I just bought a 84 corvette with a 5.7 crossfire double tbi any suggestions i know the heads and intake are junk highly restrictive it needs a cam but dont know the size until i flow test the heads has anyone done a crossfire how am i going to get the fuel required to run this thing
early 454 injectors, extrude hone the intake(that's the restrictor, not the heads and sand blast the inside to roughen after extrude hone) and the rest is pretty standard buildup. Ditch the stock 'puter and do at least a '7747.
-Carl
Thanks carl what about cam
Ohhh... Asking about Crossfire Injection is kind of like asking about the Illuminati. The information you seek is out there, but the average person cannot help you in your quest.
Crossfire was built to create a torque peak at low rpm with low lift, emissions and computer friendly parts. It has long runners with small cross-sectional area, a relatively small plenum, and EGR. This configuration worked fairly well with numerically low final drive ratios and relatively lightweight cars such as the Vette. It can provide good fuel economy and good reliability but it is not friendly to making high horsepower.
Looking for more performance can entail a few different routes toward success. The typical hotrodder path is to move the torque peak to higher rpm. This requires improving airflow throughout the engine and supplying enough fuel to make use of the air. This can also include changing the final drive ratio to a numerically higher ratio to better match the engine's torque peak to desired acceleration. This manifold quickly turns the Return on Investment into a low number when attempting large airflow gains.
The other approach is to follow GM's lead and build for improved torque at low rpm. Since Crossfire already has long runners which are beneficial to a low rpm torque peak, and since the vehicle is already built to work with the engine, it seems like this is a good route to follow if you want a mild build. Look for cams with high lift and early valve timing for a low rpm power peak. Roller cams can offer more aggressive profiles and greater ramp rates. Keep compression up and quench down and if possible move to a cylinder head with a fast burn chamber. Open up the intake runners as Carl mentioned and if you have the ambition and means, remove the EGR tube. Switch to a 7427 ecm for a better controller and store the stock Vette 'puter away as there are very few people around who can chip that one. (Anyone know if Ron Zimmer still makes tunes?) Cam choices for flat tappets might include XE249H or 260XFI-H13. Switching to hydraulic roller, the 260XFI-HR13 might work well.
Over the years there have been some very interesting crossfire projects and a number of passionate, or dedicated, or maybe just plain crazy Crossfire fans have achieved impressive results with this system. If you are interested in looking at what other folks have done, you should make friends with the Wayback Machine.
There was a Crossfire specific forum at http://www.crossfire.homeip.net/ or http://www.crossfire.webhop.net/. Some of the pages from that forum may have been saved in the Internet Archive but unfortunately it doesn't look like all of the forum was archived. Maybe the archived site is accessible with a valid username and password?
Once upon a time a company named DCS was manufacturing their own Crossfire specific intakes, The Renegade. Lots of work went into this project and a number of manifolds were sold. Maybe there are a few floating around today?
You can read about a number of crossfire manifold and TB improvements here.
Digital Corvettes is still active and has a number of archived threads regarding Crossfire performance.
I've had a Crossfire system since the mid '80s. It was removed from an '83 F car long before custom tuning was easily available. In '92 or '93 I installed it on a mild 302 in my '57 pickup with a copy of the 350hp 327 Corvette cam. It's travelled across country, worked and pulled trailers, been driven in all kinds of different weather with very few problems. If I ever get excited about upgrades I have an SY1 intake I can use to retire the mostly stock Crossfire system.
Thanks for the info 1 project 2 many i will research those places
Hi Jason,
I used to work for Erson cams and am glad to talk about camshaft design any time. People on the interweb like to argue about cams, so I don't usually comment. I sell custom cams that work, lol. Just a quick note that you can't compare numbers between manufacturer's, even @.050".
It's the heart of the engine, and is not a simple subject.
-Carl
Posting Permissions
Reply With Quote
Bookmarks