Rocker ratio

seawalkersee

Registered User
So I picked up a set of heads the other day with a set of 1.6 full rollers on it. I then just wondered what the deal was if the desire was there to put the 1.6s on the SC with a larger cam. I mean, with my 351, I checked the lift. With my 1.7s, I had .001 higher lift with my .498 cam than I would have had with a .512 cam and 1.6s.

So, can you run a larger cam with 1.6s and have better valve stability from a lighter overall rocker weight?

I believe the factory ratio is 1.6:1. So, lift the cam to what extent? Is it because the lifter is too high in the bore at max lift? Is it because the 1.7s can have a better (cheaper cam profile) cam than can be obtained with the 1.6s?

Discuss.

Chris
 
Stock is 1.73. Several have upgraded to 1.8, but I don't think thats a good idea if going with an aftermarket cam, but thats just me.

Frit
 
I have a set of SVO's on mine and they are HEAVY. I would like to step up to a lighter set to get a few extra RPM's. What are the lightest ones that you know of that will fit the factory heads.

Chris
 
Chris,

The rockers may feel heavy in your hand, but that is because you now have the added weight of the roller trunion as well. The actual realized weight, though, is only the body of the rock as the trunion is stationary when the rocker is bolted down.
 
I'm using 1.65 ratio rockers intended for an oldsmobile. I've thought about switching to 1.73s, but with my history of valvetrain problems, I'm leary of doing anything that will add more stress.

David
 
"I'm leary of doing anything that will add more stress"

David, not sure what you mean by this. If you are using the factory ratio and a correct bodied rocker for the application, how could you add stress?
 
1.8

I'm using 1.8 roller rockers that I ordered a good while back from Morana V6 Racing. They're made by Harland Sharp.

Put them on when the engine was stock and I'm still running them with a 519 cam - .300 lobe lift 284/224 duration. With 1.8 rollers I'm actually getting a 540 lift.

Haven't had any problems with them.

eddie
'90 5-speed SC
'97 LX sport
 
"I'm leary of doing anything that will add more stress"

David, not sure what you mean by this. If you are using the factory ratio and a correct bodied rocker for the application, how could you add stress?

I mean....more stress than what I have now. I've been running 1.65:1 ratio since this motor was built back in early 2002. If I switch to a 1.73:1 ratio I'll be increasing the valve spring pressure and put more load on the pushrods, lifters, rockers and rocker studs.

Since I'm constantly bouncing it off the rev limiter (6500) or (6800 w/nitrous), and I've already had to repair studs that were yanked out of the heads numerous times, bent valve from rocker coming off, broken valve springs, broken lifter retainer that resulted in a trashed lifter and cam along with a few other less serious problems.....I'm not wanting to do anything that might cause another valve train failure.

David
 
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