What's the Diff. between 1.5 and 1.6 rockers.

[hey-you]

I'm on the market for a set of mech. rockers for my 440, MP 509, 9.7comp, Bee.
Would it be an advantage in getting 1.6 in place of a standard 1.5 ratio rocker.
What would I inspect as an end result.

[jelsr]

The 1.5 ratio yields .509 lift with a lobe lift of approx. .3393, the 1.6's would give you approx .543 lift with the same cam lobe.

[goldcharger]

hey back at ya 1.5 are in most cases stock 1.6 will get you more lift out of the cam without haveing to change the cam but you need to be careful your 509 cam already has a lot of lift you dont want a valve to hit a piston ill bet well good luck MOPARS ARE THE ONLY WAY TO FLY

[Trat]

Hey Jelsr,
That sounds like quite a racecar, a lot like an " I stock ". I use the HUGHES HEV 5000 in my 371SB. Why didn't ya go with the 1.6s in your car?

[70 charger R/T]

So if I put 1.6 rockers in my 440 / 509 cam with 10:1 comp. I might bump a piston???

[goldcharger]

yes 70 unless you have relifs cut in you pistons it is very likely id go with the 1.5 on that macine i have 10to1 in my 383 with mopar 474 and 1.6 and thats as far as i can lift without releifs

[hey-you]

I realize that the 1.5's are a stock ratio.But what would the power advantage would be??????? or would there be any.

[goldcharger]

yes they will be a power gain as long they dont cause valve vs piston collision absolutly a power gain and if you have reliefs in you pistons go for it you should be able to pull a plug and check with a mirror and a small flashlight hope this helps

[CL440]

IF YOU HAVE FLAT TOP PISTONS, WITH OR WITHOUT RELEIFS IN A BIG BLOCK MOPAR, YOU SHOULD BE GOOD TO ABOUT .550 LIFT. AS LONG AS YOU HAVE A NEG.(PISTON IN THE HOLE) DECK HEIGHT OF APPROX. .050 AND AN OPEN CHAMBER HEAD UNSHAVED OR MINIMAL SHAVE.

MAKE SURE YOUR VALVE SPRINGS WILL HANDLE THE EXTRA LIFT ALSO!

WHAT IS YOUR:

DECK HEIGHT
HEAD(OPEN OR CLOSED CHAMBER?,SHAVED?HOW MUCH?)
PISTON TYPE
HEAD GASKET TYPE(COMPRESSED THICKNESS?)

**BUT REMEMBER THE BEST WAY TO KNOW IF YOU HAVE THE PROPER CLEARANCE IS TO PHYSICALLY CHECK IT.

[jelsr]

Trat,
Thought I would save something for later if I needed it. Was shooting for 475HP when I built it, Hughes didn't have the engine on their website then. Seems I kind of overshot it a little. Has a powerband flatter than a pool table though, can run smaller 3/8ths up to long 1/2 miles without changing anything. Really a hoot to drive.

[Trat]

I BET!!
Sounds like fun!
What do ya run for leafs? I use a landrum 200 and 175. Takes a 3" lowering blocks to keep it from looping if the track dries out. Seems to like no blocks when it's muddy.

[cuda66273]

You better start by pulling a valve spring and compressing it to the new lift to be sure you don't get coil bind.

Warning: Coil bind is dangerous, causing injury or death to you motor.

[jelsr]

Trat,
Running 175 landrums. Have the front hangers turned upside down and the rears raised the same amount to keep geometry the same as it was. Lowers the car little over an inch. Also changes roll center somewhat. Mine is not a looper by nature, actually tiny bit of a pusher. It will roast the tires at the slightest provacation so it's easy to power out of a little push. Here in sunny southwest Kansas, dry slick is a way of life. Raced a Harley for 20 years so I'm pretty comfortable on the dry slick.

[Dart]

One thing to remember is that the stock rockers aren't a true 1.5 ratio, more like 1.42-1.44. This would put you car at the following lift:

.509/1.5=.339 rated cam lift

.339x1.42=.481 actual lift

to

.339x1.44=.488 lift

If you went to the true ratio of 1.5 you would have .509 actual lift. If you went to 1.6 rockers, here is what you would have:

.339x1.6=.542 lift

This would make a serious change.

