Cam choice
Thread Starter
Melting Slicks
Joined: Nov 2000
Posts: 2,469
Likes: 6
From: Winchester Ontario
Cam choice
Right now I have a very mild ( too mild for my liking) cam that my machinist picked for me 3 and a half years ago when my engine was being put back together. I didn't have any input, cuz I didn't know anything (still don't know much).
It's a 222/226 split duration with 0.464 " lift with 1.5 rr's.
I'm planning on using 1.6 rr's.
It's a 383 @ 9.5 :1 (maybe 10:1 -- just found out cuz of heads).
What factors determine what duration and lift I should be looking for.
I mean, I know durations of 210-220 are good for low end power and cams with durations of 230 + are for high RPM engines, right?
So, should I stay with the 222/226 split or should I look for something a tad lower (219 cam? but for money reason right now I'd stay hydraulic non roller).
What lift should I go with? Does a higher lift hurt performance at some point? What should determine total lift?
Check site for mods. corvette.da.ru
It's a 222/226 split duration with 0.464 " lift with 1.5 rr's.
I'm planning on using 1.6 rr's.
It's a 383 @ 9.5 :1 (maybe 10:1 -- just found out cuz of heads).
What factors determine what duration and lift I should be looking for.
I mean, I know durations of 210-220 are good for low end power and cams with durations of 230 + are for high RPM engines, right?
So, should I stay with the 222/226 split or should I look for something a tad lower (219 cam? but for money reason right now I'd stay hydraulic non roller).
What lift should I go with? Does a higher lift hurt performance at some point? What should determine total lift?
Check site for mods. corvette.da.ru
Pro
Joined: Dec 2002
Posts: 603
Likes: 0
From: 84 383 XFire Chandler, AZ
I went with this cam for my 383. I have a 84. This is similar to the 219 I think but I used 1.6 roller rockers. You are correct with the durations on the cams - lower duration more low end, higher duration more high end. This is why I went with the 1.6 rockers. Basically, shorter duration higher lift. I have only had the motor running for a couple of days but I can tell you that it is definately a tire shredder. 
Heads - TFS 195cc intake runners, 64 cc chambers. My CR calcs to 10.4:1.
Cam - Compcams CS XR269HR-12 (pn 08-502-8)
Duration @ 0.05 218/228 LSA 112
Lift with 1.5 Rockers - .495/.503
Lift with 1.6 Rockers - .528/.536 (I did this)
Heads - TFS 195cc intake runners, 64 cc chambers. My CR calcs to 10.4:1.
Cam - Compcams CS XR269HR-12 (pn 08-502-8)
Duration @ 0.05 218/228 LSA 112
Lift with 1.5 Rockers - .495/.503
Lift with 1.6 Rockers - .528/.536 (I did this)
Thread Starter
Melting Slicks
Joined: Nov 2000
Posts: 2,469
Likes: 6
From: Winchester Ontario
I think I have the duration in the right range, I certainly don't need more torque, cuz when it was under injected and not running right it put out 398 rwtq on a mustang dyno.
What would stop me from going to say .560 lift ( with 1.6 rr).
I mean, how would the .560 lift help me more than say a .525 lift (1.5 rr)?
Is there any horsepower co-relation between different lifts?
What would stop me from going to say .560 lift ( with 1.6 rr).
I mean, how would the .560 lift help me more than say a .525 lift (1.5 rr)?
Is there any horsepower co-relation between different lifts?
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
There is, if your heads and intake mainifold will support the additional air flow. You have a flat tappet cam in an '89??? you will have a problem finding a flat tappet cam that will lift the valves .525" (1.5:1 rockers) with that duration. If your heads and intake are up to it, you may want to go a step up, into the 228*/234* range, with all the lift you can get. And use the 1.6:1 rodkers.
RACE ON!!!
RACE ON!!!
Thread Starter
Melting Slicks
Joined: Nov 2000
Posts: 2,469
Likes: 6
From: Winchester Ontario
I do have a flat tappet in an 89 cuz it's not the stock motor. My brother blew it up and cracked the block and the oil pan had holes the size of golfballs in it.
So, I bought a crate 383 (old style block with a 2pc rear main seal) which turned to be put together rather crappy, so my mechanic took it apart and put it together his way.
I have the stock 89 aluminum d port 113 heads ported and polished ( no flow #'s, but done by a guy who does all the dirt mods around here with a reputable name) and I have the super ram plenum, runners and base.
I'm kind of avoiding the roller cams due to too much cash to convert everything right now.
Since torque is not an issue, I think maybe going into the 228/234 range would be ideal with as much lift as possible to keep it under the valve covers. By the way, the covers aren't stock either so I don't know how much clearance I'll have.
Maybe up to .560- .600 lift with the 1.6's?
So, I bought a crate 383 (old style block with a 2pc rear main seal) which turned to be put together rather crappy, so my mechanic took it apart and put it together his way.
I have the stock 89 aluminum d port 113 heads ported and polished ( no flow #'s, but done by a guy who does all the dirt mods around here with a reputable name) and I have the super ram plenum, runners and base.
I'm kind of avoiding the roller cams due to too much cash to convert everything right now.
Since torque is not an issue, I think maybe going into the 228/234 range would be ideal with as much lift as possible to keep it under the valve covers. By the way, the covers aren't stock either so I don't know how much clearance I'll have.
