I just recently found out that i have a collapsed lifter. needles to say the cam is trashed. the question is ;
1.)what do all the lift duration numbers mean?
2.) what would you guys recomend for a cam?
3.)what else should i look for while ihave the engine apart.
4.)is it posibble to do this while the engine is in the car?

i have a gen IV 454 gig block casting number # 14015445 with heads that have this casting number on them #3909802 mortec .com states....67......oval..CLOSED..396, 427, 101cc chamber (what does all this mean) . i have a edelbrock 1910 carb. (850 cfm). and a automatic with 3.70 gear in the back. please help me learn.

 

The cam isn't neccesarily trashed just because the lifter collapsed.

OK I am back....you can install lifters by removing the intake manifold. Changing the cam is a little more involved and requires removing the radiator, water pump, timing cover, and fuel pump in addition to removing the intake manifold. Of course, in both cases you must remove the distributor.

Cam lobes are egg shaped and actually do the work by raising the lifters and push rods which in turn push the rockers and open the valves. Cam lobes are measured in 1000ths of inches. If you measure the height of the lobe (or egg) then measure the side and subtract that from the first measurement, the result is the cam lift. Valve lift is the cam lift multiplied by 1.6. (rocker ratio of big blocks.)
Duration is the amount (in degrees) that a valve stays open. Then there is lobe centers which is the degrees between the intake valve opening and the exhaust valve opening. This is the center of the lobe we are talking about here. You can research cams on any of the manufacturer's websites for a more detailed description and tech info.
Because the cam change is rather involved you should make certain the cam is actually bad before you change it.
You can check this by comparing the valve lift on a suspected bad lobe to another lobe as long as it is intake vs intake or exhaust vs exhaust.
Simple enough, right???!!!???!!!?



[Modified by silvervetteman, 6:49 PM 8/12/2002]

 

OK...I'll give you my 2 cents with the understanding that I am NOT mechanically inclined. I just had a ton of work done as the result of a similar incident. From what I have been able to gather the lift/duration has to do with how long it takes for the cam shaft to rotate and also how long it leaves the valves open (please understand I am regurgitating what I have read/heard). I had the stock cam installed in my 350 (262 I think). While he was in there I had the mechanic put in a new timing chain and obviously new lifters (I think when you buy a cam it's usually a cam/lifter combo). My mechanic did mine with the engine still in, he just had to take the hood and radiator off.

There are some VERY mechanically intelligent people on this forum so I'm sure my post will be corrected where inaccurate.

Hope I helped a little. :)

I just found this, it helped me to understand how camshafts work:
http://www.howstuffworks.com/engine-cam2.htm


[Modified by Mystery Machine, 11:54 PM 8/12/2002]

 

Cam reccomendations can get tricky, it's all what you're looking for. The bigger the cam the more horsepower you will make, but the less torque you will make also. If you go with a smaller cam you get more torque less horsepower. But the bigger you go the rougher the idle, and it makes the car less streetable. So if you just want crazy power, go with a big cam. But, if you want a daily driver, go with something lower or in the middle. I wanted power, but for the car to be tolerable on the street. So, since I have a small block, I got the Comp Cams XE268. The say the cam is "a great high performance cam for small blocks and a powerful cam for big blocks", according to Comp Cams. The idle is not bad at all, I really don't notice anything. So, I'd imagine it would be a little tamer in the big block. If that's what you would like, get the XE268, but if you want the same results I got in your big block, you could go with a little more cam, like the XE274. The best thing to do would be to call Comp or Crane Cams or whoever you want to buy your cam from, and tell them what you would like, and ask for a reccomendation. You could also call Jegs (where I ordered from) or Summit Racing and ask them for a reccomendation also, since they carry many different brands of cams. Sorry for the rant, but I hope this helps. Feel free to e-mail me or post more questions here on the Forum.


[Modified by Ryan77, 8:57 PM 8/12/2002]


[Modified by Ryan77, 8:58 PM 8/12/2002]

 

trust me. the cam is trashed. not only did the lifter colaspse, but it had aprox 1/8" ground off of it on the cam side. after removing the intake you can see that one of the lobes is clearly work down. thanks for the helpguys any info is welcome, so keep it coming....

 

OK..... then I guess it's cam change time for you. There are quite a few cams out there and some are very good while others are for specific uses. Just do not compare them to Small block cams. Big blocks are not even all the same because of the variious haed designs. If someone really like his comp. cams 262 in his 78 350 does not mean the a similar big block cam will be the thing to use. You might consider something like a GM LS-5 com for daily driving. They have TONS of low end torque.

 

Check out http://www.cranecams.com for a better understanding of how different cams can change your HP/Torque. Remember, the engine, trans, and rear end have to work together.