well, i finally rebuilt my 383 motor here are the specs
8.5 to 1 je forged dished inv pistons with steal plasma rings
forged eagle h beam rods
forged4340 gm 3.80 crank
main studs with head studs as well
cam is a 226/240 with 560/558 114lsa
fast burn gm heads 210cc with 1.5 roller rockers
accel superram with bbk 52mm throttle body
d1sc procharger no boost for right now, but i want to run a safe amount of boost on pump gas. no idea on the power this engine will make,but hoping 600hp.

 

I've hit 18 psi on 93 octane on my 9 to 1 401 twin turbo car so far and no problems with a richer tune and conservative timing. Its intercooled but no idea what my true intake temps are. I'm hoping once I lean it out it will still run on 18 psi.

You should be capable of 20 with that low compression, just my guess.

For 600 crank hp you will do that on just 7-8 psi. For 600whp, you wont need much more than 14-15psi I'm guessing. All should run on 93 octane.

 

thanks for fast response, i was thinking 10psi should be enough for the street, now i just need to plan my fuel system out make sure it is ok. my current setup is a tpis 340lph fuel pump with procharger booster pump and 42lb svo injectors, sound ok?

 

I think you should be ok at 10 psi. Depends on how much extra voltage your boost-a-pump gives, it should beable to provide 16-17 volts. I think most single 255 pumps are rated to 550-ish whp which you may be near with 10 psi. Being a 340lph pump, racetronix advertises these for 600+whp so you should be covered.

 

The GSS340 is a 255LPH pump, it's considered the "high performance" version of the same pump which has slightly better higher pressure characteristics (I would argue for 90% of applications you won't see _any_ difference). Racetronics takes the crimped on filter end and "machines" (as far as I can tell that means installs) the pump for the older style end that uses the older style larger filter inlet (the walbro GSS340 uses a smaller one), again, I don't know that there is any real difference performance wise but it makes it easier to use in late model setups. I beleave that TPIS's GSS340 is just the current model walbro with the small offset inlet.

that said, 255lph pumps have been known to push slightly more than 700hp with a boost a pump and perfect conditions, which shouldn't matter because your 42pph injectors won't come near feeding that.

the amount of boost you can run is nowhere near as simple as saying you have x compression, this cam... yep.... rpm, boost curve, cylinder pressures, exhaust, timing... all have major effects. That said you'd have to get things really wrong to have problems running 10psi from a centrifugal blower on that setup (of course, you probably won't see 10psi from the "10psi pulley" but that's another story)

 

If his pump is indeed that model then yeah it may not do more than 700hp. Racetronix has told me it wont do more than 600-650 crank hp and to do more you will need two.

Racetronix does sell a 340 LPH pump. LSx kits use one and they are rated to over 700hp with boostapump. Maybe even 800. I"m not sure what TPIS sells, I searched their site and do not see anything pumps on there.

 

Do you have a link or PN, I don't see anything on their site that isn't just one flavor or another of the 255LPH pump under different names (well, besides the assortment of 190LPH pumps that they also sell under half a dozen different names).

 

I thought the LS1 kit on racetronix's website was a 340 lph pump, as i thought I read on ls1tech it was. Its advertised to 700hp which is likely beyond a 255's range.

I know bosch makes a 320 or so lph pump but not sure its a drop in replacement. I'll ask Lonnie from Lonnies performance who does fuel systems. He's a dealer for racetronix and would know what pumps are available.

I've seen someone use a Denso made pump for a supra that flows 290 lph at 14 volts and 43 psi pressure but it isnt a drop in replacement.

 

the denso and bosch pumps are a bit of a mystery. There are people that claim that they flow quite a bit, but the flow tests that I've seen usually have them flowing less then a 255. I know of a local porsche race shop that sells these things as the hot solution to their customers but runs the walbros in their own cars (don't ask, I've had sooo many run ins with them, they seem to be pissed off with me for something else every time I have a reason to stop by)

Like I already said, there are a bunch of LSx powered vettes in the >700hp range with one of the 255lph walbros and a BAP. I've run a similar setup in blown mustang into the high 6xxhp range and it still had more, and my brother's 4 door LTD ran into the low 11's/high 10's powered by an eaton blown 302 with a 190lph intank.

Unfortunately, I haven't been able to test this back to back to work out he limits/finer details, but I think the trick is to not run too big a fuel line _and_ good sized fuel rails to buffer the injector pulses (My brother's 5.0 was running out of fuel with 1/2" aluminum lines, the intank pump just couldn't keep them full, but actually when we ditched them and put in 3/8" lines, and before that we couldn't get it tuned right with stock mustang fuel rails and 36pph injectors but just installing larger fuel rails made a BIG difference in tuning)

I know that I come across as rather opinionated at times, but between working at a speed shop selling this stuff (and knowing a lot of the owners of these companies by name), doing installs and custom work for a speed shop, having worked on/built a number of cars that have been in magazines and having a somewhat strange engineering background... most of that opinionatedness is just "this is what works, or this is what exists and I don't have time to mince words."

 

You are usually right with what you post. The math seems to back up your real world experience.

Voltage plays a big role in what a pump will do. Combine that with the engine BSFC and boost will pretty much give all that is needed for pump requirements. SEFI doesn't require a big pulse of fuel like batch fire does.

With low voltage, a bad BSFC, and high boost a 255lph could only support 400HP. With high voltage, a good BSFC, and high boost a 255lph could support 800HP. It all depends on the specific application.

 

What's interesting is that a ton of people are running the walbro with a BAP at 16 and 17VDC lately. I remember when the BAP first came out there were tons of flow graphs showing the walbros falling apart and cavitating at between 14 and 15VDC. THAT I suspect is the biggest difference between the older 255lph pumps and the newer versions of the GSS340 and the current version of it, the F20000169 (My guess is to get better response from the newer PWM, feedback controlled returnless fuel systems).

It's funny how many different companies sell the same pump under different PN's, when I was at the shop I used to always buy edelbrock's reboxed ones because I could get them for much cheaper than anyone else's unless occasionally I could get an airtex/master one (funny, they're a pump manufacturer and you'd open their boxes sometimes and find a walbro in them).

 

actually, here is one of them... running a GSS310 (another of the 255lph pumps) and a BAP in an '02 turbocharged vette and puting down some serious numbers (this isn't the one that I was talking about, that one is about the same vintage but running a rear mount):
http://www.streetfire.net/video/02-c...whp_162618.htm

 

the pump that i have is the tpis the biggest one, i thought it was 340lph.

 

Keep upping the boost till you hear detonation or smell coolant. Than back off some.

 

Hey where did you get your pistons for the 3.8 crank? I have a zz383 bottom end and would like to boost it, but i'll need a much deeper dish and forged ones at that. Also wondered if they come in a 4.005 stock bore for my block? Thanks a bunch!

 

I was going to get custom ones made from JE, but i decided not to go this way. I just bought a LSX 376 crate motor and plan to boost that. I got the motor cheaper than you can buy it anywhere else and it's new so thats why i went that way.

 

Yeah I hear that, it was the same for my zz383, couldn't pass up the offer. But I built it to be an all motor car from the start and milled my afr's to 55cc. Now i'll need custom forged pistons, oh well! Hope your lsx get finished, they're well worth the efforts!

 

I run 22 lbs. through my Ford GT (860whp at that level). 1026 whp on C16 and 29 lbs.

 

sig test

 

better get a wideband an take some of the guess work out of it .

 

Thats badass!

 

here are a few numbers from the Vbox

60-130mph in 4.52 seconds
0-200 mph in 18.65 seconds

standing mile at 226.2 mph

fun car

 

nice...