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not really any such thing as too much... You need the clearance so you're not whacking pistons of course, but beyoind that you just give up money and longevity.

Many run .550 - .600" lift cams on the street successfully, tho they keep a careful on on valve springs, roller lifters, and valve lash. Some run more, even .650. These guys replace springs seasonally, and have other longevity related troubles, right Mark?
 

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Discussion Starter · #4 ·
ok thanks, i am freshening up my small block and my uncle gave me a cam with a .585 lift and was just wondering how it would b on the street, i won't have any clearance issues because i have flat top pistons. I have good springs for it to hold up and everything else. so thanks
 

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One thing mentioned above, but can't be overstated -- don't exceed the lift of your head's spring pockets. In other words, if you try to open the valves too far, the spring coils will bind up and the valve train will tear itself apart. Stock heads usually can't withstand more than 0.400 (number pulled out of the air) or so lift. If you want to exceed that figure, you have to machine the spring pockets deeper or replace the heads with a set that can handle the extra lift. In other words, how much lift depends on some measurements that you'll have to make in advance.

Also, many stock heads have pressed-in rocker studs. If you put too much pressure on the valve train by using an agressive lift, the studs can pull out of the heads. If you end up machining the spring pockets deeper, have your machinist thread the rocker stud holes as well.

If you're lucky, your existing heads have decent flow specs and a casting that will allow for the extra machining (enough meat under the springs). If not, aftermarket heads are an attractive option. Machine work for a pair of stock heads can be done for less than $500.

Also, beware that the cam lift and valve lift are different figures. The rocker arm ratio is the relationship between the two. For example, a cam with 0.300 lift when used with a 1.5:1 rocker arm ratio will actually give 0.450 valve lift. The same 0.300 cam lift will provide 0.480 valve lift with a 1.6:1 rocker. When reading cam specs, this can be a bit confusing if you've never dealt with it before.
 

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Even with flattop pistons you still have to mock up the engine and check piston to valve clearance. Remember the intake valve chases the piston and the piston chases the exhaust valve. I have had to flycut Wiseco flattops to obtain correct valve to piston clearance.

Dan E.
69 SS396 4spd 4.10 posi x66 coupe
 

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When you go big on the lift, it is very important to make sure the valve springs are installed at the correct height (you do have the correct springs for this cam, right?) In the past I have had my machine shop check this for me so I know it's done right.

Big cams rule!
 

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Correct me if I'm wrong but cam duration is the major factor when worrying about piston to valve clearance. When the valve is at max lift, the piston is no where near it. Piston to valve clearance issues most often occur when the valve has not shut all the way before the piston gets to tdc. Also, lift has alot less to do with how an engine runs than does duration. I think to really determine if that cam is ok for the street we need to now what the duration is. In addition, I agree with everything else that has been said about lift, springs, and head flow. Just my .02
 

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I agree with George. Duration is what hampers street friendliness.
I also agree that you are wasting the cam if the heads can't take the lift.
But I think of lift and duration kinda like bore and stroke. Kinda. Lift and duration is another part of the equation, yeah that's what I mean.
More cubes make more torque, more bore or stroke doesn't matter how.
Now you got to fill those holes with gases.
The cam just tries to open the valves to fill/empty the cylinders at the right time.
More opening, or open longer, allows more gases in/out. If it's timed right. Big IF.
More duration tends to make the engine 'stupid' down low, and not real happy to do civilized things.
So what.
I drive mine on the street any chance I get. I just tell Deb to be prepared to come bail my juvenile 47 year old butt out of jail, but she's usually with me. But mine's a toy I don't have to depend on to get groceries.
Later
Tim
77 Camaro, Wolf by name, NO JUICE YET
412 SBC, Brodix T1 CNC 227's, Comp solid roller .651 /.652=693 w/ Jesel 1.6 shaft minus lash, which has been perfect every time, but I watch it like a hawk.
265/270 [email protected],107 center
[email protected] if driver ain't sleepin
currently doing rearend work, but have 4.56 gears, TH400 rev/man w/2.71 first gear, 5000 Tq con
 

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Lots of good points.
I didn't mention anything about the right springs and piston to valve clearance. Thats what happens when you assume :clonk:
 

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Dart 400M Block-421?ci, Arias stroker rotating assembly with 7cc dome pistons, Track 10 SBC 58cc heads 2.08/1.60 valves, Custom ground 630 Erson Roller. This is an older motor I did, cant remeber all the specs, been drinkin a few times. It was/is great motor.

Ran pretty good on the street and it would get sideways in 4th-anywhere, anytime.
Sheriff hated me.
 

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Hi,
Let me ask this. With a 350 that has never had the block decked, has flat top pistons withthe 4 valve reliefs cut in them, Canfield haluminum heads that will take over 700 lift, could a person use a cam with 550 lift without risking valve to piston problems, or would that be too much.
rj
 

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I believe when you get to that level, everything has to be mocked up and checked. Not all 4 valve relief flat top pistons are the same dimension. Do the reliefs fit the size valve you're using? Rod length, cam profile, gasket thickness, compression height, deck height, rocker arm ratio, and valve lash are among the many factors that affect piston to valve clearance. The only way to know is to check it.
 

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Hi,
Let me ask this. With a 350 that has never had the block decked, has flat top pistons withthe 4 valve reliefs cut in them, Canfield haluminum heads that will take over 700 lift, could a person use a cam with 550 lift without risking valve to piston problems, or would that be too much.
rj

You would need to mock that up thats pretty close to the 'area' that it would behoove you to mock up the assembly and check it. I put to gether a few street motors but all I got was LUCKY that I never had a problem. the guy that taught me was a good teacher. he was old school. :yes:
 

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Hi,
Let me ask this. With a 350 that has never had the block decked, has flat top pistons withthe 4 valve reliefs cut in them, Canfield haluminum heads that will take over 700 lift, could a person use a cam with 550 lift without risking valve to piston problems, or would that be too much.
rj

Sure it will, but rule here is to always check. Be a gearhead, know what is in your motor and why.
 

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As said by others, mock it up with a used head gasket, and stick some Play-Doh under the valves and turn it by hand for a min of two crankshaft revolutions. If it stops during rotation, then you know you have a problem.

If not, then remove the head, and check the thickness of the clay. Iron/steel rods need a min of 0.060", alum rods need a min of 0.100".
 
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