Topic: tbi cross fire
in Forum: C4 Engines
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i found out something interesting about the cross fire tbs injection. gm used these throttle bodies off a four cly engine called the iron duke. remember the 4 cly cast iron in the early 80s. they came in the Pontiac's and chevet. any small car because of fuel shortage. they also used the iron duke in sprint car racing in it's day. well gm didn't have any tbi's for the corvette cross fire so the used the one off the 4 cly. they are to small for the cross fire to have allot of hp. most guy's and gal's think it's the manifold that is the problem not true. these tbi's are way to small and the iac'motors are to small to. this is why the cross fire doesn't have any hp. you can send them out and have some boring to them among other mods. you'll see a big boost in the hp.
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Vette(s): 1985 Coupe-L98/Auto,Bright Red/Carmine.
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Everything I've ever seen/read on the origins of those TBIs was that they are a Cadillac design, not that it really matters. The "Iron Duke" was used in the Vegas, too, btw.
If you have ever taken the intake manifold off of a crossfire engine, you would know exactly why it doesn't breath well....and it ain't all about the size of the infector bores. Since the intake/TBI set-up had to fit under the hood, the intake had to be sunk down severely. The ports of the intake manifold are only about 1/2 the size of the ports in the heads. There was no other way to get the package to fit.
It would be similar to putting an oval port intake on a square port big block head, except there are no open holes from the mis-match. At that point, there's really no need to use a larger TBI....the restriction at the intake/head junction is still there.
The Crossfire engine gets a bad rep for not being a high horse deal, but they still run fine...just not at higher rpms.
|UPDATED|2/28/2013 10:50:31 AM (AZT)|/UPDATED|
If you have ever taken the intake manifold off of a crossfire engine, you would know exactly why it doesn't breath well....and it ain't all about the size of the infector bores. Since the intake/TBI set-up had to fit under the hood, the intake had to be sunk down severely. The ports of the intake manifold are only about 1/2 the size of the ports in the heads. There was no other way to get the package to fit.
It would be similar to putting an oval port intake on a square port big block head, except there are no open holes from the mis-match. At that point, there's really no need to use a larger TBI....the restriction at the intake/head junction is still there.
The Crossfire engine gets a bad rep for not being a high horse deal, but they still run fine...just not at higher rpms.
|UPDATED|2/28/2013 10:50:31 AM (AZT)|/UPDATED|
Joel Adams 
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i agree some what. so why is it that gm put the tunnel port injection in the 85 c4 it sittes allot higher. i found this article on a web site. about the crossfire tbi's. just thought i would share it. i also read about the runners being half the size of the heads. heck Ive read allot of stuff lately about the crossfire, allot of it is bull crap. so tell me did they change the hood to except the tune port injection in 85. 
I don't need HP, I love the torque. :) I'm a cruizer type anyway. I think my 90 L98 only has 20 or 30 HP more anyway. 345 ft lbs of torque is where the fun is.
If it isn't broke, I haven't fixed it yet....
my l83 only has 205 hp at 4500 rpms and 260 ft pounds of tourqe. as far as i know. i just know this about my 84 it will snap your neck when you stand on it.
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jonneyone said: i agree some what. so why is it that gm put the tunnel port injection in the 85 c4 it sittes allot higher. i found this article on a web site. about the crossfire tbi's. just thought i would share it. i also read about the runners being half the size of the heads. heck Ive read allot of stuff lately about the crossfire, allot of it is bull crap. so tell me did they change the hood to except the tune port injection in 85.
Remember, the Crossfire was originally designed/used in the '82 Corvette. It was always intended as a "stop gap" until the TPI system was ready. The '84-'96 cars had more room under the hood(compared to the Shark era cars), since there's really no "frame".
Joel Adams
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my friend has an 82 and its a cross fire, however it's nothing like my 84. the air cleaner is different and the manifold is to. not sure about the tbi being the same. are they. is the 85 hood differant than the 84. i think i remember reading that a camaro had a crossfire .
Yes there is a difference. Your 84 Breathes through the hood directly ot the TBs my84 had 290 tourqe.get more air in by cutting the cowl in front of the radiator to FORCE AIR into the hood and put in an 85 Fuelpump you will be HAPPY
Wingnut
Where is this location to cut in the cowl, can you submit a diagram
|UPDATED|9/8/2015 8:14:58 PM (AZT)|/UPDATED|
|UPDATED|9/8/2015 8:14:58 PM (AZT)|/UPDATED|
I was told that the 1988/89 GM trucks TBI has larger ports and would increase the horse power? Has anyone tried this.
in Forum: C4 Engines
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