I know there are many folks who have done this and I’d like your advice and feedback on using a second generation SBC roller block in my 71 4-PSD Manual. Need to understand a couple of items before I move on:

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  1. Is the bell housing bolt pattern from the OEM SBC 350 4 speed manual bell housing the same as the second generation roller block bolt pattern?
  2. Since the 400 crank shaft requires an externally balanced flywheel, the change appears to require a 168 tooth 14” flywheel vice the OEM 153 tooth 12” flywheel. Will the 14” flywheel fit within the original gen I block manual transmission bell housing? Would the 14” 168 tooth flywheel require a different starter? It would seem that there must be a stand-off to accommodate the additional 1” in radius. Or is there a 12” flywheel that accommodate the external balancing requirement of the 400 crank?

 

Yes Yes Yes and not sure but I think no

 

71 has 168 tooth flywheel. 153 is for 6's and 283-307, atuff like that. it is NOT a 400 crank. it is a 383 stroker crank. 2 piece seal (flat tappet block) would use a 400 flywheel and balancer except nobody uses the short OEM 400 rods, so rods and pistons weighted differently. any crank or rotating assy or engine you buy, the person selling it will tell you which flywheel and balancer and/or add-on counterweight you need for his setup. and if they can't tell you, buy from someone else...
starters. the staggered bolt 350 starter (3510) has the drive gear cast into the housing farther outboard than the smaller flywheel (3664) starter nose. those are universal rebuilder's numbers...

 

OP
? what do you mean by "second generation sbc roller block" ??

fwiw Gen II sbc is typically the first appearance of LS motor and yes, all LS have roller But virtually NO LS parts interchange w/ Gen I or Gen Ie motors.

fwiw, an rpo L31 iron head Vortec motor from production Chev/GMC trucks with vin code "R" from '96-2002 are Gen Ie and their bellhousing bolt pattern is identical to any C3 block. BTW, rpo L31 is THE final iteration of classic sbc design.

Approx '86-'87 Gen I motors' blocks got a One-piece rear main seal to fit new style crank. The bolt circle/pattern on rear of crank became smaller and requires different flexplate/flywheel as well. Another major difference occurred same time is block's ability to receive OE Roller Lifters. Not all motors had those OE rollers but were capable of using them.

Starter: Regardless of year, 168T typically requires OE starter w/ Staggered mounting bolt pattern, while 153T requires OE starter w/ Straight mounting bolt pattern.
JMO, I do NOT like aftermarket starters which have no "Nose" to support flywheel end of shaft. No matter which starter, using its Correct starter mounting bolts is critical. I Do like starters like those Permanent Magnet Gear Reduction starters (aka PG260) which are OE on late model GM trucks.

All OE 400 and most cheaper aftermarket 383 are indeed externally balanced and use both an external balance damper & external balance flexplate/flywheel.

Many aftermarket cranks are available that are fully Internal Balance; but at a $ premium.

168T flywheel & ring gear should fit inside OE manual bellhousing.

The newer OE One-piece seal cranks are actually a "Hybrid balance" in that they use a Neutral/Internal balance Damper but its flexplate/flywheel has a small counterweight.

Suggest Don't source a block that'll end up with relatively thin cylinder walls once it's bored & honed. Do source a crank that say's it'll balance Internal w/ 6" rods. Along with that, choose appropriate rods & pistons. Also, DO choose pistons which require thin, metric ringpaks; ALL the OEM did so a generation ago.

FYI, most cranks which specify "for 6" or longer rod" will balance Internally. This because the crank itself has larger diameter counterweights (than stock) which accommodates locating weight where it's needed. FYI, when balancing a motor, if machinist has to ADD weight to crank (typically Mallory Metal aka tungsten) the job cost will cost much more. Warning: bargain cranks often require lotsa Mallory and thus are No bargain. It's typically much cheaper to remove weight from crank (drill bit) than to add it (drill & press-fit tungsten slugs). The better cranks typically specify their "bobweight" so you choose rod & piston weights accordingly. Study up; limit failed/poor choices.

JMO, you can make one helluva sporty street motor from a roller block; without a stroker crank.

 

Sorry Gen 2 SBC is the '92 LT1, not the LS series

https://www.motortrend.com/how-to/cc...2-small-block/

 

true that,
sorry, forgot about those as their reverse flow & limited parts interchange ability places them low on my radar. But you're quite right.

 

If this is a factory roller cam setup then it will be a 1-piece rear seal block. From the factory, the flywheels on 1-piece rear seal small blocks were all weighted. A 383 using a 1-piece rear seal could go either way for the flywheel, weighted like factory or zero balanced.

You should be able to find either size of flywheel to fit this engine, weighted or not. I expect some of the GM 1-piece rear seal applications had the smaller flywheel and you can find a stock replacement. I know the LT1 did, but it had a pull clutch and I'm not sure a standard push clutch pressure plate would bolt to it. If there isn't a stock application, then the aftermarket has you covered.

https://www.summitracing.com/parts/p...make/chevrolet

 

so will this Pioneer FW 148 ... it's Not SFI but plenty of these used in CT racing ... especially x602 motors
https://www.summitracing.com/parts/pio-fw-148

so will this LuK LFW 130 ... it's Not SFI but plenty of these used in CT racing ... especially x602 motors
https://www.summitracing.com/parts/luk-lfw130

both are modern-day equivalent of 153 Tooth L88 flywheel

 

I'm replacing a L48 with a ZZ383 GM crate motor. The only thing needing to be changed is the flywheel. Mcloud makes an exterior balance , 1 piece main seal that bolts right up. I bought the whole clutch setup from them as well and had the PP balanced to the flywheel. They even come with a new throwout brg and all the bolts. Everything else will bolt up from your old 350. I went with solid motor mounts and a new trans mount.Using the Zbar clutch linkage, and the 4 speed Muncie

 

repeating what i said earlier. do not buy a 383 crank or rotating assy or short block without the builder-supplier's balance instructions. absolute best way is get rotating assy, flywheel and balancer all balanced together by builder.

