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2/28/13 9:51am - Original Message: 'tbi cross fire'
jonneyone
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galion, OH - USA

Vette(s):
1984 base coupe 17,000 miles all original. very low production number.red on red 3853. pro num.

Joined: 5/31/2012
Posts: 413
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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2/28/13 12:50pm - Reply: 'Re: tbi cross fire'
Adams' Apple
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Duncanville, TX - USA

Vette(s):
1985 Coupe-L98/Auto,Bright Red/Carmine. 1974 Coupe-L48/4speed, Medium Red Metallic/Black Deluxe.

Joined: 3/18/2009
Posts: 2094
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.Thumbs Up


|UPDATED|2/28/2013 10:50:31 AM (AZT)|/UPDATED|


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Joel Adams  
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2/28/13 6:07pm - Reply: 'Re: tbi cross fire'
jonneyone
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galion, OH - USA

Vette(s):
1984 base coupe 17,000 miles all original. very low production number.red on red 3853. pro num.

Joined: 5/31/2012
Posts: 413
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. Confused

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2/28/13 7:05pm - Reply: 'Re: tbi cross fire'
tbirdsps
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Ridgecrest, CA - USA

Vette(s):
1990 Coupe

Joined: 2/19/2013
Posts: 117
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.

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2/28/13 7:43pm - Reply: 'Re: tbi cross fire'
jonneyone
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galion, OH - USA

Vette(s):
1984 base coupe 17,000 miles all original. very low production number.red on red 3853. pro num.

Joined: 5/31/2012
Posts: 413
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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2/28/13 10:37pm - Reply: 'Re: tbi cross fire'
Adams' Apple
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Duncanville, TX - USA

Vette(s):
1985 Coupe-L98/Auto,Bright Red/Carmine. 1974 Coupe-L48/4speed, Medium Red Metallic/Black Deluxe.

Joined: 3/18/2009
Posts: 2094
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. Confused


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". Thumbs Up


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Joel Adams  
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3/1/13 8:14am - Reply: 'Re: tbi cross fire'
jonneyone
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galion, OH - USA

Vette(s):
1984 base coupe 17,000 miles all original. very low production number.red on red 3853. pro num.

Joined: 5/31/2012
Posts: 413
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 .  

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3/1/13 9:02am - Reply: 'Re: tbi cross fire'
wingnut
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Naples, FL - USA

Vette(s):
1984 C4 Mild mods.85 fuelpump,Accel ignition, TCI, shiftkit, ramAir, Boshplat plugs, duels straight, VP 106 fuel mix, 1990 wheels,, Silver/Gray 1996 LT 4 Stock muffler eliminators Torch Red ZR1 Wheels

Joined: 6/19/2011
Posts: 46
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 HAPPYThumbs Up

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9/8/15 10:14pm - Reply: 'Re: tbi cross fire'
Smackworth
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Brentwood, CA - USA

Vette(s):
1984 C4 Corvette

Joined: 9/8/2015
Posts: 2
Where is this location to cut in the cowl, can you submit a diagram

|UPDATED|9/8/2015 8:14:58 PM (AZT)|/UPDATED|
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9/8/15 10:11pm - Reply: 'Re: tbi cross fire'
Smackworth
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Brentwood, CA - USA

Vette(s):
1984 C4 Corvette

Joined: 9/8/2015
Posts: 2
I was told that the 1988/89 GM trucks TBI has larger ports and would increase the horse power? Has anyone tried this.
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9/14/15 12:12am - Reply: 'Re: tbi cross fire'
Hot Rod Roy
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Mission Viejo, CA - USA

Vette(s):
Yellow '84 Coupe

Joined: 3/18/2015
Posts: 39
jonneyone said:  Most guy's and gal's think it's the manifold that is the problem.   Not true.  These tbi's are way too small and the iac motors are too small too.   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.

Have you done this mod?   Unless you can post some "before" and "after" test results, this comment goes right into the "bad rumor" round file.


I've read a lot of stuff lately about the crossfire.  A lot of it is bull crap.

You've got that one right!





|UPDATED|9/13/2015 10:12:26 PM (AZT)|/UPDATED|


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9/18/16 12:21pm - Reply: 'Re: tbi cross fire'
brad1951
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homosassa, FL - USA

Vette(s):
1984 z51

Joined: 9/18/2016
Posts: 1
The X fires get a bad rep that is partly bs. With some minor port matching of the intake a lot can be gained. My 84 has been decated with true duel exhaust and targa mufflers, a 1985 fuel pump. With the automatic trans it will smoke the tires in first and chirp them hard after it shifts to second.It is not a drag racer and does lose power on the top end but it still leaves most of the kids in their Jap tuners in it rear view mirror.
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