348 max cam lift?

johnnyrod

Well Known Member
Supporting Member 3
#1
I ran a cam from crane #150291 grind #H-218/300-12 It has @valve525 intake lift @valve 543 exhaust. I was told today this is too much cam lift for a 348 with 9 to one pistons is this too big or what is the max lift for a 348 with 333 truck heads. Thanks John:dunno
 

tripowerguy

Well Known Member
Supporting Member 3
#2
You're right that is to much if you didn't fly cut the pistons. Also your valve guides will need to be cut down if you did't go to long vavle stems. If you run stock vavle guide height anything over .500 will run the keepers into the guide and ruin push rods or cams. I am talking from experience. The stock cams were in the .350 range. The high lift cams in those days were in the .450 range. Also you might run into spring bind if you didn't go to springs for that lift. :doh Roy
 

johnnyrod

Well Known Member
Supporting Member 3
#3
Would this high of a cam push the valve into the piston? I did eat a cam pushrods are looking ok. I used the springs that are called for with the cam from crane. So I think and hope that the keepers hitting did it in? John
 

BlueSwede

Well Known Member
Supporting Member 1
#4
Hello Johnnyrod!

I am almost shure the valves hit the pistons on your engine, I am in the middle of reassembling my 348 that had a Isky 264 hydra cam with .525 lift on intake and exhaust and intake valve had been in contact vith the pistons. Because of my cam uses hudralic lifters they took up most of it and the cam lobes where ok, I just had noisy lifters and a brooken rocker.
If you ran solids then nothing but the other stuff i.e cam would take the beating.
I think yours would hit more because of the longer duration cam, my Isky was 214 deg. and at .050" lift intake would be -3 before TDC.

The new cam I am going for now is the Isky 262 hydra and that is .488 lift and the .050 is -6 before TDC giving clearance enough I hope.
I have checked with Moroso light springs without head gasket and now have a calculated .060" clearance on the intake valve. The exhaust valve have much more clearance because of it sitting above the slooping area of the piston.
On your cam I think you have even more lift on the exhaust.:eek:

I could be wrong on your cam but this is my feeling on your problem, The best thing is to check the Valve Piston clearance thoroughly EVERY TIME!!
I am mad at my self for not doing this the first time, keeping me from the hustle I have had on the noisy valvetrain :takethat :doh

PS! When I am comparing my 2 specs from Isky I se that my old cam is said to have cam lift .300 (valve lift .450 with 1.7/1 rocker ratio) and the new one is said to have camlift .278 (valve lift .488 with 1.7/1 rocker ration).
The .450 lift should work but if you calculate thoroghly .300 * 1.7 IS .510 (.525 with 1.75 rockers)!!!
ISKY MUST HAVE DONE A MISSTAKE IN THAT SPEC.....:nono1:
But once again.... newer assume it should work, TEST valve piston clearance before running the engine (with clay or with light spring method).
:bang
 

johnnyrod

Well Known Member
Supporting Member 3
#5
Thanks blueswede I am checking and yes the valve is hitting the piston so now I have to find the best cam combo i need to get best low end power and not damage anything. Thanks John
 
#6
Valves hit

It is usually duration that kills clearance and not lift. The interference will happen at TDC on the exhaust stroke when both valves are open at the same time and you would be surprised how little they are open at this time. I cant speek for the heads themselves though because some engines run out of clearance at the seal location because this boss sticks up too high. My brother's 403 Olds ran into this problem. He just had the heads machined. Be advised I'm no 409 expert.


Have fun guys,

Henry
 
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