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Hi everyone, brand new member here! Just got a bone stock 84 crossfire. The car is in excellent shape, and runs like a champ. But we all know about the poochiness of the stock crossfire.. I don't need anything that's gonna pull 12's or anything, but I'd like to wake this thing up a little bit. I'm gonna have an extremely low budget for this, because my wife is already super pissed at me for getting the car. So my question is, if I port the hell out of my stock intake, and have my throttle bodies bored to 2" or so, throw a fairly mild cam in it, and some long tube headers, would that get me near the 250hp mark? I know there are a couple other more subtle things I can do with advancing my timing, raising fuel pressure and so on, but will I even be in the ballpark? I know the stock heads are killing me, but I can't swing a set of heads any time soon. Would it be worth my while, or cost efficient to have my stock heads ported? Thanks in advance!
Port the stock intake and bump the timing. Headers and a cam won't do much with the stock heads. If you do a cam keep it mild otherwise the ecm will freak out. You can get to stock l98 territory with a very mild cam and a ton of porting. (250 at the crank) port the intake and see how you like it. It makes a huge difference. Depending on the driver it could get you almost a second in the quarter from stock iirc. You're not gaining much power but you are extending the range of the power you have a considerable amount.
Port the stock intake and bump the timing. Headers and a cam won't do much with the stock heads. If you do a cam keep it mild otherwise the ecm will freak out. You can get to stock l98 territory with a very mild cam and a ton of porting. (250 at the crank) port the intake and see how you like it. It makes a huge difference. Depending on the driver it could get you almost a second in the quarter from stock iirc. You're not gaining much power but you are extending the range of the power you have a considerable amount.
Thanks for the advice! Are there any other stock gm heads that would be better than what's on it? Like, something I could grab from a junkyard? And do you know if there's any truth to the 85 and newer fuel pump doing wonders for it? I've seen a lot of guys say it's completely pointless unless the stock pump is already failing. Thanks again!
Thanks for the advice! Are there any other stock gm heads that would be better than what's on it? Like, something I could grab from a junkyard? And do you know if there's any truth to the 85 and newer fuel pump doing wonders for it? I've seen a lot of guys say it's completely pointless unless the stock pump is already failing. Thanks again!
Check your fuel pressure under full load. If you cannot maintain 13 then you're losing power. Mine would set fine at idle but just free revving would knock it down to 10. Getting the pressure set right does wonders for how it drives.
The stock heads on that engine flow way better than the intake manifold. If you port the beejesus out of the intake manifold, you'll be able to approach the flow capacity of the stock heads. At best, some 1.6:1 rocker arms in the stock heads will be all you'll ever really be able to make use of.
Stick some wide band sensors in it and watch your mixtures. If you get to the point where you need more fuel, bumping the pressure up and the later fuel pump will help out. Until you get enough air in the thing (by porting the intake), there's no need for any fuel system mods either.
The biggest restriction on that engine is the intake, and it's a major restriction. That's the first thing to modify to get more power.
That article puts some numbers on the intake manifold issue. The throttle bodies (two 2" bore throttle bodies) can flow 750cfm +/-, but they are hampered by the stock intake manifold, which on a flow bench can only flow 475cfm. That's a huge restriction. That article mentions a long gone company called "Performance Plus Systems" that used to make a replacement intake manifold they called the "X-Ram" manifold for the L83 Crossfire engine. That manifold was capable of flowing what the engine needs (up over 1000 cfm), and changing only the intake manifold, they went from 15.6 seconds/86 mph in the quarter mile with the stock manifold to 14.3 seconds/97mph in the quarter mile changing only the intake manifold to the X-Ram product.
The Performance Plus X-Ram manifold is no longer made, and most of the after market manifolds for the crossfire V8 aren't anywhere near as good as that product was. Porting the heck out of the stock manifold is probably the best course of action today.
Last edited by C6_Racer_X; 09-19-2018 at 09:38 AM.
The stock heads on that engine flow way better than the intake manifold. If you port the beejesus out of the intake manifold, you'll be able to approach the flow capacity of the stock heads. At best, some 1.6:1 rocker arms in the stock heads will be all you'll ever really be able to make use of.
