Cam lift ?

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DesertRat

DesertRat

Leading edge boomer
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I am taking my block & heads to the machinest this week.
273 being built with 10.5:1 Egge pistons. Does anyone know
the max safe cam lift with this combo using the stock rockers?
I will stay with the stock sized valves but am thinking about
going to a hydraulic lifter setup with matched springs & retainers.
TIA, DM
 
I ran a Comp Cam roller setup with my 340. The lift of the cam was somewhere around .534 with stock rocker arms....you will need to check your valve to piston clearance....8)
 
I used Egge 10.5/1's in my 273 build and with .030 shaved from the heads to make up for the fat Perma-torque head gaskets, I ended up with .395 piston to head clearance and .188 exhaust and .200 intake piston to valve clearance @ full lift with zero lash. I'm using a Isky #390144 (E-4) cam with .425 lift and 260 duration installed at 108 deg. It wouldn't hurt to put a little bigger lift cam in there. My ..425 lift cam ended up .407 exhaust and .401 intake lift (actual lift measured at the retainer on #1 cylinder.) When the books say the rockers are not truly 1.5:1 ratio that's true. Mine were 1.438 and 1.416 ratio.

I will have to look and see what clearance is recommended but I would imagine .100 would be good. I will post info if I find it.
 
you want >070" minimum intake and >.090" on the exhaust valve....no less...more is fine...assemble bottom end
set heads on with actual "gasket torqued compressed thickness" shims, snugged down, and clay on piston(s)...depending on how neurotic you are, check one or all!
you wanna open the valves a specific measured amount so you can measure how thick the clay is...do the math and that is your clearance for a given valve lift.

Hughes $475 rockers are worth every penny!

don't forget to properly check your pushrod length after machine work and cam selection
 
I agree with the Huges rockers. There beautiful parts. I myself have Comp roller rockers. Years old. Also worth every penny.
If valve clearance is an issue, you can cut valve reliefs into the pistons crown. Ask Egge how thick the pistons are and the approx. valve lift abilties. They should be able to answer the thickness quaetion easy. Also ask them how much you can go into the piston safely. Your machinest, if a racer, will also know this and basic saftey limits.

OH, OE hyd. rockers are terrible on there ratio being even close. They normally fall in around 1.4 or less. Use roller rockers for a true ratio and all the power freed up.

Nice post Toolman!!!
 
I'm running Crane Gold Race Roller Rockers right now but, if I up the ratio, I'll be running the Hughes. They are friggin beautiful!
I may even get wacky and run the Magnum heads with the Hughes new shaft rockers for them...we shall see.
http://www.hughesengines.com/Index/...a2VyIEFybXMgJiBBY2Nlc3Nvcmllcw==&partid=24529

Correction! The Magnum shaft rocker setup is $475

The LA shaft rocker setup is only $440!!!! Forget the Magnums for me!
http://www.hughesengines.com/Index/products.php?partid=25628
 
OH, OE hyd. rockers are terrible on there ratio being even close. They normally fall in around 1.4 or less. Use roller rockers for a true ratio and all the power freed up.
Click to expand...

Rumble, I might have to ask Santa for a set next Christmas. LOL Dave has the specs I was lookin' for.
 
what perfect actual ratio would you like? LOL

1.5 or 1.6 for LA

1.65 for Magnums
 
Thanks Rumble. I need to learn how to do quotes. LOL
 
I plan on using the stock rocker assy's as they are set
up for solid lifters and show no wear at all. I measure
1.25" from center of shaft to center of valve stem and
1" from center of shaft to center of pushrod landing. I
could be a bit off but I calculate that at 1.25:1 lift ratio
for the stock setup. I guess I should stay somewhere
around 4.35" lobe lift and be safe not touching anything
else?????? Thanks for the input.
DR:read2:
 
Build the motor (piston to valve clearances) as if you actually have a 1.5 or 1.6 rocker. That way, if you upgrade to better rockers later you can just bolt them on with no worries.
.435" lobe lift is way too much.
You wanna be at no more than .500" valve lift....maybe .475"I/.485"E w/duration at .050" lift in the 220/230 range

Good 273 info here but these are max effort drag setups for Stock class racing:
http://users.erols.com/dmapes/THIRD.HTM
Keep in mind that more duration requires more gear.
 
Just talked to Lunati tech about my application.
He mentioned 235 I 243 E @ 50
528 I lift 546 E lift W 110 lobe seperation
solid lifter setup with 120# double springs
@ 1.66". I think i got it all correct.
Is that too much cam for my 273 10.5:1
screamer???? Seems like it might be a bit much
but on the other hand=P~=P~
 
That cam will get it to scream. I like the specs. Do you have a decent stall converter to match up-ish and gear to get it rocken and rollin quick?
 
My transmission builder said he could build me
a 2800/3000 stall and build the 904 to take the
hp. My gearing is 8 1/4 3.21:1 locker.
Should launch fine & still be able to hiway cruise
i am hoping:profilel:
 
I think you'll need more gear but it will be worth it if you really want it to haul ***! LOL
My 69 dart swinger 340 4 speed and 3.91's ran like a raped ape!
Clay Smith solid cam 258* at .050", .525" lift...mildly worked X heads with roller rockers and torker II 340...tires were 245/60r14....
The 3.91 gears were the least gear I could run and I hated it in the parkin lot.
Yes, I was running more duration, but on a bigger engine with a lot more gear...
 
If your using stock 273 heads, you should keep the lift at around .450 because they really don't flow more air after .420 lift.
With this being the max lift you can run, just run way more duration.
My 273 heads stopped dead after .420 and then started going backwards at .450 lift.
They flowed 181.3 at .400 and 174.3 at .450 lift.
If you have a chance, flow your heads before you pick your cam.
I was talking to a amc racer at the track last week and he has to run a stock lift cam in his class ,but as much duration as he cares to.
I don't think you should go anywhere near this but it's an example of how to make power if your willing to run low gears and and high stall converter.
The duration @ 50 was 276.
How much gear are you willing to run and how much converter stall speed.
I would at least run a 3800 stall converter and a cam thats at least .241 @ 50 \\ you will have enough compresion at 10.5:1

You will run into detonation problems with a cam with any thing less then 240ish @50 :pale:
Pick your cam after you can know what those three things are.
(gear)
(stall speed)
(head flow)
 
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