hey guys, got a bone stock 350 in my 87 trans am gta...

could someone tell me the stock spec for the rockers?? i dont know much about the motor itself yet, looking just for some info... plus

my buddys got a set of comp cams rollertips not sure what they are 1 5's or 1 6's i really dont know but on a stock motor what is the best way to go with the rockers? thanks,


matt

 

Stock rockers fit a 3/8" stud, and are 1.5:1 ratio.

If they are self-aligning or not is determined by the shape of the end of the rocker where it touches the tip of the valve. Self-aligning rockers mold around the tip of the valve so the rocker doesn't slide off to the side.

Factory studs are pressed in. This has to change if you want to use NON-self-aligning rocker arms. It also has to change if you run rockers that fit 7/16" studs.

 

ah okay yea ill defenately have to figure this out a little bit more then, not sure what rockers they are so thats first.. but lets say they are self aligning and 3/8ths, what is the best set ratio to go with?? 1.6, 1.7 ??

 

Cam lift * rocker ratio = valve lift
example:
0.2866" * 1.5 = 0.430"
0.2866" * 1.6 = 0.459"

If the valve lift exceeds the physical limitations of the cylinder heads, - retainer-to-guide or seal clearance, the spring travel before binding, or if the lift causes piston-to-valve contact, then you can't run it without causing engine damage.

Most stock SBC1 heads are physically limited between 0.470" and 0.480" of valve lift.

For more valve lift you can swap springs and retainers, and/or pull the heads and have them machined for more clearance. Some spring & retainer upgrades can increase the lift limitation on stock heads.

 

yea thats exactly what i was looking for lol, ive built 350s but dont have a clue what the specs of the stock stuff is, ive only started with bare blocks, aluminum heads and everything else aftermarket lol... so just trying to get some specs on this motor cause i havent even tried googling it or anything, so yea thanks man apprectiate it

 

Whatever you do PLZ don't do what I did...

After I had my motor built I decided to have some 1.6 full roller rockers installed..

To make a long story short the extra lift that the 1.6 rockers gave me ended up causing major binding in my valve springs, and about a year and a half later I had 2 valve springs break on me within a month, while slowly but surely ruining some of my lifters in the process..

MAKE SURE your motor can support the extra lift those new rockers are gonna give you or else you will have some very expensive repairs on your hands, not to mention being left stranded somewhere when something does decide to break

 

Did you change your valve springs when you installed the 1.6 rockers? I've been curious about this mod too. I've heard that you can run 1.6 rockers with an otherwise stock setup as long as you upgrade the valve springs to match the rockers. However, I've yet to talk to anyone who has actually done this so if anyone has successfully done this please let us know how it worked out and what you used. Thanks.

 

During the rebuild a had a Comp Cams Camshaft installed that was rated at .500/.510 lift. The kit came with new springs, etc, etc...

My case may be a little more unique than others simply for the fact that when I wanted to install my new 1.6 rockers, I called the mechanic shop that was rebuilding my engine and directly asked them, "Since I now have springs rated at the lift the camshaft is at, will it be able to support 1.6 roller rockers?"

He gave me the green light to go ahead and throw them on there... WRONG!!!

(Sadly the guy who told me this information in the first place has now passed away, therefore we had no way to blame it on the shop that it was their fault to begin with)

At the time I didn't know as much about engines as I do now (Hind-sight is 20/20 eh?)

It turns out that the newly added rockers increased my lift to .545, way too much for the springs that came with the camshaft. To fix this the mechanic ended up having to set my motor up to support the extra lift, I think it can now safely support up to .560 lift now? lol

Just remember that whenever you add lift in one part of the motor, it HAS to be properly compensated elsewhere in the motor.. Unless you wanna end up having to buy and install a whole new set of valve springs, a new set of lifters, and replace a bent-to-hell push rod

 

If I were to install 1.6 rockers what else should be replaced and/or upgraded at the same time other than valve springs? Is it necesarry to replace the rods and lifters? Love the gunmetal GTA by the way.