Welcome to the Corvette Forums at the Corvette Action Center!

Rocker Arm Upgrade

minifridge1138

Well-known member
Joined
Feb 2, 2007
Messages
908
Location
USA
Corvette
1982 Black Fastback
Hey everyone,

This is a newb question, but i have to ask.

How big of a difference would upgrading my rocker arms make?
I have the stock 1.5:1 and I'm thinking of moving to 1.7:1 (or 1.65 if that is better for a small block).
Is this a "you'll might sort of notice" difference, or a "kick you in the a$$" difference?

Also, would i need to replace the lifters and push rods, or can i just pop off the valve covers and replace the rocker arms?

This should increase compression/stroke without the trouble of getting to the camshaft. (i know it isn't that hard, but a bigger PITA than taking off valve covers and the springs).

Thanks for the input, it is always appreciated!!!
 

Crimson Thunder

Well-known member
Joined
Dec 16, 2001
Messages
814
Location
Orange Park FL USA
Corvette
1970 Marboro Maroon Convertible
A rocker arm upgrade is a "might sort of notice" upgrade.A swap from 1.5 to 1.6 rockers(1.7 is for big blocks and small block Fords) will increase valve lift around .030 inches and slightly increase duration.Your stock lifters and pushrods will work but you will have to check for valve spring bind with the new rockers.
 

ratflinger

Well-known member
Joined
Sep 4, 2005
Messages
74
Location
South Central Texas
Corvette
1979 Black Coupe, 396 SBC
Hey everyone,

This is a newb question, but i have to ask.

How big of a difference would upgrading my rocker arms make?
I have the stock 1.5:1 and I'm thinking of moving to 1.7:1 (or 1.65 if that is better for a small block).
Is this a "you'll might sort of notice" difference, or a "kick you in the a$$" difference?

Also, would i need to replace the lifters and push rods, or can i just pop off the valve covers and replace the rocker arms?

This should increase compression/stroke without the trouble of getting to the camshaft. (i know it isn't that hard, but a bigger PITA than taking off valve covers and the springs).

Thanks for the input, it is always appreciated!!!


Ummm, neither rocker arms nor camshaft changes will affect compression or stroke. As sharkcar71 pointed out, this is not something you just do. It has to part of a well though out upgrade. The best you can expect is a small difference in performance and then it does downhill from there, from a total waste of money to complete engine destruction. There are many other items that will add noticeable performance gains, ie headers w/high flow exhaust system, intake, carb, quality distributor, etc. Don't bother with the 1.6 rockers until you at least change the heads.
 

Vette79

Well-known member
Joined
Jan 23, 2007
Messages
1,392
Location
Millersville, MD
Corvette
1979 L-48 Black Coupe
I have the headers and exhaust work completed. Aside from changing the heads, would upgrading the cam and intake give me a noticeable difference and is it worth it?
 

ratflinger

Well-known member
Joined
Sep 4, 2005
Messages
74
Location
South Central Texas
Corvette
1979 Black Coupe, 396 SBC
I don't think you are going to see much difference. It's kind of a package thing, couple horses here & a couple there and you wind up with 20 more than you might have had.

You have to recalc your lifts. Once you know the lifts on your cam take your installed spring height, subtract the lift (be it intake or exhaust), and subtract .060, if the number you get is still larger than the listed max compression height then theoretically the 1.6 rockers will work. You still have to be concerned about valve to piston clearances and spring pressures. This is why you usually don't switch unless you are familiar with your engine's internals.

Even on a roller upgrade I'd stick w/1.52 unless you are rebuilding your heads.
 

ratflinger

Well-known member
Joined
Sep 4, 2005
Messages
74
Location
South Central Texas
Corvette
1979 Black Coupe, 396 SBC
I have the headers and exhaust work completed. Aside from changing the heads, would upgrading the cam and intake give me a noticeable difference and is it worth it?


A cam & intake change can make a huge difference. You will want to decide what carb you are going to use ahead of time as it is a package consideration also. You will want this to be a package decision (not to be confused with a package deal from a vendor), the chosen setup must work together or you might see zero to negative gain. If your engine is stock moderate then stick with a nice dual-plane intake from Wieand, Edlebrock, Performance, or Holley. Most of these will be available for Q-jet or Holley/Demon carbs. (Be sure to check hood height) Edelbrock has some carb, cam, & intakes packages; perhaps the others do too.
 

