Stock injectors should be fine....What are the rest of you mods on your build?

Cam profile
Intake Manifold? 2bbl, 4bbl?
TB size?
Compression?
Header size?
Exhaust?

Depending on the above, your 1.92 R/T heads migh be robbing you of some power.

 

it was built about 5 yrs ago by a local race shop, left in a dakota and never buttoned up. with that said she just needs a good teardown, clean up and a light hone.

ill know the cam size once its dissasembled. im using a port matched M1 intake. 53mm TB, compression based on the KB dish pistons and i beleive 60cc combustion chambers would be about 9.8:1. JBA shortys. exhaust is TBD.

my machinist said for my application- daily driver/street. 1.92's will be more appropriate. more flow is not always better. with the ported 1.92s ill get more velocity which will equate to more low end power and better street driveability.

i was told somewhere in the range of a 32# injector...

 

You'll run pig rich with 32s. I'm rich on 24's...And my mod list is a mile long.

1.92s will be fine...But I'd do 2.02s, especially on a 408. The loss of torque with 2.02s is a fallacy just like the "gotta have restriction in the exhaust". Loss of torque depends on the cam, how you degree it in (advanced/retarded) etc... Do you have a 2bbl or 4bbl m1, the 2bbls don't flow very well. Hopefully with a 408, you have a 4bbl with 2bbl adaptor. Is that a Fastman 53 TB?

One piece or two piece valves? 1.92 Magnum R/T heads came bare or assembled with .525 springs and stock Magnum two piece valves....And the two piece valves are junk on anything but a stock 4500 RPM motor, Lot's of guys guys have ruined some nice motors snaping those things into two pieces.

I just hate to see someone not take advantage of a 408 by choking it down...

 

24# should be fine. They will actually flow 25.5 at 49 PSI.

The reason people say to run giant injectors is because there is some HP rating that certain lbs per hour can feed. They claim that 24# injectors can only feed 350 HP. But that is at 80% duty cycle. All our injectors never see more than 80% duty cycle unless it is programmed into the PCM.

 

really think ill run rich with a 408? it will be tuned by hemifever of course.

titanium valves

think i need long tubes?

jbomb has a 408 w/ 32's

 

bruce holt at five o performance told me to run 30's and jbomb like his 32's... so im kinda stuck because you guys think i should stick with 24's

 

It isn't so much "loss of torque" with larger valves, its more like "won't develop as much LOW END torque" with larger valves. Smaller valves make for higher intake charge velocities, and promote better cylinder filling at lower RPM. Sure, you sacrifice top end power, but, when building a motor, there are always compromises to be made.

That said.... The 408 is going to have GOBS of low end grunt, no matter which way you go.

 

I seriously doubt you have titanium valves.

You don't need long tubes, get some Spintech mid length headers 1-7/8" primaries/3" collectors...The JBAs are killing you; hardly better than stock.

Sean tunes my Dakota, he's had to pull fuel with the 24s. I know of a number of guys with 11 second 408 Dakotas running stock fuel systems and stock injectors.

 

Agreed on the 408 having torque....I know all about velocity, valve size etc. 2.02s will develope more torque, just at a higher RPM. Use the cam, gears/stall to move the power band.. It's all good.

But then again I have a 238/242 547/548 @104º cam, heads that flow 300 cfm, 4.56 gears, a 727 and a 4000 stall converter, etc etc etc....On my Dakota

Weeeeeeeeeeeeeeeeeeeee!!!

But I'd love to do a 408 in my 98 Ram, it tows my Dakota to the strip, but I sure wouldn't put 1.92s on it...No way.

 

You are building for an entirely different purpose though. Its all about what you want. If you WANT all the low end grunt you can squeeze out of the motor, then the smaller valves are the way to go. You, on the other hand, seem to be more inclined to build for the upper RPM range, and the bigger valves would most certainly be advantageous for that.