Stick some wide band sensors in it and watch your mixtures. If you get to the point where you need more fuel, bumping the pressure up and the later fuel pump will help out. Until you get enough air in the thing (by porting the intake), there's no need for any fuel system mods either.
The biggest restriction on that engine is the intake, and it's a major restriction. That's the first thing to modify to get more power.
That article puts some numbers on the intake manifold issue. The throttle bodies (two 2" bore throttle bodies) can flow 750cfm +/-, but they are hampered by the stock intake manifold, which on a flow bench can only flow 475cfm. That's a huge restriction. That article mentions a long gone company called "Performance Plus Systems" that used to make a replacement intake manifold they called the "X-Ram" manifold for the L83 Crossfire engine. That manifold was capable of flowing what the engine needs (up over 1000 cfm), and changing only the intake manifold, they went from 15.6 seconds/86 mph in the quarter mile with the stock manifold to 14.3 seconds/97mph in the quarter mile changing only the intake manifold to the X-Ram product.
The Performance Plus X-Ram manifold is no longer made, and most of the after market manifolds for the crossfire V8 aren't anywhere near as good as that product was. Porting the heck out of the stock manifold is probably the best course of action today.
Wow, you guys are on top of stuff! Thanks so much for the help. As far as camming it goes, my understanding is that I can put some lift to it, as long as I stay at the stock duration.. does that sound right? And can anybody suggest a specific cam? I guess that honestly I don't really even care if I don't have big gains from it, but it would be nice to chop up the idle a little bit.
Wow, you guys are on top of stuff! Thanks so much for the help. As far as camming it goes, my understanding is that I can put some lift to it, as long as I stay at the stock duration.. does that sound right? And can anybody suggest a specific cam? I guess that honestly I don't really even care if I don't have big gains from it, but it would be nice to chop up the idle a little bit.
The 1.6:1 rocker arms will open the valves more with the stock cam. It's the same effect as a stock duration, higher lift cam, but much easier to install. RockAuto.com even has some inexpensive 1.6:1 rocker arms. They want $7.08 each for the "standard" ones and $10.19 each for the roller tipped rocker arms in 1.6:1 ratio. Find a 5% discount code (I'll see if I can find one, mine has expired) and it's less than that.
You could even go 1.7:1, although those tend to be a bit much for that engine.
The only way I'd mess with the cam on that engine is if you're having low oil pressure and you suspect cam bearings are excessively worn.
And, to reiterate, in case you didn't fully understand, with a stock (unported) manifold, nothing you do to that engine will make any more power. The manifold is the biggest restriction, and it's crazy restrictive compared to the rest of the motor. Once you port the intake, some headers would also help flow. But everything is a waste of time and money if you don't port the heck out of the manifold first.
Wow.. Had no idea the quality was so low on those.
It's hit or miss. If you skim through the reviews there are various complaints and satisfied customers. I just happened to get one that was really bad. And generally that is my luck. If you call summit and ask them to check it over before they send it they probably will because at least they care. They exchanged enough of them that they will most likely understand.
I think the problem is that each one is cast then machined so there is a lot of room for error. On top of that it is low volume so they really can't be making much on them. Porting the stock one is free (Well, bits and rolls are cheap) and it'll get you to 85% of what that can do. Unless you are going all out that is more than enough. And you can say you did that yourself. I will say that the stock one literally stops at 4300. That one let me wind out to 5200. Porting would do the same but probably won't allow you to get to 6500 like that one will. The ports match a 195cc runner almost exactly so that thing was designed to accommodate a pretty serious mill. Again, my luck is what ever the worst case scenario is, it will happen to me.
The stock heads on that engine flow way better than the intake manifold. If you port the beejesus out of the intake manifold, you'll be able to approach the flow capacity of the stock heads. At best, some 1.6:1 rocker arms in the stock heads will be all you'll ever really be able to make use of.
Stick some wide band sensors in it and watch your mixtures. If you get to the point where you need more fuel, bumping the pressure up and the later fuel pump will help out. Until you get enough air in the thing (by porting the intake), there's no need for any fuel system mods either.
