l78vetteman

I am looking at the June Hot Rod magazine. Nice article on BB engine build up. In the side bar regarding Crane Roller rockers (page 39), they comment about a typical HP gain of 5 - 8 HP with the addition of RR based on previous engine build ups ( i assume they have dyno number to substantiate). I see several bits on information suggesting 15+ HP gain from RR. What is the scoop? Is 15+ and marketing number so that we all go buy a set? If the gain is only 5 to 8 HP, I would stick with the stock rockers and save my money.

BTW, I am building a 396 / 425 HP engine for my 65. I am looking for an easy 25 HP gain. Any suggestions?

Thanks,

Engo

I don´t think there is a gain from the rollers that you actually can measure with a dyno. The theoretical gain would come from reduced friction.

But the thing is that roller rockers usually have a slightly bigger ratio than a stock rocker. This makes the dyno comparison inconclusive when it comes evaluate the effect of the reduced friction itself. Claims like + 5, 10 15 20 hp are, because of this, nothing but marketing in my opinion.
If there is an actual increase it is most likely due to the roller having a higher ratio than the one it is compared too. Even if the manufacturer state 1:5 ratio they actually are more, often as much as 1.55. On top of that, stock rockers usually have less ratio than they are supposed to have making the comparison even more screwed.
I have a set of Harland Sharp alu roller rockers. The manufacturer say they are 1.65 ratio. However, I have measured the ratio and it is 1.74!!!
I also have a bunch of old stamped steel rockers that are supposed to be 1.5 ratio. I have measured a couple of them too just for fun. They measure between 1.45-1.5 in ratio!!

But of course roller rockers do have a use and that is in applications with high valve spring pressure. :D


[Modified by Engo, 2:43 PM 5/23/2003]

l78vetteman

Engo'
Thanks for your comments.
rob

Vetterodder

I agree with Engo. If you read those ads closely, they don't seem to mention any reference to ratios, only that their product increased power. Some of the power increase does come from reduced friction but I suspect that most of it comes from the increased ratios.

l78vetteman

Vetterodder,
Another Stockton guy! I grew up in Stockton (actually in Morada) and still remember when you could run at Kindon Drag strip. Did a bit of street racing with my 13 sec Chevy Nova 25 years ago...

My folks are still in town.

Take care,
Rob McPherson

vader86

All i can say is that for C4s, 1.6rr typically give us 10-15hp, measurable on dynos.

Someone just tried 1.7s on their modded motor and got 17hp, If i recall.

Taijutsu

I can't comment on BB. On my 74 SB the 1.6 rrs made the engine run cooler and the "sweet spot" went from 2800 to 3000 rpm. Those that have dynoed their engine usually report 8-12 hp gain.
Rick

l78vetteman

Rick,
I would guess that the big difference in your application is the change from 1.5 to 1.6 ratio - like putting in a higher lift cam shaft with slightly more duration.

As suggested by others in this thread, the increased ratio is likely the bigger effect.

Rob

Taijutsu

No flames here! Gaining approx .030 lift for 2 deg more dur is a nice trade. I was more impressed w/lower temps. My engine ran at least 10 deg cooler under high temps w/AC on! For stk C3s I highly recomend this change for both reasons.
Rick

CFI-EFI

These later comments seem to be indicating power gains and rpm "shifts" from a switch from 1.5:1 stock sbc rockers to 1.6:1 roller rockers. The gain/change is more a result of the increase in ratio than the change to roller rockers. The initial comments, citing minor or negligible power gains, seem to be more on the mark, where a ratio change is not involved. Roller rockers DO reduce friction and can produce very minimal power gains. The biggest advantages *I* see are a more accurate rocker ratio, slightly lower oil temps, and lower valve stem/guide wear. The big block you are building has a 1.7:1 ratio, stock. For the engine you describe you are building, increased rocker ratio probably isn't worth the added stress a 1.8:1 rocker would impose. Rollers won't give you the power increase you're looking for, but they will provide the cited benefits. Good luck, and...

RACE ON!!!

wallyknoch

Probably ZERO. Did you ever read a Mid America book and see how much horsepower can be bought over the counter by there adds. I went page by page through out the book and came up with over 1000hp with just bolt ons. Thats a Baghdad Bobs intelligence. On the 396 engine, a little taller solid lifter cam, and matching the ports would be a better choice than roller rockers. :D

porchrd

Hey Guys:

What are the real engine UPGRADES that one can attain on the C-5 2004 Z-06 aspirated
engine.

I was told that you do not mess around with computer chips is this fact or just blowin
smoke.

I have owned 8 Corvettes in my 68 years and now with all of this high technology that is
in these cars today I am pretty much lost.

I guess I am like Tim Allen on Home Improvement always wanting to make more H.P.
I have never dealt with the juice but I have had supercharger experience in the past.

It has been 14 years now since my last Vette 1990 yellow 6-spd convert and now I am once aagain a proud Corvette owner and loin it.!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!

I hope you Vette owners will share some our knowledge and experience on your Z-06
engine upgrades.

Thanks to all of you

porchrd

dankhts

minimal gains, but they can enhance your other mods and even allow you to make additional mods by allowing more precise valve train control........and stability... I have them in my C5, I like them, also have a set of them in our '88 Iroc 355 TPI, like them there too... they go along well with the other mods the engines have...

wingjohn2

marketing...how to twist the truth to meet your goals. Same twisted truth is involved with all the phoney octane boosters on the market.

Manuel Azevedo

Well can't really say how much but you will get more valve lift at the same advertised ratio. That is compared to stock stamp steel rockers. The stock rockers decrease ratio as they slide back via the slot in the bottom of them. granted even rollers have a decreasing ratio as the tip moves closer the the stud but no where near what the stock ones do.