tbanzer

I currently have a 502 mag with an intercooled vortech supercharger installed. Motor runs flawless with updated springs, head gaskets and Inconel exhaust valves. I came across a 540 in pieces very low hours no real reason to take apart other than the guy liked taking things apart. Currently has scat crank, crower rods srp pistons as near as I can tell 9-9.5 -1 internally balanced. Dart aluminum 320 heads as near as I can tell they are from Champion machine and were from 1999 vintage only ports matched. I am thinking 8-8.5-1 would be a good compression ratio. I am looking for 750 to 800hp with mild boost on pump fuel. I would like to keep the 502 mag intact other than using the supercharger and accessories.
1st, how much difference in piston weight would require rebalance thinking 5600-5800 rpm red line.
2nd mechanical or hydraulic roller cam.
3rd should I ditch the MPI for a blow threw carb or some other form of fuel injection.
4th I am looking for a turn key low maintenance, something that should run for a few hundred hours before valve train issues.
5th Am I being realistic.
Thanks

mcollinstn

Realistic? 800 hp on pump gas with several hundred hours of reliable valvetrain operation is only realistic if your budget is fat enough to include expensive exotic items. A more realistic goal would be 800hp on pump gas with a scheduled tear down and inspection and replacement of at least lifters and springs at 125 hours. You can do that with good "normal" parts.

You need to decide what bore you will be reassembling with. Existing bore, or next over? Then double check your crank stroke. The 320's came with a couple of different chamber sizes, so you'll need to know what you have, and you need to know your piston-to-deck ht before you know what CR you currently have, and you'll need to know those to be able to target the correct piston also. Be sure to plan on setting your piston-to-deck ht to allow between .035" to .040" of squish ht.

Before you start choosing pistons, you need:

Bore (cylinder bore, not piston diameter).
Stroke
Piston to deck ht
Head Gasket compressed thickness
Head Gasket Fire Ring diameter.
Combustion Chamber volume (measure it since any decking will change it).
Piston factor (add or subtract cc).

A "9.5:1" piston is an approximation on a specific bore/stroke/CR and small variations affect the end result.
Tight squish is very important for whatever combo you end up with.

A 540 with Dart 320 heads will certainly support the HP levels you are after. They flow well all the way to .750" lift.
300 hours on a 5800 rpm valvetrain with over .650 lift is not really feasible. It can be done, but you're gonna have to throw a lot of money into stabilizing the valvetrain, getting exotic springs, and running spring coolers. Tossing in fresh "normal" springs every 125 hours is going to be cheaper and make more sense.

How easy is it for you to pull your valve covers and adjust a mechanical cam? If it's easy to do on your rig, then run a solid roller. If it's not easy on your rig, run a hyd roller and plan on replacing the lifters when you replace the springs. The lifters should still be good enough to sell to the kid down the street for his Chevelle.

ANY piston change, change from iron to moly rings, etc SHOULD get a rebalance.
SCAT cranks can have weird fillet radii on the journals. Make sure your bearings are clearanced accordingly.

what SIZE Vortech do you have? and what Intercooler do you have? Both of those pieces need to be larger than the "base units" to support 800 hp for any sustained periods of time.

the MPI flat out WONT flow enough to support 800hp regardless of how much boost you cram into it. Carb or other EFI, that's your choice, but you'll have to do something there to get the numbers you're after. These days, you have a lot of price effective EFI options to choose from. A blow thru carb works great with a supercharger, but if you aren't carb-savvy you'll end up with close to a grand in a carb once you've purchased it, paid somebody to modify it for blow thru, and tuned it on your motor. With the EFI you just keep tweaking the map until you have what you want. No need to turn a wrench once it's installed, just plug in a laptop and make changes.

kennyo

I've got 920hp with the MPI set up. Heavily massaged lower plenum,modified fuel rail and bigger injectors, 8 pounds of boost. THe ol "few Hundred hrs" is where you're going to come up short! Good seeing you spreading the knowledge again Mr Collins

tbanzer

Thanks for the information guys. Im getting the information on the supercharger and intercooler to see if it will support the boost needed first of all, then Ill decide if I will mod the MPI to flow enough air , but I am leaning towards a blow through carb. I see there are some applications where the carb has a snout on it and others where use an enclosed box is used.

Unlimited jd

iTrader: (5)

Use the mpi it's 2014 not 1994. You already have it and need minimal upgrades to keep using it. You want turn key reliable? Efi is a nice step in that direction.

tbanzer

Well acording to Vortech the supercharger will support 850 hp and still be in its effficiency range and the intercooler is good to about 1000hp, good news. Still not sold on keeping the merc MPI and doing mods to alow it to flow enough for this applications but I will look into what is needed to get it to deliver enough fuel and air for this hp. I would really like to keep the MPI fully intact and not modified in case I want to back to the 502 in its current tune. Looking for ideas for fuel injection on a blow through application, or i will just go with a carb.

Black Baja

iTrader: (2)

With the right heads, cam and compression 750hp is very attainable with 540ci and a single carb. Just saying might be something to think about. This can be done with a hydraulic roller cam and give you many trouble free hours.

tbanzer

Thanks I have thought about that. My thinking was with a low boost application the camshaft would be quite a bit tamer and easier on the rest of the valvetrain.

TooLateVTEC

iTrader: (1)

A nice single plane intake with port fuel injection and a 4150 flanged throttle body is what you want for that HP and keeping your MPI intake for the back up motor intact.

We have a knock off victor jr intake on the Checkmate, T/B with a hat, running a M3SC ProCharger at 6psi. We're running megasquirt EFI on it instead of the merc stuff though, much easier and cheaper to work with.

What you're wanting power wise on pump gas isn't far fetched, IMO.

Any questions about our setup feel free to ask.

tbanzer

So your running tbi with a hat? Any concerns with fuel being pushed out of the throttle shafts, Did you get the base tune from a dyno secession and fine tune on the water with a wideband o2 sensor?