ck76239

Hi guys, I just picked up an 82 z-28 with a 305 Crossfire in it... It will not be my daily driver, I just want to fix it up for cruising and maybe an occasional trip down the strip...

Anyway, I'm concerned about the crossfire... I really want to build a 383 stroker for it, but I would like to leave the crossfire. I like fuel injection, so I see no reason why I should rip the crossfire out, to replace with a $1300 Holley unit.... Has anyone sucessfully used a crossfire from a 305 on 383, or at least a 350?

Why does the crossfire seem to get such a bad rap, mine runs pretty good.

Thanks!
ck76239

kdrolt

You can go into the 14s with the CFI and the 305 if you mod it right. If the engine runs well, then it's a good choice for a daily-driver.

Tomm400cfi kept his CFI (Crossfire Intake) when he dropped it onto his 400 sbc engine. If he did it with success (low 13s @ 102+ mph IIRC), then you can too. You will need to, at the minimum, do the mods he did to make sure you have enough air+fuel to feed the 383. Search for his posts.

As far as the bad-rap, it's misplaced and undeserved. The CFI was not ever intended to make huge power, and the power output of the TPI that replaced it (as designed by the same people at GM) was only slightly better. If you look at the evolution of engines from the worst of the low-power smog era when the Corvette ran 16.0 in the quarter mile, then the CFI looked pretty damn good in 1982 to make the Vette gain 0.5 sec in the quarter and +2 mpg.... achieving the goals that GM targeted. The fuel distribution needed to be improved in the middle 80s, GM saw that coming so they approved a redesign of the CFI and that became the TPI. It still had long tube runners, but it gained port injection. That made the engine another 0.5 sec (or better) quicker in the quarter and the IIRC the mpg also improved. You could make similar arguments about improvement in performance and economy if you compare TPI to the Gen II LT1, but the newer item always has the benefit of more development, more computer technology, and evolution.

CFI married the TBI from the 8-6-4 Caddy engine (search for Bowler) and adapted it to a cosmetic copy of the 68-69 Crossram racing manifold used in the Camaro Trans Am engines. It was a fairly inexpensive way to gain performance and economy while at the same time putting a racing-style manifold onto the Vette. No one whined about it back then.... but many owners decided that the TPI looked (and performed) even better so they swapped them. The other issue is that the CFI, like any TBI engine, won't run well if it is not maintained (IAC cleaning, TPS replacement, CTS replacement, and general TB cleaning plus balancing if needed).

So it's rather unfair, and probably more ignorant, to compare the 25-year-old CFI to engines that are more modern that have improved computer control, better flowing cats, and roller valve gear. The right comparison is the 1982 200 hp CFI L-83 to the 1981 computer-controlled carb 190 hp L-82, both Corvette engines of the same period and having the same basic ingredients.

Do a search here for Midgley and you'll find the other posts discussing the history of the CFI. HTH.

EDIT: the CFI can be modified to reduce some of the shortcomings. Tom400cfi got into the low 13s with a 400 engine, Grumpy ran mid 13s using a 350, so it follows that high 13s or low 14s are achievable with a 305.

People that own and mod TPI are in exactly the same boat, because their manifolds share long small-area runners so their engines are also airflow limited. There are more aftermarket parts available to mod the TPI but they are pricey and the intake stops being a TPI once the Superram or miniram (or LT1 intake) is used. The same thing can be said for the replacements for the CFI: the XRam and the Offy-type cross ram manifolds. More power is available but it's not really stock CFI anymore.

ck76239

Thanks for the reply.... I did a seach in the forum for those names, but came up empty handed....

Do you remember if that had to do any mods to their ECM, I hope not, as I'm not knowledgeable....

I bought a Haynes manual for 82-92 Camaro's, but it does not say much in particualr about the Crossfire...

Like I said, this car will not be my daily driver, so I'm not scared to get into and get dirty

But, in the end, I would like a car that is somewhat streetable, and run in the 13's. I would like to use the crossfire, if i can learn more about it, but if it becomes too much, I wouldn't be opposed to a carb

CK

kdrolt

Just do a search for cfi under the TBI forum. You'll find all the posts you'll need. It will also steer you to the Crossfire Vault website. I can't answer the ECM question.

Get a used FSM (factory service manual) -- it will be MUCH better than the Haynes. Try eBay, and also try www.helm.com because they have had specials on older FSMs recently.

Going to a carb is always an option but I doubt you'll need to do that.

DM91RS

Try this and other posts by ben to see how far a "crossfire" can be taken.


https://www.thirdgen.org/techbb2/sho...readid=298691:)

Street Lethal

iTrader: (16)

How so? Both the Super-Ram, Mini-Ram and Stealth-Ram (and don't forget about the T-Ram) are all port injected set-ups, and are all tuned via the ECM....

kdrolt

Hah! Nice try. I don't think GM meant (ecm) tuning as much as they meant acoustic tuning.

