lance m p

OK, Im WELL aware of the limitations of the STOCK crossfire intake, however I have a race shop that allows me to use there flow bench. I first flow tested the stock intake, uderwhelming to say the least since the intake was designed to be used on a 305 cid engine. Well i was commetted to keep this car as close as stock as possible. I researched my options junk the system and go to a carb set-up w/ many intakes to choose from? Well do that and you just decreased the vaue of your vette. OR go to the X-ram or renagade intake? STILL not stock!! Well after many hours of research and discussion with the race shop I decided I would try and increase the flow rating as much as possible with the STOCK crossfire intake. Using a Holley contender intake as my goal for flow. 1st I cut the egr casing out, then cut the runners down by 1 inch removed all casting flaws, using a Dremel w/flex head curved intake ports, and CAREFULLY increased the total port volume by about 3/8" or more total. on the flow bench now out performed the Holley contender!!!!!

qwank

that's great that you got the stock manifold to flow well. now just rebuild/upgrade your throttle bodies, new heads, get a cam and burn a new chip and you'll be good to go!

Learning_Curve

I've always thought the crossram was a cool idea, just poorly engineered.
Do you have before and after pictures?

lance m p

Sorry no before pics, howevever do have after, will post soon. You should'nt have any problem finding stock pic of intake.

lance m p

If you would like, go to the tech/performance section and I covered most of the rebuild there.

alconk

I bought a used intake for my CFI not to hurt my original and did exactly what what you and must say WOW what a difference. Did you port match them as well? If so notice how much they close off the flow, supposely GM did that to get more torque. Who knows... Anyway did you also get rid of the vanes under the throttle body.

alconk

With these motors you have to be carefull on cam selection, these computers can't handle the adjustments (80Bps). The biggest would be a Comp U Cam 2040 unless you upgrade to a Ham board.

lance m p

I think you meant swirl plates? No I trimed them down SLIGHTLY and CAREFULLY bent them in just a lil, There installed from the factory to help automize the air/fuel mixture and help keep the fuel from puddlng in the bottom of the intake. keep in mind I SPEANT MANY hrs on this port job, go to the tech/performance forum on what all I did on the re-build of the engine. The factory casting [heads] was poor at best, I used a newer much heavier casting head if you take your time and do alot of measuring you can take quite of bit of material from the ports, just be very carefully on the bottom of the ports [water jacket!!]The Holly contender port size was smaller then the head intake port size, however there closely matched now, slightly smaller, which is fine, YOU DON'T want the head ports smaller.

lance m p

You are exactly RIGHT i used that EXACT cam 440-I/454-E, .50 dur 210-I/216-E, IMHO the real power is in the heads AND CAREFULLY matching all parts. I did MANY hrs of research before I came up with combination I have. I ALMOST went to a carb system ALMOST! do that and you just decreased the value of your vette!

lance m p

the casting where junk it did'nt even flow what the engineers came up with, because of the poor castings, theres ALOT of improvment to be made on that intake IF you got the patience!!

alconk

Exactly . Did you change out the rear gear or is it stock? Mine is the optional 2.87, believe that. Pretty pethetic for optional.

So which head did you use i.e. year , make?

lance m p

There a late casting 1990 head. dam can't remember the casting #s I think they were used on the goodwrench 350 crate motor, heavy casting though VERY! no worries about cracks between the valves LIKE the original heads. Meaning you can really do some HEAVY porting that the org. heads could'nt take all about the flow right? Yeah I got the same gear, personally I like it w/ the R4 700 decent lowend and barely idling at cruising speeds good for mpg's! Before the re-build I could get about 25-26 mpg's on the hwy.

alconk

My car averages about 15-16 mph on the highway and don't know why...All the maintenance items are new except the fuel pump, only getting 10psi.

74 LS4-454

Good thread, I also have a spare CFI set-up and would like to attempt this mod in the future. Sounds like it is really worth the time to get great results.

Wrecked82

In the late 90's, I did a basic port matching of my crossfire manifold, did away with the egr tunnel, smoothed the inside everywhere I could, did not cut back the runners (wish I did, but no one advised to do so, at that time), cut the sides of the swirl plate insert down, leaving only the vanes, new fuel pump, bumped fuel pressure to 15 psi, 1/2" tbi spacers (custom made for me). For those that might remember Twinnie/Twin Turbo, he made fun of my setup, calling it a Submarine sandwich. But I can break rubber in second gear on concrete. I only get 17 mpg at best, most of the time 15. But with high flow cat and borla's (for an 84 given to me with only 500 miles on them), my car accelerates great and sounds more powerful than it is. I know I am now below 7 secs in 0-60, which is a nice improvement from stock. Oh - engine replaced with the basic GM motor in about '98, which is suppose to have 249hp but with a carb and open headers.

alconk

Hmmm, very interesting Larry. I still can't decide to either install my extra manifold (already ported) or wait for the Renegade. I'm on the waiting list but they keep pushing it back.

lance m p

Thats not very good on the mpg's?? I had a 1987 C-10 W/ A 350 3.55 rear gears w/a R4 700 getting 17.5 on the highway? That does'nt make sense? A buddy of mine has a 1980 [carbed]vette getting 15 mpg's on the highway? That fp is kinda low, you can take the rear tb off [drivers side] and cut the weld off the rod to make it adjustable, shoot for about 15psi. Turn the rod COUNTER clockwise to increase fp, not sure if your stock pump will produce 15psi? Min.13psi, the 25-26 mpg I got was on a flat hwy and at 60mph.

lance m p

Yes it was a good mod. HOWEVER be ready to SPEND ALOT of time on it, the factory castings were terrible at best! I took more off the sides and top on the ports EXCEPT at the exit there your able to take alot off the bottom of the port and make sure you go ALL the way through the port. A flex headed porting tool is needed, I burnt up 1 dremel on this porting job! Oops! "sir I just bought this Dremel and it just quit working"?????
BTW do alot of measuring to get the ports as close AS possible.

alconk

I already did that but can't get up in there to adjust it. DCS just got there tool back in stock so I will be ordering that plus I'm gonna change out the fuel pump to the 85 unit. And maybe my fuel pump sock might be plugged a little because when the tank gets down to a 1/4 it starts to bog and going around a corner the car will die then come back on .

lance m p

Runner length, the looooong runners were supposed to increase low-end torque HOWEVER there to long and too SMALL for any real top-end power. You have to take alot of material out of the port size [CAREFULLY] don't forget you got a water jacket on the bottom. and on the length cut about 1" off the port inlet and angle the port at about 35 degrees that opens up the top of the port allowing the intake charge to inter the port at a higher velocity then the stock port which has to go down and around slowing the velocity down quite a bit.