JohnGrawcock

Well-known member
Joined
Sep 22, 2003
Messages
318
Location
Kokomo, IN
Corvette
Claret 82, Light Bronze 84, and Black 69 Vert
Go for it.

Hey everyone,

This is a newb question, but i have to ask.

How big of a difference would upgrading my rocker arms make?
I have the stock 1.5:1 and I'm thinking of moving to 1.7:1 (or 1.65 if that is better for a small block).
Is this a "you'll might sort of notice" difference, or a "kick you in the a$$" difference?

Also, would i need to replace the lifters and push rods, or can i just pop off the valve covers and replace the rocker arms?

This should increase compression/stroke without the trouble of getting to the camshaft. (i know it isn't that hard, but a bigger PITA than taking off valve covers and the springs).

Thanks for the input, it is always appreciated!!!
I'm going to have to disagree with the others here. If you want a little more power without getting carried away, the right rocker arm swap is an excellent upgrade for your 82.

Go with 1.6 ratio roller tip rockers. Available from Summit racing for approximately $95. The reduction in fictional losses from the roller tips is very significant. The 1.6 ratio is as high as you can go without problems, but your crossfire wants the added lift and duration so bad on the intake side that your efforts will be handsomely rewarded. Wish I had before and after dino numbers, but that doesn't come cheep. All I can say is that for me
$95 + afternoon in garage = :lou

Yes, you can produce bigger changes with a CAM and/or other extensive modifications. However, it will cost you a lot more time and money. If you go too far you'll need to custom tune the ECM to handle the changes.

Check out this sight. These guys have tried a lot of things with the L83 and at times gotten into trouble.
http://www.crossfire.homeip.net/
 

LT4man

Well-known member
Joined
Jun 25, 2003
Messages
2,214
Location
Chicago
Corvette
96 Collectors Edition LT4
I agree with you, John, totally!

SAVE THE :w
 

JohnGrawcock

Well-known member
Joined
Sep 22, 2003
Messages
318
Location
Kokomo, IN
Corvette
Claret 82, Light Bronze 84, and Black 69 Vert
I agree with you, John, totally!

SAVE THE :w
I'm not sure anyone else noticed the model year of the original poster. The Crossfire is a different animal built for low end torque. The modes need to complement the original setup if your not looking to recreate the whole thing. For example: I wouldn't do the typical long tube headers on an 82. Those are designed for high RPM. The stock exhaust manifold is designed like a shorty header. Great for low RPM torque on the street .
 

Vette79

Well-known member
Joined
Jan 23, 2007
Messages
1,392
Location
Millersville, MD
Corvette
1979 L-48 Black Coupe
John, for a 79 L-48 dual chambered exhaust and headers, emissions removed, what would you suggest for a cam or cam kit? I want to install an Edlebrock Performer Intake and use my original QJet.
 

ratflinger

Well-known member
Joined
Sep 4, 2005
Messages
74
Location
South Central Texas
Corvette
1979 Black Coupe, 396 SBC
Go with 1.6 ratio roller tip rockers. Available from Summit racing for approximately $95. The reduction in fictional losses from the roller tips is very significant. The 1.6 ratio is as high as you can go without problems, but your crossfire wants the added lift and duration so bad on the intake side that your efforts will be handsomely rewarded. Wish I had before and after dino numbers, but that doesn't come cheep. All I can say is that for me


:confused Frictional losses from the roller tip? There is some frictional loss, true, but not a lot. Most frictional losses occur at the trunnion, not the tip. I have nothing against going to roller tipped rockers, but the hp gain here is nil. I still stick by my statements, while putting 1.6 rockers on your engine has worked, you can not make a blanket statement that it will work on all 82's. The chances are good that no harm will come from this, but if a previous owner has modded the engine enough, then you could kill it.
 

ratflinger

Well-known member
Joined
Sep 4, 2005
Messages
74
Location
South Central Texas
Corvette
1979 Black Coupe, 396 SBC
I'm not sure anyone else noticed the model year of the original poster. The Crossfire is a different animal built for low end torque. The modes need to complement the original setup if your not looking to recreate the whole thing. For example: I wouldn't do the typical long tube headers on an 82. Those are designed for high RPM. The stock exhaust manifold is designed like a shorty header. Great for low RPM torque on the street .


