shifting from first to second and second to third. Went to three local tranny shops and they all had different answers. Tremec advised to index the trans/bell housing. Apparently a T56 only has .05 tolerance and must be indexed and shimmed to get within tolerances. Looking at my bill for the starter it indicates that it is a Powermaster 9502. I used the bell housing from the T56 and we replaced the flywheel. Please check that the starter I have listed will work for you before you purchase. I’m not sure if the mechanic was required to drill the block but I don’t think so. Having said all that, the car will not start when it is warm (180) so it is in line at a local shop to be given a once over front to rear to include engine and tranny pull to get to the bottom of multiple issues.
All the best
Jim
 
brushwolf

brushwolf

Well Known Member
Thanks for the reply Jim. Hope the new shop gets the issues resolved. I intend on using the original T56 bell also and crossing my fingers on GM's work on that being in spec. I know that with aftermarket bellhousings they always recommend the indexing to make sure it's centered.

Did you have to modify the floor and if so got any pic's? I'll look back on the thread to see if there were some and I missed them, because Ihave been off here for awhile as mentioned

Thanks, Mike
 
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