hi all

i wanna know if i can use the 1.6 roller rockers with my next modifications!


here are the modifications that i have done: crane cam Duration 264/270, Lift .438/.452, Speed pro Piston/Ring Kit, Forged, Flat, Heddman headers,
corvette aluminum heads,edelbrock performer rpm,holley 650 dp

is it worth to do it?
the engine is a 350 0.30 oversize 1988 from the corvette C4

dennis

 

1.6 ratio wont net you any noticeable gains, but it wont hurt you either.

 

The 1.6 rockers will net a bit more lift and slightly more duration.
the current cam lobe lift is .292/.301 so,
with 1.5's it's .438/.452
with 1.6's it's .467/.482
There will also be about 2 or 3 degrees of duration increase, so it is worth it to use the 1.6 rockers. Just my opinion, but math doesn't lie.

 

If they are real production line Vette heads (not ZZ4 crate engine take-off heads) you are pushing your luck around .470" lift. Above that point, the retainers hit the guide seals.

Intake side should be no problem with 1.6s. Exhaust side you're pushing your luck.

On the cheap, I've run without valve guide seals on the exhaust side. Buys you the necessary clearance for higher ratio rockers, and exhausts aren't nearly as sensitive to guide seal issues (oil consumption). But never on the intake side.

 

can sombody confirm this??


if i buy some of that rockers,should i use the aluminum or the steel rockers?

is there a good brand to use?
and do i only need the roller rockers 1.6 or must i use other studs to?

dennis

 

Good thread, I was about to do the same thing, run corvette heads (casting 10088113) with about .500 lift.
I guess I will grab some +.050'' valve locks.
I don't believe machining down the valve guides and valve spring seats is great idea on these thinly cast ultra light weight heads.

 

i`ve got the same heads

 

Both the ZZ4 heads and the old production line Vette heads are 113 castings. The difference is in the machining operations. ZZ4 motors have about .510-.520 lift on the exhaust side so the heads obviously had to be made to accomodate that. Origianal Vette engines only had about .430" on the exhaust, which is why they never built them for huge lift.

I've worked on both (mostly roiginal Vette heads) and there are definitely differences.

If in doubt, pop a valve spring off and measure clearance between the bottom of the retainer and top of the guide seal.

 

I put a set of ZZ4 /LT4 springs ( Good for .525 lift ) and retainers on my 113 heads and ran the ZZ4 cam @.510 exh with no clearance problems

$40 for springs
http://www.jegs.com/i/GM-Performance...oductId=761647
$20 for LT4 Retainers

 

My take on it; why try to reinvent the wheel?
You effectively have a ZZ4 engine ( with the carb).Why not run the ZZ4 cam and springs as designed by the factory for this engine which made a impressive 355Hp. (Before anybody points it out I know there are slight differences in the porting from the factory)
GM spent a lot more $$ than you will ever have specing a cam
For the money you waste on buying 1.6 rockers to get F-all gain in lift it would be better spent on a cam to suit.

ZZ4 take outs from new crate engines can be had for under $130 on eBay. Add the springs / retainers and for under $200 you have proven performance

Often available in 3rd Gen For sale
https://www.thirdgen.org/forums/engi...-shipping.html
https://www.thirdgen.org/forums/engi...8-zz4-cam.html

 

Hmmm, I really wish the machine shop would finish my heads already.
I need to get my heads back so I can take some measurements.

 

I went to the machine shop that has my heads and measured them for clearance with the new stock valve guides installed, stock valve locks, stock retainer and a seal on the exhaust side. Any thing over .550'' looks like it would be pushing the stock guide, valve, retainer and lock setup.

 

Unless you do some porting you need that much
Even Lingenfelter ported ones don't flow a lot over .500

LPE cnc-ported L98 vette heads
.200 140 116
.300 198 157
.400 242 185
.450 249 195
.500 254 199
.550 260 203
.600 263 206

https://www.thirdgen.org/forums/tech...num-vette.html

 

That sounds cool a nearly stock cam with 1.6 rockers should do pretty good.