The biggest restriction on that engine is the intake, and it's a major restriction. That's the first thing to modify to get more power.
That article puts some numbers on the intake manifold issue. The throttle bodies (two 2" bore throttle bodies) can flow 750cfm +/-, but they are hampered by the stock intake manifold, which on a flow bench can only flow 475cfm. That's a huge restriction. That article mentions a long gone company called "Performance Plus Systems" that used to make a replacement intake manifold they called the "X-Ram" manifold for the L83 Crossfire engine. That manifold was capable of flowing what the engine needs (up over 1000 cfm), and changing only the intake manifold, they went from 15.6 seconds/86 mph in the quarter mile with the stock manifold to 14.3 seconds/97mph in the quarter mile changing only the intake manifold to the X-Ram product.
The Performance Plus X-Ram manifold is no longer made, and most of the after market manifolds for the crossfire V8 aren't anywhere near as good as that product was. Porting the heck out of the stock manifold is probably the best course of action today.
Hey, what are wide band sensors? I'm assuming it's a different o2 sensor? And do I replace my existing 02's, or do I just add them? Also, are my stock injectors gonna keep up with the extra air after my intake is ported? Will I need to have my computer tuned? Sorry if these are retarded questions. I've always been a carb guy.
Hey, what are wide band sensors? I'm assuming it's a different o2 sensor? And do I replace my existing 02's, or do I just add them? Also, are my stock injectors gonna keep up with the extra air after my intake is ported? Will I need to have my computer tuned? Sorry if these are retarded questions. I've always been a carb guy.
Wideband = wideband O2 sensor AKA Air Fuel Ratio sensor. Search Amazon or fleaBay for "Air Fuel ratio meter kit" and you'll find many choices. That's how you monitor the air fuel ratio. Some of the kits include a harness and electronics to feed a traditional O2 sensor signal to the existing PCM/engine management system. Others use an additional sensor not connected to the fuel injection system.
You want to monitor the mixture specifically so you can tell if your existing injectors and system are keeping up with the added air flow. If it starts going lean, especially WOT at high RPM's, you have a capacity issue.
Tuning the computer isn't very easy in these older cars. Fortunately, the computer is pretty simple and easily tricked into providing more fuel. Higher fuel pressure (the newer pump and regulator), and/or larger injectors can deliver more fuel from the existing system without retuning the computer.
Wideband = wideband O2 sensor AKA Air Fuel Ratio sensor. Search Amazon or fleaBay for "Air Fuel ratio meter kit" and you'll find many choices. That's how you monitor the air fuel ratio. Some of the kits include a harness and electronics to feed a traditional O2 sensor signal to the existing PCM/engine management system. Others use an additional sensor not connected to the fuel injection system.
You want to monitor the mixture specifically so you can tell if your existing injectors and system are keeping up with the added air flow. If it starts going lean, especially WOT at high RPM's, you have a capacity issue.
Tuning the computer isn't very easy in these older cars. Fortunately, the computer is pretty simple and easily tricked into providing more fuel. Higher fuel pressure (the newer pump and regulator), and/or larger injectors can deliver more fuel from the existing system without retuning the computer.
Thanks so much!! I'll get some stuff on order and let you know how it goes!
I'll even post a pic or two of the manifold ports (the ends that mate to the head). Before porting. The FelPro Intake gasket is there to show how much material to remove. After porting. Note how much larger (taller) the ports are on this manifold.
You might want to buy a spare manifold for this project. You'll be grinding on the thing for a few days. Read the full page there for some tips and some things to watch out for. If you have it sandblasted/media blasted, make sure you take all the shields and other bits off so no sand is trapped within the part to get into the engine.
Also use stones that are specifically for working on aluminum. They don't clog up as badly as "standard" metal grinding stones that are for steel/cast iron.
Last edited by C6_Racer_X; 09-20-2018 at 06:01 PM.
I'll even post a pic or two of the manifold ports (the ends that mate to the head). Before porting. The FelPro Intake gasket is there to show how much material to remove. After porting. Note how much larger (taller) the ports are on this manifold.
You might want to buy a spare manifold for this project. You'll be grinding on the thing for a few days. Read the full page there for some tips and some things to watch out for. If you have it sandblasted/media blasted, make sure you take all the shields and other bits off so no sand is trapped within the part to get into the engine.
