JLeatherman

Ok,
Perhaps some of you have seen my other posts regarding my engine rebuild and the different directions it has taken. When I dropped the engine off with the builder last Friday, the route it was going to take was a carbed 355 built to rev high.
Well, I called the builder today to see how it was progressing, and he said he wanted to talk to me about something. So, I went down there this afternoon to take a pic or 2 and find out what has changed. You guys will not believe what he said. He told me that he had been thinking about my build and he'd never done one for a C4. So he started calling other engine builders he knew. He's been doing builds for 30 years, so he had quite an extensive list of contacts including a senior engineer at a cam company (I think he said Comp Cams, but I was too stunned at this point to remember). Everyone he talked to actually said the same thing. They said the actual downfall of the crossfire injection system was that the engine was too small. They said on an engine that needs more air, the system was fine and that a 383 with a crossfire system on it was great. The guy who works for the cam company actually said he had just the cam for it. It sounded a little big to me, but this guy designs them so I'm gonna listen. I'll post the exact specs on the cam when I get them, but it's about 236/230 duration and ~480 lift. I talked to my guy and he has agreed to port the manifold and bore the TBs for me to go along with the motor.
The final engine is going to be a 383 stroker with 9.3:1 compression, all forged internals, Hedman LT headers, ported crossfire manifold matched to ported 624 heads, pretty radical cam, and all the little stuff (screw-in studs, guide plates, high volume oil pump, etc.).
Now, here are a number of questions. Now that I'm keeping the crossfire, I need to learn about tuning. Exactly what computer do I need? Do I need "Prominator" or are all EProms the same? I already have WinALDL, do I need anything else to tune with? Realistically, what kind of horsepower can I get out of this system? What do I need to do to the crossfire (Injectors, FP Regulator, etc.)? The guy buidling the engine can get me cheap parts, so I need to round up a parts list of stuff I need. I figure I'll replace the TPS, both IACs, both Injectors, all the sensors (knock, coolant temp, oil pressure and temp, etc), all the front accessories, etc.

CFI-EFI

Once again, you have misunderstood. The Crossfire intake system was designed and built for the 305. If the Crossfire manifold needs a bigger engine to operate efficiently. why are you going to port the manifold and bore the TBs? If the stock Crossfire is best on a 383, then ported and bored, you will need a 406 or maybe a 434 to use it all. THINK!!! Does what you've written here, make sense?


Why replace the IACs, TPS, and all the sensors? Are you having trouble with any of them? If so, TEST and replace only the defective items.

My 13 second Crossfire has a totally stock (and original) long block. My ECM is factory, as is my prom. No tuning. I have a stock Crossfire fuel pump, stock injectors and the stock adjustable fuel pressure regulator. Of course, you may have greater aspirations than the level of performance I have achieved, thus far. Bear in mind, that other than the Vigilanti torque converter, I haven't spent much over $500.00 on improvements.

RACE ON!!!

JLeatherman

What I believe he meant was the general concept of the crossfire wirks better on larger motors, not this particular manifold. And who said the crossfire was designed for the 305? I thought the first crossfire was on the 82 Corvette with a 350.

Before I pulled the motor it was running very poorly. I never quite got it nailed down as to the cause, in spite of checking everything based on the FSM procedures. Since I'm going to have to tune this motor with a prominator, I want to know for a fact that all my sensors and such are working properly, or the motor will never get tuned. Stuff like the TPS that is 20 years old and only 30 bucks to replace is getting replaced before I try and tune the motor.

I do in fact have greater aspirations for horsepower. I'd like to see 400+ at the crank when the motor is done, and I'd like to see the car running respectable mid twelves. Granted, I have some trans improvements to make before I'll see that, but for now I think that between the port work, cam, stroker crank, and LTs the engine should definitely put out 400hp at the crank. Anyone got any guesses on torque?

LS6 Motor

They put the Crossfire on Z28's with 305's, starting in I believe 82, if I'm not mistaken. I had an 83 Z28 with the Crossfire, and that was definitely a 305.

CFI-EFI definitely knows what he is talking about with this setup, and is a big advocate of it, as I think he is one of the people that throughly understands the principles behind it.

CFI-EFI

Chew on that for a while before you swallow it. Why would a properly designed cross ram work better on a bigger engine it was designed for, than one properly designed for a smaller engine? Does that make any sense?



I did. Aren't you paying attention? The Crossfire injection system was also used on the 1982, 1983, and 1984, F bodied cars with 305 engines. If the CFI had been properly developed for a 350, they never would have been able to sell a TPI.



