After doing the valve seals and removing the rocker arms, I realized this was a pretty easy job to do. I'm considering putting roller rockers on, as it seems like an easy way to get a few extra HP out of the engine without getting too crazy on mods.I was thinking about this set of roller rockers because they aren't terribly pricey but appear to be decent quality. I'm not building a racing engine, and I don't need the absolute BEST money can buy. So, that said, I'd like to get your opinion on these rocker arms-will they work for what I'm doing? Will I need other parts to install them? In reading, I saw that I may need some hardened pushrods to go along with them? Oh, I also have read that I really want 1.5 and 1.6 mixed on exhaust/intake for best gains. I messaged the seller and they are willing to sell me a set of mixed so I don't have to buy two sets, but the link is just for the 1.6 rockers.

Again, my goal here is a mild HP boost with an otherwise stock engine.

Thanks!

 

You are not going gain much hp. Save up for headers instead.

 

I've heard 10-20 HP? that's not too shabby. Headers are probably more than I'm going to do realistically.

 

Those aren't roller rockers. Those are roller tipped rockers. The real horsepower boost (reduction in friction) comes from rockers with a roller trunnion, not just a roller tip. Roller rockers will net you about 10 horsepower at best, no way 20.

Besides reducing friction, roller rockers help by keeping the ratio a true 1.5 or 1.6. As ball rockers depress the valve, the ratio shortens due to the inherent design. I forget where I read it (Vizard, most likely), but as I recall, the rocker ratio for 1.5 ball rockers shortens from 1.5 to about 1.35 as the valve is depressed, more or less depending on the specs of the specific rocker.

If you're going to do the rockers, good upgrades would also be beehive springs and hardened pushrods. The stock springs are probably tired, and the beehive springs (Such as come stock on the LS6) reduce friction and improve valve control over your stock L98 springs. The hardened pushrods help because they don't flex as much as the stockers do, which helps maintain valve control. If you do all these mods - 1.6 roller trunnion rockers, LS6 springs, and hardened pushrods - you might pick up 15-20 hp and will certainly improve the reliability of your valvetrain. Some sort of heavy duty timing gear is worth looking into as well, and is cheap for any gen 1 smallblock.

 

Don't buy junk. You might lose a motor.

 

Fair point. Are the linked rockers junk? I honestly wouldn't know, that's why I'm asking.

Alright. Looks like it's time for me to learn something. Thank you for the info. Can you link me to a set of roller rockers that are what I would need? Also, I was reading on another forum thread that 1.6 rockers without elongating the pushrod slots in the head will lead to bent pushrods-that's a result I would definitely not want. If that's the case I could just do 1.5s. To your point, my biggest goal would be more having a better valvetrain, even more than HP gains. This is a fun street car and nothing more-I can't afford a full-on race car, just thought I'd have a little fun improving something relatively cheaply.

EDIT: Looked up some full roller name brand rockers, and holy crap those are a lot pricier. For those dollars I'll spend on something else that will do more for my car.

 

Those comps are what I have on my car. Summit has an in-house brand that is reasonably priced. I agree that looking elsewhere may be of more benefit though.

https://www.summitracing.com/parts/s...make/chevrolet

 

Thanks 84-did you have to do any other modifications to your engine to run those? Also, if I were to spend the money on another bolt-on upgrade, where would I start? I'm nowhere near disassembling the engine, was just looking for a few extra horses relatively cheaply from a more-or-less stock setup.

 

OK, I'll try to help you out without breaking the bank. There are two reasons to upgrade your valve train. Performance and reliability. The stock L98 valve train was designed by GM to work to 5000 rpm, and it just barely manages that (good engineering, but bad for performance). Adding the correct mix of aftermarket parts will add reliability as well as performance, primarily by improving valve train control.

There are two kinds of roller rockers - self-aligning and non-self-aligning. The non-self-aligning require the use of guide plates and hardened pushrods, and only offer an advantage for high rpm use. Self-aligning rockers are fine for 95% of the street cars out there. Other folks may chime in here, but I've never heard of any roller rockers that have a reputation for failure.

Springs - Adding new springs, even new stockers, is one of the best ways to improve valve train stability. They keep the valve from bouncing off the seat as it closes and keep the lifters in positive contact with the cam at max lift. With a stock cam, I'd look for around 90 to 120 lbs seat pressure at stock install height, and somewhere around 280 to 350 pounds per inch spring rate. This will give you a stable valve train well above 6000 rpm, not that you'd ever go there with a stock cam, and yet is still mild enough not to cause undue wear on the rest of the valve train. And springs are definitely a place where you do not want to go cheap. They are the part of the valve train that will wear out quickest. Having said that, GM makes springs in such huge quantities, they may have some of the cheapest springs and still offer good quality.

