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Discussion Starter #1
Hi:waving:....I just got done pulling the race cam out of my 327, I'm going with the L-79 hydraulic cam.....The motor is equipped with what appears to be new stamped steel roller tipped rocker arms along with adjustable rocker nuts.....I'd like to make sure, before I reinstall these rockers, that they are 1.5 ratio.....Is there a way to tell the differences between the various ratio rocker arms?.....If these rockers aren't 1.5 ratio, what would happen if I installed them with the L-79 camshaft?.....Would it change or alter the cam timing specs because that's something I don't want to do?:noway:
 

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Ron,
The difference is in the distance from the center of the pivot point to the pushrod. The distance from the pivot to the valve has to stay the same. So if you have a known 1.5 rocker, and a good way to measure it, compare it to the ones you have and see what you got. Only other way is to actually measure valve lift on a cam with a known lobe lift and a solid lifter.
 

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Discussion Starter #3
That's just it, Bill!.....I don't have any other rockers to measure for comparison!.....I don't know what the rocker ratio is on these rockers!....Do you think you could measure one of your 1.5 and 1.6 ratio rockers?.....I don't want to get into anything other than the stock 1.5 ratio rockers as I read that an increase in rocker ratio will increase the cam lobe lift, something I don't want to do!
 

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And check your valvetrain geometry.Chances are the race cam has a small base circle and uses longer than stock push rods.Verify the sweep across the valve stem tip with the new camshaft, even with confirmed 1.5/1 rockers.
 

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Ron,
. Only other way is to actually measure valve lift on a cam with a known lobe lift and a solid lifter.
Like Bill stated..you know your lobe lift off the cam card..install a rocker with a solid lifter at 0 lash and mount a dial indicator on the spring retainer with some preload and then zero the indicator.Rotate the engine to max lift and record the reading.If you have a .300" lobe and measure .450" ..you have a 1.5/1 rocker ratio.If you have a 1.6/1 rocker..you most likely will see .480".
 

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Discussion Starter #7
Like Bill stated..you know your lobe lift off the cam card..install a rocker with a solid lifter at 0 lash and mount a dial indicator on the spring retainer with some preload and then zero the indicator.Rotate the engine to max lift and record the reading.If you have a .300" lobe and measure .450" ..you have a 1.5/1 rocker ratio.If you have a 1.6/1 rocker..you most likely will see .480".

George....I don't have a solid lifter nor a dial indicator to check this out.....Probably best to just purchase stock rods and rockers, pretty cheap for a small block mouse motor!:yes:
 

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George....I don't have a solid lifter nor a dial indicator to check this out.....Probably best to just purchase stock rods and rockers, pretty cheap for a small block mouse motor!:yes:
I agree that the initial cost is minimal.At least spend the time to insure the rocker sweep is valve stem tip/guide friendly.
If it is not..your looking at e-baying the new oem pushrods and purchasing customs.Why are you concerned with an increase of .030' lift and maybe 2* more duration with the L79 with 1.6/1 rockers?I doubt you have pv clearance issues after swapping out a race cam with tons of overlap.If i am reading you right..you are detuning for the street.Nothing wrong with that.How big was the race cam and why the old school/blueprint grind?
 

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Discussion Starter #10
I don't know the specs on the race cam as I didn't install it, it was in the motor when I bought the car....All I know is what I was told from the previous owner that there was a small fortune spent on this motor and I believe it!....The previous owner bought the car non running so all he knew is what he was told!....The car was a non running project when I purchased it and it's obvious that this car was intended strictly for the drag strip!....The "old school/blueprint grind" is just my personal preference!.....I just want to finish and detune this motor to my liking and that includes the L-79 cam, stock pushrods and stock rocker arms.....There is no need to mess with the valve springs, if they handled the race cam then they will handle the L-79 cam!
 

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Are your head's p/r slots longer?

I say this b/c I bought a "Louis/Slotting" tool from Jegs to lengthen mine towards the rocker studs just to make dam sure that my CHEAP 1.6 ratio STOCK type rockers w/ a tall cam would be OK.

I'm shooting for right at .500" here.

pdq67
 

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Ron..any numbers on the old cam that can help identify it?
Was it a flat tappet hydraulic camshaft that you removed?Prior to the cam swap..did you ever do a cranking compression test and if so,what was the psi?
Typically..high rpm performance shafts have a later intake valve closing point and the builder will up the static compression ratio to compensate.
What happens when you back down on the cam..the ivc point is sooner and builds cylinder pressure quicker at lower rpm.Great for torque..but now the higher static cr is not reqd and may bump you up and over 200 psi on the starter motor.This is not really pump gas friendly.
Interested in how it works out for you.:thumbsup:
 

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aren't the ratios of most non stock ratio rocker arms stamped on them?
 

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FYI, stock chevy rockers arent exactly 1.5.they are more somewhere between 1.45 and 1.47 so make sure you use true 1.5 rocker. I just finished a flattop 882 headed 350 with the L79 cam and used true procomp 1.5 rockers on the exhaust and true procomp 1.6 rockers on the intake and its in a 68 short wife p/u. raost the tires at will and gets abbout 14MPG. more cab tuning and Ill probably get 15-16mpg if he keeps his foot out of it, but its so much fun to roast the tires at will even while moving 30 mph. ...lol
 

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Discussion Starter #17
Ron..any numbers on the old cam that can help identify it?
Was it a flat tappet hydraulic camshaft that you removed?Prior to the cam swap..did you ever do a cranking compression test and if so,what was the psi?
Typically..high rpm performance shafts have a later intake valve closing point and the builder will up the static compression ratio to compensate.
What happens when you back down on the cam..the ivc point is sooner and builds cylinder pressure quicker at lower rpm.Great for torque..but now the higher static cr is not reqd and may bump you up and over 200 psi on the starter motor.This is not really pump gas friendly.
Interested in how it works out for you.:thumbsup:

I wish I could identify this cam, George.....Yes, it is a hydraulic cam.....Some of the numbers on the cam are as follows: #930962 then in another area: K293 then in another area: #1579.....I remember performing a compression test a couple years ago with this cam and thought that it was a little odd that this high compression 327 motor was only getting around 135-145 psi, probably due to the cam bleeding off cylinder pressure....I always thought that a high compression 327 motor should be pushing around 180-190 psi!....As little as I drive this race car, "pump gas friendly" doesn't really concern me!.....There's a Sunoco station on Ann Arbor Trail and Inkster Road that has the 110 octane leaded racing fuel that I could use, if needed!....I like to cruise down Hines Drive, when it's not flooded, if you know where that is!....I hope you have luck in discovering the specs on this cam!
 

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Discussion Starter #18
OK, I recently received my stock 1.5 ratio rockers and stock length pushrods from Summit....It's confirmed that the rockers originally on this motor are not stock ratio!.....The pushrods however are the same length as the new ones!.....I'm really anxious to get this motor up and running now as I'll know exactly what the valve train consists of!.....I also received my Summit double roller timing chain set up because who knows if that gear drive that was on the motor didn't have a bushing in it to either advance or retard the cam!
 
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