So test them! More power to you if you have that kind of money to burn. By the way, IF you have money to burn, why are you messing with a Crossfire?



Twelves are possible. Good luck.

RACE ON!!!

JLeatherman

I know CFI-EFI likes CFI. He gave me the most crap when I said I wanted to convert to a carb. I have a few questions.

First, can a heavily ported stock manifold feed a 383? What should I bore the TBs to? Injectors?

Can I really get away with 236/230 duration on a CFI 383?

What compression should I shoot for? I want to keep it on 87 octane.

xrcrx

A ported stocker should work well with your build. If you want to read a bit and see a few decent comparative photos check out x-ram.com They convert a Weiand single plane intake to accept the crossfire system using the top of the crossfire manifold. Take some of the promotional side of their articles with a grain of salt-they're selling a product so they downplay modding the stock intake. Some people I've been in contact with that use the x-ram swear by it, some swear at it and say a stock, ported manifold works better. There are definately 12 and 13 second Crossfire cars out there, and though the system is primitive it's reliable and simple, while effective. When the 84 debuted it had performance that was hard to match. My 84 is stock except for the cold air mod and K&N filter-don't overoil it if you get one, it will decrease airflow. That said , i'll drive my 84 anywhere anytime and get mid to high 20's on the highway and 18-19mpg around town. I'll be sticking with crossfire set-up when I build a 355 later next year. Do your homework and good luck!

qws

The crossfire forum has some excellent info on this subject under fuel in the message boards. Most of those guys are either using the X-ram or siamesed intakes, 2" TB's, and 80lb injectors @ 25 psi. Some using 90lb. I would think that you will need to use the 85 FP, that will give you up to 45 psi I think.

bogus

For reference, the TPI setup was designed for the 305, too.... in both cases, the 350 with either the Xfire or the TPI, they starve for air way too soon.

JLeatherman

I've been a member of the crossfire forum since I bought the car. I have another post running there right now, where everyone is telling me that the ported manifold isn't enough and go with the Xram. At the moment, though, I can't afford an Xram so I guess we'll just have to see what a stock manifold is capable of. Anyone running a siamesed manifold around here? Also, I replaced the FP with one from an 85 when the original one failed and it was one of the best things I ever did for the car. Even on a stocker it was great.

qws

I've been following that one as well.

cv67

Could the throttle bodies be adapted to one of these? THey would flow.

http://forums.corvetteforum.com/show....php?t=1490447

JLeatherman

Ok, I'm trying to figure out a lot of things on the engine at once. At the moment, I'm ordering bottom end parts. I need to get a concensus on the following things:

Compression ratio: is 9.3 good, or do I need closer to 10? I'm trying to keep it to 87 octane gas.

Cam: Is 236/230 duration ok for a crossfire setup? Do I need to run more compression to get away with that compression?

Manifold: Anyone here have anything good to say about siamesing?

bogus

you want a performance engine to run 87? You are really going to be sorely disappointed. Build this motor to run on 91 and you will be much happier.

Siamesing? That's done to the TPI. I don't think it will buy you much here.

I can't help you with cam.

Dominic Sorresso

J,

I think we've been through this at least once before.
http://forums.corvetteforum.com/show...ight=corssfire

Anybody that tells you they know just the cam for your motor without knowing the airflow through the heads is throwing around.
Several guys here and on the Xfire Forum have successfully built
12 sec 383s (Elkabong and Ben73). Mine is a stock block 350 using a Xfire manifold. Much of what I've done can be found here http://home.comcast.net/~surrexi2/xf...Enthusiast.pdf. A lot of the experimentation has already been done for you.
There are differences of opinion on tuning. I use Dynamic EFIs EBL ECM so you know what side of the street I'm on for that issue.
Go have some fun.

NitrousSam

The CFI won't like bigger cubic inches overall because airflow is the limitation of the CFI. If you want to run a bigger cubic inch engine like a 383 or 406 you will limit yourself and reduce your RPM potential even more.

bogus

ported 624 heads? stock iron? damn... get some aluminum 113s or something.

Torque Monster

I heard the crossfires were crappy so i wanted to get a tpi.

but maybe i should buy a crossfire instead? so I can do a stroker later on?

JLeatherman

If you want more info on crossfires, check out the forum:

crossfire.homeip.net

This is Ben's crossfire. I believe it is currently in the 12.50s or 40s.

http://www.crossfire.homeip.net/cfte...&TOPIC_ID=7657

CFI-EFI

Technologically, the TPI is a step up from the Crossfire. Performancewise, they are closer than most TPI owners care to admit.

RACE ON!!!