91formula-fbody

i have a 355 borred 30 over with flattops with 9.8 to1 compression, ported 083 heads with 2.02 1.60 valves 1.5 rockers, lt4 hotcam, hsr intake, edlebrock headers with 3in y pipe, 700r4 with 3000stall stage 2 shift kit, 323 gears because my old rear with the 4.10`s blew out. my question is how big of a difference would it be if i put the 1.6 roller rockers on, and would it be woth it? Some guy told me that the heads wont support the cam if i put the 1.6 rockers on and it will not make as much powerso i need to find out before i pay 300$ too have the hsr tunned?

91formula-fbody

please guys i need opinions asap the guy thats gonna tune it wants too do it tomarrow but ima have too call him and postpone the tune and order the roller rockers if its gonna be worth it, and not choke out the heads

Orr89RocZ

iTrader: (20)

How ported are the heads? If they are opened up pretty good then go with the 1.6's since the cam was designed for 1.6's. That gives .525" lift which will show a few more ponies if the heads were ported well.

91formula-fbody

they are opened up pretty good, when u say a few more ponies how many would you estimate? For only a few more hp i think i will wait till i get some better heads, but if it will be at least around 10 to 15 hp difference then it would be worth it too me.

camaronewbie

IF you have to replace rockers anyway, you could. But I wouldn't spend the time/money for it unless I had to go into the heads anyway.

SR-71

In my opinion-- and that's all it would be without flow numbers for the heads-- You won't get 300 bucks worth of extra power. The power difference would probably be measurable on a dyno, but will you feel it? Probably not. Maybe a tenth quicker in the quarter. Or it might actually have less power.

What you want in valve lift is for the valve to pass through the maximum flow point twice. Going up and coming down.

It seems to me that most cast iron small-block heads have their max flow at about 0.5" lift stock, and at 0.4" after porting. My full-ported 081 heads were that way. Since mine flow the most a 0.4", I used 1.5:1 rollers with my cam, for a total lift of 0.495" The valve passes max flow point twice, going up and coming down, which gives it the most overall flow when running. That's the ideal setup.

In general, by and large, all disclaimers applied, your results may vary--
With stock heads, you get a small power gain with 1.6 rockers. With ported heads, you probably get better with 1.5 rockers, but you can't know for sure without having the heads flow-tested.

With your build, the LT4 Hot Cam is worth about 40 horses. If I remember right, lift is 0.492" with 1.5 rockers, 0.525" with 1.6 rockers. If your heads' max flow is at about 0.5, then 1.6 rockers would add about 5 horses. If max flow is around 0.4 like mine, they could make no difference, or actually kill about 5 horses.

So if you get max gain with 1.6 rockers, 60 bucks per horsepower isn't very good bang for your buck.

cuisinartvette

pass.

Orr89RocZ

iTrader: (20)

YOu can get 1.6 rockers for 170 bucks and thats not a bad price for a few ponies but agree with the above, i dont think you'd feel the gain. maybe 10hp but you dont feel that. That cam can produce power with the right heads, the more ported the better. Lift will help but without detailed head information such as port flow numbers/velocity and port CSA, you cant really determine the power gain if any at all.

91formula-fbody

ok cool ty for the info, i guess i should have had the heads flowed before i installed them. with the stock tpi intake and 58mm tb and this same setup it made 287rwhp but only at 4000rpms and 308flbs torque because my tuner guy told me that the stock intake manifold cannot breath enough for the cam and heads, and also my rear end broke and the brakeswere kinda holding the whole time because the c-clips broke when the rear end went and i didnt know til after the dyno runs lol.... With the new hsr im hoping too make alot better numbers and rpms

91formula-fbody

oh ya and i also upgraded too 3 inch y pipe and full manderal bent exhaust

camaronewbie

You can get 1.6 rockers for well under $100 if you get plain jane stamped rockers. Summit sells a nice middle-of-the-road roller tipped rockers for about $100. You don't have to have fancy expensive full roller rockers to get the extra lift - those are designed for radical builds that need the strength of the full roller. But as mentioned, no real noticeable gains probably.

sofakingdom

iTrader: (1)

Difference means:

What you have after a change, minus what you have before.

Therefore in order to talk about "difference", we have to know NOT ONLY what you will have after this change, BUT ALSO what you have now. Which you haven't really told us, except for the ratio.

