1.7 roller rockers? draw backs?
Thread Starter
Burning Brakes
Joined: Apr 2005
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From: JUPITER FLORIDA
1.7 roller rockers? draw backs?
I was thinking of upping the lift of my cam by using the 1.7 or 1.65 roller rockers that I have seen for sale on tpis or summit.
My question is, changing the lift without changing the duration. I know the duration will go up a little more as the lift does, but will there be any drivability problems?
my specs: .474 int/exh Duration is: 210/int 214/exh
With 1.7 rockers I think I would have like a .530 lift but how much would my duration go up?
As far as power from the lift change what could I expect?
86 corvette with vortec heads, long tube headers, largetube runners, big base intake, 24lbs injectors.
My question is, changing the lift without changing the duration. I know the duration will go up a little more as the lift does, but will there be any drivability problems?
my specs: .474 int/exh Duration is: 210/int 214/exh
With 1.7 rockers I think I would have like a .530 lift but how much would my duration go up?
As far as power from the lift change what could I expect?
86 corvette with vortec heads, long tube headers, largetube runners, big base intake, 24lbs injectors.
Le Mans Master
Joined: Jul 1999
Posts: 8,683
Likes: 6
From: Phoenix AZ
The amount of duration increase will be extremely small, virtually unnoticable.
As for a power increase, well too hard to tell. Do you have flow numbers for those heads? I don't know them off the top of my head, but if your heads flow as much or more at the new lift numbers you may see an increase...and as always, I don't know how the TPI intake will affect things either!
As for a power increase, well too hard to tell. Do you have flow numbers for those heads? I don't know them off the top of my head, but if your heads flow as much or more at the new lift numbers you may see an increase...and as always, I don't know how the TPI intake will affect things either!
Thread Starter
Burning Brakes
Joined: Apr 2005
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From: JUPITER FLORIDA
http://www.carcraft.com/techarticles/41598/index4.html
If you scroll down you can see the flow numbers on the right.
If you scroll down you can see the flow numbers on the right.
Last edited by cplonner; Dec 22, 2005 at 07:14 PM.
Drifting
Joined: Oct 2005
Posts: 1,259
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From: bakersfield cali
rockers
it's probably cheaper if you get another cam if its a hydralic flat tappet.
are your're springs up to the task of handling the added lift? check that first before you buy the 1.7's Also check to see if you have enough pushrod clearance through the heads. If you get another cam and keep your rockers the pushrod clearance should not even be an issue.
are your're springs up to the task of handling the added lift? check that first before you buy the 1.7's Also check to see if you have enough pushrod clearance through the heads. If you get another cam and keep your rockers the pushrod clearance should not even be an issue.
Last edited by 86VX1; Dec 22, 2005 at 07:23 PM.
Le Mans Master
Joined: Apr 2000
Posts: 5,713
Likes: 105
From: Manassas VA
Check Nathans page. On his hotcam, when going from 1.6 to 1.7 he picked up 14hp. I have been thinking about doing this as well. Also, check flatlander racing for the rockers. I believe they had them for $222.00
Le Mans Master
Joined: Oct 2004
Posts: 5,841
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From: CLT, North Carolina
Some's Good, Is More Better?
Duration actually won't increase because that is a function of the cam lobe but area under the valve lift curve sure will. If you could plot it you would see the valve begin to open at the same time as before but at a faster rate. At say 10 degrees ATDC the Intake valve would be open further than with your old ratio. Now the question is will your springs be strong enough to control the faster valve motion along with the increased lift? Will you have enough clearance between the bottoms of the retainers and tops of the valve guides and is there a safety margin before coil bind? As long as the heads can flow air you will see an increase in power and torque. So if this is good what about more? Well...the thing about rocker ratio increase is it gets the engine closer to the theoretically ideal square lift curve but the penalty is in the difficulty in maintaining valve control and as the ratio continues to increase you start getting into some pretty expensive valve train components to maintain control.
Greg
Greg
Thread Starter
Burning Brakes
Joined: Apr 2005
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From: JUPITER FLORIDA
Originally Posted by 86VX1
it's probably cheaper if you get another cam if its a hydralic flat tappet.
are your're springs up to the task of handling the added lift? check that first before you buy the 1.7's Also check to see if you have enough pushrod clearance through the heads. If you get another cam and keep your rockers the pushrod clearance should not even be an issue.
are your're springs up to the task of handling the added lift? check that first before you buy the 1.7's Also check to see if you have enough pushrod clearance through the heads. If you get another cam and keep your rockers the pushrod clearance should not even be an issue.
