Cams

[CDMA]

I am thinking about a cam for my new engine and I am a little lost. The engine is a 9.5 to 1 compression, 1.94 heads ported and polished, edelbrock intake, Hei ignition, 750 Quadrajet, and stock exhaust.

I hear a lot of good things about the roller cams but do they give enough extra power to justify the cost? Also someone suggested the lift might cause piston /valve contact ont eh TRW flat top pistons. Any thoughts would really be helpful.

Chris

[CDMA]

To anyone who has not noticed the reason I am becoming a Naval Architect (sp...see) is my spelling and typing ability or lack there of.

[GEOO]

Chris, I had a Crane Hyd roller Cam in my 383. Part # 119631, Duration 222,230; adv dur. 284, 292; lift 509,528. Great idle good power. Used with my Stainless Marine Exhaust. With good heads build's 360 to 400 hp in a 383ci. GEOO

[GeneD]

Chris,
Rule of thumb on the cam lift thing is...
More than .500 lift requires piston valve relief notching, flycutting, whatever.
There is nothing wrong with a flat tappet cam for performance work. All the big guys have done it for years successfully.
Sure, a roller cam would be awesome. I have one sitting in the shop that I planned on using in my 400. But from what I have read from other guys, you need the special exhaust to make it work properly. You know, one of those units that cost mega dollars?
Horsepower is a function of the wallet.

------------------
GeneD
007
Melbourne, Florida

[rayjay]

A roller cam, whether or not using hydraulic lifters, enables the use of more aggressive, faster opening, ramp rates. One reason for wanting this is that you can use a short duration with a high lift, and still have the cam open for a long enough time. Two cams can have the same duration and lift (and timing), but may not be the same as one could have steeper ramps, getting the valve off the seat and fully open quicker than the other cam.

The disadvantage is that the "roller" lifter is usually heavier and can require stronger valve springs or a special spring kit that works directly on the lifter. Also non-roller blocks may require a special (expensive) set up to use roller lifters. Many years ago I used a non-hydraulic roller cam in a 289 that was shifted between 6800 and 7200. The roller cam was very simular in specs as the non-roller cam and made simular hp. However the roller set up went much further between problems and was more reliable, after being set up correctly.

I have also built truck/towing engines that used "Rhoads" lifters and a fairly aggressive (than one for low to mid-range torque) cam. The Rhoads lifters bled down at low rpm (low oil pressure) effectively shortening the duration and overlap, and then went back to normal at higher rpm's. This increased the low end torque withiut sacrificing all the top and mid-range power. There are now other brands of these types of lifters, and I have often thought of using these in a boat engine. These types of lifters may be a viable alternative. rayjay


[This message has been edited by rayjay (edited 09-06-2000).]

[BigGrizzly]

Rollers- Well lets get to the real reasion. They came out because -not for agressive lift advantage but rather durability. They have been around since the model "T". As was told to me by Babe Erson, one of the designers of ERSON cams and the brother of Sig, "The most important thing to remember is, if a flat tappet cam will do the job, use it. If the stress levels in the engine are high or if valve opening and closing velosity too high for flat tappets then use a roller" . In our applications - unless the block is already set up for a roller it is a waste of money, buy a new PROP. Nascar uses flat tappets (rules demand this)and turn in excess of 7000 Rpms, for 500 miles. Anyone here have a Donzi that does this and goes to a Donzi weekend.
For information, heavy springs are not necessary with rollers, and are frouned upon by high dollar engine builders. They use REV-KITS instead. Heavy springs cause more problems then not, valves popping off the seats, broken valves excessive seat wear, shall I go on? The answer to the next question. What is a REV_KIT? It is a suplemental spring set used on top of the lifters.
Be careful people keep trying give you cams with low end. WRONG. A boat is sitting on the worlds largest high stall speed torque converter. Top end power is what you need. The boat, unlike the car, gets heavier the faster you go. To go fast you need two things, big horse power and big money.First you run out of money then you run out of hull,it never ends .
Answer to piston question. most high performance piston are already notched, but ask the maker how much lift they can stand. if you can't aford good pistons, leave it stock. A broken piston cost as much or more then a broken valve.

[This message has been edited by BigGrizzly (edited 09-06-2000).]

[CDMA]

Thank you very much Big Grizzly. I don't know where you came from but over the last couple weeks you really seem to know your stuff. It is nice to have someone so knowedgable on the board.

Chris

[BigGrizzly]

Chris, thanks for the compliment. Knowlage is the wrong word. Experience is the word. I have broken everthing that there is to break at least twice. Ok Ok at least four times, and thats as far as i will go. Just trying to save you money. Been broke and still am. Just lucky, good wife, good kids, and two good DONZI's!

[CDMA]

Gig Grizzly,

I know you have a Criterion but what else.

Chris

[BigGrizzly]

I also have a 1971 Corsican with a 351 Ford Cleveland with V4 heads (big port heads) CMI headders and a closed cooling system. This is my baby, it does any thing I want it to when I want it to do it. The sound from the pipes is the ultament high. You know it is when a guy with a 50 foot Carry Craft, with four staggered superchared 502s, stops you and says "good sounding boat"
I use the same type engine in my 1971 MACH 1 to show the high school kids in their vets and stangs, that this old fart can still do it. That was untill my oldest boy cleaned my clock, with his super charged 5.0 that we built.
Just a note here ---he just bough a DONZI 22ZX double stepper-- Here we go folks dads gonna get his butt kicked again. Remind me not to teach my youngest son this stuff!