So i read somewhere that changing out stock rocker arms for a 1.6 ratio set can get some decent gain in power for pretty cheap. I have a 10243880 Vortec ZZ4 according to numbers on block. Just wondering if anyone had experience swapping and had positive results. Also i am not sure what is actually in the car right now honestly but i would assume that they are not the roller kind so maybe that would be a nice upgrade aswell.

 

Depends on the rest of the motor.

Remember, these aren't imports, where you buy this air intake and it "adds" 15 HP, that fart-can muffler and it "adds" 7 HP, some kind of "gimmick" spark plugs that "add" 13 HP, this other gewgaw that "adds" however many more, a "tune" that "adds" 18 HP, ... and before you know it, you've DOUBLED the HP of your [econobox], although you can't really tell much difference except the girls all laugh at you now and won't even get in your car anymore because they'd be embarrassed to be seen near it.

The way it REALLY works is, there is some one thing about a car (sometimes it's in the engine, sometimes not) that is, MORE THAN ANYTHING ELSE, keeping it slow. Let's call that The Bottleneck. As long as that remains, NOTHING ELSE MATTERS. It's a bit like if you had a string of pieces of hose all hooked up to each other, so you could fill up a bucket way out in the back 40 somewhere. Let's say you had a 50' piece of 1/2", followed by 10' of 1/4", followed by 25' of 3/4", followed by 100' of 5/8". Would your bucket fill up any faster if you shortened the 5/8", or if you raised the 3/4" to 1"? Of course not. As long as that section of 1/4" is in there, it DOESN'T MATTER what you do to any of the others. A car works alot the same way, particularly the engine.

A higher rocker ratio will only help if the valve opening is The Bottleneck. Sometimes it is: some heads will flow ALOT more if the valves are opened farther. Sometimes it's not: sometimes the heads have low enough flow capacity that the cam is ALREADY opening the valves to the point that no further improvement can be made.

One thing that WILL happen with better rockers compared to stock ones though, independent of the ratio, is more consistency from one valve to another. Stock rockers are very limp and do a very poor job of transferring the motion of the cam lobe to the valve. They may have a "nominal" ratio of 1.5, but if you ACTUALLY MEAUSRE the push rod movement and the valve opening, you will find that they AVERAGE something closer to about 1.43 - 1.45, and some may have an effective ratio less than 1.40. Of course, if you already have some sort of better than stock rockers, there's less of that deficiency that you can make up by changing them.

The block casting number has very little to do with any of this. And, the ZZ4 is not "Vortec"; it had the same heads that the Vette L98 came with. So, it's hard to say what might happen with whatever it is that you REALLY have, which is not clear from your rather jumbled description. Might be a good idea to post up what heads you have, what cam is in the motor, and what rockers are on it now; and maybe we can make a somewhat ballpark-ish guess for you.

 

You might achieve a 5hp gain. Some stock cylinder heads gain only 5 or 6 cfm of flow going from .400 lift to .500 lift. It's like Sofa said; if the valve lift is the bottleneck, then an increase will be beneficial...

 

I gained about 12 ft/lbs at the wheels across the whole powerband when I bothered to test 1.5 stamped to 1.6 full roller on a stock TBI 350 with headers. Engine was noticeably smoother running as well.

 

I cant find any numbers on the heads when i looked, ill have to look around better and pop off one cover to see what rocker arms are on it. Someone already has put an edlebrock intake and carb on it and said it has a different cam. No idea how i would check what cam really but ill see what all exactly i got and report back. Seems like the stock rocker arms are not great from what you guys are sayin so maybe ill replace anyway.

 

The casting numbers on the heads will be under the valve cover. That casting number you listed is for the block and just means that it started life as a 350 destined to be an L31 truck engine or a ZZ4/ZZ5/ZZ6 crate engine. They used the same block, but different internals and different heads. If the cam was swapped and perhaps other work was done, who knows what it is. Does it run well?

Swapping the rocker arms may or may not give a power gain, but also since it is unknown what cam, heads and valvesprings are in the motor, it would be best to leave the rockers alone until you know more about the combination of parts that are there. For example, 1.6 rockers with stock vortec heads can cause the pushrod to rub. Often, the pushrod holes need to be clearanced for that. Also, some heads can't take a lot of valve lift and if the cam has been swapped to something with higher lift already, retainer to guide clearance would definitely need to be checked before adding more lift. And, as was previously stated, if the cam that is in there has a lot of lift already and depending on the heads, more lift might not add any benefit. You need to figure out what you have before changing out parts for upgrades.

 

Ok ill have to grab some gaskets before i take em off to check then. It runs decent but i swear its been missing recently, tried swapping sparkplugs but i think its still there, havent got to drive it since i did it though honestly. I think it needs tuned.

 

I did this exact swap on my 92 Z28 about 9 years ago... Its an LB9, T5WC car.

I don't know if it really added any top end horsepower, but it definitely added a bottom end kick. The car jumps a lot more when you step on the gas.. not nearly as sluggish as it was stock. I was very happy with the results. It get air and fuel in faster at low rpms...

that said... this is a speed density car and those seem to adapt to changes much better... my 88 LB9 might not be so easy as i keep getting a high airflow error code.... it might be more problematic.

This is my personal experience with my car (bone stock)... it had 90k miles on it when i did this... made driving it more enjoyable as i am not a top end, petal to the floor kinda guy.... i do my summer commute to work in this car...

 

Best to get it to run well before thinking about doing any upgrades.

 

Definitely get the engine sorted out and running well before making any performance changes. Often the boring maintenance like coil, wires, plugs, distributor cap, button, rotor, fuel filter, air filter, belts, radiator hose(s), brake fluid change, oil change & filter, coolant system flush, cleaning the trash and leaves out between the radiator & AC condenser, good tires, alignment, good struts & shocks make a world 🌎 of difference.

FWIW - depending on the engine 4 whp to 12 whp is what I'd hope to see for a set of 1.6 roller rockers replacing stock 1.5's.

That's based on the results friends in an fbody car club typically got with their 305 TBI's, 350 L98's & LT1's & LS1's.

1.) Basically 1.6's will "improve" a .470 lift cam to .500 lift

2.) The roller tip helps reduce friction

3) There is also a very slight increase in duration ~1 degree.

 

Hi @Fast355 trying to send you a message but for some reason it will not let me, this is boomer from East Coast Mud Monster Trucks & Performance Cars, I want to ask you some questions on a 5.7 gm TBI engine, overheating issues, I have gone through everything and replaced everything and it still overheating, wondering if you would have some advice and shoot me a message please and thank you

 

My engine is not stock but I had very noticeable gains going from 1.5 to 1.6 rockers. I also had to add more fuel on my curves to meet my target ratios again with my sniper EFI

 

When you say everything, have you been into the engine? Are you sure it is actually overheating? Under what condition does it overheat, idling, driving slow, heavy load?

 

yeah I found out the issue @Fast355 both head gaskets between 3&5 and 4&6 were expansion flattened from overheating initially caused by a faulty thermostat