enkeivette

Pretty much all in the title. I want to upgrade to some 1.7 full roller rockers. Will the 1.7 rockers cause any kind of pushrod clearance issues? If so, how about the 1.65 rockers? I am using guideplates if that matters.

Also, 1.7 rockers for a SB are hard to come by, and the ones that are out there are pricey. So stupid question, would it be possible to use BBC rockers on a SBC? If so what needs to be done?

*I just read on another forum that SBF and BBF rockers will work without modification on a SBC? Can anyone confirm or deny this?

Vette Crazzy

why would you want to do this? all you are doing is asking for all kinds of trouble. like: spring bind or broken springs, bent or broken pushrods, piston to valve clearance.

put a bigger cam in it!

vc

Bee Jay

I use 1.65 ratio rockers with the summit equivelant of the Edelbrock performer rpm cam. No problems.

ratflinger

You need to know your current lift, cam specs, spring rates, piston to valve clearance, etc. before you even contemplate this. Once you know all the specs you will then be able to calculate whether or not you can move to 1.7's. BeeJay knows what he has & that's why he can run 1.65's. As far as running BB or Ford rockers you'll need to know the physical specs of each (shaft size, overall length, trunnion to end lengths). I don't know the answers & I'd check for myself before outright believing someones opinion, especially concerning my own engine.

Little Mouse

The length of a big block chevy rocker from the fulcrum to the valve
tip is longer then a small block rocker they will not work.

gkull

Bigger cam is not always an option. Bigger ratio rocker arms is. I use CC 1.7 steel roller rocker with 7/16th rocker studs

When I looked through the lobe profiles of racing solid lifter lobes you have to use 1.7 or higher to exceed .700 lift.

IMO - ratios above 1.6 are not recommended for any kind of H cam. The higher ratio multiplies the pressure on the h-push rod plunger. also the lower pound springs rates are not made for very high lifts. Valve float becomes an issue

Solid cams I would say go for it!

Deakins

We run 1.7's on a solid lift cam to get to 0.740 lift and don't have any problems but again; lots of expensive parts and an engine that was built that way.. You need to do a lot of math before you make the jump to a bigger ratio.

enkeivette

Wow, thanks moms for worrying about me. Don't worry about whether or not my springs will handle the lift or whether I'll have piston to valve clearance issues. Obviously I will measure that when I pull of the heads before I buy the rockers.

My question was:
Will the 1.7 rockers cause any kind of pushrod clearance issues? And will SBF or BBF rockers will work without modification on a SBC?

gkull, thanks for the warning. What do you mean pushrod plunger? Are you talking about the lifter or the pushrod? My pushrods are one piece chromeoly, do you think that they would be able to handle the added stress?

Vette Crazzy

Wow, thanks moms for worrying about me. Don't worry about whether or not my springs will handle the lift or whether I'll have piston to valve clearance issues. Obviously I will measure that when I pull of the heads before I buy the rockers.

how do you measure piston to valve clearance after you pull the heads off? THIS IS WHY WE ARE TALKING TO YOU LIKE YOUR MOM!

hey wtf just throw them on and fire it up and see what happens!

vc

gkull

I have not seen a engineering diagram on differences between rocker arms for different manufactures. I did look on the comp cams sight and they give a different part number for like ratio rockers for chevy, ford, pontiac, oldsmobile. so I would say that something is different. I used to own a Dodge and the pushrod tips are actually a different shape and size compared to Chevy

Plungeron the h-roller or h-flat lifter. Oil pressure brings them up to being nearly solid in function. But they do have a max valve spring limitation. All H-lifters have a max valve spring weight of @ 145 pounds. About that limit you start to depress the "Plunger" and it will result in loss of lift.

In effect, higher ratio rockers multiply the felt spring pressure on the pushrod and lifter. If you look at the comp Cams graph on a spring it might be made to 440 inch pounds. You only have .500 inches of lift cam. you start with 120# seat pressure and add 220pounds for an open pressure of 340# open. Now add 1.7 ratio rockers and the the lift goes to .600. That adds 44 pounds to 384 pounds of open pressure. At some point it will exceed the lifters internal construction and you get loss of lift or damage to the lifters and push rods.

most

enkeivette

Okay, thank gkull. So I need to find some info about my lifters then...

Well, first you pull the heads off, then you put a piece of clay on top of the piston. Then you torque the head on, rotate the engine, pull the head off again, cut the clay, and measure the thickness of it. That would be your piston to valve clearance.

A better question would be: How do you measure piston to valve clearance before you pull the heads off?

gkull

Modern bore scope with fiber optics is a very easy way to look down the spark plug hole and see the clearance

enkeivette

You're kidding me. I guess I need to jump in my Delorean and travel to your time. So how expensive is this fiber optic tool? And where can I get one?

Regardless I will be pulling the heads off, to give you guys some background from my other thread: I need to mill my heads a bunch to up the compression.

Vette Crazzy

thanks gkull.

these are real popular in the claimer classes at your local dirt track. the inspectors use them alot to check for cheaters using dome pistons

vc

gkull

I borrowed one from a shop years ago (fiber bore scope)when i was doing a port match job on my single plane intake to the head port.

73C34me

I had interest in this years ago & was told that sbc geometry wouldn't be good w/ 1.7 rockers. Any thoughts?

gkull

First of all you are not talking about stock heads. You are talking about .100 longer valve stems with higher installed height springs for the additional lift. You are also forced to use longer pushrods and rocker studs.

For 10 years and 100,000 miles I used 1.6 roller tips with near .600 lift on 186 and 292 casting heads

hugie82

tORQVETTE, if your engine is a mild build under 10 to 1 comp, less than 460 lift ,overlap is civil,ect... 1.6 would be OK, 1.7 sometimes run into problems with the pushrod guides wearing,studs pulling out, spring and valve damage. Also keep in mind if your heads aren't ported your gains will be small. On stock engines I've played around with 1.6 rockers on the exhaust side only. The engine revved-up pretty good.

Solid LT1

NO! BBC or Ford rockers wont work on a SB Chevy head without modifications. Valetrain Geometry is all screwed up by going to high ratio rocker arms. Years ago a guy in New Jersey mounted BBC rockers onto a small block head, you may have heard of him: Dan Jessel as in Jessel rocker systems, to put the BBC rockers on he had to plug exisitng rocker holes and move them back towards the intake manifold, then the valve covers wouldn't fit then something else screwed up then after years of working on a system, he made a set of shaft rockers for a SB Chevy. Thing have been good for Dan Jessel ever since although I am putting on some Larry Torres shaft rockers on my new motor (T&D rockers.) You can run a 1.65 ratio rocker with the stock stud location but, if you ever watch the geometry of a stud mounted high ratio system you would be very afraid for the long term reliability of any system. Get the right cam profile and run 1.5 or 1.6:1 rocker arms on your Vette.