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Hello everyone, and Thank You all for the invite. I would really appreciate any knowledge about high performance tuning on a 1984 Corvette Crossfire Injection. Thanks in advance.
Hark, incoming battle cry of the "I've never actually owned a Cross-fire, but they all suck" crowd....
The short list is, be ready to swap out the heads, exhaust, fuel pump and the ECM. Be willing to port the intake until you've poked thru the walls and top of the runners and refilled with epoxy a few times. Then port it some more. Then you can use the words "performance" and "Cross-fire" in the same sentence and not get flamed by the non experienced haters ( I've had my '84 since 2001 )
At that point you're well past any stock TPI. The 85 and a handful of the early 86s actually had the exact same block and heads as the 84; they fail to admit that fact when they beat the drum of how the 84 engines suck... Of course their intake base wasn't cast with a 1inch by 1.2 inch intake port with 1/4" thick runners
The 624 heads are a "lightweight" cast iron low compression (76cc) head that were never intended for performance and have a tendency to crack at the exhaust valve seats when overheated. Plus they flow abysmally low without a different cam and 1.6 rockers. So of course, slap em in a Corvette and design it to run at a higher than average V8 operating temperature for emissions...
The stock unported intake actually flows almost decent, when it's on a 305. Slap it on a 350 and it flows just enough to run down the highway and put a stranglehold on the extra cubes' potential
What is your goal for the car, and your budget? The Cross-fire community here will get you sorted out with a plan of action. Even if it's just balancing the throttle bodies and replacing old rotten vacuum lines to keep it purring along reliably for a few more decades
Last edited by flannel_man; Jul 27, 2024 at 08:14 PM.
Hello everyone, and Thank You all for the invite. I would really appreciate any knowledge about high performance tuning on a 1984 Corvette Crossfire Injection. Thanks in advance.
headers with free-flowing exhaust, heated O2 sensor, 1985 fuel pump, 13psi fuel pressure, port intake manifold without changing ECM. I did port intake without grinding threw runner walls. using an inexpensive sonic tester. after this it gets more complicated.
better flowing heads, camshaft, tunable ECM. bigger fuel injectors, parallel plumbing TB's, external fuel pressure regulator. that's about it.
Just did the Cross Fire conversion to TBI. Used a unit from SPR Performance. The car is insane fast compared to what it was. The TBI was a little pricey, it came in at $650ish. I went this option because it is plug and play. If you are looking to do an aggressive camshaft later than you will have to go with a standalone EFI system like sniper. If you go with a cam like a Edelbrock performer plus you should not have any problems. I also did the smog delete specifically for the 84, it comes with a nice pulley.
As for changing cams, heads and doing a bunch of other stuff to the engine it really is not worth it. Once you start adding up the cost of everything it is cheaper to buy the entry level 350 from Blueprint. I know because I just bought summit heads, rocker arms, and cam for my 84. Not to mention a new TKX from silver sport. Long story short by the time you spend 2k on your top end (hydraulic flat tappet cam) and a bunch of bolt-on goodies you are halfway to the cost of a new 350 crate engine. Less than that if you sell your old engine on CL for $500. The benefit with a Blueprint engine is that comes with a roller cam and one-piece rear main seal.
As for the CF engine it is a fine platform to build off of. The induction system is very restrictive, I have provided pics. Don't bother with porting either it's a waste of time unless you are bored and just want to find something to do. Several good videos on CF porting on YouTube with the end result being everyone ditching the intake later anyway. I put the Weiand X-Celerator intake on for hood clearance. It is the worst intake you can put on a small block, and I still had more power "everywhere" in the power band. I thought I was going to lose power down low, not at all. I picked the open plenum design for better fuel atomization, and I think the spacer/adapter plate provided by SPR and the injector spacer plate helped with increasing the plenum volume.
The best bang for the buck is to change the intake and put in 1.6 roller rockers. You will pick up 50hp and some torque (this is not normal; the CF intake is really that bad). All this can be done for 600-800 dollars depending on the cost of your TBI. I just bought headers had them coated and bought true duals with Corsa cat back. The exhaust with jet hot coated headers came in at $2200. Considering I will get 30hp if I am lucky the bang for buck is not there. Summit cylinder heads is another great bang for the buck addition great Motor Trend article on them. 50hp for about $1200 bucks.
