hey guys, i just got finished serching through the net and a few mags/catalogs of mine and see company's sayin a 15-40 hp increase for roller rockers. is this true, is this a good mod???


how bout this order for the mods: exhaust, headers(high flow cat also), intake, cam, rockers. how does this sound???

these roller rockers are only just a lil over 100 bucks is this a good mod for a fairly stock motor or not??? thanks

 

Those companies are testing these rockers on engines like 383,454 that have been rebuild to make 500 hp.

That is why they are claiming to get 30hp compare to stock rockers.

On a 305 with no restrictive exhaust and a stock cam the swap to 1.6 rollers is probably worth 5 to max of 10hp depending on the condition of your engine.

Good luck.

 

Actually, the roller rockers are supposed to be worth up to 20 hp because they reduce friction so much. The rocker arm ratio of 1.6 over 1.5 can also add some good hp on a 350 or 400 hp engine. But, unlike the roller rockers, will not add much on an otherwise stock 305.

 

I just installed al. vette heads on my 305 tpi. What size roller rockers should I get?

Im having my friend portmatch my intake and I have a front to back free flowing exhaust also im using the stock cam.

 

That is hard to say. If you are planning on more mods, like a more aggressive cam, then I'd say go for the 1.6s. Otherwise the change from 1.5 to 1.6 is miniscule, maybe 5 hp on a 200 hp engne. It is when you are getting toward 400 hp that things liven up quite a bit

 

It really depends on the lift of the cam if you still have some lift to go before your springs are at their limit then you can get the 1.6 rockers but if your cams lift is already at the peak of your springs lift then get the 1.5 rockers. 1.6 rockers will typically give you approximatly .030 more lift than the 1.5 rockers but that all depends on the lift of the cam. the formula to find out how much lift the 1.6 rocker will give you you take

valve lift and divided by 1.5 then take the number you get and then multiply by 1.6 and that will give you the total lift

ex
.525/1.5=.35 total cam lift
.35X1.6=.56 total valve lift

 

At least as important as the ratio change, is the change from weak flexible stamped sheet metal, to some material with a little rigidity. If you ever look at stock rockers in operation with a Strobotach or even a "dial-back" timing light, you would be utterly amazed at how they really behave. They look like rubber, they bend so much. As much as 10% of overall valve lift is wasted in them. Plus, they're all different, both in strength and in their ratio; so you're going from a largely random collection of valve events, to a much more consistent situation. For that reason it's impossible to make an accurate prediction of how much added HP you'll get from upgrading them.

I'd guess that if you went from 1.5 rockers to 1.6s of the same design (say from Comp 1301s to 1302s) on a motor with stock cam and heads, you'd see less than 5 HP. You'd probably see 10 HP going from stock rockers to 1.5 steel rollers (1301). On a motor with more flow, the difference could be alot greater, depending on how much flow the added lift provides.

WIth sheet metal rockers your actual lift is nowhere near the "theoretical" lift. Even with steel bodied rollers the actual lift is only about 98% of theoretical, depending on what studs you use, etc. (they bend too)

 

i was gonna get the comp cams energizer cam and then the rockers, so am i looking at more with the better than stock cam??? hell even 5 to 10 hp is some increase, and with the cam there is more torque. so is this good mod, bad mod, ok mod, or what

 

Well the numbers the companys claim are somewhat best case scenarios situations, but on a 350 tpi car i witnessed get tuned and dynoed last week, the roller rockered were good for 18 hp at the flywheel.

I was told by the engine builder (engine was a rebuild, but was all stock parts, nuthing done...) that the biggest gains from roller rockers are that they are stiff, and do not flex, and the biggest part was the friction reduction. he hinted that about 7-8 hp of the 18 hp freed up was just from friction alone, he said another 2-3 from the flex being aliminated and another 4-7 from the small increases in lift and duration from the 1.6 ratio.

on the race motor, we actually saw less than that on the dyno, this was a 400 horse 350. switching to roller rockers only netted us about 10hp.

BUT we were not allowed to go any higher than 1.5 rockers...

Steve

 

Well, all hp is good, it just depends on how much it costs. Lots of people will find the price of admission for a roller cam and roller rockers to be more than they are willing to pay.

How deep are your pockets?

 

true enough... especialy if you have centerbolt heads. 300 bucks for rockers sux.

Unfortunately, this will be the way i am gonna be going for my new motor. Its going to be full roller- roller cam, lifters, and rockers. Its A LOT of money to convert to roller cams (i'm using an old 350 block, so it neds to be machined to accept the roller lifters) plus the costs are high. But, the advantages is a stoable valve train, that is strong, and very friction free, allowing the motor to rev up more quickly.

Steve

 

how do i tell if i have centerbolt heads, that sounds like it will blow cause these roller rockers and cam total was only bout a lil over 225. does anybody if i have the centerbolt heads, i sure as hell hope not. the pockets are basically as deep as need be, but the deeper they get the longer it will take. you guys know how it is.

 

It's real easy. Just pop the hood and look at the valve covers. If there are four bolts that hold 'em on going right down the center, they're centerbolts. If the bolts are around the perimeter of the valve covers they're not centerbolts.

 

well, i am outta town and will go to church b4 i get back and i will have to pray that they are not cause if they are i will be quite upset. but what will i be able to do, i guess pay more money

 

Your sig says you have an '86. The centerbolt heads didn't arrive untill '87, so unless you don't have an original engine, you should have perimeter style valve covers, and no restrictions on rockers.

I also have an '86 and am considering a roller rocker upgrade. My question to the valve train gurus is :

Should I consider a stud girdle if i use the stock rocker studs with roller rockers?

 

correct me if Im wrong, but wont that give you a very low compression ratio. the vette heads have a much larger chamber i believe. Maybe you had them shaved?

 

Nope, 'vette aluminum heads have the same combustion chamber size as the iron 305 heads, 58cc. The iron L98 heads have 64cc heads and would lower compression.

 

i did not know that, thank you sir.

 

No. A stud girdle is not necessary until much higher horsepower applications. What you might want to look into, if you have an aftermarket cam, is the valve spring seats pressures. The studs will pull out with too much seat pressure, or extra lift. With a stock cam, you will have no problem. But if you have an aftermarket cam, it would be something to consider converting your heads to screw in studs. To do this, the heads need to be removed from the engine, the old studs pulled out and then the holes drilled, tapped and the new studs screwed in.

Steve