Pushrods - the stock pushrods are kind of whippy. Hardened pushrods are not necessary with self-aligning rockers, but larger diameter and/or thicker wall pushrods will be stiffer and will help with valve control.

Timing chain/gear - The stock timing chain stretches over time, adding slop to the valve train and throwing off the valve timing events. A new double roller timing chain and gear set is only around 50 to 80 bucks for a gen 1 small block. However, getting to it on the engine is a pain in the *** and unless you're planning on swapping the cam, may not be worth the effort.

I'm not an L98 expert so I don't have particular part numbers, but hopefully the above suggestions will help you narrow down your choices.

 

If you think those full roller rockers are a large investment you may need to rethink what you want to do to the car.

L98 cars are really limited by the TPI intake manifold which limits the engines ability to breathe above 5000 rpm. So cam or valve train changes often result in very limited gains in horsepower until the manifold is changed at a significant cost. Headers can help the L98 breathe during its peak torque curve giving you a car that feels stronger while driving it.

I am over $4000 into my 90 L98 engine and although it feels stronger I need to add a superram intake (or something similar) to realize the true benefits of the cam, valve train, headers, machine work, etc. that has already gone into it.

The old adage that speed cost money, how fast can you afford to go is never more true than with our C4s.

 

I did a lot of other work before adding those but I was told they fit under the stock valve covers if you cut out the drip tabs.

For bolt on I would look at a take out exhaust from a lt1 car or something and maybe bump up the base timing a degree or two. The exhaust would help a lot I would think. @Tom400CFI and his vette kart dynoed a bit higher than stock with just a free flowing exhaust I believe. And then down the road you already have the room to grow.

 

Thank you your post is insanely helpful and informative. I'll take a look into all of your suggestions.

You may absolutely be right. I bought this car because the price was right and I've always wanted a Corvette since I was a little kid. It's intended to be a cheap, fun project car that satisfies my need to tinker without breaking the bank. It was never intended to be a race or track car, simply fun to drive on weekends and nice days. Before I would do anything major, I would rebuild the engine. It's running fine but I believe it's just tired after 30+ years. And at that point, why not get a new 383 crate motor or something? It's pretty similar in price honestly and I'm sure would make more power than the stock ever could.

 

The worst thing about real roller rockers is the weight. They are typically significantly heavier than stock rockers.
This means you will have to swap out your tired valve springs if you want to pick up any power at all.
Swapping valve springs is significantly more labor intensive than swapping rockers.

 

I should've swapped them when I did valve seals, as I already had them off the car. They seemed to have plenty of life left in them at the time though. Hindsight 20/20.

 

How do you do the "@Tom400CFI" thing? That is handy.

84 4+3 is right; The Kart has dual 2.5" exhaust that I made, straight thru muff's and no cats. That, along with bumped up ignition timing produced 240 RWHP and 350 RWTQ. The exhaust on the L98 cars is low hanging fruit, IMO.

On another note, Engine Masters (HRM) did a dyno shoot out of Rockers, on a ~500hp 383 Chev. The stock, stamped, POS rocker made more hp than a Comp brand, roller tip. Stock made more hp than an aluminum full roller rocker. Finally, with aluminum, 1.6 roller rockers, it made 18hp more than the others...but only showed gains, above 5300 RPM -well above the operating range of a stock TPI engine.

There was no measured gain going from a stamped rocker to a full roller. Spend the money on exhaust.

 

On my phone, if I just type @ and start typing a screen name it comes up and I tap it. Looks like this:


And yes, I agree it is better spent elsewhere. Thats why I 'summoned' you lol.

 

Cool. Thanks for the tip!

 

I have a brand new set of Erson PBM 802-16 that are 3/8”, 1.6 ratio I’d let you have cheap, PM me.

 

Thanks @Tom400CFI (hah, it worked!) for the tip. Funny thing is, I actually HAVE 3" full dual straight piped exhaust just sitting in my garage already. Would just have to have it installed! By which I mean, I cut it off at the headers on the previous car (another '85 Vette) that it was attached to, so someone other than me will have to fab a connector for it. The old headers weren't worth saving. Probably cost me ~$50 to get an exhaust shop to take care of that for me. So you really saw ~45hp gain just from swapping the exhaust? Very nice!

Sounds like rockers might be a waste of time, although I do like the idea of strengthening the valve train and running cooler oil temps...we will see. I think you guys have convinced me to figure something out with this exhaust I've got.

 

Roller tipped rockers won't show an increase in hp. But they WILL decrease valve stem and valve guide wear. For the money, I like roller tipped rockers; they are a real upgrade over stamped rockers; just not in the hp department.