I have to get new injectors. Should I get 22 or 24's? See sig for mods.

 

well it kind of depends on your future plans?are going to stick with the 305 or are you going to swap to a larger motor?or will you ever put boost to her?
the 24's are pretty big for a 305.

 

New engine in the future. Probably 350 or maybe 383.

 

I would recommend against either unless you've got the capability of prom burning. If you absolutely must, 22's at the most.

 

I don't have the prom burning equipment. My engine has 19's right now, but it isn't getting enough fuel when it gets hot and is causing a spark ping. I figured larger injectors would solve the problem. Is this not the case? Would I still need a coustom prom?

 

How do you know its not getting enough fuel? Have you verified this or assuming it?

Most stock timing tables are slightly agressive, with a few mods the timing becomes to much, anybody who prom burns more than likely has lowered timing throughout vs raised timing.

 

btw

I had a crane compucamn 2030 on a 305 and It caused alot of knock. This seems to be a trend ......

 

have you checked fuel pressure?you could have a bad FPR.

 

the afrp is good. It hold the pressure steady with the vaccuum off. I have the fuel pressure set at 50lbs right now. I have had the pressure set anywhere from 35 to 50 and it doesn't make a difference. I have also played with the timing. Setting it anywhere from 16* to 3* and that doesn't seem to help either. My feeling that is a fuel problem is an assuption. Someone else told me that is most likely the problem, so that is the direction that I am leaning towards.

Just so you know what is happening, when the engine gets warm(200* or so) it makes an awefull rattling sound, blows smoke and the ses light comes on when you try to accellerate more than abou 1/4 throttle. It stores a code 42 and 43. The esc module and knock sensor are good. Sorry about the book.

 

i will have to agree with tpi_roc with the size.... unless you have a servirely modded 305 24's are a wee bit too much.... ford 302 mustangs use 19lb and iv'e seen mustangs with stage 2 canfeilds and huge cam only running 24lb.... yes you can get away with 24's if you lower your pressure to like 20psi.. factory 34... but like said above you won't benifent until that chip is there..... also i would check the pickup in the dist.... sounds like it's bad and the car isn't burning all the fuel and igniting whats left causing the ping....

 

I've read a couple of posts of guys who have installed then removed 24s from a 305. They say the car ran like crap and slowed down in the 1/4.

I always figured 19s with an AFPR for 305s ?

RP.

 

While on that topic, I was wondering if an adjustable fuel pressure regulator is a good idea on a TPI305 with an otherwise stock fuel system? I have heard and read that by bumping up the fuel pressure just a few psi, it will result in a few extra horses. Is it worth it?

 

What should be the Injector size for a 383 with AFR190 heads?

Thanks,

 

At least #24s. I'd go with #30s if you have PROM burning equipment.

 

The ABSOLUTE most HP 24#s can support is 384 HP @ 100% Duty Cycle (which is impossible). At 80% Duty Cycle, the most they can support 307 HP.

A lot of people say you should never exceed 80% DC and others say 85%. But everyone agrees that once you approach 90% DC, that you need larger injectors. 90% DC is only 346 HP. ANY halfass 383 should make more than 346 HP.

Raising fuel press will give you a little more "breathing room", but no more than 30-35 HP over the numbers I have given.

Definitely, consider 30#s and possibly 36#s if it is REALLY healty.

The formula for sizing injectors is HP = Injector size x 2 x #cylinders x %DC. And you should never exceed 90% and probably should keep the max DC somewhere between 80-85%.

 

ok Glenn with that figure for horse and Injectors if i do mine and I have 19lbs injectors I dynoed at 221 RWHP so at the crank (given 15% loss because of 5 Speed) I would be 254 horse at the crank now using your formula for injectors they should only make 243 horse... why em I above that? I have a stock chip aswell running it. I think there has to be a beg leeniace somewhere.. maybe the stock chip has a bigger %DC??
But why the discrepency?

 

I dont know where you got that formulat at, but I have seen several Lt1 cars making 500+fwhp on the stock 24's. Of course they are not batch fire like ours so.... I am making around 400 fwhp right now on my 24lb lt1 injectors, and with the previous engine I was making around 450 fwhp. I plan on pushing over 450 fwhp as soon as I get rid of this tinny little cam. Probably gonna switch to svo 24's just to play it safe though.