So I'm doing and have done the following mods to our 99TA.

Circle D stall
New flexplate
LT headers
TSP cam
New springs
New timing chain
New hi flow oil pump
New lifters
Possibly under drive pulley

Should I use the stock injectors or bump them up?

 

No mention of a cam...?

 

Depending on the cam size, you probably should upgrade to higher flowing ones.

 

My bad its a TSP 224/228 .581/.588 112 LSA

TSP 7.40 pushrods

 

Also how to determine the right size. Is there some form of calculation to determine.

 

I'm using the stock ones . They're at 96% duty cycle tho, so once I throw heads and intake on im going ford racing green tops. 42lb.

 

You're cutting it close but should be ok.

There's no real calculator that actually works in the real world. You just go to the next size up (or two) depending on what your future goals are.

 

This is an EXTERNAL engine question.

You should be looking for some bigger injectors, the stockers will be at their limit.

 

I'd say this is a fueling question... but I'll let it slide in internal.

Without heads, you'll be just within the capability of the stock injectors. Once you add heads or if you step up to a bigger cam, you'll need more injector. Some 42s would be a good choice.

 

Stick with the 42#, if you are delivering too much you can change the pulse. Its better to have room to grow than to get cut short.

 

If you're absolutely DONE upgrading and are happy with everything, Ford Red Top 36# injectors and call it done.

If you ever plan on even a small 100 shot or heads, them grab the 42's

 

please move if needed, I figured since it was fuel related, it was internal, but if there is no future mods anytime soon or who knows if ever, am I hearing to bump up to 36# or is the consensus go to 42# so that no need to change later if more mods do come?

 

FWIW I went with white bosch 42# injectors and I am cam only also. IIRC my tuner said I'm at less than 80% duty cycle with them and have plenty of room if I decide to do heads.

 

I run those as well. They are cheap and effective and GM OEM so the quality is good.

 

Thats why I went with them .

 

is there a part number? is it something I can get from the dealer since they are OEM? I just looked on summit and didn't see them, atleast doing just a generic search for fuel injectors, the ones I found for bosch came up for other cars nothing for mine.

 

I got mine off of here for like $100. Check the classifieds

 

We offer brand new 36#+ and also resizing and flowmatching services for less $$$ than a brand new set. The best thing on the resized are everything is new as far as o rings, filters and baskets and they are guaranteed good with verified spray pattern.
Let us know if we can be of any help!

 

I'm really happy with my Accel 44lb/hr injectors. Got them off here brand new for a steal. Plenty of room to grow as well.

 

Alot of the accel injectors are an older design so be careful. The disk style can cause idle and tuning issues esp over the pintle style.