TBIThrottle Body Injection discussion and questions. L03/CFI tech and other performance enhancements.
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have a 1982 crossfire Z, GETTING READY TOO replace stock regulator spring with one from topdown solutions.--------as of now i have my 355 eng set up for 16 psi fuel and BPW SET TOO MATCH MY injectors[stock vett 82]. WAS TOLD stock injectors were 55# and also was told they were 65# ?? anyone know the true injector lbs, ----- then im shooting for 17 too 20 psi with new spring. and then need too reset BPW. ANY HELP would be great.-------think i need too go with about 20 lbs fuel, so what is true injector rating and can anyone figure my BPW FOR 355,
Last edited by carls1982z; 05-09-2006 at 05:29 PM.
You really need to get the part number from the top of the injectors. Most 350 engines used GM 5235206 *RPD which are rated as 55 lb/hr at about 12psi but GM would set the BPC for 61lb/hr. If we assume a rating of 61# at 12psi and increase fp to 20psi they should be good for about 78.8#. Therefore I would start with a BPC of 107. This should be good for just short of 300 hp.
But I should stress, you need to verify your injector part number first, then you should be able to search for the number to find the rating. Then you should have an idea of how much hp you expect the motor to make and use that to determine the required fp to get enough flow to support your expected hp. Then calculate the BPC.
The Crossfire injectors use a difference size for each of the throttle bodies. I can't remember which is which, but one is slightly larger then the other. This is done to balance the system that has the regulator on one TBI unit and an accumulator on the other. With the fuel delivery in serial with the TBI's.
The best method of setting up an x-fire is to have both injectors the same. Then rework the fuel delivery system so that the feed line T's with each end of the T feeding an individual TBI unit. Then have both return lines T together to a common regulator. Then back to the tank.
i wanna say they are 64-66. the caprice cop car used i will guess 65 but that was a "traditional" 2 barrell TBI.
as a side note i suspect GM could have run parallel plumbing with an single FPR rather than in series with accumulator and fpr. seems would have been a better thought but additional plumbing lines to deal with.
was going too buy new injectors or rebuilt BUT ALL THE PLACES cant give me flow specs ???? if they do what they say in the rebuild process they should know the specs, how can u trust they flow at what they suppose too ???
You really need to get the part number from the top of the injectors. Most 350 engines used GM 5235206 *RPD which are rated as 55 lb/hr at about 12psi but GM would set the BPC for 61lb/hr. If we assume a rating of 61# at 12psi and increase fp to 20psi they should be good for about 78.8#. Therefore I would start with a BPC of 107. This should be good for just short of 300 hp.
The GM 5235206 *RPD orange/black is 61 lbs/hr NOT 55 lb/hr so stop spreading the false information. I have flowed many of them and clean they are all right around 61 lb/hr +/- 1/2 lb. Most 305s have 55 lb/hr injectors with the green/white color code, again I have flowed many pair of them.
EDIT- I am not trying to be an ***, just once the information gets around, it is impossible to go back. 55 lb/hr designation was given to them many years ago, when in reality they truely are 61 lb/hr. 305 injectors have been given a 40 lb/hr rating in the same WRONG chart (it was the best guess around 10+ years ago). Most 305 injectors really are 55 lb/hr. 40 lb/hr would not even feed the L03s stock 175 FWHP rating.
but what about the ones i got???--and/or will those work in crossfire
Somewhere burried in this forum, I have a listing of the flow numbers from every TBI injector I could find at the time, including Crossfire, V6, I4, BBC, etc. I am looking for it as I type this.
Well, I have the injector numbers on the list but no flow numbers. IIRC, one is 65 lb/hr and the other is 68 lb/hr. I know for a fact they are slightly different and slightly higher flowing than a regular TBI 350.
