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Old 04-26-2012, 01:24 PM
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Best Rocker Ratio For Performer Camshaft

having had a chat with one of my club members about my engine build specs, it was recommended to me to increase my rocker ratio to 1.6 from the stock 1.5 & I was thinking 1.52 as im using stock replacement springs. but am uncertain to what the best combo would be.

as i believe its best to get more than 1 opinion on matters I thought ide see what the forum thinks as I want a poky motor but more important to me is reliability & some level of friendly highway manners.

engine specs are as follows:

sb chevy 357ci

speed pro hypertectic flat top pistons 4v reliefs

will have rhs pro torker 67cc heads

clevite performer cam .
Duration @ .050� lift = In 204, Ex 214, Valve lift = In .420�, Ex .443�, Lobe sep 112.

valve springs are part no: bY VS-677
guessing sealed power vs-677
Single Spring w/Damper
1.238" O.D.
1.150" Coil Bind Height

Installed Height (in) 1.700 in.
Seat Pressure at Installed Height (lbs) 76 lbs.
Open Height (in) 1.250 in.
Open Pressure (lbs) 194 lbs.


by my reckonings if I went from stock stamped rockers to magnum 1.52 ratio rockers that would give me: Valve lift = In .425.6�, Ex .448.9

& 1.6 ratio rockers: Valve lift = In .448�, Ex .472.5

Now my questions are:
would the vs-677 springs likely handle this added lift?
will this increase in lift affect the reliability of the motor?
will i be likely to encounter valve to piston clearance issues?
Also could I use hooded style valve seals as those little black o rings seem pointless.


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Last edited by swompz; 04-26-2012 at 01:29 PM.
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Old 04-26-2012, 02:06 PM
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this looks to be a hyd flat tappet cam, correct. i wouldn't use a larger ratio rocker with this cam, a 1.52 would be pointless and the 1.6 is more likely to were out your valve train than it is to give you any noticable power.
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Old 04-26-2012, 02:09 PM
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Run 1.6's on the intake, 1.5's on exhaust.
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Old 04-26-2012, 02:26 PM
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Quote:
Originally Posted by ap72
Run 1.6's on the intake, 1.5's on exhaust.


i was going to comment on this but then i notice that he has aftermarket heads, that will have a better exhaust flow.

i still dont know that i would run the 1.6's on a hyd f/t cam though, JMO
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Old 04-26-2012, 02:39 PM
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sorry should have clarified , yes its a hydrolic flat tappet cam, affectively clevites own grind of the edelbrock performer plus cam.

ive decided to buy new rockers as the original stamped were so often inacurate
on there actual ratio , so the comp cams magnum roller tips in 1.52 would be my equivilant to stock replacement , all be it with ever so silght increase in lift.

can you tell me if the lift of 447 on exhaust would be safe with the valve springs listed?
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Old 04-26-2012, 02:57 PM
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Run 1.6's on the intake, 1.5's on exhaust.
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Old 04-26-2012, 03:11 PM
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I think your GROSS VALVE LIFT is .420/.443" with a 1.5 rocker. Which would mean your LOBE LIFT is 0.280/0.295". You should verify these numbers on your cam card/website.

So if you plug in the numbers...
1.50: .420/.443"
1.52: .425/.448"
1.60: .448/.472"

Installed height 1.700"
Coil bind height 1.150"
Allowable lift=0.550"

So going by the numbers you would be fine coil bind wise. But you would need to verify for sure. Also you would have to verify for sure you have clearance with the valve seal and the valve guide. You would also have to verify piston/valve clearance as well.

You might pick up a few HP with 1.52's. I would avoid 1.6's as they might actually hurt performance on that tame cam and only increase valve train wear. If it were my motor I would go 1.5's.
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Old 04-26-2012, 03:45 PM
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Quote:
Originally Posted by Silver Surfer
I think your GROSS VALVE LIFT is .420/.443" with a 1.5 rocker. Which would mean your LOBE LIFT is 0.280/0.295". You should verify these numbers on your cam card/website.

So if you plug in the numbers...
1.50: .420/.443"
1.52: .425/.448"
1.60: .448/.472"

Installed height 1.700"
Coil bind height 1.150"
Allowable lift=0.550"

So going by the numbers you would be fine coil bind wise. But you would need to verify for sure. Also you would have to verify for sure you have clearance with the valve seal and the valve guide. You would also have to verify piston/valve clearance as well.

