to be more specific:

I have a '87 305ci block and 305 stock cam, new GM vortech 350 heads (1.94" intake and 1.50" exhaust valves w/ L31 valve springs and 64cc chambers), Holley intake and Holley 670cfm TBI.
I want to installs roller rockers ( Harland-Sharp), since this is an unusual configuration, I don't know what the clearances are.

My Questions are: Can I install 1.6 rockers without a valve collision? would it yield any improvement over 1.5s? Are rollers rockers worth putting on this engine that already runs good <14.5s.

 

You will need to have the valve guides cut down, they are too tall.
They will work for anything under .500 valve lift without the valve
spring retainer touching them. With 1.6 rockers your valve lift will
be .443 on the intake and .459 on the exhaust. The exhaust valve
retainer will hit the valve guide before the valve opens all the way

 

i'm not sure about shaving the guides. Is it worth it? Would 1.6 rollers make any significant improvement over 1.5?

 

Tom.....I am running a .480 lift cam on stock Vortec's with a .060 shim under each spring and .060 offset Crane retainer locks. Plenty of clearance... You can also shave some off the bottom of the stock Vortec retainers and it should probably be enough in your case.

Later Darrell

 

i just don't know the lift/dur on stock '87 305 cam. I'd really like to avoid taking the motor appart, again, but if I can get more lift out of the valve train using 1.6's than it worth $190 rather than a new cam.
-tominator

 

Remember... 1.6 rockers give you greater lift in the same duration (not from .50) This means that the acceleration of the valve is greater. This can wreake havoc on the stock springs and the steep ramps on your roller cam just make it that much worse.

I dont know why the saying is 'When the **** the fan...' because (in my opinion,) it is a lot messier 'when the valve hits the piston." Not only does this ruin you piston, valve, and pushrod, for sure: to put icing on the cake your springs (all of them) are probably toasted because of valve float, and your rockers are probably damaged as well.

I am not trying to scare you out of bolting on the performance ratio, I would use extreme caution because you may not know how good you valve springs are, and you dont know your piston to valve clearance.

 

remember now, I have the L31 corvette springs, 1.94 -vortech steel heads, but the bottom-end (and cam) is a stock 305. The stock 305 pistons probably have smaller reliefs cut into them, that is what i'm not sure of.

maybe i'll just get 1.5s
-tominator

 

If you have the stock TBI cam, then you are in no danger of anything hitting anything else with 1.6 rockers. You can find the cam's specs on the tech data page on this site.

I'd still recommend putting some halfway decent springs on those heads. If you have the actual L31 springs, they are garbage. They are replacement truck parts, not high performance ones, totally unsuitable for any sort of hi-perf usage. Get rid of them even though you are keeping the stock cam and put the entry-level spring from some one of the major cam mfrs. on there, such as Comp 981. Having been erroneously associated somehow by someone with the miraculous "V" word does not somehow magically impart mystical romantic characteristics to them. Since there is no such thing as a L31 Corvette anyway, any magic that even might be available from the "V" word does not apply.

 

Dont let me scare you out of buying what u want. Just make sure you take RB's advice and swap the springs.

 

Amen on your thoughts Green

 

1.52 roller rockers will add .006 to your lift on the intake and exhaust over stock rockers. 1.6 roller rockers will add .012 to your lift on the intake and exhaust over stock rockers.

Also something I don't think anyone mentioned (if they did I apologize) is that in addition to having the guides cut down, you also have to have the push rod slots elongated toward the outter edge of the heads just slightly.