thebuffalo

Okay right now I have my bottom end of my 350sbc put together, it is a pre 86 4 bolt bored .060 over , 190cc aluminum heads ,link to heads here, stock replacement Eagle Crankshaft, summit racing brand stock size rods, 4.060 flat top pistons.

Few questions on what I need from here to achieve a low boost (4-6psi at most) setup.

1. What thickness / material head gasket should I get?
2. How well does a turbo work with a carb'd 350, 170gph mechanical fuel pump
3. Which would be better for low-boost? Turbo or supercharger? I know superchargers are parasitic so I was wondering if a low boost setup would actually give me a loss in power?
4. Should I just wait until I get a new block to work with and go all forged then boost?
5. Anybody have any idea what my deck height would be? or how I could go about mathematically figuring it out?
6. My goal is 8.5:1 N/A comp so that I won't have any problems with boost, if my deck clearance is 2.42mm and I use a .040in thick head gasket, I can achieve 8.5:1. Is this a good CR to have for going boost?

Orr89RocZ

iTrader: (20)

Are pistons in the hole below deck? If so by how much? Most kits are setup for 9" deckheights while stock unmachined blocks are 9.025". If its below deck .025" and block hasnt been decked id go .020-.028 gasket. If pistons are even with deck run standard .039-.041" gasket.

Flatops and 64cc heads will give around 10 to 1 comp with standard piston to head clearances. Thats ok for few psi. Dont need to drop comp. just run good 93 oct gas and keep timit conservative. 2 steps colder than stock atleast spark plugs. Id run ngk heat range 7's to be honest. 6's may work.

If you had hood clearance a simple roots 142-144 type blower would work good. But needs probably 3-4" cowl hood to clear. Else go single turbo, something around a T70 perhaps. T4 .96 a/r hotside.

Not to familar with the hp limit on 170 gph pumps i would need to do some estimates on ho capability but a mild 355 on 6 psi should get 375-400 whp. Bigger cam more power. Its not hard to get 350 whp all motor so a 6 psi adder should net good gains. Fuel pump needs to be rated for likely 550-600 hp to be safe

thebuffalo

This is the part that really confuses me, I had my block bored from .030 to .060 and I'm not sure if they did any "deck work", I know the stock deck clearence is 9.025" but from what I know the clearance is the distance between the head and the top of the pistol at its highest point? so is the 9.00" is the distance from the crank to the top of the "deck", or the top of the piston at its highest point? Then would the "clearance" be the difference?

I've been looking at your 400 TT build for a little over a year now, I love the way the turbos poke out of the side of the cowl... really nice eyegasm.

My math was wrong, I guess if I use a .040" thick gasket and I have .025" of deck clearance I will have a CR of 11.28:1, much much higher than what I am hoping for.
With a .120" thick gasket I would have 8.94:1, I can't find any thicker gaskets than that though, is this a good CR?

Orr89RocZ

iTrader: (20)

Piston at top dead center or highest point to crank centerline is usually 9" on sbc's, for most rotating assemblies. Now it depends on piston compression height. You can put different height pistons to get different lengths. My motor is 9.020". It uses a taller piston than normally used.

Now deck height of 9.025" is from crank to top of block deck where head gasket sits on factory motors. So you can see how pistons will be in the hole if they are only 9" from crank and head deck surface is 9.025" away.

Thats why when you machine a block you have it decked to your rotating assembly so pistons at highest point are flush with block. Allows use of thicker standard size gaskets for best sealing. Now some guys deck so pistons are .005-.010" in hole to allow for more decking of block in case of another rebuild.

You just need to pull heads and find piston tdc and measure how far down they are to determine what gasket to buy.

fasteddi

iTrader: (2)

I know you need to measure some things in your current block/engine but personally I wouldnt get a fresh block and build it for boost unless youve boosted a car before. Being that your going with a blow through set up(carbed) I would experiment with what you have now if the compression is decent(9.5:1 or under) for low boost.

I think turbos are easier personally. But I am bias since Ive never touched superchargers. There is so many turbos out there, you can size up the right size you want for a certain amount of Boost vs. Hp. vs Rpm. Look into compressor maps and you'll see what a turbo is best for. Let me add though that boost(psi) doesnt have much to do with power output, at least I can confidently say that for turbochargers. PSI is just resistance. So one turbo set up may push 12psi and make the same exact power to the crank that another turbo needed only 8psi to make. Im no expert at ALL but there is alot to figure into effect when it comes to turbos and what works best for one engine compared to the next.



A tip that I think is important regardless what you choose to do:

Make sure to get a wideband o2 sensor on that car. I don't care what others say about them and that you "may not need one" Its a must in my mind and anymore they are very affordable.

A timing retard master, or somthing like that, would be a nessasity also since you wont be having a ecm to do it for you. Compression over 9.5 or so with low boost is ok but the timing will have to be more and more conservitive the higher psi or comp ratio you have.

I cant say it enought... tuning the car is what (90% of the time) will either let the car run great or blow it up in a split second. Only takes one good hicup (detination/ and or lean spots) and you could have real problems. Tuning tuning tuning!! Very important

thebuffalo

Going to measure this when I get off work and order me some gaskets.

I don't know how I would setup an o2 sensor, I ripped my ECU out and removed all of the wiring that wasn't needed. I would need a standalone I'm guessing. But when I run the low boost I also plan on running water injection with the standalone ecu for it. I watched a 10 minute video about water/meth injection and was convinced that I need it.

fasteddi

iTrader: (2)

Man, thats what i like to read!! I have alky injection and its a awsome thing. Easy as cake to install also and help keep that detination to a minimum. Its something I wish I would have gotten right off the bat when I first turboed my car.

You can get a stand alone but there is other options out there if you want to look arround. Id say for a stand alone, a megasquirt, is a common ecm that alot of ppl on these forums have played with.

A wideband is very very to set up also, easier then the alky injection in my mind.
My DIY-SLC2 wideband controler wired into my ecm but there is also another way you could use something such as that. This controler gives you the option to literly record almost any sensor on the vehicle and also datalogg right off of the controler onto a lap top. Its read only only information but it also is nice for ppl that have non ecm cars so that they can still read real time information and then later on read it back when they want to. 14point7.com the site that has that specific controler/02 kit.

Alky injection/wideband o2 sensor are definitly must have items if you can afford to do it all. Treat the alky injection as a saftey device and you will have much more confidence in your car preforming correctly.

Im just laying out some of my ideas since Im a person that likes to look at every possible choice first before making a clear cut desision. So I hope that they help a little from my stand point.

Orr89RocZ

iTrader: (20)

Simple wideband doesnt need a computer. You dont even need to log it vs rpm if you are good enough at watching rpm and air fuel at same time. I tuned my old 383 like this and still do it on turbo car sometimes when i need to make global changes because its way off or something.

I run innovate lc-1's in my cars and they work great. Just need power source and ground then run signal wires to the G series gauges they offer. Complete air fuel monitoring automatically. Permanent install. If you want removeable hand held i think you need to go FAST wideband kit or innovates lm2 unit