How much I win with 1.6 againts 1.5 rockers ratio

Posted By: NachoRT74

How much I win with 1.6 againts 1.5 rockers ratio - 10/06/09 05:19 PM

what you read. I dunno how to calculate that.

IN FACT, WHATS THE ROCKER RATIO ? lol... where is that spec located on rocker geometry

Posted By: Dodgem

Re: How much I win with 1.6 instead 1.5 rockers ratio - 10/06/09 05:30 PM

well say a cam has .500 lift with 1.5 rockers that means the cam lobe itself lifts .334 so .334 X 1.5 = .500
so .334 X 1.6 = .534 so on this lobe the gain would be .034 with very little change in cam duration.

Posted By: Mr.Yuck

Re: How much I win with 1.6 againts 1.5 rockers ratio - 10/06/09 05:33 PM

Or you can take your cam say 509/1.5=339.3 and multi by 1.6=542.9

Posted By: Dodgem

Re: How much I win with 1.6 againts 1.5 rockers ratio - 10/06/09 05:37 PM

Quote:

Or you can take your cam say 509/1.5=339.3 and multi by 1.6=542.9

I forgot to show the first step!

Posted By: 68CoronetRT

Re: How much I win with 1.6 againts 1.5 rockers ratio - 10/06/09 05:50 PM

Quote:

. . . IN FACT, WHATS THE ROCKER RATIO ? lol... where is that spec located on rocker geometry

A stock 440 rocker has a 1.5 ratio. What that means is the rocker arm opens the valve 1.5 times more than the actual lift of the cam lobe.
In the examples above a cam that has a lobe .334" high will open the valve .334 x 1.5 (rocker ratio) for a total of .501"
That same cam using a 1.6 ratio would open the valve .334 x 1.6 (rocker ratio) for a total of .5344"

NOTE: Caution should be used when changing cams and rocker ratios because without pulling the heads and checking for clearance you may cause the valves to extend so far the piston smashes into them.

Posted By: NachoRT74

Re: How much I win with 1.6 againts 1.5 rockers ratio - 10/06/09 06:13 PM

so, then...

Stock Hp Mopar resto camshaft with .450/.458 will convert in to:

.450/1.5=.300x1.6=.480
.458/1.5=.3053x1.6=.48853

new resto cam will be:
268/284 dur with .480/.48853 lift

and the 474 MP cam

.474/1.5=316x1.6=.5056

new 474 cam will be:
280 dur with .5056 lift

Posted By: MoparforLife

Re: How much I win with 1.6 againts 1.5 rockers ratio - 10/06/09 06:18 PM

Quote:

Quote:

. . . IN FACT, WHATS THE ROCKER RATIO ? lol... where is that spec located on rocker geometry

A stock 440 rocker has a 1.5 ratio. What that means is the rocker arm opens the valve 1.5 times more than the actual lift of the cam lobe.
In the examples above a cam that has a lobe .334" high will open the valve .334 x 1.5 (rocker ratio) for a total of .501"
That same cam using a 1.6 ratio would open the valve .334 x 1.6 (rocker ratio) for a total of .5344"

NOTE: Caution should be used when changing cams and rocker ratios because without pulling the heads and checking for clearance you may cause the valves to extend so far the piston smashes into them.

No need to pull heads to measue valve to head clearance. Very easy to do with heads in place.

Posted By: NachoRT74

Re: How much I win with 1.6 againts 1.5 rockers ratio - 10/06/09 06:21 PM

where in rocker is that difference ? I mean physically.

I got a nice deal trying to get adjustable valve train to use with round end pushrods but now I'm unsure if get 1.5 or 1.6 ratio rockers ( 1.7 will be too much ). I'm planing to use 474 cam, but I have a resto cam as a backup.

Posted By: patrick

Re: How much I win with 1.6 againts 1.5 rockers ratio - 10/06/09 06:32 PM

your lift calculations are correct. 1.6 ratio rockers have the pushrod tip slightly closer to the pivot. you may have to clearance the pushrod holes for your pushrods because of this.

Posted By: NachoRT74

Re: How much I win with 1.6 againts 1.5 rockers ratio - 10/06/09 06:42 PM

More stuff to check !! I think have enough with what I already have... I think I'll keep with stock ratio then. Is enough trying to get this valvetrain to be able to mill down heads without headaches about pushrod lenghts. ( already have rocker shims if I need to correct rocker/valve geometry after the mill down job )

being in USA wouldn't be a problem, but outside USA and being my driver I don't want to comfront more problems trying to get some change and park my car waiting for more parts.

even there is LOT OF TEMPTATION on use a resto cam with those new lift values using 1.6 rockers and resto 115 centerline, being a driver car.

although, still thinking

will .505 be to much lift on a 400 engine if I get... lets say 10:1 CR ( milling heads OR if KB240 pistons gets zero deck ? )

Does that lift value needs some job on heads at valve guides or wherever at head ?

Posted By: patrick

Re: How much I win with 1.6 againts 1.5 rockers ratio - 10/06/09 07:08 PM

duration is a bigger influence on drivability and low RPM performance, not lift. lift is an indicator of potential power if head flow can support it.

