1.65rr or 1.7rr's......Can it be done?
Banned
Joined: Oct 2002
Posts: 6,518
Originally posted by twells
Ken,
thanks for letting me know of that option. I don't know why i didn't think of that before. If i was to go with a custom grind, i would want to make sure that i did it right the first time. I will most likely use your idea to further my quest for power.
Thanks all
thomas
Ken,
thanks for letting me know of that option. I don't know why i didn't think of that before. If i was to go with a custom grind, i would want to make sure that i did it right the first time. I will most likely use your idea to further my quest for power.
Thanks all
thomas
If you add too much lift to the cam, then the base circle will change and you'll need different pushrods.
The Rocker Arm choice is probably the easiest.
But a custom cam is a good idea, just not for cutting costs.
Bret
West South Central Moderator
Joined: Oct 2000
Posts: 3,371
From: Kilgore TX 75662
Try these Comp lobes
XE- 3313- 270adv--218@.050-139@.200-.495w/1.5-.528w/1.6
XE- 3315- 282adv- 230@.050-151@.200-.510w/1.5-.544w/1.6
I'm going with these with my stock iron heads w/1.5 rockers so I don't have any problems with possibly pulling the studs out of the heads. These have a much steeper ramp design that should help with more torque, but the exhaust is a little bigger, so it should get the same top end power as the hot cam. I'm strongly considering this on a 110LSA with no advance/retard. The idle should be more aggressive than the hot cam and it will be a beast NA. I know it won't be the best for use on the spray, but I have my reasons for that.
If I had the screwed in rocker studs like in the aluminum LT1 heads, I'd go with one of these for the exhaust
mag-3111- 286adv- 230@.050- 152@.200- .560w/1.5 -.598w/1.6
XE - 3194 - 282adv- 230@.050- 157@.200- .584w/1.5 -.622w/1.6
XE- 3313- 270adv--218@.050-139@.200-.495w/1.5-.528w/1.6
XE- 3315- 282adv- 230@.050-151@.200-.510w/1.5-.544w/1.6
I'm going with these with my stock iron heads w/1.5 rockers so I don't have any problems with possibly pulling the studs out of the heads. These have a much steeper ramp design that should help with more torque, but the exhaust is a little bigger, so it should get the same top end power as the hot cam. I'm strongly considering this on a 110LSA with no advance/retard. The idle should be more aggressive than the hot cam and it will be a beast NA. I know it won't be the best for use on the spray, but I have my reasons for that.
If I had the screwed in rocker studs like in the aluminum LT1 heads, I'd go with one of these for the exhaust
mag-3111- 286adv- 230@.050- 152@.200- .560w/1.5 -.598w/1.6
XE - 3194 - 282adv- 230@.050- 157@.200- .584w/1.5 -.622w/1.6
Last edited by AdioSS; Oct 25, 2002 at 12:33 PM.
Registered User
Joined: Sep 2002
Posts: 1,429
From: plano texas
Wait wouldnt a lower lift cam with a higher rocker ratio slide across the tip of the valve stem less than a high lift cam on a lower rocker ratio since the angular movement of the rocker is less extreme? Seems like on the same lobes a higher rocker ratio would rub a little more but the difference between 1.5 and 1.7 is just that 2/17ths not a lot, or maybe it is I dunno....
Registered User
Joined: Oct 2001
Posts: 1,462
From: smog zone adjacent to a great lake
One needs to determine what the diff is between the 1.5 and ...whatever. Hint: from the pivot to the valve stem, they should be the same specs. When the valve is being pushed down, it isn't able to differentiate whether the movement is from the rocker arm or the cam lobe.
Registered User
Joined: Jul 2001
Posts: 752
From: Double Oak TX
I just read the entire post and it’s quite obvious, the real issue is intended use vs cost vs. effort. Sounds like you’re really trying to make a somewhat mainstream cam perform like a slightly more aggressive mainstream cam.
Simple answer: Hell, don’t reinvent the wheel…. Buy a slightly bigger cam that everyone knows works. Sure it may be $50 bucks more, but a hell lot less hassle than trying to RD something unproven.
My view is unless you’re willing to spend the bucks and take your chances………. Buy something that you know works. You just might come out $ ahead and sleep better at night.
Simple answer: Hell, don’t reinvent the wheel…. Buy a slightly bigger cam that everyone knows works. Sure it may be $50 bucks more, but a hell lot less hassle than trying to RD something unproven.
My view is unless you’re willing to spend the bucks and take your chances………. Buy something that you know works. You just might come out $ ahead and sleep better at night.
Registered User
Joined: Jan 2001
Posts: 657
From: Farmington Hills, MI
My view is unless you’re willing to spend the bucks and take your chances………. Buy something that you know works. You just might come out $ ahead and sleep better at night.
You CAN run a rocker arm that will lift the valve higher and there for increase duration some etc. But why mess around with custom rockers, different length pushrods, and setting up valvetrain GEOMETRY.