Also use stones that are specifically for working on aluminum. They don't clog up as badly as "standard" metal grinding stones that are for steel/cast iron.
Holy *****!!! I honestly might just leave it alone after I port that thing. By the looks of that picture, this thing is gonna come right to life once it can breathe. Hey also, should I remove the entire egr channel, and block it off, and if I do will it throw a code?
This is interesting reading, even for someone has no stake in the Crossfire discussion. I had no idea that intake was so restrictive! Here's some interesting reading that basically backs up everything that's been said so far: http://garage.grumpysperformance.com...ire-383.10240/.
PS - To the OP, yeah, if you can add 30rwhp just with the intake work, that would be a seriously obvious improvement in speed. And not only would it pull harder at peak torque and rpm numbers, but you'd gain a lot more usable powerband on the top end too. I agree with your plan to just do the intake first and then see what you think.
Last edited by MatthewMiller; 09-20-2018 at 06:14 PM.
Holy *****!!! I honestly might just leave it alone after I port that thing. By the looks of that picture, this thing is gonna come right to life once it can breathe. Hey also, should I remove the entire egr channel, and block it off, and if I do will it throw a code?
OK. I'll throw another tip or two in here. That guy matched the ports to the manifold gasket. That may be bigger than you want to go. A more "optimum" solution, if you have the intake off already is to stick some cardboard between the manifold and the heads and tighten down the manifold bolts with the cardboard in place of the gasket to get an impression of the head ports. "Best" porting on the intake is to match it exactly to the ports in the heads. A smooth surface with just a small "groove" in the wall where the gasket is will flow better than any "step" between the intake and the head.
Another strategy is to do a "port to gasket match" on the port in the head, making the head match the gasket just like you make the intake match the gasket. If you do that, be careful not to change the volume or shape of the port near the valve (unless you really, really know what you're doing). I try to stay within a half inch to three quarters of an inch from the head/manifold joint and go no further into the port than that.
Oh, and on the intake manifold side, IIRC, there isn't enough metal in the runners to make the opening on the inner end of the runner as big as the outlet at the head end. You'll have to make an expanding passage there. A "trumpet" shape for that is better than a "cone" shape. Inside the plenum, you only want to remove obstructions to the runner entry passages. Don't shorten the runners themselves. They are already short enough (borderline too short).
I've seen dyno sheets on 1984s (and 1982s) with the crossfire engine. With the old X-ram intake, or with well done porting on the stock intake, you can get up to or slightly over a stock 1985 TPI engine. I've seen as much as 240hp at the crank and over 200hp at the rear wheels from a ported intake or X-ram and 1.6:1 rockers. For the 1/4 mile, it will get you into the 13s (barely) and in the upper 90mph range (almost 100mph) at the end of the quarter.
On the EGR, I'm going to be in the minority. I tend to leave the EGR valve in place, even on "racing" engines. It's not difficult to stick a pipe into the header collector and connect the EGR valve that way. There's no power to be gained from removing/disabling the EGR, and the valve and pipe really don't weigh enough to worry about (less than a couple pounds total usually). I even do this on later (post 1996) engines where I could "tune out" the EGR functions in the PCM. On early fuel injection systems like the throttle body injection on the 1984 Corvette, "tuning" the PCM involves burning EPROMs and swapping chips. Even if you could find the equipment and software to do this, it's a PITA that you should probably try to avoid.
If you do remove the EGR valve and block the ports for that, I doubt the computer in this system would notice. The EGR on the 1984 is entirely mechanical, vacuum operated, and I doubt the computer would notice you removed it.
Oh, and once you've ported the manifold, this engine will actually respond to other mods to a much greater degree than the stock crossfire engine (with a bone stock, unmodified intake). You can see from the pix why adding headers and/or a big cam won't have much effect with the stock intake manifold still on the thing. Guys who stick headers and a big cam in that engine without doing anything to the intake are the ones who say, "I put a big cam and headers on it and nothing happened." Then they blame the engine, which is part of why the crossfire has such a bad reputation. If you start with the intake (and some 1.6:1 rocker arms), the other mods will actually do what you think they should.
