strokednsprayed408

iTrader: (3)

I just ordered a 408 iron block from TSP and I am not sure which injectors to go with. I have a 100 shot of N20 now but I plan on doing a much bigger shot later. Would 30lbers be sufficient for a stroker w/ mild spray, or should I go bigger?

EPP

iTrader: (22)

I would indeed go with the 42# injectors. Bob

RedHardSupra

iTrader: (1)

AT LEAST 42s, don't 408's run over 500rwhp without any spray assistance?

SSINFUL

...in an LS1?

What are they rated at (how many BAR: 3?)? Few injectors are rated at the LS1's higher fuel pressure and acquire different characteristics at that pressure.

I'd about bet the SVO's are 42 LBers at much less pressure and become 50+ in a LS1.

NemeSS

iTrader: (127)

I was also wondering what the 42 lb. Ford injectors were rated at what pressure in psi/BAR,does Ford rate these injectors on the cobra or other cars fuel pressure, i think its 43.5 psi, not sure , seems like they would act much bigger with the stock LS1 58 psi, right?

bshell

iTrader: (24)

The SVO 42s (and 30s) are rated at 43.5psi and will give you more #/hr at ls1 fuel rail pressure. The sticky at the top of this forum has a link for the relevant fuel calculations. Here's the formula for calculating new flow rates:
sqrt = square root

sqrt(New Pressure)/sqrt(Old Pressure) X Old Flow Rate = New Flow Rate

SVO 42s would be:

sqrt(58)/sqrt(43.5) X 42 = 48.497 or about 48.5#/hr

As for the the original question in this thread...I would think you would run out of injectors spraying more than a 100shot with 42s. Unless you will be running a wet shot. Putting the car on a dyno NA first to get some baseline #s would help you determine what size injectors you need for spray.

strokednsprayed408

iTrader: (3)

Thanks for the advice, bshell makes a good point. I plan on using just a 100 shot dry for a while and I've heard that 30#rs would be enough for the 408, that would make sense taking the ls1 fuel pressure calculations in to consideration. I'm still not sure if I should go w/ 42's just to be safe for the future. Would too much fuel press hurt me at all? Also would a N/A 408 run on 28lb's?

RedHardSupra

iTrader: (1)

Josh, i'd go with 55s if not 60s for your application, 408s have gone as high as 560rwhp+ and 500rwhp is about 80-85% duty cycle (depending on rpms mostly). so could you get away with 42s? probably, but think about it: do you want to be WOT at 6000rpm+ and find out that 42s are not enough? especially when spraying? if you can afford a 408, you can afford another 200bux for big injecotors, so don't destroy your expensive motor with cheap injectors.

bshell

iTrader: (24)

If you are using a dry shot, you should not be considering 30s at all.

The 408 will run on 28# injectors. I would use the 28s to drive the car directly to the shop that will be installing the 42# or bigger injectors and not go over half throttle.

The fuel injectors are open or shut valves. They do not affect fuel pressure from the pump. Big injectors can be made to idle as smooth as stock, its all in the tune.

Will you be using the stock fuel pump? If your pump can't supply the pressure, the biggest injectors in the world won't save the engine. On a 408 with a dry shot you should probably use an aftermarket pump with a hotwire kit.

SRPerformance

346 with 28lb injectors making 402rwhp and 100% duty. listen to redhardsupra

strokednsprayed408

iTrader: (3)

I'm thinking 42#rs, I will just run the car N/A for awhile untill I put a 12 bolt in, and when I do the rear I'll go w/ a fuel pump upgrade. I want to do a direct port n2o 150- 300 eventually so I'll just hold off spray untill the rest of the car is done and ready for that.
Redhardsupra, I should have the 346 ready for you soon, I get my 408 tomorrow and I'm dropping the 346 in the cradle, I talked to Jason @ TSP and he said he'll help me get a good shipping price for you.