rocker arm choosing help...

[larryo454]

Hmm what does the aggressive ramps have to do with the 1.6 rocker arm?

I think what he is getting at is the fact that the aggressive ramps cause a lot of stress on the drivetrain. Supposedly lunati's lobe design has solved this problem over their XE counterparts, but that is a seperate debate.

Basically the 1.6 rocker is causing the valve to open farther but the duration remains constant. Therefore, the valve is traveling much faster to make up for the increase in distance. This may cause valvetrain noise or the valve not shutting gently. This may lead to other issues that I'm sure you guys can add on.

Ya something like that. An increase in rocker ratio won't increase your advertised duration but it will increase the duration seen at .050", this is due to the lift coming at a quicker rate. A roller cam has very agressive ramps that are not possible in a non-roller cam because the lifters will just dig into the side of the lobe. The XE/Voodoo cams are using a lobe design that is pushing these limits. Adding in the increased rate of the 1.6 ratio and you could have a problem of wiping out the cam. If there's is any doubt, you can always call their tech line and see what they recommend, just in case this is more of a rumor.

Hi you don't increase duration @ .050 you increase more valve opening @ .050 This in turn closes the piston to valve clearance @ .050.Lets say you need a min of so much clearance like .080 on the intake and .100 on the ext for 7000rpms and more if you go up in the rpms.With more lift you need more spring seat pressure and open pressure along with good valve and rocker geometry and might need a longer pushrod.The slots in the head may need tobe long gated and the list goes on.And for wiping out the cam is more likey do to valve guide to spring retainers and lock clearance probs.As like Jrm81bu said it might be a rumor, yeah to me it is like people don't use a dreg wheel or even know how with check springs.

 

[jrm81bu]

Ya, i screwed up on that one. For some reason I was thinking the .050" lift was valve lift instead of lobe lift.

 

[beermonkey9417]

so with my stock cam, i can use these right? cuz there already in the car and its at the shop...

 

[jrm81bu]

so with my stock cam, i can use these right? cuz there already in the car and its at the shop...

Ya, they should be fine with a stock cam.

 

[Daddie2k3]

Thanks for all the input I actually something come up and so don't have the money to sink into in now so I'm hoping I can just use the factory rocker arms that come on the vortecs because that's what I have because I bought L98 bare

 

[mickey-d]

I started using 1.6 rockers over 30 years ago, and never had a problem. They will wake up a stock cam, and I've used them on some performance cams that were 500 or a little lower lift, and just under 300 on the duration. Does it affect the lift and duration, yes, but not to the point of hurting things. On race cars, it's common practice to change rocker ratios. I have used 1.5s on the intakes, and 1.6s on the exhaust. I've also run 1.7s on my small block with the Jessel shaft rockers. Had to move the stud holes, and enlarge the pushrod holes to accept 3/8" pushrods. A couple of the pushrod holes had to be epoxied, went into the intake runner, but it worked out Ok. What matters most, is what you are going to do with the engine. Street, street/strip, or just the track. Anyway, if you're not going to go crazy with a camshaft, you can use the 1.6 rockers without hurting anything. If you get too high in you lift, and too long in your duration, you won't have enough vacuum to operate your power brakes, and any other vac operated accessories. ................mickey-d :lol:

 

[pontiacgp]

On race cars, it's common practice to change rocker ratios.

at our track it's common practice for the tech guys to check for the cheaters using the 1.6 rockers... :lol:

you're right on with changing the rockers..a real cheap way to wake up an engine

 

[87montecarlomrc]

I'm going to butt in on this post and ask a question. This is my cam i have
CAM 88-89 L98 10066049 In/Exh [email protected]" 207'/213' Lift (w/1.5) .415"/.430" LobSep 117'
I'm wanting to just put stock vortec heads on this motor and want to put 1.6 rockers with it, do you think it will be fine for the heads and motor ???

 

[mickey-d]

I believe you would be fine. One other thing, to the guy that posted above you............ Why would any track check rocker arm ratios? Makes no sense to me. Please make another post and explain. I'm really curious. ............mickey-d :lol:

 

[pontiacgp]

we run a 602 sealed crate and we can't upgrade anything. They even have a program to check the profile of the cam to make sure the cam has not been changed. I heard one team got caught using mushroom lifters last season..

OPTION A: CRATE ENGINE
1. Only approved, sealed, unaltered engines.
2. No changes, substitutions or modifications to engine.
3. No rebuilding allowed (only approved repair of crate engines allowed).
4. It is the competitor’s responsibility to have paperwork of where the engine was purchased and competitors will
be held accountable for alterations to engine.
5. Any tampering, alterations, or violations with respect to the crate engine program will result in the immediate
suspension of the driver, car owner, and chief mechanic for a minimum of 1 year (365 days) from the date of
the infraction. Further monetary fines and reduction of points will be assessed by the technical committee. The
tampered engine which must be removed at the team’s expense will be impounded at both the team’s expense
and risk until the ruling is finalized. The speedway reserves the right to destroy all tampered with parts

and Option B for the built motors they are pretty strict and you have a weight penalty along with other restrictions so they basically make it not to be worth building an engine since the crate engine doesn't get torn down at our cost if we win a race and a crate goes for around $3400 which gets eaten up real fast building an engine

B) CAMSHAFT
• Mandatory flat tappet hydraulic camshafts. Maximum valve lift .500 inch measured at valve with zero lash. No
mushroom lifters. No rollers. Must use stock-type timing chain and gears.
• Cams with excessively steep ramping and high overlap will not be allowed.
• Must use manufacturer’s firing order.

D) CYLINDER HEADS
• Only stock O.E.M. cast iron heads allowed. Absolutely no deburring, grinding, acid dipping, acid porting or
polishing of intake or exhaust ports allowed.
• Must use 11/32” stem. No undercut valves. No hollow valves. No titanium. No sodium.
• Maximum valve size: General Motors 1.94” intake and 1.50” exhaust, Ford and Chrysler 1.94” intake and 1.60”
exhaust