If you have REAL rockers (some kind of solid body, NOT stamped sheet rubber) now, that happen to be 1.5, and you go to REAL rockers that are 1.6, I doubt you will notice any diffference.

If you have GARBAGE rockers now (stamped sheet rubber), and go to GARBAGE 1.6 rockers (also stamped sheet rubber), I doubt you will notice any diffference.

If you have GARBAGE rockers now (stamped sheet rubber), regardless of the ratio, and you go to REAL rockers, regardless of the ratio, you will notice a HUGE difference; because all your valves will be opening by the same amount, and that amount will resemble the cam profile MUCH more closely.

If you have BALL FULCRUM rockers now of any ratio and you go to ROLLER FULCRUM rockers of any ratio, your oil temp wil go down about 10°, and willl get ALOT less black and take ALOT longer to get that way.

As far as "how much" difference, the slower your cam's ramps are, and/or the more your heads flow, the more difference this change will make. You have a pretty mild cam, which works in favor of the higher ratio; but only moderate flowing heads, which works against the higher ratio having much effect. Net-net, I doubt it will make 10 HP in your setup. The main difference will be in reliability, consistency from cyl to cyl, and possibly less stress on the oil.

If the 1.6 rockers are stamped, I not only wouldn't pay for them, I wouldn't waste the effort on them even if they were free. They just increase the likelihood of something failing. If you already have roller rockers I wouldn't bother because you have already picked up the 90% the benefit of the usual change just by getting the roller system in there. If you have stock rockers and the 1.6s are rollers, then it's probably "worth it", not for the 1.6 ratio, but for the roller feature. OTOH, if you're buying good rockers anyway, why not get the higher ratio.

I would also not put aluminum ones on it, if it will run on the street AT ALL. Fine for the track, very unreliable for the street.

305sbc

iTrader: (3)

Putting larger valves into stock heads usually increases valve shrouding. Shrouding is worse at low valve lifts, but quickly diminishes the higher you lift the valve off the seat.
Ported heads also often respond very favorably to valve lifts around 0.500" to 0.550".
If all things are working correctly, and your tune lets you use extra air flow through the heads, then you could see between 10 and 20 hp from just the ratio change.
Be sure to check all of your clearances for the higher valve lift. Any binding will damage parts no matter what your rockers are made of.

dimented24x7

iTrader: (2)

Kind of off topic, but for less than that, you can get the equipment to tune it yourself rather than a one-shot dyno tune. Also, whats your fuel pressure? The 24s are right on the edge of being able to supply that setup at high RPMs. You may also want to get an AFPR or bigger injectors as well if you want to get the most out of the engine. If your going to get it tuned, you will want to address that before you take it in to the shop or you will have to go back again once you upgrade the injectors.

AlkyIROC

How much gain with 1.6 rockers depends on what you're starting from. If going from stamped steel factory style rockers then you should see a noticeable gain. However, if you're swapping from a 1.5 full roller rocker to a 1.6 full roller rocker, and changing nothing else, you should only see about a 5 hp increase.

There are a couple of issues when going to increased lift with either a cam or higher ratio rockers which is probably why you were told the heads won't support it.

The piston to valve clearance everyone should know about. Valve timing of when the valves open and close also plays a big part in that clearance so a higher lift cam with different valve timing may actually have more clearance than a lower lift cam so you can't just go by how much lift it has.

Valve train geometry. Changing valve train parts means the valve train geometry needs to be checked to make sure the pushrods are the correct length to maintain the proper geometry.

Valve springs. Are the installed springs able to handle the increased lift without binding the coils? At max lift, there should be a minimum of .060" between the coils. Knowing the spring specs and installed height could tell you what the maximum lift they're capable of.

Valve guides. If the heads were modified properly, there usually isn't an issue but increasing the lift means the bottom of the spring retainer may hit the top of the valve guide or valve seal. For increased lift, the top of the guide is normally machined down.

If all those tolerances are acceptable then putting on 1.6 rockers to get a little more lift out of an already higher than stock cam should work.

91formula-fbody

ok cool ty for the info guys, i do only have the stock stamped steal factory rockers on it now. If i put the full roller rocker 1.5`s on will i have too have it retuned or should it still bo ok?