Posted By: MoparforLife

Re: How much I win with 1.6 againts 1.5 rockers ratio - 10/06/09 07:09 PM

You will need valve springs that are compatable with the valve lift and make sure that there is enough clearance between the valve retainer and the seal/guide surface. 5.05 lift shoudl be fine but in never hurts to check. with KB pistons there will be no problem with 505 either. They have some pretty deep valve reliefs.
Depending of course on how much your are going to mill the heads the lifters preload should not be a problem as long as you don't bottom out the lifter cup. Hyd. lifters have a lot of forgiveness built in. Again unless you are foing to mill a h of a lot shims will not be needed. They are not made to correct/make up for pushrod length.

Posted By: NachoRT74

Re: How much I win with 1.6 againts 1.5 rockers ratio - 10/06/09 07:28 PM

I have around 120 lbs at stock installed height hughes springs... can't recall the PN... I think they are 1016... got them used on Carlisle last year

rest of setup

-Magnum 400 engine standart bore sleeved ( 25K miles on it, so will be just honed )
-KB240 pistons
-850cfm stock TQ carb
-MP 280/474 camshaft ( resto HiPo cam as back up )
-166K TC ( 175K TC to arrive someday as backup )
-basic 2186 eddy intake
-452 heads ported and milled ( dunno how much yet, will be defined when pistons are measured in the holes )
-stock HiPo exhauts manifolds
-exhaust pipes already upgraded to 2.5"
-Summit double timming chain setup
-3.55 SG axle
-27" wheels
-Lunati 75713 retainers
-Stock valves
-Metallic headgasket
-stock pushrods

Posted By: NachoRT74

Re: How much I win with 1.6 againts 1.5 rockers ratio - 10/06/09 07:32 PM

Quote:

Again unless you are foing to mill a h of a lot shims will not be needed. They are not made to correct/make up for pushrod length.

yes Just learnt about that at lunati PDF catalog. Shimming I will help on a correct load over valve stem ( centered on stem ) IF NEEDED.

EDIT:

forgott to say, working A/C is MANDATORY

Posted By: 68CoronetRT

Re: How much I win with 1.6 againts 1.5 rockers ratio - 10/07/09 02:32 AM

Quote:

No need to pull heads to measure valve to head clearance. Very easy to do with heads in place.

Here's my guess:
Cylinder TDC, install weak spring, set depth gauge to top of valve stem and then measure total distance to contact on piston. Subtract known lift?

Posted By: MoparforLife

Re: How much I win with 1.6 againts 1.5 rockers ratio - 10/07/09 04:08 AM

Quote:

Quote:

No need to pull heads to measure valve to head clearance. Very easy to do with heads in place.

Here's my guess:
Cylinder TDC, install weak spring, set depth gauge to top of valve stem and then measure total distance to contact on piston. Subtract known lift?

Starting a few degrees before and ending few degrees after TDC. Valve to piston clearance is not the closest at TDC but usually a few degrees after.

Posted By: 1_WILD_RT

Re: How much I win with 1.6 againts 1.5 rockers ratio - 10/07/09 05:42 AM

Something else to keep in mind when changing rocker ratios... It isn't only valve to piston clearance thats an issue... There is also pushrod to cylinder head & block interferance that can be a problem... To change the ratio the effective leverage (ratio) is changed.. Your not changing the distance of the valve stem to the center of the rocker fulcrum so therefore you must be changing the distance from the center of the rocker fulcrum to the pushrod.. To increase the valve lift you need to shorten the distance from the center of the rocker fulcrum to the pushrod... So that potentially brings the pushrod into contact with the block or head...

Posted By: Reggie

Re: How much I win with 1.6 againts 1.5 rockers ratio - 10/07/09 06:25 AM

Quote:

so, then...

Stock Hp Mopar resto camshaft with .450/.458 will convert in to:

.450/1.5=.300x1.6=.480
.458/1.5=.3053x1.6=.48853

new resto cam will be:
268/284 dur with .480/.48853 lift

and the 474 MP cam

.474/1.5=316x1.6=.5056

new 474 cam will be:
280 dur with .5056 lift

The quick method for converting 1.5 ratio lift to 1.6 ratio lift is to multiply the 1.5 ratio lift X 1.067.

Posted By: NachoRT74

Re: How much I win with 1.6 againts 1.5 rockers ratio - 10/07/09 01:59 PM

well yes I guess, same than changing to 1.7 the multiply factor will be 1.1333

but I wanted better to know where it was exactly the difference.

Posted By: DrCharles

Re: How much I win with 1.6 againts 1.5 rockers ratio - 10/07/09 11:19 PM

Quote:

Starting a few degrees before and ending few degrees after TDC. Valve to piston clearance is not the closest at TDC but usually a few degrees after.

Correct me if I'm wrong here, but isn't the exhaust valve-to-piston closest just before TDC, and the intake closest just after TDC?

-Charles

Posted By: 68CoronetRT

Re: How much I win with 1.6 againts 1.5 rockers ratio - 10/08/09 03:02 PM

Quote:

Correct me if I'm wrong here, but isn't the exhaust valve-to-piston closest just before TDC, and the intake closest just after TDC?

-Charles

That sounds like it would be correct to me.

Would your cam duration be used to determine what degree before/after TDC?