You might look at tri-y headers, like from Stan's Headers. These are designed for power at lower RPM. For near stock applications the stock exhaust manifolds are perfectly adequate. True duals w/high flow cats (if emission testing is a concern) & mufflers would be a good investment.
 

minifridge1138

Well-known member
Joined
Feb 2, 2007
Messages
908
Location
USA
Corvette
1982 Black Fastback
Hello again,

I appreciate all of the information i've gotten. Let me clarify a few things about my car and see if that changes anything.

It is an L83 motor, but the crossfire is gone. I have a Holley Street Dominator intake and a 600 CFM carb. The emissions stuff is long gone (It still passed the last emissions test, so I'm legal). The cam, crank, headers, exhaust manifold, rocker arms, transmission, rear-end are all stock.

Since I don't have the crossfire, would I still benefit from added duration and lift?

I also have a set of Hooker Competition headers in my garage that I'm going to install. That shouldn't hurt anything, right?

Thanks
 

ratflinger

Well-known member
Joined
Sep 4, 2005
Messages
74
Location
South Central Texas
Corvette
1979 Black Coupe, 396 SBC
The Hookers will be fine. If you feel that the engine has not been internally modded then give the rocker arms a try. Your current pushrods will be fine. Just make sure the new ratio rockers don't contact the spring retainers at max lift. I assume you know how to set the lash on hyd lifters.
 
Joined
Jan 1, 2002
Messages
7,246
Location
Washington, Michigan
Corvette
'67 Marina Blue Convertible
Waste of money, hardly any difference; HOT ROD did a comparison about a year ago between stock and 1.6 rockers on the same engine with four different cams and intakes, and all they got was 3-5hp. In most cases, you'd also need new pushrods, after measuring for them, due to different rocker geometry. Spend it somewhere else where you can benefit from the investment.

:beer
 

Hib Halverson

Technical Writer for Internet & Print Media
Joined
Jan 10, 2001
Messages
13,453
Location
CenCoast CA
Corvette
71 04 12 19
In reading this thread, I see there are a few misconceptions about rocker arm changes.

First, on an L83 engine, which has 200-205hp dependiing on model year, the typical SBV8 rocker arm ration change, 1.5-1.6 ratio, will result in only a modest gain in performance. The 3-5hp number listed above is possible but might be overstating the case on a 200hp engine.

The statement about roller tips significantly decreasing friction is incorrect. In fact, there is very little decrease in friction in using a roller in the tip of a rocker arm especially at the stress levels in a 200hp engine. The big decrease in friction comes when you use a roller bearing in the trunnion. This is why all current GM OE rocker arm designs on V8s have roller fulcrums but not roller tips. In reality the roller tip increases weight of the rocker but is used by aftermarket companies either 1) to mislead the consumer into thinking the rocker is better because of the fancy-looking roller tip or 2) in the case of aluminum rocker arms, to avoid the cost of adding a hardened steel insert on the tip.

We must be careful when we discuss the effects the ratio change has on duration. At lash point, there is no change in duration, however, once the rocker begins to translate the motion of the lifter and pushrod, duration begins to slightly increase above the duration which was present with the 1.5 rocker. The overal change in duration is slight with the chief advantage being extra lift.

As stated earlier, when changing the rocker ratio, it's best to check for coil bind and interferrance between the retainer and the valve guide, however, on an L83 getting only a 0.1 increase in ratio, it's unlikely there would be a problem.

Lastly, a more aggressive rocker arm ratio moves the engine speed at which valve float will occur lower in the rpm range. Again, with the L83 and only a 0.1 change in ratio, it's unlikely that the limiting rpm of the valve train would be reduced enough to matter, however, if the valve train has been in service a long time, the normal wear and fatigue that occurs may have the valve springs already weak enough to put a valve train with 1.6:1 ratio rockers into valve float in the upper rpm range you'd see in street driving.
 