Smokey Yunick HAD to use 1.75 BB rockers on a SB chevy when rules limited you to a , more-or-less stock cam. So it can be done with reliability in mind. However, I'd just get the proper cam for the application with alot less hastle.
Registered User
Joined: Jul 2000
Posts: 520
From: MD
Originally posted by SStrokerAce
Also Piston to Valve clearance is another problem. This means you need to check that. If you run into problems you gotta take the pistons out and fly cut valve reliefs in them. If you are not building up a engine to drop in this is not going to be a fun undertaking.
Also Piston to Valve clearance is another problem. This means you need to check that. If you run into problems you gotta take the pistons out and fly cut valve reliefs in them. If you are not building up a engine to drop in this is not going to be a fun undertaking.
Originally posted by arnie
Rocker ratio can be a big deal, but as Bret stated, the bottom line is the lift that the rocker ratio is generating. Frankly, the valve end of the rocker arm doesn't care where (or from whom) the extra 'push' came from. It is a case of one end doesn't know or care how the other end generated the extra lift. It just knows that now, it, the valve stem end of the RA, is now moving the valve more off it's seat. Along with the reasons given by Bret, the kicker is, with the poor rocker arm geometry that is characteristic of the sbc, an engine that originally possessed a lift all of .400", it (RA) now finds itself moving from one side of the valve stem to the other during it's travel from zero to full lift. That is cuz the rocker tip is scrubbing across the stem tip as it is pushing down on the stem. This puts side thrust on the stem, generating unnecessary guide wear. One has theeir hands full, what with .600-650" lift, to keep the rocker tip on the stem. This the reason relocated rocker studs and shaft mounted rockers came into being, along with roller rocker arms. It cuts down on the friction by improving the RA geometry.
Rocker ratio can be a big deal, but as Bret stated, the bottom line is the lift that the rocker ratio is generating. Frankly, the valve end of the rocker arm doesn't care where (or from whom) the extra 'push' came from. It is a case of one end doesn't know or care how the other end generated the extra lift. It just knows that now, it, the valve stem end of the RA, is now moving the valve more off it's seat. Along with the reasons given by Bret, the kicker is, with the poor rocker arm geometry that is characteristic of the sbc, an engine that originally possessed a lift all of .400", it (RA) now finds itself moving from one side of the valve stem to the other during it's travel from zero to full lift. That is cuz the rocker tip is scrubbing across the stem tip as it is pushing down on the stem. This puts side thrust on the stem, generating unnecessary guide wear. One has theeir hands full, what with .600-650" lift, to keep the rocker tip on the stem. This the reason relocated rocker studs and shaft mounted rockers came into being, along with roller rocker arms. It cuts down on the friction by improving the RA geometry.
Assuming that you don’t change anything else, the side load on the valve stems is going to be the same whether you get more lift via longer ratio rockers or cam lobes. As long as the lift is the same so is the side load.
The disadvantage is that the spring pressure is multiplied by the higher ratio so the lifters/cam see the more pressure. This shouldn’t be a problem from a wear perspective on a roller cam, but it may be a problem with the lifters on an HR cam (or any hydraulic cam)
Originally posted by Mindgame
In my opinion..... a 1.7:1 rocker ratio will work just as well as a 1.6:1. I don't necessarily agree with the wear issues either... especially when you look at the geometry of a (1.7:1) long-arm/backset type rocker arm like the ones Crower makes. I'd venture to say that they're easier on valve guides than your standard 1.5:1 non-roller type rockers are too. Look at the ratios being run on the new engines.
Not a bolt on and go deal and it definitely shouldn't be looked at in that way, but when you're looking for every last little tinkle of power... hey who cares what it takes. I don't.
In my opinion..... a 1.7:1 rocker ratio will work just as well as a 1.6:1. I don't necessarily agree with the wear issues either... especially when you look at the geometry of a (1.7:1) long-arm/backset type rocker arm like the ones Crower makes. I'd venture to say that they're easier on valve guides than your standard 1.5:1 non-roller type rockers are too. Look at the ratios being run on the new engines.
Not a bolt on and go deal and it definitely shouldn't be looked at in that way, but when you're looking for every last little tinkle of power... hey who cares what it takes. I don't.
2 basic facts:
- the sbc rocker design sucks, it’s been shown to waste quite a bit of power in friction (and increases in oil temp)
- any car modded for more power will kill parts faster, accept that and move on.
Registered User
Joined: Aug 2000
Posts: 586
From: Oklahoma City, OK
This link might help. The guy is running 1.7 rockers w/ a HOT cam.
http://forums.corvetteforum.com/zerothread?id=563883
http://forums.corvetteforum.com/zerothread?id=563883
Thread
Thread Starter
Forum
Replies
Last Post
BluBiU
3rd Gen / L98 Engine Tech
0
Jan 28, 2005 09:05 PM