You might pick up a few HP with 1.52's. I would avoid 1.6's as they might actually hurt performance on that tame cam and only increase valve train wear. If it were my motor I would go 1.5's.
thanks silver , think ill plump for the 1.52`s as this shouldgive me good margin for valve seal & valve to piston , although i will check measurments as point of course.
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Old 04-26-2012, 03:56 PM
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Well keep in mind if your old stamped steel rockers were irregular (and from what I have read they usually run about 1.46:1), that would mean there is a substantial jump from 1.46 to 1.52.
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Old 04-26-2012, 04:53 PM
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Quote:
Originally Posted by Silver Surfer
Well keep in mind if your old stamped steel rockers were irregular (and from what I have read they usually run about 1.46:1), that would mean there is a substantial jump from 1.46 to 1.52.

Aftermarket rockers can be just as irregular. There's no sense in not running 1.6's on the cam with those nice heads you'll be giving up tq across the board.
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Old 04-26-2012, 05:08 PM
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The 1.52:1 ratio says "Comp Magnum". Correct? The added .02 of "ratio" is of little consequence. A hydraulic cam won't "notice". The advantage the Magnums do bring is the accuracy. They are much better than the "cheaper" roller-tips. We've measured them for Chevy small blocks, Fords and Pontiacs, and they're all very good. Nice "street" rocker, IMO.

Running a 1.6:1 rocker will increase lift by about 8%. You MAY gain a degree or so (@.050) in duration. It is "current thinking" in race engines (I know, this is NOT a a race engine) to run as high a ratio as possible, to reduce the movement of the lifter/pushrod, theorhetically moving less "unsprung" weight and still getting the valve open as far as possible. For a cam such as this one, I agree with the majority, no need for 1.6s.

The specs listed for the springs do insure you won't have coil-bind. The other cautions are valid. Measure the seat pressure. It should not exceed 100 or so lbs. with that cam, 110 at the VERY most. Don't run a rotator on the exhaust side with those heads.

FWIW

Jim
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Old 04-26-2012, 05:23 PM
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Quote:
Originally Posted by Mr. P-Body
The 1.52:1 ratio says "Comp Magnum". Correct? The added .02 of "ratio" is of little consequence. A hydraulic cam won't "notice". The advantage the Magnums do bring is the accuracy. They are much better than the "cheaper" roller-tips. We've measured them for Chevy small blocks, Fords and Pontiacs, and they're all very good. Nice "street" rocker, IMO.

Running a 1.6:1 rocker will increase lift by about 8%. You MAY gain a degree or so (@.050) in duration. It is "current thinking" in race engines (I know, this is NOT a a race engine) to run as high a ratio as possible, to reduce the movement of the lifter/pushrod, theorhetically moving less "unsprung" weight and still getting the valve open as far as possible. For a cam such as this one, I agree with the majority, no need for 1.6s.

The specs listed for the springs do insure you won't have coil-bind. The other cautions are valid. Measure the seat pressure. It should not exceed 100 or so lbs. with that cam, 110 at the VERY most. Don't run a rotator on the exhaust side with those heads.

FWIW

Jim
thanks for your input Jim,
I know Ive kind of touched on this subject before , but going on a tangent, have you had any expierience with comp cams high energy die cast roller rockers? Ive pritty much decided to run the magnum roller tips , but cant shake the fasination with this alternitive rocker, partualy due to there price & equaly because I cant find any reference of peoples expierience with them. maybe a seperate post, just to satisfy my curiosity.
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Old 04-26-2012, 05:44 PM
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Quote:
Originally Posted by swompz
thanks for your input Jim,
I know Ive kind of touched on this subject before , but going on a tangent, have you had any expierience with comp cams high energy die cast roller rockers? Ive pritty much decided to run the magnum roller tips , but cant shake the fasination with this alternitive rocker, partualy due to there price & equaly because I cant find any reference of peoples expierience with them. maybe a seperate post, just to satisfy my curiosity.
Those rockers are an inexpensive replacement for your stock rockers. I have a set and so far I like them. Easier to adjust the valves( Solids anyway). I think the accuracy has got to be better than some old wore out stock rockers. However, you still get the friction in the fulcrum which adds to the oil temp. Full rollers have much less friction there thus promote lower oil temp.
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Old 04-27-2012, 06:33 AM
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No experience with the Comp "High Energy" rockers. We use Scorpions when an aluminum rocker is called for (lower budgets).

The Magnums are fine for most street applications. Aluminum rockers are known to "work harden" in street engines, making them brittle. The modern ones seem to be much better than say, 15 years ago. Comp "Hi Tech" rockers are the "ultimate" in a stud-mounted rocker, but $$$...

Jim
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Old 04-27-2012, 06:36 AM
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For this cam a set of stamped steel 1.6 rockers would be more than sufficent. Just be sure to use the poper length pushrod.
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