Rockers?

well i am going to do the LT1 cam swap on my 305, will 1.6 rockers help at all? will they fit? how do they improve power?

yes to all of that

They improve power by increasing the lift.
Multiply the lift of the cam by the ratio of the rockers you are going to use and that is your new gross lift value.

sweet, i will order them soon.

Um, I'm not too sure if the 1.6s will be too much for the stock heads, it's deffinatley pushing it. Whatever cam/rocker ratio you go with don't go over .450" lift with the stock heads or you'll be hurtin'.

damn, i hope it works. I don't want to get new heads on the 305 because it is not worth it. I am just going to do a diffrent intake manifold and TBI and some bolt on's untill i get my 355.

well i am going to do the LT1 cam swap on my 305, will 1.6 rockers help at all? will they fit? how do they improve power?

I've heard there's a good chance the pushrods will rub in the cyl head if you put on 1.6 rockers.

Why don't you just put all that extra money you're gonna spend dinking around with the 305 towards the 355?

ya, i did not know they were that close to rubbing. i think i will still do the swap, but i will stick with stock rockers. Thanx alot guys!

You need to make sure your springs are adequate for the lift you can get with 1.6's. You need to look at the lift on your cam you are using. Then divide by 1.5 and then multiple by 1.6. Then look at the closed height of your spring and the bind height and figure out how much you have there to play with. You definetly don't want your springs binding.

ya i am putting a stock LT1 cam in my 305 with bigger springs.

Be sure to check the specs of the cam. Most LT1s were created equal, but not all.

Early LT1's had slightly more lift than later models. http://www.automotiverebuilder.com/ar/elements/99928p.gif

well john, i am getting the cam off you so whats the specs?

I just sent you a reply PM and its out of a 93. So it would be the 93 - 95 F-body/Vette specs and like I said, to figure out the lift with 1.6 rockers you would divide by 1.5 and then multiply by 1.6.

Wow, talk about weak cams. After looking at aftermarket cam specs, those factory cams seem as if they wouldn't even allow an engine to run. But I guess that seems right from the factory.

So, you should end up with about 480"/.490" of lift I/E respectively with 1.6 rockers. I still say go with a slightly more aggressive cam.

ok so .480 intake and .490 for exhaust.

but i will be on stock heads. i don't want to put new heads on a 305. So will the 1.6 rockers work with my LT1 cam?

The duration is what creates lope and such but the lift numbers aren't bad with some 1.6 rockers. You also have to remember that the head and intake of a car doesn't change even though you increase the lift. So you don't want to go too radical or the rest of the engine won't efficiently keep up with the vaccuum demand.

but i will be on stock heads. i don't want to put new heads on a 305. So will the 1.6 rockers work with my LT1 cam?Yes, it will work as long as you have adequate springs (which you stated you do)

but i will be on stock heads. i don't want to put new heads on a 305. So will the 1.6 rockers work with my LT1 cam?

Yes, the rockers should work. That's actually one of the bolt-ons for the LT1 is 1.6 rr to increase lift. They apparently advertise 15-20 hp gain for just swapping the rockers on an LT1. I don't know much about the 305's, but they should work, but will you have to modify the valve covers so they don't hit?

sweet, so they won't hit the stock heads like nate said? if not i will do that with a new intake mainifold and put my headders on and a good tune should be some good numbers then.

so what will i have to do with the valve covers? do they sell some kind of spacer for them?

so what will i have to do with the valve covers? do they sell some kind of spacer for them?

Not completely sure on that one. You may not even have to worry about it. But if they do hit, you could just buy some deeper valve covers that look all nice and respectable-like. But I know they do sell something like a spacer that will raise the cover a tad for adaquate clearance if you need it.

I believe the max lift for stock swirl port L03 head is right at .480 so that would be pushing it.

You think those number are low, the cam he has now is something like 178/194 @ .050, .350"/.385". Big reason why L03 have low output.

Ahh...that factory cam spec is pathetic. I'm amazed it actually works.

where can i get the spacers at? like jegs or something?

I dunno, check summit or something. It would help if someone knew the actual name of the part.

so what will i have to do with the valve covers? do they sell some kind of spacer for them?
You will need to remove some material from inside the cover to keep the rockers from hitting the top or you could just buy some 93 - 96 Vette valve covers which are already clearanced for 1.6's.

You will need to remove some material from inside the cover to keep the rockers from hitting the top or you could just buy some 93 - 96 Vette valve covers which are already clearanced for 1.6's.

Damn, I was just gonna say that.
In GM High Tech Performance mag, they home-built an LS1 383 and they had valve cover clearance problems and they just scraped some of the shit from under the valve cover off for clearance.

they also make a "tall" style valve cover exactly for this. Aftermarket only.

The name says it all there taller to clear 1.6 rockers. I have some chrome ones from holley paid 80$ for a pair, not that bad.

they also make a "tall" style valve cover exactly for this. Aftermarket only.

The name says it all there taller to clear 1.6 rockers. I have some chrome ones from holley paid 80$ for a pair, not that bad.
That may be a good option for 3rd gens but alot of times those tall valve covers don't work on LT1's without having to be modified because of the alternator lip on the passenger side (which is not a issue on vettes but like I said there valve covers are already clearanced for 1.6's)

Wow, talk about weak cams. After looking at aftermarket cam specs, those factory cams seem as if they wouldn't even allow an engine to run. But I guess that seems right from the factory.

So, you should end up with about 480"/.490" of lift I/E respectively with 1.6 rockers. I still say go with a slightly more aggressive cam.
Well, they have a few more "little" things to worry about like warranty, emissions compliance, and overall customer satisfaction on what, a couple million vehicles each year?

Whereas you and I have only ourselves to contend with if we muck it up. :wink:

OTOH, the mileage and power they get from these engines is actually pretty amazing considering how things were in the mid 70s through mid-late 80s. It's a testament to how well properly matched components can perform considering what's in there for lift/duration.

Just imagine how well lots of engines could perform if more people actually matched parts rather than just trying to jam some big-assed cam into an otherwise stock rig that maybe has a cat-back system. :2cents:

That may be a good option for 3rd gens but alot of times those tall valve covers don't work on LT1's without having to be modified because of the alternator lip on the passenger side (which is not a issue on vettes but like I said there valve covers are already clearanced for 1.6's)

I didnt know the LT1 had a clearnce problem with them. Learned something new, lol.

Ive only used them on Gen I SBC my knowledge is limited :icon16:

Just be sure to change your oil and filter frequently until those pushrods wear clearance into the cylinder heads with those 1.6 rockers.... ;)

i don't think they will rub (the push rods) they are like right at the limit.I just sent off for the cam, and i get payed tomarow so i will order the rockers next, then i think i will try to find some valve covers.

I'm just saying that the max lift for the stock valve guides is around .480", it could be lower like around .450"-.460" because there is some variation. It would be a good idea to double check your heads and make sure your not going to mess them up by running a net lift that's pushing the very limits of what a stock head might be able to handle. I really suggest you have the heads worked over first, or just get some 1.5 rockers. Your probably going to bend a few pushrods and break some rocker arms, but if it were me I would save the money spent on the 1.6s and put it toward gears and posi :2cents:

well the more i think about it, i think i will stay with 1.5 rockers. That is stock size right?

1.5 is stock. I think that's a good choice, it'll make it easier tuning I know that. You'll still get good power out of 1.5s, and if you want to step up to 1.6 and get a little head work done it won't be too hard and you'll have a pretty hot 305.

thanx alot for all your guys help, with out you guys i would probly have a blown up 305,lol. thanx alot