Art Jett

Well-known member
Joined
Mar 25, 2004
Messages
366
Location
Azle Tx.
Corvette
1977 TPI 383 stroker, 700R-4/ 2002 6 spd.
Maybe I'm hijacking this thread but I don't think so. I am thinking of changing from a flat tappet cam to hyd roller. In order to get the proper seat pressure from my current springs Crane cams suggested I use .030" shims. The springs have a max lift of .575" now. The cam I am considering has an exh lift of .539". With the spacers, this only leaves .006" of compression. Can this be acceptable? The rocker ratio would be staying the same--1.5.
 

Hib Halverson

Technical Writer for Internet & Print Media
Joined
Jan 10, 2001
Messages
13,453
Location
CenCoast CA
Corvette
71 04 12 19
You're going to be real close to coil bind. When that happens, parts break.

I wouldn't do it.

I'd purchase the proper springs for the hyd. roller.
 

Art Jett

Well-known member
Joined
Mar 25, 2004
Messages
366
Location
Azle Tx.
Corvette
1977 TPI 383 stroker, 700R-4/ 2002 6 spd.
You're going to be real close to coil bind. When that happens, parts break.

I wouldn't do it.

I'd purchase the proper springs for the hyd. roller.

I got on the Crane cams website and the specs for the cam call for 112 lbs seat pressure @ 1.650
open 318 lbs @ 1.140
The cam has a max lift of .539
The springs on the heads are
installed height 1.800
seat pressure 120 lbs
open 320 lbs @ .500 lift
The part # for the cam is Crane # 119701, the heads are Edelbrock Performer RPM 64cc
Thanks, Art

Does this look like it will work?
 

Jack

Well-known member
Joined
Dec 27, 2000
Messages
1,825
Location
Florence, SC (Timmonsville SC)
Corvette
71 War Bonnet Yellow VERT 71 BH Blue CPE (SOLD)
Whatever the max lift at spring is you MUST have an additional approx 0.060" to 0.075" it can compress to avoid coil bind. Does the .575 mean it can compress 575 and then 060 more until it becomes solid? or ... or does it mean .515 + .060 = .575??? Does it mean 1.800 spring is solid at 1.225" ?? ...OR ... on seat at 1.800" / solid at 1.150" ?? Springs specs often shown with both open AND solid heights ... check it & reply. VERY important.

Letsee your springs = 1.800" (usually means on seat) and 120# on seat AND max lift .575".

And your new cam requires only 112# on seat but lifts .539.

If your springs Truly have an additional approx .060 more travel beyond .575 'til solid ... and they're Truly 120# on seat ... then I'd stick the cam in just as it is. But ... what things are supposed to be and what they really are ain't always the same. So ... there ain't but one way to know ... that's measure stuff ... HIGHLY recommended!

as for rollertips ... don't waste your time on em ... and if you add ANY roller rocker arm to sbc/BBC ... you must check that roller is centered on valve tip & adjust guideplates as needed ... more often than not they're Not aligned w/vt... if roller runs off edge of valve tip it can easily drop a valve & destroy motor ... that's happened alot. IIRC, CAC member fine69 (ralph) had similar problems w/ misaligned rollers-VTs & guideplates w/rpm heads nearly 3 years ago ... fugly but not destroyed.

as for changing ratios ... Not mentioned so far is: clearancing head for pushrod. When you change from 1.5 to a higher#/ratio ... the lever arm between valve tip & trunnion always stays same as stock ... BUT the lever arm between pushrod cup & trunnion changes ... it Shortens ... and pushrod gets closer to head ... head usually needs grinding clearancing. Also, when you change increase ra ratios ... it usually adds a degree or 2 to the 0.050" duration.
 

Corvette Forums

Not a member of the Corvette Action Center?  Join now!  It's free!

Help support the Corvette Action Center!

Supporting Vendors

Dealers:

MacMulkin Chevrolet - The Second Largest Corvette Dealer in the Country!

Parts/Accessories:

Vetteskins

Advertise with the Corvette Action Center!

Double Your Chances!

Partners

Top Bottom