i know what the mechanical differences are but im not entirely sure how the different cam types affect performance, maybe someone more experienced could fill me in a bit?
thanks

 

2 minute cam lessons.

Hydraulic cams have the advantage of not having to have the valve lash set after the initial setting. But traditionally, they're limited to about a 6500 rpm ceiling due to lifter pump up and valve float.

Solid cams have to be adjusted about every 500 miles, but they are capable of revving above 6500 rpm, with the right grind, and definitely make better torque through the midrange too, all else equal.

Roller cams, whether hydraulic or solid, are capable of steeper ramps due to the lower friction of the roller lifter, and therefore make better power and torque than flat tappet cams. BUT, they cost major money in comparison too. Money that could be better spent on other modifications maybe.

However, if you're building an all out motor, then oftentimes nothing else but a good roller set up will do. With today's technology, you can build a big block with L88 power, without having to split atoms at 12.5:1 compression to do it, by using roller cams, and modern carburetion and intake designs. And still be streetable, which they weren't when the L88's came out.

 

Here's a little more.....

When comparing two cams, a hyd and a solid, you need to take into account the valve lash. It will take a LARGER solid cam to make the same power as a hyd. That is only because they always advertise them at "0" lash. When you subtract the lash setting you find .020 or so less lift and a few degrees less duration. But when comparing two comparable cams, the solid will make the most power becasue they typically have faster ramps and open the valve quicker. A Hyd. can't utilize ramps that are as fast because they have to gently set valve back on seat. A solid has that nice clearance ramp to help designers do that.

The other thing with hyd.'s that amazes me, is folks will spend half their time trying ot mess it up. The ONE thing a hyd. cam does best is keep valvetrain nice and quiet for a long time. Works great in a pickup truck. But you typically see folks try to get a very aggressive hyd cam that has a hard time controlling the valve properly and you get noise. Then on top of it all, they "0" lash the valves/lifters to keep it from pumping up and run high bleed down "anti-pump up" lifters. Just defeated the whole purpose of using a hyd...it now makes noise!! Or they use something like Rhodes lifters to try and calm down that big hyd cam. Now it makes noise and you have effectively made a clearance ramp on the cam because the lifter bleeds off so fast. Just makes NO sense to me.

JUST PUT A SOLID IN IT and be done with it!

Also, solids don't require adjustment anywhere as much as folklore would have you believe. I've run them on the street for many,many years and it's no big deal. If you have to adjust it alot, something is wrong. Regular rockers will hold settings for a long time as long as the nuts are good. A cheap set of locking nuts solves about 90% of the issues. Using a set of decent roller rockers eliminates most of the others. If running real radical roller stuff, a stud girdle help control the ridiculous spring pressure.

I mean Toyotas. Datsuns. VW's etc used solid cams for many many years. How many folks ever actually set them??? The worst were the air cooled VW's, and they sure didn't need set that often. The others were just for fun or if you got bored! Granted. Hot Rod stuff has more aggressive cams, but it really isn't bad. Gives you something to do a couple of times a year!


JIM

 

Lift and ADVERTISED duration...Yes. But with the more meaningful, duration @ .050", the lash has been taken up. Also, keep in mind that the .050" is LIFTER travel, not valve lift.


Properly applied, the Rhodes lifters are a crude, variable, duration device. With the increasing oil pressure of higher rpms, they bleed down, less and increase the duration, at the rpms where it can be used.

Don't forget the higher HP Chevy engines. Many of the '50s and '60s Fuelies, IROC Z28 302, and the infamous (orig) LT1.

RACE ON!!!
1984 Crossfire
Membe NHRA

 

Just a slight correction. The 1969 Z28 had the solid cam 302. The IROC-Z28 was a carbed 305 from 84-85, tuned port injected 305 as an option in 86-87, and went to the tuned port 350 in 88. And I'm pretty sure in the latter few years of the IROC, they had factory OEM hydraulic roller cams.

Everything I've ever read said the solid cam made more torque down low than a hydraulic with the same duration, due to less efficiency in the hydraulic lifter. But everything else, I agree with.

Disclaimer: I'm no cam expert, I probably only know a lot of the basics.

 

Possibly, I misspoke saying "IROC". I was refering to the 1968-69 302s built to compete in the Trans-Am series. These are the only 302s, *I* know of. The LT1s I refer to replaced the 302 in 1970-71. Maybe the Corvette used them a year earlier.

 

That is correct. :) The 302 was only used on the 1969 Z28 Camaro. It was essentially a 283 with a 1/8" overbore. Some of the good 283's were capable of that. In fact, I'm building up a 283 to replace a blown up 305 in my friend's 1982 Trans Am. He's going to see more than twice the horsepower, even though a few less cubes. But I'm a little worried about his rear end gearing. If I can talk him into 3.73's from a 1985 Camaro IROC-Z rear end, I will.

The LT1 was available in 1970-72 (I think) in both the Corvette and the Camaro Z28. This was a solid lifter, high compression 350, but strongest in 1970. The Z28 was slightly quicker and faster than the Corvette, with the same LT1 engine, earning the Camaro the nickname "Poor man's Corvette". It was a performance bargain at half the price. But we all know the Corvette was cooler. :cool:

The LT1 was Zora's idea of an ideal Vette, even though he wanted it lighter still. He preferred handling and a peppy small block, over the straight line brutality of the powerful big blocks.

 

The 1967 ,68 and 69 Z-28's had the 302.

Check out http://www.67z28.com/history.htm and http://www.68z28.com for more info.

Good little motors but stock from the factory they were anemic and needed modded in which many were to include a friend of mine who bought his new in 67 and still owns it.

If I had my choice of any Camaro ever made it would be a 68 Z-28 Cortez Silver w/Black stripe car or possibly a 70 1/2 Z-28 -same color

But I don't so I'm stuck with a mid to low 11 second pump gas small block" before I push the RED button " between the fenders of my 74 Vette and loving every minute of it ;)

edit cause I forgot the 68 model :chevy


[Modified by mountainmotor, 5:46 PM 6/20/2003]

 

If I ever get around to installing that solid LT-1 cam, I'm going to get a set of the new Crower Cool-Face lifters. Someone finally got smart & drilled a hole in the lifter face for cam oiling.

 

Solid Cam, stud girdle? Have you been looking under my hood? -haha