No tuning required with TBI upgrade, and it will run better than the CF setup. This is most likely the reason GM ditched even the TPI setup and went with TBI units later. I had a 92 Camaro 305 H.O with the TBI and it laid rubber everywhere. I will say this the long runners on the TPI do produce a ton of torque down low, it just runs out of air at about 4500rpm.
OLD Cross-Fire Intake ports New Intake ports X-Cellarator Intake 30% increase in area New bored TBI 675cfm Smog delete pulley direct bolt in
Last edited by Lamike121; Jul 28, 2024 at 10:01 AM.
A patient shopper can wait and find these parts on market place for a good deal, I went with the Holley direct replacement unit for 87-89 Chevy trucks. It has 2" bore, I also you a Holley tbi intake too, good to 6500rpm, has an egr mount, but hood clearance is tight but not impossible.
Just did the Cross Fire conversion to TBI. Used a unit from SPR Performance. The car is insane fast compared to what it was. The TBI was a little pricey, it came in at $650ish. I went this option because it is plug and play. If you are looking to do an aggressive camshaft later than you will have to go with a standalone EFI system like sniper. If you go with a cam like a Edelbrock performer plus you should not have any problems. I also did the smog delete specifically for the 84, it comes with a nice pulley.
As for changing cams, heads and doing a bunch of other stuff to the engine it really is not worth it. Once you start adding up the cost of everything it is cheaper to buy the entry level 350 from Blueprint. I know because I just bought summit heads, rocker arms, and cam for my 84. Not to mention a new TKX from silver sport. Long story short by the time you spend 2k on your top end (hydraulic flat tappet cam) and a bunch of bolt-on goodies you are halfway to the cost of a new 350 crate engine. Less than that if you sell your old engine on CL for $500. The benefit with a Blueprint engine is that comes with a roller cam and one-piece rear main seal.
As for the CF engine it is a fine platform to build off of. The induction system is very restrictive, I have provided pics. Don't bother with porting either it's a waste of time unless you are bored and just want to find something to do. Several good videos on CF porting on YouTube with the end result being everyone ditching the intake later anyway. I put the Weiand X-Celerator intake on for hood clearance. It is the worst intake you can put on a small block, and I still had more power "everywhere" in the power band. I thought I was going to lose power down low, not at all. I picked the open plenum design for better fuel atomization, and I think the spacer/adapter plate provided by SPR and the injector spacer plate helped with increasing the plenum volume.
The best bang for the buck is to change the intake and put in 1.6 roller rockers. You will pick up 50hp and some torque (this is not normal; the CF intake is really that bad). All this can be done for 600-800 dollars depending on the cost of your TBI. I just bought headers had them coated and bought true duals with Corsa cat back. The exhaust with jet hot coated headers came in at $2200. Considering I will get 30hp if I am lucky the bang for buck is not there. Summit cylinder heads is another great bang for the buck addition great Motor Trend article on them. 50hp for about $1200 bucks.
No tuning required with TBI upgrade, and it will run better than the CF setup. This is most likely the reason GM ditched even the TPI setup and went with TBI units later. I had a 92 Camaro 305 H.O with the TBI and it laid rubber everywhere. I will say this the long runners on the TPI do produce a ton of torque down low, it just runs out of air at about 4500rpm.
OLD Cross-Fire Intake ports New Intake ports X-Cellarator Intake 30% increase in area New bored TBI 675cfm Smog delete pulley direct bolt in
stock crossfire intake flows about 150cfm, a maxed out ported stock crossfire intake flows about 230cfm (without getting into water jacket), X-Cellarator Intake manifold flows 250cfm and a renegade should flow at least 260 cfm. renegade isn't available at this time. X-Cellarator flows 100cfm more that stock crossfire.X-Cellarator would be good with some high flowing 195cc heads. stock crossfire intake is very restrictive. the stock exhaust manifold is also restrictive.
stock crossfire intake flows about 150cfm, a maxed out ported stock crossfire intake flows about 230cfm (without getting into water jacket), X-Cellarator Intake manifold flows 250cfm and a renegade should flow at least 260 cfm. renegade isn't available at this time. X-Cellarator flows 100cfm more that stock crossfire.X-Cellarator would be good with some high flowing 195cc heads. stock crossfire intake is very restrictive. the stock exhaust manifold is also restrictive.
