1.8 Rockers for stock LS1

I have a relatively stock LS1. The only mods that effect the engine are an SLP lid w/K+N filter and SLP Loudmouth which I hate. The sound is terrible. I am thinking of buying 1.8 rockers and new springs. Can I use the rockers on a stock LS1 motor w/o valve to piston issues? Does GM make a spring that will work with the 1.8 rocker. Any suggestions on part numbers? I did this on my '94 LT1 and it made a big difference w/ headers.

No point in doing that. All you'll do is increase your chances of PtV issues later if you get a cam.

The LS1 already comes with great roller rockers and the only real upgrade is when you're doing stuff that requires you to really spin the motor 7000+ or you're making SERIOUS power, which in that case Jesel rockers would be the alternative.

Mike

For how much the roller rockers cost, you might as well pony up and get a cam that comes w/more lift.

There are certainly differing opinions about the 1.8 rockers. Doesn't the new LS7 come with 1.8 ratio rockers?

Anyhow, there's no question that rockers can be an expensive proposition. I have the Crane/Vinci VHP 1.8 rockers that start off at a ratio of 1.89 and transition to 1.8 as lift increases. If you don't want to put in a new cam, these rockers will give you the effect of a cam with more overlap and more lift. If later on, you decided to upgrade your cam, you would be more limited in your camshaft selection and you would be limited to a cam with around
.500 lift @ 1.7/1 rocker ratio, which would give you about .582 in of lift. Whether you go with a bigger cam or higher ratio rockers, your stock valve springs will have to be replaced. There is an argument that the higher ratio rockers are heavier than the OEM rockers and can cause problems, but the counter argument is that the lifters and pushrods are not being thrown as high and that is an advantage. Another advantage is that my rockers are adjustable. What does that mean? It means that I can set the lifter preload with the simple turn of an allen wrench. It isn't that simple with the stockers. Another issue with the stockers is that they occasionally will spit out the roller bearings on which they rotate. Next is the issue of pushrods. The OEM pushrods are notoriously week, and if you put in a new cam you will necessarily need hardened pushrods. The hardened pushrods are $100 or more and they were included with my rocker set. Also included with the rocker set was pushrod guide plates to keep everything in alignment.

More to the point in answering your questions, there will not be piston to valve issues with 1.8 rockers and your LS1 OEM cam. I would not suggest any OEM valve springs because to the best of my knowledge, none of them are dual springs, and dual springs will give you some added protection against severe damage should a valve spring fail. Also, Crane contends that the beehive style spring causes the knock sensors in the LS1 to detect a false knock and retard the timing. That's contrary to the design theory of the beehive spring, but that's what Crane contends.

When you start upgrading these LS1's, whether you do a cam or higher ratio rockers, it gets expensive. Right now there is a guy on LS1tech.com selling a used 1.8 ratio Crane set and a used Vinci cam for $500. I see the 1.8 rockers for sale used quite often for around half the retail price of over $650.

Good luck.

KPI, are you running these rockers on a stock cam, how much of an increase did you get?

Thanks for the response guys. I was hoping that it would be as easy as it was with the LT1. I put Comp Cams 1.6 roller rockers on it with the LT4 springs, retainers and seals it runs great. I was hoping that changing the rocker ratio in the LS1 and adding LT headers and hi-flow cat that it would really wake things up. I still want the motor to breathe better. Can anyone make a recommendation on throttle body size?

Get a ported stock TB.

ANGEL71RS, I am running the Crane Gold 1.8 on a OEM 02 cam. Unfortunately I do not have any before and after dyno numbers.

SOTP it made a solid difference. Also, it changed the sound of my exhaust note at idle. Seemed to make it deeper. I also upgraded to an SDPC/Manley valve spring and titanium retainers when I installed the rockers. Prior to the rockers my engine really didn't like to go above about 5900 rpm. I run it to 6100-6200 now, no problem. There are articles out there where there was a 15 - 20 RWHP gain after the 1.8 Crane Golds, but I can't substantiate that. At the time I did the rockers I didn't plan on a cam upgrade and I wanted to try the rockers because theoretically it made sense. Now I'm getting ready to swap to 243 heads with the 02 Z06 light weight valves, and the Crane dual springs, and I'm going to do a cam swap too. You are much more restricted with what you can do if you committ to the 1.8 rockers. Actually, knowing what I know now, I would probably go with the 1.7 ratio Crane Gold rockers. Fortunately, Crane and Comp both have a pretty fair compliment of cams at or under .551 lift @ the 1.7 ratio. I'm looking at the Comp XR273HR and XR277HR and a Crane that's 220/224 duration and .583 lift with the
1.8's. The Comp cams are 220/224 .561/.565 and 224/228 .565/.570 lift @ the 1.8 ratio.

Thanks for the info.

TB isn't going to pick up much unless you have a cam.

eh, just get the cam and eventually have a set of rockers to match it.

I was getting my car tuned and I asked about it. The tech told me the stockers are fine. They have a roller fulcrum.

What are your future mod plans?

I am just looking to get this motor to flow better than stock. Obviously, flow is horsepower. The car came with SLP CAI and loudmouth catback. So, future mods would include LT headers, high-flow CAT and 80mm Throttle body. Another way to increase flow is 1.8 rockers. That is why I posted this thread. I really want to know if 1.8 rockers will work on a stock motor without clearence issues. I am not interested in pulling the engine apart to put a cam in. I am just looking for good solid bolt on mods.

Yeah, the 1.8s will work on the stock motor, but don't expect anything magical to happen as far as gains over the stock rockers. The 80mm TB is also a waste of money... You can get the stock one ported for around $100 or do it yourself (ls1howto.com)

Mike

here's my dynos from installing the vinci/crane 1.8 accelerated lift rockers on the wife's 99 formula. all this on stock tune and stock cam.

dyno 9 before
dyno 11 500 miles later
dyno 14 10 months later

http://www.stealthram.com/familypics/formula/dynos/dyno91114rockersandsprings.jpg