|
![]() |
#1 |
Senior Member
Join Date: Jun 2005
Posts: 663
Likes: 0
Liked 7 Times in 7 Posts
|
![]()
I know I asked this before...but am getting old and forgot.....
WHICH is better way? Smaller lobe lift and LOTS of rocker arm ratio.... Larger lobe lift and lesser ratio.... Pros/cons of each way.... Which is more common today? Would running stud-mounted rockers dictate pretty much what could be done? (ie...ratios above 1.65 not available for stud mounts...) Combo is 283 Chevy....on a budget...with the stud-mounted rockers.... |
![]() |
![]() |
![]() |
#2 |
Senior Member
Join Date: Aug 2006
Location: Pukwana SD
Posts: 860
Likes: 554
Liked 99 Times in 49 Posts
|
![]()
The trend has been bigger cam or lobe lift and less rocker ratio. JimHanig
|
![]() |
![]() |
![]() |
#3 |
VIP Member
Join Date: Jul 2007
Location: Anthem, Arizona
Posts: 2,766
Likes: 0
Liked 3 Times in 3 Posts
|
![]()
budget a shaft rocker system in!
__________________
Jeff Lee 7494 D/S '70 AMX |
![]() |
![]() |
![]() |
#4 |
Veteran Member
Join Date: May 2006
Location: Murfreesboro TN
Posts: 5,107
Likes: 1,564
Liked 1,796 Times in 409 Posts
|
![]()
Get the lift at the lobe not at the rocker. Run shaft rockers. And all the pushrod that will fit.
To let you know how much I believe in what Tim and Billy told me about getting the lift at the lobe, I'm buying a half set of T&D rockers, because I bought 1.75:1 rockers for the intake last time, and I'm going back to 1.7:1. I can tell you that a 1/2 set of T&D rockers are more than 1/2 the cost of a new set. And not by a small amount. If I didn't think lift at the lobe instead of the rocker was important, I'd save myself a ton of cash.
__________________
Alan Roehrich 212A G/S Last edited by Alan Roehrich; 07-12-2013 at 05:44 PM. |
![]() |
![]() |
![]() |
#5 |
Senior Member
Join Date: Oct 2002
Location: Pittsburgh
Posts: 575
Likes: 298
Liked 747 Times in 136 Posts
|
![]()
And why exactly is this all of a sudden in fashion??
With lower lobe lift, and higher rocker ratio's, a larger portion of the valvetrain mass undergoes lower acceleration. And that is nothing but good. If you can move the lifter, the pushrod and half of the rocker mass less distance and less quickly for a given valve lift and rate, then how can that be bad?? high rocker ratios allow more 'area under the curve' of the valve for a given duration and given cam ramp.. It blows my mind, how all of a sudden high ratio rockers are now out of fashion, and the old ratios are back in.... Perhaps Im missing something, but there is nothing at all technically negative about high ratio rockers other than increased load on the lifter, cam bearings, pushrod, and thus potential pushrod flex,.. And roller cam bearings, large diameter roller lifters, and pushrod quality and design have taken care of that problem.... Tell, you what, its all fine with me, because all I have right now is a set of 1.7's, on the intakes and 1.6's on the exhaust, and I'd like to get some 1.8's, and 1.7's, so this means I should be able to trade someone and even make a few bucks, eh ?? So there you go, all you guys with the 1.8's Intakes and 1.7 exahusts on a SBC jesel shaft, thats OLD SCHOOL.. You are sooooooo lame..... I have what you need right here... some 1.7's and 1.6's.. PM me asap, so you can trade with me, and you can go faster.... |
![]() |
![]() |
![]() |
#6 |
Veteran Member
Join Date: Mar 2005
Location: Sand Springs, OK
Posts: 8,132
Likes: 896
Liked 390 Times in 170 Posts
|
![]()
I'm doing it all wrong. LOL
__________________
Ed Wright 4156 SS/JA |
![]() |
![]() |
![]() |
#7 |
Senior Member
Join Date: Jun 2005
Posts: 663
Likes: 0
Liked 7 Times in 7 Posts
|
![]()
Well...my engine program's not so stable anyhow...so I should be just fine...w/o the
shaft-mounts... Just hoping that the car gets down the track....period! |
![]() |
![]() |
![]() |
#8 | |
Veteran Member
Join Date: May 2006
Location: Murfreesboro TN
Posts: 5,107
Likes: 1,564
Liked 1,796 Times in 409 Posts
|
![]() Quote:
I'll stick with what I'm getting from the guys who developed the SpinTron and the guys who use it to refine my valvetrain components. All of whom say that weight/mass on the cam side of the rocker fulcrum is nearly irelevant compared to weight on the valve side.
__________________
Alan Roehrich 212A G/S |
|
![]() |
![]() |
![]() |
#9 |
Senior Member
Join Date: Oct 2002
Location: Pittsburgh
Posts: 575
Likes: 298
Liked 747 Times in 136 Posts
|
![]()
While Im a budget racer as well, I have to agree with what others have said.... Do not waste any time at all with stud mount rockers... You really need to figure in a shaft system... Particuarly with the engine size you have chosen... You are going to need to turn some good RPM.
We can argue on the ratios... But Im sure we can all agree, you need to have a shaft system and forget about stud mounted rockers.... By the time you get done with roller rockers, locks, stud girdles, you are going to be approaching 60% of the cost of a nice used Jesel setup. And that additional 40% is money well spent. |
![]() |
![]() |
![]() |
#10 |
Senior Member
Join Date: Jun 2005
Posts: 663
Likes: 0
Liked 7 Times in 7 Posts
|
![]()
Guys, ALL solid advice by everyone....
Kevin...I realize this combo works with high rpm...and that the Jesel has been the norm for many years.... Already have my roller rockers in ALL the popular sizes....some full sets...including some rare 1.7 ratio that were made by Crane years ago... There are some other aspects of my "build" that might seem a bit "old" to people.... don't want to get into them....but when I say "budget" I mean it in the truest sense... I'm down on bucks...who isn't these days?. Stock Eliminator is NOT an option for me...Tried that back in the OEM piston and camshaft spec days...didn't go too fast... but learned a lot.... Don't agree with TODAYS Stock rules..... The main reason I asked the question...is that some time ago...maybe just after the SS cyl head porting rules change...there was an ad in Dragster by a major camshaft company indicating some "new" SBC SS roller grinds.... The cams seemed "small"...with lobe lifts just over .400"....but the ad suggested to run them with 1.7/1.8 ratios....hence the Jesel...which I don't have anyway... Realize that ad is probably about 20 years old now...maybe not relevant information today? Heads being done differently, etc? I have some older cams...in that neighborhood...probably obsolete today...but thought I had a chance to make use of them....I'm run them anyway...with the lower ratios and see what happens.... Just was wondering if racers favored getting the valve lift THAT way...for whatever reason...I guess physics comes into play here.... Bottom line is it's taking too long to complete this car....many obstacles along the way... Enough of this sob story...as they've said in the Army..."BETTER to do something NOW and TALK about it LATER!!" Onward!!!! |
![]() |
![]() |
![]() |
|
|