air to my 331 ?'s

riceslayer302 · Jul 12, 2008

im trying to decide what size fuel injectors, mass air, and throttle body to get for my 331 stroker project. this will be a N/A 331 at 10:1. I am using a 280/286 .598 lift comp cam, AFR185 58cc heads, and an edelbrock rpm 2. I am hoping to make some good power with this combo, but how much, i dont really know, AFR's website has cars with setups like mine making 475 to the crank.

My questions are, what do you guys think i should use for fuel injectors on this setup? what brand is best? i was thinking of going with MSD or FRPP. I was thinking somewhere between 24 and 30# injectors, but what do you guys think?

Mass air, i know i need to get mass air that is calibrated to my injectors, but what size? they have them all the way up to 90mm, which i dont understand because 90mm mass air going into a 75mm throttle body doesnt make much sense.

Throttle body, i am not sure but i think the throttle body opening on the RPM II is 70mm? Should i get a 70mm throttle body or get a 75 and open up the intake a little bit?

thanks for the advice in advance! :SNSign:

Markus · Jul 12, 2008

Hi,

i drive a 331 stroker too. On the top i have a GT40 with ported lower. I use a 65mm tb and a matched 75mm pro-m mass air with a cold air intake. The injectors are 24#.
Heads are AFR185 (10.7:1) and a ed curtis custom cam (.5728/.5632 lift, 224/228 @.05). Long tube headers, off road exhaust. A Tweecer RT is on board too.
My car is pulling 350PS (DIN, rear wheel).
I think with your intake and a 70 or 75mm tb the 475 hp are not unreachable. Is a 90mm mass air not too big for a na 331?
The mass air should be a little bigger than the tb.
I don´t use the full capacity of my 24 pounders. I drive with stock fuel pressure.

Markus

Grn92LX · Jul 12, 2008

75tb open the inlet, 80-90mm mass air, 30-42lb injectors.

My 30lb injectors are 100% maxed out @ 96% duty cycle before I hit my shift point in my 347.

riceslayer302 · Jul 12, 2008

holy **** you think i need 42s?

5spd GT · Jul 12, 2008

Killercanary has some very accurate datalogging material and he hit 36X RWHP in his N/A 331 with just 24 lb injectors. He was running 82% duty cycle by the way.

A 70 mm TB will flow plenty for your combination, I promise.

As for the MAF, read this from a guy that has a 352 cubic inch engine and runs low 11's @ 122 MPH in the quarter mile:

It made 411 rwhp with the pro m 77. I then put the abaco 97 dbx MAF with the bell on it and it made the exact same power, 411.

You do not NEED a 80-90 mm MAF for flow reasons, but they make some very accurate ones in that range. Just thought I would make that clear.

Venom351R · Jul 13, 2008

Nothing new to add from what's already been said b/c I agree but I do have a set of FMS #24 injectors that need a new home.

1991vert · Jul 13, 2008

mike, a 90mm MAF for sam's 331? are you joking?

sam who is tuning this car? it's best to call and ask for opinions. i'd go one step up from 24#'ers though

Grn92LX · Jul 13, 2008

1991vert said:
mike, a 90mm MAF for sam's 331? are you joking?

Size doesn't matter, calibration does.

Like I was saying I don't know how wild your combo is, but im 100% maxed out with my 30lb injectors @ a very accurate 96% duty cycle before I hit my shift point in my 347.

riceslayer302 · Jul 13, 2008

i listed a rough idea of my combo up top. right now i think i am going to go with 32#'s with a 75mm TB, and open up the RPM II a little. how does this sound? as for the mass air i thought it was supposed to be a little bigger than the TB? so 80-90mm would be ideal correct?

1991vert · Jul 13, 2008

riceslayer302 said:
i listed a rough idea of my combo up top. right now i think i am going to go with 32#'s with a 75mm TB, and open up the RPM II a little. how does this sound? as for the mass air i thought it was supposed to be a little bigger than the TB? so 80-90mm would be ideal correct?

when i talked to mike in CT, i told him i was planning on using a 90mm MAF for my blown 363. he simply asked, "why?"

Grn92LX · Jul 13, 2008

riceslayer302 said:
i listed a rough idea of my combo up top. right now i think i am going to go with 32#'s with a 75mm TB, and open up the RPM II a little. how does this sound? as for the mass air i thought it was supposed to be a little bigger than the TB? so 80-90mm would be ideal correct?

Yup 30's, 75tb and 80-90 mass air should work fine

5spd GT · Jul 13, 2008

riceslayer302 said:
i listed a rough idea of my combo up top. right now i think i am going to go with 32#'s with a 75mm TB, and open up the RPM II a little. how does this sound? as for the mass air i thought it was supposed to be a little bigger than the TB? so 80-90mm would be ideal correct?

No need to open up anything, but that is up to you.

Many people think that size in MM is how to judge a MAF or TB, but they all flow differently, even if they are both 80 mm and 80 mm.

The bigger is better idea is not needed, if you understand how much air an engine actually pumps in and out. The parts quoted above flow in the 1000 + CFM range, when your engine may pump out 600 CFM.

air to my 331 ?'s

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