Im putting new heads, intake, carb, and a supercharger on my 305. Im trying to do things I can easily do in a weekend as its my only car to work. I dont want to put a new cam in it for that reason and im going to be building up a 383 next year which all these parts are bought to fit. I know my stock cam is going to be strangling this motor a bit, so I was wondering if there would be a benefit to put 1.6 ratio rockers on my new heads to bump up the lift??

 

Yes. More lift means more air into the engine - anything to help the craptastic camshaft that the factory gave you.

 

OK, here's the follow-on question. On a LB9 with stock innards, would changing the rockers to 1.6 be doable? Will the stock heads, springs and valves take the extra lift? Will there be any noticable difference in performance?

TIA

 

1. Yes

2. Yes

3. No

The slight increase in lift AND duration (let's don't go there again - use the button) will not make any noticable difference. But it can't hurt, either. I changed mine to 1.6 only because they had roller tips, and were a good deal.

 

hmm, I've heard that it increases duration as well, and in my vizard book, it explains it, due to extra lift, it increases the area under the curve, which is "like" having more duration... or something like that.... Does it actually make the motor act like it's got more duration?

I did a search, found one post by Ede that said not to bring back that hornets nest, and to do a search.... is this a sore topic, that loves to get argues over?
hmm, maybe i'll just go with 1.5 roller tips then, but they are the same price... :shrug:

 

I got 1.6 rockers for mine and I didnt feel it in the butt, but I like to think it did help a bit. I think it would help more if I installed my headers, too.

It's like artificial duration.

 

Since cam profile duration is commonly measured in degrees of rotation that the valve is 0.075" or more off the seat, a higher ratio rocker will slightly increase the duration at the valve but obviously cannot alter the cam lobe profile. The difference is very slight, but exists nonetheless.

The LB9 cam is so pitiful, that even higher ration rockers don;t make a great deal of difference. On the other hand, it's so pitiful, that anything would be an improvement. If you have to replace rockers for some reason, you might as well go with the higher ratio. If you don't need to replace rockers due to wear or damage, don't bother spending the money. The cost of a set of decent rockers will just about get you a new cam, and a far better one at that.

 

Well, I just have to say it. Theres no way it increases duration. The rocker simply multiplies the movement of the pushrod x5 x6 etc. When the cam's lobe is done, its done. 0x5=0. Well so does 0x6. The lift is just increased at every part of the lobe, which may act like more duration. The only way you would see more duration is if your springs couldnt respond to the extra lift and the valve floated.

 

geez! give'm to me, i'll install 'em in my car! c'mon college boy, you need the cash right ?

yea batass, I agree, that's how it works.... but lets not argue here, I don't want this to get locked....

anyway, point is it won't help you much... get a new cam.

 

Bat,

You're absolutely right about the duration at the cam lobe, and therefore, duiration at 0.006" lift. However, most cam grinders rate duration in degrees of rotation @ 0.050" lift, or 0.075" valve lift with standard rockers. That's why a "268" grind will have advertised duration around 218° (at 0.050" lobe lift/0.075" valve lift), while the duration at 0.006" of lobe lift is 268°. Since higher ratio rockers will amplify the lobe motion a little more than a standard rocker, they will open the valves to that 0.075" limit a little earlier and hold them above that lift a little later, duration (as the valve sees it) is increased. Granted, we're only talking about a few degrees in even the most extreme cases, but it is added duration nonetheless. And duration at the valve is really what it's all about, isn't it? What is the purpose of having a camshaft, anyway?

That's what these are all about:

 

Ok, I understand what your saying. The reason I dont want to buy a new cam is that I plan on building a 383 when I get back to the states, and the cam that I am going to need then will not work with my 305 setup. Im not really trying to sqeeze every oz of power out of this thing, I just want more power and something that I can do easily in a weekend as its my daily driver.
I wont even be changing the headers. I only want to buy things once and 1 3/4 would hurt my 305's low end.But I will need roller rockers anyway, and Im thinking that any improvement in the lift of the stock cam will net some decent hp. Vortec heads, performer rpm intake, 4150 holley 650, and a vortech supercharger.

 

Yes, any cam that would be decent in a 305 probably isn't going to be optimal in a 383. It sounds like the stroker is going to solve most of your power problems anyway.

Save your cash for that 383 and its parts, since higher ratio rockers on the 305 aren't going to make any notable difference. For what you would spend on a good set of rockers should be able to get you an engine stand and possibly a 350 short block to start on.

 

I am going to do valve seals on my L-98 Iroc,,,,I figure I may as well change to a 1.6 roller rocker while I am in there. The final outcome may be different than the 305 you are working on but I am doing one change at a time on my Iroc and doing dragtrip comparisons to get real world answers to alot of these questions on here. The 1.6 rockers are just one change among many others I will try to improve my ET,,,and I plan to post each change on here and what it did for my ET and MPH and hopefully put an end to this long controversy,,,,at least for me anyway.
Some people have posted on this site and claim the 1.6 rollers were worth some ET and others say it didn't do anything,,,I think it depends alot on the car they are working on,,,,but I will find out for myself regardless,,,,and if it doesn't do anything for me,,,thats fine,,,I will move on to the next mod and keep going,,,,this car is becoming a test bed for me I want to see how fast it will go with simple bolt ons without getting inside the motor,,,Larry.

 

The rollers can't hurt. At the very least, you'll reduce some friction.

 

The biggest reason I want to install rollers Vader is to cut down on valve guide wear. Since I am already in there to do the valve seals I figure it's a good time. To be honest about the 1.6 rollers,,,,the only reason I decided to go with those is because they cost the same as the 1.5's so I figure lets get a little more lift and duration out of it at the same time and the cost is the same and see if it helps the car out at the same time. If not thats okay because I was going to spend money on roller rockers anyway whether it be 1.5's or 1.6's. Plus since my car only has 50,XXX miles on it there is no reason for me to get inside the engine, I am not interested in a cam change at the moment unless the timing chain goes out and gives me a reason to dive in there. I am interested in seeing how quick the car will go with simple outside boltons (rockers are somewhat outside ) I would like to see the car go 13's at some point,,,,it went 14.60 at 94 mph bone stock with 2.77 gears,,,,LOL I am keeping track of any and all improvements and plan to have a nice post about it on this site in the near future,,,kinda like what Car Craft did with that Firebird recently,,,I am sure you are aware of that car,,,and I am already ahead of the game since that car bone stock only ran bottom 15's when they started,,,I am almost 1/2 second ahead to start with,,,LOL enough babbling,,,,,happy Thanksgiving,,Larry.

 

Hey thats awesome man, but I would be concerned about relying on slight changes in et. Theres a lot of variables there, unless you are awesome at the pedals and always get a pretty constant time. If only I had a dyno.
You dont think I would notice the extra lift in the stocker?
I would love to start the 383 now but Im in Germany and they would charge a lot for machining and balancing. Also, if I got the 383 I like to do things once and right, so Id be modifying the vortec heads for extra lift, forged rotating assembly, headers. Anyway Id have 400 ft/lb, and then I wouldnt be able to stop myself from putting my supercharger on. That much power would probably destroy my trans or rear. Something not easily replaced over here. Now say I didnt put it on, I could reach close to 400 ft/lbs with my blown 305, and would never have to pull the motor.