Is it possible to just change the cam without removing the heads? (pull push rods out, remove radiator and belt components?)
Im assuming that its more duration that adds power than lift?
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Le Mans Master
Joined: Oct 2004
Posts: 5,841
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From: CLT, North Carolina
Duration is Really a Function of the Cam Lobe
Originally Posted by Zix
Nope, duration WILL increase, though very slightly.
Regards, Greg
Last edited by Greg Gore; Dec 23, 2005 at 02:58 PM.
Burning Brakes
Joined: Jun 2005
Posts: 802
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From: What do I know anyway? I'm just a 50 year old No0b
Originally Posted by cplonner
how would it be cheaper if i had to pull apart the whole engine to get to the cam? meanwhile i can just put new springs and change the rocker arms?
Is it possible to just change the cam without removing the heads? (pull push rods out, remove radiator and belt components?)
Im assuming that its more duration that adds power than lift?
Is it possible to just change the cam without removing the heads? (pull push rods out, remove radiator and belt components?)
Im assuming that its more duration that adds power than lift?
Drifting
Joined: Oct 2005
Posts: 1,259
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From: bakersfield cali
vortechs
even if you just change the springs and the rockers, you still have to check for pushrod interference, vortech are notorious for having a lot of casting material where the pushrods go through the heads.
let's say that there is some casting material there and you do have some slight interference, how are you going to fix that? Are you going to grind it away with the heads still on the car?
do you have a roller cam? If you have a roller cam, then go for the rockker change, but if you have flat tappet, change the cam.
YOu can do a full cam swap in a couple of hours. You definately ahve to0 remove the radiator, intake, belt system and timing chain. good chance to know your car a little more intimate.
let's say that there is some casting material there and you do have some slight interference, how are you going to fix that? Are you going to grind it away with the heads still on the car?
do you have a roller cam? If you have a roller cam, then go for the rockker change, but if you have flat tappet, change the cam.
YOu can do a full cam swap in a couple of hours. You definately ahve to0 remove the radiator, intake, belt system and timing chain. good chance to know your car a little more intimate.
Thread Starter
Burning Brakes
Joined: Apr 2005
Posts: 1,110
Likes: 0
From: JUPITER FLORIDA
Originally Posted by 86VX1
even if you just change the springs and the rockers, you still have to check for pushrod interference, vortech are notorious for having a lot of casting material where the pushrods go through the heads.
let's say that there is some casting material there and you do have some slight interference, how are you going to fix that? Are you going to grind it away with the heads still on the car?
do you have a roller cam? If you have a roller cam, then go for the rockker change, but if you have flat tappet, change the cam.
YOu can do a full cam swap in a couple of hours. You definately ahve to0 remove the radiator, intake, belt system and timing chain. good chance to know your car a little more intimate.
let's say that there is some casting material there and you do have some slight interference, how are you going to fix that? Are you going to grind it away with the heads still on the car?
do you have a roller cam? If you have a roller cam, then go for the rockker change, but if you have flat tappet, change the cam.
YOu can do a full cam swap in a couple of hours. You definately ahve to0 remove the radiator, intake, belt system and timing chain. good chance to know your car a little more intimate.
Race Director
Joined: Sep 2003
Posts: 16,838
Likes: 341
From: Database Error Indiana
YOu can do a full cam swap in a couple of hours. You definately ahve to0 remove the radiator, intake, belt system and timing chain. good chance to know your car a little more intimate.[/QUOTE]
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Maybe you can do a cam swap in a couple of hours.... On an L98 it takes that long to disassemble the intake. Then you have to remove everything on the front of the block. Then do the cam. Then put it all back together. Not 2 hours on my 87.
________________________________________ ________________________________________ ___
Maybe you can do a cam swap in a couple of hours.... On an L98 it takes that long to disassemble the intake. Then you have to remove everything on the front of the block. Then do the cam. Then put it all back together. Not 2 hours on my 87.
Last edited by JackDidley; Dec 23, 2005 at 05:32 PM.
Le Mans Master
Joined: Feb 1999
Posts: 6,172
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From: somers, ny
I'd like to see anybody do it in 2 hours. I probably spend 1/2 that just cleaning off the gasket surfaces. And the other 1/2 mess'n with the damper. If anyone is willing to take 2 hours pay at mechanics rate, they can do mine anytime.
would probably take most people more than 2 hours just to do the rockers.
would probably take most people more than 2 hours just to do the rockers.
