prostreet1967

iTrader: (1)

i recently got a bbc thats a fresh rebuild its got a solid lift cam in it i put it in my truck and going to set the valves not sure what to set them at i have no specs on the cam at all any ideas

1997bird

iTrader: (2)

The best thing to do is pull the cam out and get the cam maker & part #. Then look the cam up in their catolog to get the specs for it.

prostreet1967

iTrader: (1)

thats alot of work but i guess its probalby the only way thats what im trying to avoid

WE TODD DID

iTrader: (2)

Set them around .022 and you'll be fine. Don't bother pulling the cam back out.

1997bird

iTrader: (2)

Thats a good way to kill the cam. BBC's are hard on flat tappets anyway, I would personally find out whose cam I had and set it right the first time.

WE TODD DID

iTrader: (2)

Explain to me exactly how that will kill a cam? I have never heard such nonsense! The manufacturer's settings on valve lash is only a suggestion. What kills a cam is improper break in, and seat pressures!

ulakovic22

iTrader: (12)

From my experience, which is limited, I always hear about .020 hot.

ws6t3rror

iTrader: (3)

thats what i thought, it must really be murder on em when vary the lash on the drag strip trying to find what the motor likes huh.

1997bird

iTrader: (2)

Depending on the cam lobe design 0.022" maybe to tight. Also depending on the lobe design if the peak of the lobe is to sharp of a angle (say a .390" lobe) and you run that too tight you can take the top of the lobe off. After that the hardness of the cam is gone and then you create a bunch of metel shavings. The manufacture's lash setting is a safe starting point, you usually don't want to decrease your specified lash more than 0.004". Without knowing what cam you even have, you don't know were that starting point even is at. If you are going to suggest a safe lash point without pulling the cam out, atleast give him a safe lash of 0.028" on the intake and 0.030" on the exhaust!

edcmat-l1

iTrader: (10)

Yeah, and shitty material, and low zinc in oil, and just the fact that BBCs dont like flat tappets.
Just curious, but what is your break in procedure for a flat tappet solid lifter BBC?
I saw you told him set them at .022 and he would be fine, yet you did not give him any rec on break in procedure. Those motors are very temperamental about flat tappets.

edcmat-l1

iTrader: (10)

Are you varying the lash on a solid FLAT TAPPET, or SOLID ROLLER? If you're tightening the lash on a solid flat tappet you're asking for trouble.

prostreet1967

iTrader: (1)

im more confused now more than before

WE TODD DID

iTrader: (2)

He didn't ask about break in. I take the inner springs out, and run the engine about 15 minutes varying the rpm between 1500-2000. After that, I put the inners back in and let it rip. The only time that I've ever had trouble with wiping lobes off camshafts, is when the lifter bores are worn out. Most older BBCs have to be bushed. I've even machined a groove on the lower half of the lifters to let more oil reach the lobs.

WE TODD DID

iTrader: (2)

LOL.....call a reputable cam manufacturer (comp, crane, etc...) and ask them.

ws6t3rror

iTrader: (3)

both

well since most of the new "street" stuff is tight lash anyways .016-.018 there really isnt much point in tightening that. but some of the race stuff i have out there is pretty loose like say a touch over .030 or more. my cam grinder gives me an allowable range that i have to play in when i get a cam from him anyways.

edcmat-l1

iTrader: (10)

Well, at least you know.....Not many people take out the inner springs. That was the exact answer I was looking for.
I hate flat tappet cams. I've seen little ones in small blocks wipe out during break in. For absolutely no apparent reason. No geometry issues, plenty of cam assembly lube, get the motor fired quickly, get it right up to 2000, and still wipe em out.
I'm done ranting, sorry for the hijack......

jakeshoe

iTrader: (14)

Just as an example,
Comps Magnum series lash specs are .022/.024, but the allowed variation is .018-.030"
Their tight lash series lashes at .016" and IIRC the variance is .012-.020".

You could put a dial indicator on it and a degree wheel and get a good idea what the ramp heights are.

Ed,
Lifters...
I think a lot of the failures have been lifter issues. A SBC should be relatively easy on cams but when they fail and everything looks right I think it is a lifter or possibly the cam not having enough taper to the lobe to spin the lifter.

ulakovic22

iTrader: (12)

That happened to my engine builder once. He runs dirt and has someone regrind cams for him to keep it cheap. He wiped out the lobes in 20 minutes during break in (kinda ironic that it's called break in). He went back to the guy and found out that on flat tappet cams you have to offset the lobes something like .080 to get the lifter to spin. His wasn't so the lifter was digging straight into the lobes and took them right off. Roller's you don't have to do that apparently.

ws6t3rror

iTrader: (3)

the only lifters i will even use that are flat tappets are the gm ones with the hardened 'foot' and even then i eye them pretty close. on cheap lifters you can sit the lifters tight against each other and it'll sit basicly flat as in theres no crown on the lifter to speak of. the gm lifter is one that was used for taxi cabs police cars and heavy duty apps that did alot of sitting and idling they have a pretty good crown on them and a "hardened" foot. those are the only ones i've ever pulled out that looked like new in recent memory.

edcmat-l1

iTrader: (10)

I agree completely. With both degreeing the cam to get an idea of what the lash should be, and the part about shitty lifters.
But I've seen it too many times. Not just stuff I've/we've built, but in other peoples cars. Motors fresh outta pro machine shops, assembled in those shops, wipe em practically on start up.
Its really discouraging when it happens in a SBC with a cam thats barely .500.
Not too long ago, I wouldnt hesitate to run a flat tappet. Had a BBc back in the very early 90s with a solid lifter over .600. Ran that sucker for almost 10,000 miles before taking it apart to go faster. Cam still looked fine. Lifters too. Now I wont build an engine with one, at all.