[jelsr]

Dart,
Without changing the cam lobe the duration will not be changed with a rocker ratio change. The opening and closing events are dictated by the camshaft. The opening and closing rates and total lift are all that is changed.

[moparmikey]

Don't forget to check retainer to valve guide clearance also!!! A collision here could also lead to serious injury or death to your engine! Good valve springs are also a must!

[Trat]

<grin> us small blocks can't quite roast 'em that easily!
Over here at Boone, Iowa we run in a Mud Hole for the heat races, and the track finally starts getting right about feature time.
The only time it seems to get really dry slick is during the SuperNats.

[jelsr]

Trat,
There is something to be said for 2 bazillion ft lbs of torque (really toothy grin). Silly as it seems, it doesn't seem to hurt when it's really wet like you're talking about. Jetmore has a new track, small 3/8ths with good banking, that requires 4WD for mud laps. I'm serious, haven't seen that much mud since it rained for 40 days and 40 nights. Lane county only got 1/4" by the way! That's where Dighton is, county seat no less. Back to the subject, I can throw a rooster tail that has to be seen to be believed almost all the way around it and very seldom do I get passed during this exercise in futility. Maybe they can't see where they are going? Sometimes it gets better for the heats and main. The last race of the season there was a slick spot coming out of 4 that would sidestep the car about 2 widths right toward the concrete. My seatcover suffered some serious pucker marks. Enough of my bullshipping, enjoy talking to you, but don't need to take up the space on the forums. Give me a holler at jelsr@st-tel.net, would really enjoy comparing the I-stock to my Super. You might have to put up with some serious bullshipping though!
Jim

[djswwg]

Jelsr, you're statement that duration won't be changed is correct, but EFFECTIVE duration will increase slightly, because the valve is opening faster with the 1.6 ratio rockers..........djs

[jelsr]

djswwg,
That's where the term "under the curve" comes in.

[hey-you]

Thanks Dart, I think that was the answer I was looking for.
I never realized that the stock ratio was that far off. So I would think that the 1.6's would be pushing my luck a bit.

[Dart]

Hey hey-you....LOL

You should look for some true ratio 1.5 I think. The 1.6's are a bit much and you should do some checking before running them. I don't think you want to take the heads off and mock the motor up at this point.

[hey-you]

Are MP rockers a true 1.5.???????

[folke]

I went from stock rockers and push rods to 1.5 roller rockers and 3/8" push rods. That put some of the push rods in contact with the runners in the head (906). If you go with 1.6 rocker that will reduce the clearance between push rods and head even more. If you are using iron heads: Be prepared to use your grinder.

[DartGT66]

Defeinitely one concern more, especially in SB heads with the smallish pushrod holes. Had to do a lot of grinding in Stage VI's since the holes were way off from the factory. Because of the added lift and quicker opening rate your valvespring choice will be more complicated too. I have actually tried three different rockers at the track with the 292 cam, although the CR was lower at 8.8:1. We had the stock stamped steelers and Crane gold rollers in 1.5 & 1.6 ratios. Run them all during the same day and changing the rockers didn't have any effect on that cars ET or speed.

[charger500guy]

I am using Crane Gold 1.6 rr's in my 1970 Charger with original 383 Magnum. The bottom end is UNTOUCHED, and the heads have been shaved slightly (.020 ?), with Fel-Pro permatorque blue head gaskets. I am able to use a Comp Cams XE274H cam w/ .488/.491 lift at 1.5 ratio; with my 1.6's it is something like .520/.524. I haven't bumped a piston yet, rotating at about 6200 rpm....

[Dart]

Yes the MP rockers are true 1.5 ratio.

[crowellusmc71]

Thanks dart for the good word. I have 340 with 0 deck height 30 off of the heads and the purple cam 509. I am using stock rockers that are shimmed. I have about 3000 clearance at max lift with valve releifs in the piston. running around 11:1 compression.

[hey-you]

Well I'm sold, I ordered the 1.5's today, hope to get them by mid next week.