kevin89formula

Thought I would go ahead and get some opions on what size injectors to run. Specs, 383, superam, afr heads, 219/219 cam, all bolt ons. Im thinking about using 30lb svo injectors. Is this the right size? or will 24 lb svo be enough?

Edmond

This tech article will help you:

http://www.holley.com/HiOctn/TechSer...l/Artcl07.html

Scrote

24lb injectors will be enough...I have seen the duty cycle withthese injectors on 383's and they seem to work out great...

The Denzo 24lb is a really nice unit, you wont be dissapointed

take care,

Erik

doc

I'm running SVO 24# injectors at 52psi in my 395. Pretty much got what you have but more cubes.

I also burned my own Eproms, and found out that I needed more fuel for a hot start.

kevin89formula

DOC

I ran my 383 with long tubes and stock injectors for about 2 years. always had hot start problems. (tried all the tricks never got much better) Changed over to a superam and put in 24 lb injectors and the hot start problem seem to get worse. ONly had about 50 miles on this combo before I cracked a Piston.(probably running to lean) If I bumped up the fuel pressure to much the damm car wouldn't even start.

Are you saying that you needed that much fuel pressure for Hot starts, Or did you adjust something in the eprom? Bring the knowledge.

doc

Having a 395, I needed more fuel for hot starts. I accomplished this by increasing the cranking PW vs coolant temp table.

Also, I have 22.5#/hr as the fuel injector constant. I had to do this to get the BLMs under control. If I used the coorect flow rate, the BLMs would be around 148 or above, so the ECM would have to add fuel to maintain 14.7. So in effect, I force the ECM to calculate a longer PW with the 22.5#/hr entry. Now the BLMs are between 118 and 130.

Back to the lead question about fuel injectors and a 383.

I strongly prefer to run fuel pressure in the low 50s for my '87 car. I think that increased fuel pressure is good for atomization (sp) of the fuel. So I tune the Eprom with 52psi in mind and go from there. The 24s at 52psi theoretically flow 27.5#/hr.

For a 383, I think that 24#/hr SVO injectors are big enough if you run high fuel pressure. If you go with the 30s, then I think that you will find it necessary to run low fuel pressure like around 40psi.

John Millican

iTrader: (1)

I ran brand new SVO 24# injectors at 48psi in my 383. I had duty cycles close to 90% so I upgraded to Acell 30# injactors and now my duty cycle is better at 75%. You don't want to run all the way to 100% DC unless you had the injectors flow tested and matched.

doc

John, what is your PW at idle? That would be the only main issue I can think of why not to use 30# injectors.

BTW: my DC at WOT is around 90% as yours was with 24#ers.
But that is no problem for these injectors. However, I agree that max of 80% would be better.

Kevin, go with the 30s, then you will have more room to grow in the future. If John has a good AFR at WOT with 48psi fuel pressure and a good idle, then I would go with the 30s. I was thinking with 30#ers, the fuel pressure might need to be 40 or less.

BTW: you got to have a AFPR and a new Eprom.

jfreeman74

What about SVO 36lb? I'm not sure what your HP is on this motor. I am looking at a 440hp 383 and I was thinking about putting 36's in it. I'll run the fuel pressure around 45. I'm afraid the 30's will be too low for that much HP but I'm not sure if the 36's will be too high. What do you guys think?

doc

30#/hr SVO injectors at 52psi at 80% duty cycle will support 440Hp.

36#/hr SVO injectors (do they actually make these?) at 45psi at 80% duty cycle will support 490Hp. These injectors (I estimate) will PW at 1.0msec at idle. So this should work out OK.

jfreeman74

Thanks for the reply. I don't really want to run the fuel pressure up that high. I don't know that my 19 year old fuel pump could take it.

BrandenCali

Don't for get you do want a good spray pattern.. a 36 with that pressure or lower I see it not working out so well..

doc

Even with a 350 which is built up nicely, the fuel pump needs to be changed. A 383 is nearly 10% bigger than a 350, the fuel pump does not have the reserve needed here for a 383, especially a well built 383.

It is my conclusion that us thirdgenners just need to accept the fact that our fuel pumps are not up to the task. When I built up my original 350, I was running out of fuel during WOT runs.

I installed the TTA fuel pump, no more fuel problems.