Hi...

I am in the middle of a tuning process of my new rebuild 305TPI engine.
The engine got some performance upgrades also:
Hot cam, Hooker 2055's, Ported heads, Catco 9118 Catalytic converter, Magnaflow Cat-back system, EATON POSI unit with 3.43 gears.

I have been doing some work at DYNO programs I've bought and this setup should give me about 300HP if the tuning is good.

But I was just thinking of something. I have the stock injectors of my TPI setup. I guess they are about 19lbs/hr am I right??...

Do I need bigger injectors to make my setup work perfectly???

 

F motors came with stock 24lbers. without more information on your heads and top end, I cannot make a good suggestion.

 

The 24lbers came with the 350 F-bodies. My setup came of an 305 LB9 engine and those injectors are rated to 19lbs/hr...

I have the stock heads on my engine. I have done most of the porting myself so I am not sure about the flow on them though.
But they are cleaned up and port matched with the gaskets.
The CAM I have is a COMP cam 08-412-8.

Should be a good cam for my engine...
Anyway, I need to know if I need bigger injectors to make my setup perform as good as it gets..

 

injector size is a big formula, evaluating engine VE and CFM capabilities, but as a rule I have found the average ruler is;

a 19lb/hr injector will limit you to around 200-220hp,
a 24lb/hr injector will limit you to around 260-280hp, and so on, if you are running a stock LB9 then you really shouldn't have to go over a 24-28lb injector.

I am running 72#ers because of forced induction, and the engine was dynoed at 502hp before I put the twin turbos on it, so I went big and depending on what I set the boost at, I get between 600-800hp out of 72lb/hr injectors.

hth

 

Hope this helps:

http://www.rceng.com/technical.aspx?...4r4dWeV6{hA3fL

 

Stock Factory Fuel Injectors for TPI engines for all 3rd gen cars are:
305 TPI 19#
350 TPI 22#

NOTHING ELSE was used......

 

@thewizard, thanks, I couldn't find that formula, but ya, its a biggie !

I reviewed the cam you mentioned camaro87-alex and its a very good choice. You are not going to get all 5200rpm out of it unless you swap the stock rockers for roller 1.5/1.6 ratios. Unfortunately, the torque curve for a stock TPI falls on its face around 4800 rpm, however, your port matching will help increase that by only a couple 100 revs. Switching the rockers so you have a 1.6 on the intake will improve your revs about 800-1000 top end so you can work that cam up its torque curve. Remember, the look up tables in the stock ECM are going to 'think' you still have 19#s, so if you go with 24#s, keep an eye on your fuel pressure.

 

@DJP87Z28, when rebuilding my '92 '8' motor, its a 25th anniversary heritage TPI, the part number of the injectors matched 24# with my GM parts guy, this is why I was under the impression both 'F's and '8's came with 24#ers.

 

Someone gave you incorrect info..The above was ALL models.

 

thanks, I replaced mine with 72#ers anyway.

 

Thanks thewizard for this web site.
It actually tells me that if I am making about 300HP I will need injectors of
24lb/hr.

I have also tuning equipment so I can tune my ECM so it will work perfectly.

 

Thanks for the information Z28TT. I relly appreciate it.
I guess I would have to buy some roller rockers also then, so I can
get the most out of my cam choice.
I also wanted to tell you that I have some chip burning equipment so I can made my own chips. That would help me out if I go with bigger injectors..