What Cam?
07-04-2004, 09:57 PM
#1
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Join Date: Jul 2004
Posts: 3
What Cam?
I have a 91 camaro and i want to put a cam in it. I was wondering what brand of cam to go with and what lift to go with bc im not to sure what to do.
Also im goign to bye a performance chip in it this summer actually in the next couple weeks. If i put this chip in and i want to put the cam in over the winter then do i have to change the chip again am i wasting my money if i want to put that on. and if i get a a new cam will i have to extend the rpm limiter? thx
Also im goign to bye a performance chip in it this summer actually in the next couple weeks. If i put this chip in and i want to put the cam in over the winter then do i have to change the chip again am i wasting my money if i want to put that on. and if i get a a new cam will i have to extend the rpm limiter? thx
07-04-2004, 10:57 PM
#2
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Join Date: Apr 2004
Location: Grand Rapids, MI
Posts: 100
The factory setup maxes out at roughly .480" of valve lift. So if you plan on keeping your factory springs and whatnot, you will want about that, probably on the lesser side. The duration for those lifts would be in the range of 210-215° @ .050". Of course, aftermarket roller cams usually give a bit more lift per givin duration that their flat tappet counterparts.
Of course, you are probably thinking you want a bit more out of that. Well, you can always yank the heads and have them machined for more lift. That involves milling the guide boss down to increase the dinstance between the bottom of the retainer at installed height and the top of the guide boss. If you do decide to do that, you would probably upgrade the springs as well. After you choose a cam, look at the recommended springs. They may or may not fit in the factory spring seat. Most aftermarket springs for any decently sized cam has an outside diameter of more than 1.26", the factory size. Any competant machine shop would be able to enlarge the spring seats and mill the guide bosses. A common valve spring recommended for their hydraulic roller line are the 986 or 987 valve springs. These run in the mid $80's. Not a bad option, considering what damage a broken valve spring can do.
Another reason you should upgrade your valve springs: valve float. valve float is directly related to the springs seat pressure, or pressure applied when the valve is closed. Considering what valve float is (the valve bouncing back off the seat once it closes, usually at higher RPM's), obviously more seat pressure is better. Factory springs only have about 85 lbs of seat pressure when they are new. Of course, as time goes on, they get weaker and lose pressure. I've seen a factory spring go on the Rimac and register at just below 60 lbs of seat. I'd hate to see where that floated at!. For hydraulic roller cams, assuming factory installed height, I've always been a fan of their 986 line. They have a 132 lb seat pressure at a 1.750" installed height (factory height). That gives plenty of resisitance to valve float. They go for $84.88 at Summit. If you do this, you will need new retainers as well.
Now, the actual camshaft part. Since you have a 91, you have the factory roller camshaft. The lifters can be reused. Just be sure to carefully inspect them upon removal. Make sure the roller bearing spins freely. Be prepared, the roller cams from Comp cost about $240, Crane is a tad bit more. For starters, i would look at this cam:
Specifications: XR264-HR
* Advertised duration: 264 intake/269 exhaust
* Duration at .050 in.: 212 intake/218 exhaust
* Gross valve lift: .488 in. intake/.495 in. exhaust
* Lobe separation: 112 degrees
* RPM range: 1,200 to 5,200
This is in their EFI lines. It is designed to run idealy with EFI applications. The intake closing event has been bumped up a bit so it closes sooner. EFI doesn't like reversion and closing the intake sooner in relation to the combustion cycle reduces that. The 986 spring i mentioned above would go good with this. You CAN go bigger, however, keep in mind, PROM tuning would most likely be needed. I know, you said you are getting an aftermarket chip. However, keep in mind, many aftermarket chips do not actually alter the fuel/air tables that are set in the ECM. They alter timng and other areas, but leave the air/fuel tables alone. To use a larger cam, modifying the air/fuel tables becomes needed. Well, not NEEDED, but recommended if you want the most out the cam.
The cam i mentioned above will work on the factory torque converter, if you have an auto transmission. It will pull enough vacuum to operate the brakes and any other vacuum operated accessories like PCV and EGR, if so equipped. It will idle just fine. I am mostly familiar with Comp's cams. I am sure Crane offers an EFI cam, much like Comp's. May want to look into what they have to offer.
What chip is this? As i said above, many leave the air and fuel tables alone, which is what needs to be modded in order to get the most out of a larger cam with EFI. As far as the rev limiter goes, depending on what it is set at, it may or may not need to be set. If it's set at roughly 6000 or so, you should be fine. Anything less than that, I would probably wait and determine what cam you are getting and where its powerband ends.
