Rockers 1.6 V.s 1.7

Grabbin' Asphalt

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Dec 4, 2013

#1

• Dec 4, 2013

• #1

So here and there I've seen a few guys with split rockers on there valve train. Mostly around a low lift Ecam or something to change it into a split lift by using a 1.7 on one valve. Does anyone like this method and does it work better on the intake side cause the exhaust is forced out??

 

Last edited: Dec 5, 2013

Don"HO"Daddy

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#2

• Dec 5, 2013

• #2

I wouldn't think there would be much benefit except to get a little extra lift from a smaller cam if the engine was naturally aspirated....although I have seen this used in turbo, and or other forced induction set-ups to get more lift on the exhaust side. I guess if you have 2 complete sets of different ratio rockers lying around its better than a tear down to switch cams.....just an easier way to get a little more valve lift when a cam swap isn't in the cards.

 

MY 85 GT

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Dec 5, 2013

#3

• Dec 5, 2013

• #3

Very interesting...I have a stock Speed density cam in my turbo fox..And i run trickflow 1.6 roller rockers wonder if i would benefit anything going to 1.7s on the exhaust side...hmmmmmm...

 

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84Ttop

They make new pistons every day, so why worry?

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Dec 5, 2013

#4

• Dec 5, 2013

• #4

In a stock type application this would be silly in my opinion. On some of the higher dollar stuff where valve train geometry and cam lobe profiles come into play the rocker ratios are adjusted to make things work the way that they need to. For example my new shaft rockers are 1.65 straight across. If I decide to go to a bigger or different cam lobe then I may need a higher ratio rocker. Currently with the way my cam is designed if it where physically any bigger it would not fit in the cam bore which means custom rocker geometry and going to a 1.8 or 2.0 ratio or running a 55mm cam core.

If anyone does decide to play with different ratio rockers please check PTV clearance, as you are effectively increasing the life of the valve.

 

srtthis

the guy doing it does every local racers rear end

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Dec 5, 2013

#5

• Dec 5, 2013

• #5

i have 1.72's in my car now... and i wish i didnt. im looking at ditching the B cam (ALL HAIL THE B CAM!) for a more nitrous friendly cam. the ones im looking at the rockers are bending me over due to the stock short block. something about 623 lift and stock pistons aint going to work lol

 

84Ttop

They make new pistons every day, so why worry?

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Dec 5, 2013

#6

• Dec 5, 2013

• #6

srtthis said:

i have 1.72's in my car now... and i wish i didnt. im looking at ditching the B cam (ALL HAIL THE B CAM!) for a more nitrous friendly cam. the ones im looking at the rockers are bending me over due to the stock short block. something about 623 lift and stock pistons aint going to work lol

Click to expand...

Want to borrow my die grinder?

 

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srtthis

the guy doing it does every local racers rear end

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Dec 5, 2013

#7

• Dec 5, 2013

• #7

haha i have a die grinder.... im worried about how much piston i will have left to get to .623 lift.

 

Grabbin' Asphalt

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#8

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• #8

Don"HO"Daddy said:

I wouldn't think there would be much benefit except to get a little extra lift from a smaller cam if the engine was naturally aspirated....although I have seen this used in turbo, and or other forced induction set-ups to get more lift on the exhaust side. I guess if you have 2 complete sets of different ratio rockers lying around its better than a tear down to switch cams.....just an easier way to get a little more valve lift when a cam swap isn't in the cards.

Click to expand...

Yeah the few guys I've seen do it just wanted to raise the lift on a particular valve side without doing an entire cam swap. They either traded a part for used rockers etc, ....I would think a turbo could benefit from that on the exhaust side and maybe a N/A and supercharger on the intake. But checking clearances would be Top priority with that much money tied up into those power adders as well as any other built engine. Just an interesting concept if one could fine tune a smaller less radical cam though

 

A5literMan

At least it is lumpy...

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Dec 6, 2013

#9

• Dec 6, 2013

• #9

I kinda remember an article about switching to 1.7s on the exhaust side in a nitrous application. Just don't remember the outcome.

 

clement

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Dec 6, 2013

#10

• Dec 6, 2013

• #10

sometimes, when you are doing a custom grind based on the lobe catalog you will find a lobe that has everything you want in terms of .006, .050 and .200 duration and ramp rate except the lift is a little off compared the other lobe you are looking at. also sometimes you have one lobe that has such a fast ramp it cant get away with a higher rocker ratio and the other is a slow ramp that can. those are pretty common reasons to split rocker ratios. putting higher ratio on a OTS cam really wont do much most of the time.

 

Last edited: Dec 6, 2013

rbohm

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tucson,az

Dec 6, 2013

#11

• Dec 6, 2013

• #11

using 1.7 rockers on one side and 1.6 on the other is a good tuning effort. sometimes it helps, sometimes it doesnt. like anything else you have to try it and give it a good testing to know for sure. it will depend on how bad your exhaust efficiency is compared to your intake efficiency. for stock heads, it can work, for aftermarket heads not so much.