PS. In addition to the X-Ram from Performance Plus, there was an Offenhauser intake offered for the Crossfire engines that was a decent upgrade for the intake. If you can locate either of those on eBay (used), they would be excellent. There's also a "Renegade" intake currently marketed by Eddie that's available on Summit Racing and you sometimes see them on fleaBay and Amazon. That one is hit or miss on quality, but if you get a good one, it's an improvement over the stock intake.
Last edited by C6_Racer_X; 09-20-2018 at 07:38 PM.
OK. I'll throw another tip or two in here. That guy matched the ports to the manifold gasket. That may be bigger than you want to go. A more "optimum" solution, if you have the intake off already is to stick some cardboard between the manifold and the heads and tighten down the manifold bolts with the cardboard in place of the gasket to get an impression of the head ports. "Best" porting on the intake is to match it exactly to the ports in the heads. A smooth surface with just a small "groove" in the wall where the gasket is will flow better than any "step" between the intake and the head.
Another strategy is to do a "port to gasket match" on the port in the head, making the head match the gasket just like you make the intake match the gasket. If you do that, be careful not to change the volume or shape of the port near the valve (unless you really, really know what you're doing). I try to stay within a half inch to three quarters of an inch from the head/manifold joint and go no further into the port than that.
Oh, and on the intake manifold side, IIRC, there isn't enough metal in the runners to make the opening on the inner end of the runner as big as the outlet at the head end. You'll have to make an expanding passage there. A "trumpet" shape for that is better than a "cone" shape. Inside the plenum, you only want to remove obstructions to the runner entry passages. Don't shorten the runners themselves. They are already short enough (borderline too short).
I've seen dyno sheets on 1984s (and 1982s) with the crossfire engine. With the old X-ram intake, or with well done porting on the stock intake, you can get up to or slightly over a stock 1985 TPI engine. I've seen as much as 240hp at the crank and over 200hp at the rear wheels from a ported intake or X-ram and 1.6:1 rockers. For the 1/4 mile, it will get you into the 13s (barely) and in the upper 90mph range (almost 100mph) at the end of the quarter.
On the EGR, I'm going to be in the minority. I tend to leave the EGR valve in place, even on "racing" engines. It's not difficult to stick a pipe into the header collector and connect the EGR valve that way. There's no power to be gained from removing/disabling the EGR, and the valve and pipe really don't weigh enough to worry about (less than a couple pounds total usually). I even do this on later (post 1996) engines where I could "tune out" the EGR functions in the PCM. On early fuel injection systems like the throttle body injection on the 1984 Corvette, "tuning" the PCM involves burning EPROMs and swapping chips. Even if you could find the equipment and software to do this, it's a PITA that you should probably try to avoid.
If you do remove the EGR valve and block the ports for that, I doubt the computer in this system would notice. The EGR on the 1984 is entirely mechanical, vacuum operated, and I doubt the computer would notice you removed it.
Oh, and once you've ported the manifold, this engine will actually respond to other mods to a much greater degree than the stock crossfire engine (with a bone stock, unmodified intake). You can see from the pix why adding headers and/or a big cam won't have much effect with the stock intake manifold still on the thing. Guys who stick headers and a big cam in that engine without doing anything to the intake are the ones who say, "I put a big cam and headers on it and nothing happened." Then they blame the engine, which is part of why the crossfire has such a bad reputation. If you start with the intake (and some 1.6:1 rocker arms), the other mods will actually do what you think they should.
PS. In addition to the X-Ram from Performance Plus, there was an Offenhauser intake offered for the Crossfire engines that was a decent upgrade for the intake. If you can locate either of those on eBay (used), they would be excellent. There's also a "Renegade" intake currently marketed by Eddie that's available on Summit Racing and you sometimes see them on fleaBay and Amazon. That one is hit or miss on quality, but if you get a good one, it's an improvement over the stock intake.
See post 10 for my thoughts on the renegade...
Everything else you've said is however spot on. I'm at a crossroad at this point.
09-18-2018, 06:35 PM
What will headers and a cam do for a crossfire?