 

As stated...you have to be very careful here. A "roller" block has a one piece seal and a weighted flywheel but this does not mean it will be weighted for a 383 crankshaft although most are external. ALL external cranks should and usually are balanced with the damper and the flexplate/flywheel. In fact....Scat and Eagle offer the pair in a lot of their rotating assemblies. There is a reason for this. With the weight that far out from the centerline....there is a LOT more chance of the manufacturing tolerances throwing off a "Nominal" balance......when I balanced cranks for World/Mitchell....I could set up and input the specs to be external but without the actual weight on it, it was a crap shoot of how close it was and they tried to keep the balance to +/- 2 grams of the bobweight (balance) card.
Pioneer is the only outfit that makes a affordable external 400 flywheel......what it is for in the OEM is a mystery...maybe 71-72' Chevy truck....but it works. If going with a stick shift, it is in your best interests to buy a rotating assembly unbalanced and have it balanced locally with your actual parts.
All GM small blocks are interchangeable for bolt pattern......and even a 283 can be made to work in a later model Silverado with shelf parts......but there are major differences in these parts.
I do not like the 153 flywheel/flexplate.....for the simple reason that it is much harder for a starter to turn. A 168 with a Quality mini-starter will last a million years. Most aftermarket starters have provisions for both 153 and 168 at the mount plate but know if yours is staggered or straight across.
A 383 crank is its own animal......they are forged/cast and machined as a 383 crank and nothing else. I believe John Ligenfelter pioneered the idea of turning the GM 400 crankshaft down to 350 main journals.....the aftermarket makes them now as their own part.
OK....so you have to do your research...the info is out there and easy to find.

Jebby

 

Not to hijack, but I am doing the same thing. Using a Vortec block.

 

You'd have to be an idiot engine builder to build an externally balanced 1-piece rear seal 383 that didn't either use the standard factory balance weight on the flywheel or a zero balanced flywheel, which are also readily available. Same having to be an idiot comment would apply to building a 2-piece rear seal 383 and not using either the stock factory 400 balance weight or zero balance.

Of course, not all of factory weighted flywheels will actually have the same balance. Neither are all zero balanced flywheels actually zero balanced. But that's another issue.

 

and stock 400 flywheel is a toss-up. i bought a 400 flywheel for my boat. same casting number as 454 wheel. so he gave me a 454 flywheel saying it was 400. boat shook like a leaf at idle. and the correct 400 wheel is balanced for 4.565 rods and big heavy pistons. and matching balancer.

 

The point I was making was that it is easy to put the neutral or the weighted one on the wrong balance and also that ANY external balanced assembly should be balanced with the flexplate/flywheel to be used.
And as far as idiot engine builder go.....they seem to have all moved here......one guy who has been doing it for 40 years has no business flipping a machine on......and I make sure that is known to everyone in the area.....at least those who have not been screwed by his idiocy......He "balanced" my 406 crank without the bolt on flywheel hub weight and welded weights to my clutch pressure plate. I wasn't sure why he wanted the clutch......but I didn't want to argue. When I got the **** home I realized what happened and had to take it to another shop to balance. I was going to flog the MF'er but cooler head prevailed......
This sure isn't the Motor City

May have been the same casting number but external 400 and 454 flywheels/flexplates do not have the same weight......they will use the same casting but drill them different for the two engines.

Jebby

 

Pioneer is great, but not only affordable flywheel that fits sbc 400 ... Perfection has both heavy or light and both 153T or 168T

My best take on why the 400 external flywheels are offered... they're mostly for the many folk who build external 383.

fyi .. OE sbc 2 pc rms OE 350 cranks which use a internal aka neutral flywheel/flexplate actually have a counterbalanced flange; seems that's why the flange has an irregular shape. A little bit of mass so close to centerline makes a large difference in balance factor.

 

Exactly, and that balance weight in the flange was replaced by the flywheel weight when the flange was made round and smaller for the 1-piece seal.

 

Exactly, and that balance weight in the flange was replaced by the flywheel weight when the flange was made round and smaller for the 1-piece seal.

 

Lingenfelter was big on stroking the sbc in the 80s/90s stil have his book on recipes but it was Joe Sherman that really made them popular in the 70s I believe.
Extra ci sure doesnt sound like much but sure runs way better!

 

Ok.....so now the weight is on the flywheel. On a 2 piece, the weight is on the crank hub and there is a weight way out on the flywheel/flexplate on a 2 piece external 383. Nobody makes a flywheel/flexplate they accommodates this extra weight.....so......the extra weight is cast into the rear counterweight. For this reason.....it is extremely important to use the customer flywheel/flexplate on a 1 piece and that the weight is in fact there on the 1 piece flywheel. Make sure you get a balance sheet from the manufacturer AND the flexplate/flywheel that they used to balance it.

Jebby