Hey all,

I'd like to get everyone's opinions on buying a forged rotating assembly for the 383 I'm building. First off, the major pieces that I have so far are:

a 1991 L98 roller block;
AFR 195 angle-plug heads;
HSR intake;
(and probably a suitable Comp cam...)

And here's what I was thinking of buying to work with the above:

Lunati "Sledgehammer" crank, 1 pc rear main seal (LUN-CJ115AN);
Scat 5.700" H-beam con rods (SCA-6570021);

and then (perhaps like a dummy), I figured I'd get with whoever I buy the pistons from -any suggestions there?- and give them the outline of what I'm trying to do (a forced-induction 383), and let them suggest which of their pistons to buy. (Especially since I haven't yet taken the block to the machine shop, & don't yet know if it'll need an overbore, decking, etc.)

But, today I'm reading the latest issue of CC (which just happens to have an article on building a stroker), and they suggested buying the whole rotating assembly at once, rather than piecing it together as I'm doing.

Now I definitely understand the issue behind having tolerances stack up one way or the other, especially when parts are from different vendors, but how advisable would each of you say this is? I guess I kinda figured that by this point, building a 383 SBC is such a common thing that you've really got a pretty good shot at having everything work together - or is that a foolish assumption?

I've nearly saved enough to get that crankshaft, but if I have to save up for the whole assembly, it's going to take a fair bit longer. And, personally, I really prefer to buy American-made products over Chinese crap, so that pushes it out a bit further...

Is it really that much of a good idea, that I should just "suck it up" & get the whole thing as a kit? And does anyone make a kit with coated pistons/bearings/etc.?

Thanks guys!

 

You will almost certainly have to get your block bored and decked. The only way you wouldn't, is if it's a brand-new block, and all of that has already been done.

Either have the block decked to a spec (for example, 9.000" ± .001" on all 4 corners); or wait until you have your pistons, and deck the block to match. You pretty much HAVE TO finish-hone the bores to match the actual pistons you intend to put in each bore.

As far as parts selection and US vs China stuff, I'm not going to get into that. I think you'll find that more of the raw forgings than most people would like to admit, come from China these days. Scat rods and cranks for example are said to be forged in China but finished in the US. Eagle may be similar. Since Holley bought Lunati, I no longer have any knowledge of where their parts come from. Given the economics of this hobby, and the way most people will make their parts decision based on even very tiny differences in $$$ (note the number of posts on here about "where's the cheapest place to get x", or "what's the cheapest x I can get"), the cheapness of Chinese labor is a fact of life. But in the end, you get AT MOST what you pay for, and that only if you're lucky; so if you buy the cheapest, what can you expect to get?

There's no technical advantage to buying a "kit". That's just somebody taking little boxes off of the shelf and putting them in a big box for you, instead of you doing that yourself. Sometimes there's price advantages though, if somebody buys a large number of something and standardizes on it, they can sell it for less than if every one they sell is different. Tolerances ALWAYS stack up, no matter who puts the parts in the big box or whose name is on the little boxes. Only an idiot or a moron, or maybe even an imbecile, would just buy some stuff and jam it into a block without checking; especially stuff of non-stock dimensions.

 

Thanks Sofa, it's much appreciated. I wasn't aware that I'd most likely need to get the block decked before buying pistons, but I knew I'd have to find out what kind of overbore might be needed.

The rest of what you've said pretty much tracks with the way I understood things, except for when you said...

OK, the way I understood it (and was planning on doing it) was to

1 - acquire most of the parts needed to build the engine;
2 - then send the block to the machine shop, where they'd check it out, & see what kind of overbore (if any) would be necessary to make the cylinders "true";
3 - order the pistons (or have the shop do that) to match what they discover the block needs...

So if I'm understanding you correctly, the above is still valid, but I'd need to make the decision on piston brand/type & rings before they can perform the final bore machining?

Thanks again!

 

Yea, that's the catch 22 right there;
you can't buy pistons until you know the size you need. You can't find out what size you need until the machine shop has the block. They need pistons in hand to finish hone the block. So it's tricky to buy the pistons yourself, since the machine shop will want to sell you pistson (generally at a decent markup...).

If you want, buy yourself a micrometer set, and measure the bores, then you can know what overbore is needed, and you can buy all the parts, and let the machinist do it all up in one fell swoop.

I installed the crank and 2 pistons, then checked deck height. Then you can remove those pistons and crank, and bring the block back and say "deck it .017" or something like that.
Or you can say "I'm buying 1.54" pin height pistons, so with my crank and rods, i'll want to deck the block to 8.980" if I want it to be "zero decked".

Then still measure it as you assemble it, just to be sure nothing got fudged.