i'm just curious about something, a friend built a 383 stroker, it had dual quads, headers, etc.... motown 220 heads, roller rockers, girdles, and a solid lifter flat tappet cam.

to make a long story short, after less than 2 hours of actual running time. the engine started to rattle and knock. when torn down, it is discovered that several cam lobes are flat. the machine shop says, that the cam went flat because they used solid lifters, on a hydrualic cam, and the part number supposedly proves it.

my question is this, why would a solid flat tappet lifter, chew up a hydrualic cam ??

if the the valves are lashed properly it should not matter, i am thinking, either the cam was not properly hardened, or the seat pressures on the springs when open, was WAY to high, or he had coil binding problems. don't ask for specs, because i was not directly involved in the buildup, so i don't know all i know is the cam was BIG, and the motor was meant to run big RPM 7000 plus



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84' Firebird, 305ci lg4, 700R4, 288/292 duration .450/.460 lift,Edelbrock Performer intake, Holley 600cfm 4 barrel, K&N filter, Pacesetter Headers, 3'single exhuast, dual out muffler, no cat,Motive 3.73's and Auburn Posi
1/4mile 15.17sec @ 92.5mph

currently in pieces, for manual swap

 

Because the cam uses different material, a solid lifter cam is made to stand up to the lifters which have no play like hydraulic lifters do.

 

you made no sense at all, either way they are a flat tappet , so it should not matter. so long as the valve lash is properly adjusted

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84' Firebird, 305ci lg4, 700R4, 288/292 duration .450/.460 lift,Edelbrock Performer intake, Holley 600cfm 4 barrel, K&N filter, Pacesetter Headers, 3'single exhuast, dual out muffler, no cat,Motive 3.73's and Auburn Posi
1/4mile 15.17sec @ 92.5mph

currently in pieces, for manual swap

 

The problem is preload/lash.

On a solid roller camshaft with a solid roller lifter you have a certain amount of "lash" - that is, when the valve is closed there is slack in the valvetrain - you can put a feeler guage between the rocker tip and the valve tip.

This is a "Safety margin" - you can't really keep it perfectly at 0 lash, but no pre-load (lifter starting to push down on the valve and opening it) since the specs drift over time - You will either start to pick up lash, or you will get tighter and the valve will never close. So the valvetrain is designed to run with a bit of lash (better alternative to having the valve never close).

Okay, now we have some slack - a solid roller lobe will initially have a VERY mild ramp (much milder than hydraulic) to take up this lash without slamming the lifter/valvetrain to hard. Once lash is taken up (why there is a maximum value normally for a given lobe) then the lobe picks up and opens the valve very quickly.

If you put a hydraulic roller cam in there and have lash then you don't have that initial takeup ramp, and you are going to be slamming your valvetrain around.

A hydraulic lifter has an internal plunger that allows you to run preload without opening the valve - so it doesn't need the slack.


Additionally hydraulic cams are most often made on cast cores, while solid roller setups are billet. This is because solid roller valvetrains are harder on the cam (and lifters) - because of the initial takeup, much higher ramp intensities, and greater spring pressures.

If you hadn't wiped out the cam the lifters would have gone - infact I would probably have them rebuild.


Chris

 

Solid and hydraulic cams with identical lift, duration, LSA and overlap are still not the same. The ramp design is different because of how hydraulic and solid lifters work.

If it were that simple then they wouldn't have hydraulic or solid cams listed. There would be just one cam.

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On this note we had a motor we found solid lifters on a Hyd cam. He had put 20K on it that way and had NO idea how long it had been that way. We put a new cam and ligters in it Ran much better

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Ellis
Team Captain
Team North West F-Body
www.teamnwfbody.org

 

I bet it would run even better if you took out the ligters and put in some lifters!



Chris

 

NAW those Bic's really come on at the top end

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Ellis
Team Captain
Team North West F-Body
www.teamnwfbody.org

 

ok i am one of the builders of this engine. the cam in question is a crane powermax solid flat tappet cam NOT A ROLLER!!! the specs are 245/255 deg @ .050, and lift is .558/.579, the springs used were the springs that came on the motown 220 heads that were good for up to .600 lift and also would have worked with roller cam according to world products. i have no idea the seat or open presures so dont ask. we were told that failure was caused be hyd cam and solid lifters, and a bit of washout caused by overfueling. lash at first was set at .045" then at .075" after consulting a local drag racer that has used solid cams for many years. just thought id share the specs.

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1984 project bird 2.5/ 5spd, soon to be 400+cu in smallblock/th350

 

How about you pull off a spring and check them..9 times out of ten any spring for a roller cam will be to strong for a flat tappet cam..Also for future refernec never buy complete heads..You have no idea what your slapping on your short block..World makes a damn good head but dont trust any company in this hobby..Not that they burn you but these parts are controlled by people..people who have bad days and good days..

Check the open spring pressure and check for any interference with your retainers/guides etc..Ive personally run solid lifters ona hydro cam with good results for years..Like mentioned above the ramps on the lobes are quite different but if the cam wasnt broken in or had a problem getting oil to it then that will kill a flat tappet cam fast..

Keep in mind that most of the heads sold complete for use with rollers are set for the 700 lift range..At any rate the springs should always match the cam and wold has no idea what cam you have when they build the heads so they run generic springs that at best are a good guess..

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None of the other stuff matters - solid lifters with a hydaulic cam will not work. The lobe does not have the initial "take-up" ground in like a solid lobe would (roller, flat tappet, etc. doesn't matter).


Chris

 

these are the only specs that the heads came with on the springs: 1.437'' dual spring, 125# @ seat, .600'' max. lift. it doesn't say anywhere what the open pressure on them is. thank you Chris B for your info and it was a solid flat, NOT A SOLID ROLLER, cam. also engine was broken in according to how crane said to break in the cam and oiling was not a problem. the lifters were also wiped out at the same time

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1984 project bird 2.5/ 5spd, soon to be 400+cu in smallblock/th350

[This message has been edited by DukeofBird (edited August 27, 2002).]

 

No info on the cam, just thought i would say hey to Chris B the first person i have seen from my hometown in the forum.

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