Maybe up to .560- .600 lift with the 1.6's?
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
There's a relationship between lift and duration in both flat tappet and roller cams.
Finding a flat tappet cam ground with .600 lift while, at the same time, keeping the .050 duration at 228 isn't likely to happen. The ramps will be too aggressive. All sorts of problems will occur.
Even with 1.6 RRs, you won't be able to get .600 valve lift. Probably more like low .500s With a roller, yes, but not with a flat tappet.
I don't believe the new cam's increase in duration, from what you're now running, is worth the expense - bang for the buck - since you'll have to buy new lifters too.
If it were me, I'd keep the current cam, which, BTW, is a nice one.
Just my thoughts.
Jake
Finding a flat tappet cam ground with .600 lift while, at the same time, keeping the .050 duration at 228 isn't likely to happen. The ramps will be too aggressive. All sorts of problems will occur.
Even with 1.6 RRs, you won't be able to get .600 valve lift. Probably more like low .500s With a roller, yes, but not with a flat tappet.
I don't believe the new cam's increase in duration, from what you're now running, is worth the expense - bang for the buck - since you'll have to buy new lifters too.
If it were me, I'd keep the current cam, which, BTW, is a nice one.
Just my thoughts.
Jake
Thread Starter
Melting Slicks
Joined: Nov 2000
Posts: 2,469
Likes: 6
From: Winchester Ontario
I have been pretty content with the current cam but since it's the only one I've had I am left wondering what I am missing by being kind of small (0.464 " lift).
I was being a bit too optimistic thinking about a .600 lift, I was thinking along the line of a .525 lift with 1.5 making it a .560 lift with 1.6's.
The 219 cam looked great, especially since it goes hand in hand with the super ram. But, not being heavy on money at the moment, I'll keep it hydraulic non-roller. I was also thinking that I might want to give up a bit of torque for a bit of hp. This is why I was thinking of going higher than the current 222/226.
CFI suggested going 228/234 and I was thinking if I could get one with .525 lift with the 1.5's. And when I go to 1.6's it'd be .560 lift.
I was being a bit too optimistic thinking about a .600 lift, I was thinking along the line of a .525 lift with 1.5 making it a .560 lift with 1.6's.
The 219 cam looked great, especially since it goes hand in hand with the super ram. But, not being heavy on money at the moment, I'll keep it hydraulic non-roller. I was also thinking that I might want to give up a bit of torque for a bit of hp. This is why I was thinking of going higher than the current 222/226.
CFI suggested going 228/234 and I was thinking if I could get one with .525 lift with the 1.5's. And when I go to 1.6's it'd be .560 lift.
Team Owner
Joined: Oct 2004
Posts: 81,241
Likes: 3,063
From: altered state
St. Jude Donor '05
Make sure you run the proper valve spring and the installed height, open and closed pressures check out. Once you r cam is in the .525 neighborhood and above, they become pretty sensitive as far as spring pressure, especially during break in. 
Good luck
Edit: Before you pull your cam, try the 1.6 rockers. If the car noticeably picks up power, a little more cam may be in order. If it runs the same or loses power, you may need a little more cylinder head.
If it were me and it ran strong, I'd leave it, JMO
Good luckEdit: Before you pull your cam, try the 1.6 rockers. If the car noticeably picks up power, a little more cam may be in order. If it runs the same or loses power, you may need a little more cylinder head.
If it were me and it ran strong, I'd leave it, JMO
Last edited by cv67; Apr 28, 2005 at 12:26 AM.
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Racer
Joined: Mar 2004
Posts: 311
Likes: 0
From: Oakley Ca
Originally Posted by JAKE
There's a relationship between lift and duration in both flat tappet and roller cams.
Finding a flat tappet cam ground with .600 lift while, at the same time, keeping the .050 duration at 228 isn't likely to happen. The ramps will be too aggressive. All sorts of problems will occur.
Even with 1.6 RRs, you won't be able to get .600 valve lift. Probably more like low .500s With a roller, yes, but not with a flat tappet.
I don't believe the new cam's increase in duration, from what you're now running, is worth the expense - bang for the buck - since you'll have to buy new lifters too.
If it were me, I'd keep the current cam, which, BTW, is a nice one.
Just my thoughts.
Jake
Finding a flat tappet cam ground with .600 lift while, at the same time, keeping the .050 duration at 228 isn't likely to happen. The ramps will be too aggressive. All sorts of problems will occur.
Even with 1.6 RRs, you won't be able to get .600 valve lift. Probably more like low .500s With a roller, yes, but not with a flat tappet.
I don't believe the new cam's increase in duration, from what you're now running, is worth the expense - bang for the buck - since you'll have to buy new lifters too.
If it were me, I'd keep the current cam, which, BTW, is a nice one.
Just my thoughts.
Jake
Pro
Joined: Jan 2002
Posts: 718
Likes: 0
From: W.V.C. Utah
I'm running the XE 274 h in my 88 haven't started it yet but it seems like a nice mild cam should be right in the powerband I want Nice street cam
http://www.jegs.com/cgi-bin/ncommerc...96&prmenbr=361
http://www.jegs.com/cgi-bin/ncommerc...96&prmenbr=361
