injector sizing on a 331 w/ S-trim

92stanglx · 10-19-2004, 08:44 AM

I just had a new 331 built and I am going to run an S-trim (8 lbs) on it. It's in the car and am working on bolting up all the accessories.

I plan on running 36lbers. Will the car run ok with these injectors or will they be too big for the stock computer (I plan on getting a tune but want to break in the motor first)?

Also, I read somewhere that if you run too big an injector on a new motor it can cause problems with the rings seating (something about too much fuel washing oil off the cylinders ?). Is there any truth to this?

My other option is to use my 24's with an FMU until the motor is broken in and then switch to 36's before I get the car tuned. Although, this sounds like a lot of trouble if I can avoid it.

Thanks!

**midnight** · 10-21-2004, 01:14 PM

U should b ok as long as the motor starts and u don't flood it to death...I start them w/42's and larger all the time...

**eades5.0** · 10-21-2004, 09:13 PM

Whats the rest of the combo?
If H/C/I i'd go 42# minimum

92stanglx · 10-23-2004, 03:48 PM

My combo is as follows:

331 (9:1 compression)
TFS TW heads
TFS stage 1 cam
GT-40 intake (ported and polished) w/ 65MM T-body
Mac unequal length headers
Bassani X-pipe
Mac cat back
Pro-M mass air 75mm
255lpr intake pump
BBK in-line pump
Adjustable FPR

Everyone I speak to says the same thing "go w/ 42's". So that is currently my plan. I just picked up a set today.

However, I still am not too sure about starting the car with the 42's. I have heard that w/o a good tune you will run pig rich. I also heard from a couple of other people about the issue of the rings not seating properly.

My current plan is to start the car w/ the 24's (w/ a properly calibrated FMU) installed and then switch over to the 42's before I get tuned.

Any thoughts?

**down** · 10-24-2004, 02:36 AM

Originally Posted by 92stanglx

My current plan is to start the car w/ the 24's (w/ a properly calibrated FMU) installed and then switch over to the 42's before I get tuned.

Any thoughts?

That's what I'd do.

Probably wouldn't spin it to 6K w/ the blower and the 24's, though :laugh:

92stanglx · 10-24-2004, 11:48 AM

Yeah, the 24's would just be used for engine breakin. I don't plan on even reving the thing to 3k until I put in the 42's and get a tune.

**Hounddog** · 10-28-2004, 08:44 PM

Originally Posted by 92stanglx

My combo is as follows:

331 (9:1 compression)
TFS TW heads
TFS stage 1 cam
GT-40 intake (ported and polished) w/ 65MM T-body
Mac unequal length headers
Bassani X-pipe
Mac cat back
Pro-M mass air 75mm
255lpr intake pump
BBK in-line pump
Adjustable FPR

Everyone I speak to says the same thing "go w/ 42's". So that is currently my plan. I just picked up a set today.

However, I still am not too sure about starting the car with the 42's. I have heard that w/o a good tune you will run pig rich. I also heard from a couple of other people about the issue of the rings not seating properly.

My current plan is to start the car w/ the 24's (w/ a properly calibrated FMU) installed and then switch over to the 42's before I get tuned.

Any thoughts?

Yeah go with larger injectors at least 42s.

I have a forged CHP302 with 8.25:1 comp
TF TW heads
B303
Cobra intake
70mmTB
80mmMAF
Lucas 38s
Strim 2.95 upper 7.0 lower (14psi)
Powerpipe
Shorties
No FMU 40psi base and 1:1 fpr increase for ea psi of boost.

Have maxed PW and duty cycle on these on pump gas.

I calculated that I need at least 42s and would be better off with 50s if I want to run C16 and a strong tune.

Car makes SAE460rwhp,440rwtq on 91 octane at 5400' altitude.
Wayne

**95snake** · 11-02-2004, 04:36 PM

I have a Sportsman block, 331cid, custom cam, 50# injectors, stage 1 Victor Jr heads, Holley SysteMax Intake, S-Trim (2.75") Powerpipe, PMS, and I make 626 RWHP and 602RWTQ on pump gas. BUT last time at the dyno, I found out I am running out of injector. I guess it depends on how far you are going to take it? I say to atleast start with 42's.