i got a lt1 t56 out of a 95 camaro and the flywheel that came with it. it looks like it’s an externally balanced flywheel.
can i use that flywheel with my 2pc main 400 sbc, or will i have to buy the centerforce flywheel that everyone it talking about? #700173

i know that the lt1 is a 1pc main so im just wondering if it’ll work. i read somewhere that it’s internally balanced or that the front was internal but the flywheel also helped with balancing it.


thanks i’m new to this so any response helps.

 

A flywheel that came out of a 95 car will not fit the 400. "Balance" is the least of its issues.

Here's what a 400 crank looks like. A 305 or 350 one from before 86 would look the same.



ALL SBCs other than the 400 are INTERNALLY balanced, even though a small amount of the INTERNAL weight was moved to the flywheel in the 1-pc RMS motors. All 400s had the 2-pc rear main seal, with the funky crank flange. That flange was the rearmost INTERNAL balance weight for 85-back 3.48" stroke cranks. (267, 305, 350) In 86 the rear main seal was changed to the 1-pc. The crank flange has to be round as a result. Because of this, that last little bit of INTERNAL balance weight that was on the older style crank, had to be moved to the flywheel. The engine is STILL "internally" balanced, just, that little bit of INTERNAL weight doesn't look like it. Butt even if it would bolt to a 400 crank though, it's NOWHERE NEAR enough to make up for the 400's EXTERNAL balance requirement.

The 1-pc round flange that the 95 motor had is the same as the 86-up 305 & 350. It's also considerably smaller, and has a much smaller bolt pattern, than the 400 crank. So that flywheel won't even bolt to a 400 crank.

Yes you will need either the 400 "conversion" flywheel (that is, one for the LT1 clutch design butt with the right center to bolt to the old 2-pc seal crank), or, get a regular non-400 "conversion" one and have it unbalanced to the stock 400 balance spec. Which is, approx 24 - 25 in-oz, with the heavy part exactly aligned with that dowel pin, or the light part, where balancing holes will be drilled, directly opposite it. It takes about 20 ½" diameter holes about ½" deep around the edge of the flywheel and centered on that spot to create the correct counterweight. There's also a "pork chop" kind of thing that bolts to the crank flange to give the right weight butt I'm personally not a fan of that.

 

thank you very much this answers all my questions

 

700173 centerforce
Spec sc66-400
McLeod 460370 with weight kit

 

Then of course, you'll have to deal with the starter bolt holes.

 

I used a LT1 flywheel on a SBC 400 back in the day. It can be done, but doing it is a personal decision.

I took the flywheel to a machine shop had them perform two machining steps on the hub, to make it match a "2 piece RMS", crank hub. This included boring the hub ID to match the 400's (or any 2 pc RMS) hub center, then had them drill new bolt holes, staggered to the original LT1 (1 piece RMS) crank bolt holes which left enough meat around the new bolt holes, that *I* was comfortable with it. Finally to address the balance issue, I had the machine shop lop off the counterweight in the LT1/1 pc RMS flywheel to neutral balance the flywheel. Thus, essentially making (at that point) a '86>earlier, two piece RMS, 153 tooth, LT1 flywheel. To address the "400 balance" part, I bought and installed THIS BALANCE PLATE, from Summit racing, and installed it under the flywheel. Total cost was <$100...or about $350+ cheaper than the options above. Machining was $80 plus the balance plate. It worked great, for me.