Street Lethal

iTrader: (16)

kdrolt, you emphasize "hah", as if I were challenging you!?

As for "acoustic" tuning, well, installing an LT1 intake, Super-Ram intake, Stealth-Ram intake, Mini-Ram intake, T-Ram intake, while keeping the stock ECM and wiring.... with all of them still being port injected, equals you dodging what I actually meant.

They are all still tuned port injection based. The only thing that changed, is the amount of air now entering the engine's combustion chambers... and at what rate.

Installing a Holley two inch TBI intake manifold, with a 454 throttle body, onto a stock 305 TBI, is the same exact principle. An increase in runner length and flow rate.... but it's still TBI.

kdrolt

Oops. Sorry.

TPI = (acoustically) tuned equal-length runners, with port (fuel) injection..... but what it really means is the GM factory intake on L98 and LB9 optional engines in 3rdgen Fcars and 85-91 era Vettes.

CFI is also acoustically tuned with equal-length runners, but non-port-injection (it uses dual small TBI)

Regular TBI and carbs for that matter, using single- or dual-plane intake manifolds, technically are also tuned but the runners are not equal length so you get slight acoustic tuning enhancement at several different rpms instead of all of them contributing near one rpm. So it would be accurate but misleading to call an ordinary manifold a tuned one, because they runners don't all do the same thing.

As far as the intake swaps are concerned --- generally speaking when someone says that their car is TPI, most people think that it has all or some of the original factory 3-piece intake. If you replace that 3-piece manifold with anything else, in my definition it's not TPI in the manner of GM. Is it still tuned? Yes, but at a different enging rpm (higher rpm for shorter runners). Is it still port injected? Yes, that's obvious to all. If you replaced only the curved runners of the TPI and used Edelbrock's or ASM's version of them, is it still TPI? Well, it still looks mostly TPI to me and most people that do those mods state them in their .sig.. while still calling it TPI. When someone swaps in a miniram or LT1 intake or a Superam, it doesn't really fit the description of TPI as I know it. I know it's semantics, but when someone tells me TPI on a 3rdgen Fcar I expect to see a 3-part mostly-GM intake.

BTW GM has been using TPI on most of their intakes now for many years, from v8s to 4 cylinders, as have most companies..... they just don't often use the "Tuned Port Injection" marketing slogan much. I wonder if GM owns it? FWIW.

Street Lethal

iTrader: (16)

I'm aware of it's definition, thanks for looking out though...

Incidently, you again emphasize "port (fuel) injection", as if it were in direct opposition to the other intakes' methods. If this is the case, and other than the fact of different runner length, and more flow capacity, how the heck are they different? Do they not work the exact same way, in principle?

In retrospect, would paying good money in getting a stock Corvette L98 head worked... to be equal (in every way) to that of an aftermarket Trick Flow head, no longer constitute the stocker as an "L98" head? Same casting number, but it no longer shares it's stock flow with other stamped/copyrighted L98 Corvette heads.

Street Lethal

iTrader: (16)

Just to add to this though, I find it very interesting that Summit embellishes it as the "TPI Stealth Ram Manifold" (for just the intake), and not, "Stealth Ram Manifold, Replacement For TPI". Maybe the people over at Summit/Holley got it all wrong. Maybe someone should give them a call and explain the principle of "acoustic" to them.....

Edit: Just so you're aware, I'm only teasing with you... so don't take it the wrong way.

kdrolt

Hey, that's why I'm here.



I was drawing a comparison between the TPI and CFI --- both are tuned single plane intakes, one is port injection and the other isn't. No one calls the CFI a TPI even though it has tuned-ports and is (fuel) injected.

Well, if I was spending your good money, I suppose it might constitute a modified stocker. <g> I'll stop splitting this hair now. <vbg>

Street Lethal

iTrader: (16)

Hey, we're only discussing, right? We're all F-Body bretheren...

BonzoHansen

I had an 82 TA with CF. It is not a great manifold, I am told it has fuel puddling issues, but you can make it a fun drive. Mine ran low 13s all day with a 350/TH350. It did not like hot, humid days.

Mine had the throttle plates punched out to 1", and bigger 350 injectors and higher fuel pressure. Cam selection and the right chip are important. Torque Converter choice is probably big too. When I did mine in the late 80s, the cool parts didn't exist. I had a Banks 3" system, the first on the market. This was even pre-Crane Compucams. Mine ran a bit rich at idle and leaned out top end. But the rich low end gave it nice throttle response.

Get the correct Helm manual. A must have for that beast. I just found mine last week sorting through boxes of stuff. It is in like 3 big pieces and lots of pages. You will end up knowing more than most GM techs did about that system.

It was nice to drive, had a nice throaty sound and started in one turn of the key. Way better than the electric carb ones!