a lot of help please, Jody or super charger guys.....

[nvawgn]

i'm in the process of getting a motor built for the wagon but i will eventially want to throw a super charger on it.
so my question is, if you were building a supercharged motor, 383 or 406 out of a 350 or a 400 gm block( i can not afford an after market block) to run on max 10lbs of boost on a primarily street driven car, what kind of facts do you need to know before starting your build?
i'm trying to figure out what kind of bottom end i need, parts and pieces, splayed caps, super light rotating assembly vs. regular 4340, 6in rod vs. 5.7in rod, which piston, bearings.

please tell me the info you need to know, thanks

[camcojb]

Originally Posted by nvawgn

i'm in the process of getting a motor built for the wagon but i will eventially want to throw a super charger on it.
so my question is, if you were building a supercharged motor, 383 or 406 out of a 350 or a 400 gm block( i can not afford an after market block) to run on max 10lbs of boost on a primarily street driven car, what kind of facts do you need to know before starting your build?
i'm trying to figure out what kind of bottom end i need, parts and pieces, splayed caps, super light rotating assembly vs. regular 4340, 6in rod vs. 5.7in rod, which piston, bearings.

please tell me the info you need to know, thanks

splayed caps are nice depending on the block, but not necessary at that level. I would definitely do ARP studs on the bottom end. On the 400's I've done I do a partial block fill which helps keep things from moving, haven't had any cooling issues either.

As far as a rotating assembly I've had good luck with the more reasonably priced Eagle and Scat 4340 stuff with good rod bolts, at that power level. I do like to use a designated blower piston with a thicker top and lowered ring pack. That also usually gets me away from 6" rods, unless they fit without getting into the oil ring. I like the plasma moly rings, file-fit, so I can get the end gaps right and they seat immediately. The Eagle/Scat cranks generally need H bearings (I use Clevite from Speed Pro, TRW, etc.), made the wider fillet radius in those cranks. They're harder than the standard P clevites, and work great in a performance application.

I would recommend a blower-specific cam also, with the wider lsa like 114 or so, as they'll build boost faster which is what you want in a good street build.

Jody

[Blown353]

First piece of advice I learned, although you can't always do it: make up your mind up front and build it ONCE. It's much cheaper!

Anyways, other pointers:

Piston coatings are your friend-- especially with boost.

Get the head & block smooth enough so you can run MLS gaskets. Most out of the box heads have the required surface finish and a machine shop with a decking machine in good condition with a knowledgeable operator will be able to put the required surface finish/flatness on the deck.

A BBC crank snout is a good idea. The BBC snout will take the loads of the supercharger much better. It's a small cost up front. Most of the time SBC crank snouts don't break, but it's much cheaper to buy a crank with the BBC snout up front rather than have an "oops" down the road and then have to pull everything back apart for a new crank.

High-quality fasteners are a must.

For crank & rods, at a reasonable price point it's hard to beat Scat. Scat is my first choice as they tend to have better machining quality than Eagle. A lightweight rotating assembly has all the same benefits it does in a naturally aspirated deal, so if you have the bucks go for it... but avoid the super light pistons.

Remember to run wider ring gaps with boost. Some guys forget. Most of the time you can get away with it... worst case you'll pinch a ring. You might also want to consider an extra .0005" piston to bore clearance. Keep the quench tight as it will help avoid detonation.

If it's going to see road-race duty then I'd highly recommend modding the block for piston oil sprayers. Not really needed for street duty but they do help.

Buy as much head as you can afford and pay very close attention to I/E ratio and exhaust port flow. If it's going to see prolonged hard use then I'd also recommend inconel exhaust valves.

Work with someone who is very experienced with supercharged engines and have them spec out a cam grind for you. There's a lot of power to be had or lost in cam selection. A good guy will want to know EVERYTHING about your specific combo before making a cam recommendation. If he doesn't pester you for lots of information, you're probably talking to the wrong person.

Induction: Assuming you are speaking of running a centrifugal supercharger, if going blowthrough carb do not skimp on the carb or the hat. There are many hats on the market. Only a few work well. It's a bit simpler going with EFI, but you have a couple options. Tunnel-ram style (holley stealthram, custom sheetmetal, etc) or a modded single plane with either a 4-hole TB or an elbow and a monoblade. All work well. For price/function, the Holley Stealthram is pretty hard to beat, it's cheap and works well. For a good cost/benefit ratio it's tough to beat a Victor Junior EFI with a Wilson Elbow and a Monoblade TB and from what I gather talking to guys the single plane/monoblade has very even airflow distribution.

Fuel system: remember to allocate enough money for it. With either blowthrough or EFI you're looking at a return-style system.

Finally, you didn't mention exactly what kind of supercharger you had in mind.... that will influence the target compression ratio. For instance, a good "street" compression ratio for a centrifugally supercharged engine is in the 9.0-9.5:1 range. It's a good mix of off-boost combustion efficiency and is still low enough to tolerate decent amounts of boost. I'm just over 9.25:1 and run 15.6 psi of boost.

[nvawgn]

thanks so much guys, a lot of good info there. i have never thought there was that much difference in building a SPCD engine but wow, that is the exact reason i wanted to ask before i jumped in. right now i am looking at different machine shops around the way and my budget seems to be right around 3k for the bottom end, so if you can recommend someone that you know that has built these motors with the specs you are talking about please throw em out there.
i have been talking with Gmachinez and he has been very knowledgeable and helpful and even pointed out i should ask the both of you guys what you think i should do. i don't know if i mentioned that this motor will not have the supercharger on it right away, it maybe a few months before i save enough to put it on there but i plan on using a procharger, the D-1SC seems to be the one a lot of people use but i could probably use some help in that area as well. am i out of the ball park for 3k on the bottom end for this build, oh and how about ignition management can you suggest something?
thanks you guys again....