Of course, there are other things that probably could use replacing such as the timing set. While you're under the valve covers and springs (if you DO decide to upgrade them, which I highly recommend, changing out the valve seals wouldn't hurt anything either. Any questions, just ask.
Sorry about the length, my g/f has a little allergy fever so i decided to stay home with her. So i typed.....and typed.....and typed. I hope this helps to clear things up a bit.
Of course, you are probably thinking you want a bit more out of that. Well, you can always yank the heads and have them machined for more lift. That involves milling the guide boss down to increase the dinstance between the bottom of the retainer at installed height and the top of the guide boss. If you do decide to do that, you would probably upgrade the springs as well. After you choose a cam, look at the recommended springs. They may or may not fit in the factory spring seat. Most aftermarket springs for any decently sized cam has an outside diameter of more than 1.26", the factory size. Any competant machine shop would be able to enlarge the spring seats and mill the guide bosses. A common valve spring recommended for their hydraulic roller line are the 986 or 987 valve springs. These run in the mid $80's. Not a bad option, considering what damage a broken valve spring can do.
Another reason you should upgrade your valve springs: valve float. valve float is directly related to the springs seat pressure, or pressure applied when the valve is closed. Considering what valve float is (the valve bouncing back off the seat once it closes, usually at higher RPM's), obviously more seat pressure is better. Factory springs only have about 85 lbs of seat pressure when they are new. Of course, as time goes on, they get weaker and lose pressure. I've seen a factory spring go on the Rimac and register at just below 60 lbs of seat. I'd hate to see where that floated at!. For hydraulic roller cams, assuming factory installed height, I've always been a fan of their 986 line. They have a 132 lb seat pressure at a 1.750" installed height (factory height). That gives plenty of resisitance to valve float. They go for $84.88 at Summit. If you do this, you will need new retainers as well.
Now, the actual camshaft part. Since you have a 91, you have the factory roller camshaft. The lifters can be reused. Just be sure to carefully inspect them upon removal. Make sure the roller bearing spins freely. Be prepared, the roller cams from Comp cost about $240, Crane is a tad bit more. For starters, i would look at this cam:
Specifications: XR264-HR
* Advertised duration: 264 intake/269 exhaust
* Duration at .050 in.: 212 intake/218 exhaust
* Gross valve lift: .488 in. intake/.495 in. exhaust
* Lobe separation: 112 degrees
* RPM range: 1,200 to 5,200
This is in their EFI lines. It is designed to run idealy with EFI applications. The intake closing event has been bumped up a bit so it closes sooner. EFI doesn't like reversion and closing the intake sooner in relation to the combustion cycle reduces that. The 986 spring i mentioned above would go good with this. You CAN go bigger, however, keep in mind, PROM tuning would most likely be needed. I know, you said you are getting an aftermarket chip. However, keep in mind, many aftermarket chips do not actually alter the fuel/air tables that are set in the ECM. They alter timng and other areas, but leave the air/fuel tables alone. To use a larger cam, modifying the air/fuel tables becomes needed. Well, not NEEDED, but recommended if you want the most out the cam.
The cam i mentioned above will work on the factory torque converter, if you have an auto transmission. It will pull enough vacuum to operate the brakes and any other vacuum operated accessories like PCV and EGR, if so equipped. It will idle just fine. I am mostly familiar with Comp's cams. I am sure Crane offers an EFI cam, much like Comp's. May want to look into what they have to offer.
What chip is this? As i said above, many leave the air and fuel tables alone, which is what needs to be modded in order to get the most out of a larger cam with EFI. As far as the rev limiter goes, depending on what it is set at, it may or may not need to be set. If it's set at roughly 6000 or so, you should be fine. Anything less than that, I would probably wait and determine what cam you are getting and where its powerband ends.
Of course, there are other things that probably could use replacing such as the timing set. While you're under the valve covers and springs (if you DO decide to upgrade them, which I highly recommend, changing out the valve seals wouldn't hurt anything either. Any questions, just ask.
Sorry about the length, my g/f has a little allergy fever so i decided to stay home with her. So i typed.....and typed.....and typed. I hope this helps to clear things up a bit.
07-05-2004, 11:14 AM
#7
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Join Date: Mar 2001
Posts: 3,249
I would spend the money on the heads before I worry about the cam. That is unless you want to do the cam at the same time. DO NOT BUY AN OFF THE SHELF CHIP. You will not get the max gains. Where are you located? I just got my chip done on a dyno for $450 and that was a custom unit. Also I have used www.fasterproms.com to make me a chip. It is about $350 and it is custom to your car. If you borrow their Diacom unit and take readings, they will fine tune the chip for you. later on if you decide to do something radical, they will repeat the process for $150.
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