dchoran

I've only had this '84 Crossfire Injection TBI Vette (50M miles - very well maintained) for a couple months now.

Car runs near perfect - just a little fluctuation at idle even after new plugs, cap, rotor, coil, wires, IAC's.

This morning I went to look at the flow pattern of the two injectors.

They look like they "fan out" OK. But I am confused.

At operating temperature and at idle with the air cleaner cover off, I noticed two "unusual" things:

1.) the "flaps" on the air intake housing were both closed completely - they open right up when I shut her down and then close right up when started up again.

2.) the injectors are spraying gas on to a closed throttle plate. Maybe I'm thinking these should be open because they look like a carb choke. Just seems kinda weird.


So are those things above normal or is something whacked out?????


THANKS in advance for your help guys.

Dave H. Appleton, WI dchoran@athenet.net 11/7 10:45am

7thvet

Yes on the fan pattern. You can put a timing light on them & see them pulse.
The throttle blades are closed cause its at idle, if you gas it they open.
The air cleaner flaps, on mine one is always open, the other closed till it warms up.

dchoran

So if BOTH my air cleaner flaps remain closed when warmed up, what do I need to replace???

7th Vette - yours looks pre-84???? Same thing on the '84???

THANKS AGAIN!!!!!!!!!!!!!!!!! (luv this forum )

dchoran

Couldn't find anything on this in my Chiltons or Haynes.

Headed for the service manual.

Looks like it involves the "THERMAC".

One temperature sensor and two vacuum diaphram motors for the damper doors.

ANY SIMPLE MODS FOR THIS???? Or do I just replace with OEM stuff???

THANKS.

dchoran

UPDATE:

When my engine is warm, the driver's side door flap is open - the passenger's side is closed.

Even getting it nice and hot, the passenger side door flap does not open.

It'll open when shut off and the close immediately when started so obviously there is vacuum.

Anybody know if these door flaps should work in UNISON???

Thanks again.

dchoran

guess not.

ex-x-fire

Ok, here's how the flaps work. Both are closed for warm up, when it's at operating temp. only one will be open (the one w/ the heat stovepipe off the exh. manifold). At WOT, both will open b/c there is no vacuum to keep 'em closed at wot. You can unhook the thermac at the throttle body vacuum line, but do this only during warm weather, or you could have a slight hestitation. One thing I did a few years ago, was make a lid in the shape of the air filter, requires alittle cutting & welding on the new lid to clear injector tops, it's like having an open element air filter, seem like I gained alittle.

ex-x-fire

Oh yeah, remove your air cleaner assembly to check for broken or leaking vacuum lines. Grab the throttle linkage, & wiggle it, there should be no sloppiness pressent, common idle problem is worn out throttle shaft bores ( they can be repaired w/ bushings or sleeves).

383vett

Seems like this mod would allow hot engine air into the motor instead of cooler ducted air during acceleration. You would lose hp over stock.

dchoran

THANK you. That is EXACTLY what mine does. Nice to know it is normal.

Linkage is solid. And there are no obvious vacuum leaks. Hoses were either cleaned/replaced.

Chalking up that minor engine idle RPM fluctuation (+/- 100 rpm) to the XFire process. Feels/sounds like my Harley Ultra



Oh yeah, it is not too often I go WOT.

Only in the rotaries (or round-a-bouts as they call them in the Mid-West)

Dave H.

ex-x-fire

I remember a Hot Rod Mag. article where they were doing mods on a V6 Camaro (early 80s 3rd gen) trying to get it to match a stock Z/28 through the 1/4. They did gears which helped alot, a factory HO cam helped somewhat, ecm for HO V6 which did nothing, then they flipped the air cleaner lid and nearly met their goal. I think the volume of air w/ an open top is more effective than keeping warm air out. Also remember the crossfire intake has a large coolant channel under the runners, it gonna be hot anyway. Thats just my experience