A lot of guys that were able to find a good Renegade casting when they were being offered often complained about a stumble or flat spot at 2500-2800 rpm. There are two guys on YouTube that have documented this problem. One guy tried to tune it out on the dyno but couldn't get it fixed. There appears to be a design problem in the plenum area. I wanted to try the Edelbrock EPS manifold, but I was worried about hood clearance. I am about to pull the trigger on a cowl hood, this would open up my manifold selection.
All factory tbi systems that run good have small plenums, these huge plenum intakes require a ton of fuel when you mat the gas. Thats probably why the crossfire intake has swirl plates and a big coolant port under the intake, that helps keep the fuel from puddling.
I'd like to try a tbi system with a 2v Victor Sportsman. I'd have the mount shaved down quite a bit to make it fit.
From: Arizona - If you don’t know CFI, STOP proliferating the myths around it...
Well, I run the crossfire system on my 82 and it runs rather well. My goal this winter is 11.99 NA, ALL CFI system. If you do CFI correctly, it will run well...Jus sayin'. GL with your project.
A lot of guys that were able to find a good Renegade casting when they were being offered often complained about a stumble or flat spot at 2500-2800 rpm. There are two guys on YouTube that have documented this problem. One guy tried to tune it out on the dyno but couldn't get it fixed. There appears to be a design problem in the plenum area. I wanted to try the Edelbrock EPS manifold, but I was worried about hood clearance. I am about to pull the trigger on a cowl hood, this would open up my manifold selection.
yes ,I've seen those video's, but I've also seen video of renegade dyno 344rwhp or about 400hp at the crank.
From: Arizona - If you don’t know CFI, STOP proliferating the myths around it...
Originally Posted by Lamike121
A lot of guys that were able to find a good Renegade casting when they were being offered often complained about a stumble or flat spot at 2500-2800 rpm. There are two guys on YouTube that have documented this problem. One guy tried to tune it out on the dyno but couldn't get it fixed. There appears to be a design problem in the plenum area. I wanted to try the Edelbrock EPS manifold, but I was worried about hood clearance. I am about to pull the trigger on a cowl hood, this would open up my manifold selection.
Post the links to those, I wanna see it. Thanks. I get NO stumbling at all.
A lot of guys that were able to find a good Renegade casting when they were being offered often complained about a stumble or flat spot at 2500-2800 rpm. There are two guys on YouTube that have documented this problem. One guy tried to tune it out on the dyno but couldn't get it fixed. There appears to be a design problem in the plenum area. I wanted to try the Edelbrock EPS manifold, but I was worried about hood clearance. I am about to pull the trigger on a cowl hood, this would open up my manifold selection.
it actually seems to be a fuel system issue some very very weird harmonics in that band. I had the issue too and made 2 small adjustments to my plumbing that pretty much eliminated it.
From: Arizona - If you don’t know CFI, STOP proliferating the myths around it...
Paul, I thought that was what he was talking about as well, but I almost think not unless they were running solid hard lines for fuel, which WILL cause an odd harmonic like you said. That is why I wanted to see the vids. With just a manifold change, that should not happen. Let see the vids on the stumble... Running rubber hose will take care of the issue a lot if not entirely. OR run a damper valve like the camaro had.
Paul, I thought that was what he was talking about as well, but I almost think not unless they were running solid hard lines for fuel, which WILL cause an odd harmonic like you said. That is why I wanted to see the vids. With just a manifold change, that should not happen. Let see the vids on the stumble... Running rubber hose will take care of the issue a lot if not entirely. OR run a damper valve like the camaro had.
Tom, when mine was on the stock ecm and engine, I did observe a similar stumble in that range. However due to all the issues I had with my manifold, I thought it was perhaps that. After my excursion with the modded engine, I feel that was happening then too.
I know the video he is referring to, guy has a bunch of videos on the manifold but never a video of the issue. I do believe it happened. I don't recall the video though.
Here a one video I can find a few others. I wanted to keep my CFI intake manifold I love the way it looks and works with the cold air intake through the hood. However, I can never find an intake and the lack of QC with the casting makes me wonder if I will even get a good intake.
This video was impressive about 50hp gain with Renegade and 1.6 rockers. He has some very weird dips in the dyno graph. I am trying to figure out if this is the similar problem the guy had in first video with the fluttering, or another issue like fuel pressure.
GL with your project.
