Big solid flat tappet compared to similar design roller HP loss
 

Hey guys I was talking to a guy at work about my car and we were discussing my cam in my engine. He was telling me that the huge solid flat tappet I was running was probably down over a 100 HP from running a similar cam in a solid roller. I know I am losing HP by not using a roller, but I would not think a 100 HP. What do you all think? I am happy with my car for now and won’t change anything till I go turbo, but I am just wondering.

100+ horsepower, doubt it.
Thats a lot of duration for a flat tappet.
To run a roller with that much duration in a 467 takes a lot of RPM, gear and converter.

I think the LSA will matter, like getting a cam near 104 LSA, and installing for ICL or/and Exh closing, to drive either cam profile toward optimal HP results.

HYD Flat or Solid Flat is capable of hitting optimal for our Street/Strip Pontiacs, whereas Roller can too but for far higher spring pressure and costs.

Still need to have the cam parameters optimal for the optimal results. What is optimal?

If only it was that easy.

Stan

In my experience I think you are only losing 10-15 HP if any at all.

Fact is that unless a roller cam has a special lobe profile a solid lifter cam kicks the valves open faster which is a big plus unless your running heads that have far more flow per tenth of a inch of lift then what your running now.

A lot is hinging on supplying the piston demand as early as possible.

It definitely likes RPM. I need to get it to a track soon. I have just been playing on the streets.

Yeah optimal is the key word. This cam serves the purpose for now.

That is what I figured. I am far from an expert, but I did put a combination of budget friendly parts together that runs pretty good.

That was my guess, but I didn’t want to argue.

It seems to do well for now. When I pull this engine for my wife’s car I will put a much tamer cam in it.

Cam is not that big in reality. Especially for 467 cid based on my previous 55 years running solid lifter camshafts.
Cam lift is not large at all. I have run .620 lift cams (after lash subtracted) for many years.

Tom V

I remember you posting about a solid cam engine you ran. Your solid is about the same lift as this one with my 1.65 rockers. I picked this cam up from Crower on a clearance sale and I like it so far.

Have Fun with it.

Tom V.

the lash plays a role, those duration numbers are at zero lash I assume. So, whats the consensus on how much that lash number listed takes the actual duration down? (I've heard 6deg per 0.010")

(FYI, I run a solid roller with very similar duration and LC as the one listed - on a 14:1 race engine and my zero lash lift numbers are right at .800 It is not a pontiac but still around 450 cubes. It goes like hell with a 5800 converter and shifting at 7400)

Not trying to argue, just learn.

I thought the advantage to a roller cam was the fast ramps that open the valve quickly to full lift and hold the valve open at full lift longer before quickly closing the valve.
The result is bigger broader power/torque curves and higher overall numbers. Making only an extra 10-20 peak power and torque isn’t the whole advantage the extra power is through the whole rpm range and both aspects help acceleration and drivability.

Also with stock heads it would matter less, but if you have good flowing heads the roller advantage shows up more.

Is my understanding wrong?

Do not think that it was the Roller Cam profiles that were ever really an issue.
Some say the Roller Lifter durability was due to several things and the people selling that stuff to Pontiac Guys was rapidly dropping.

So you are correct. Personally if I put a roller cam in a Pontiac Engine the parts would come from ISKY period.

JMO

(There is zero HP loss when the parts of the engine are laying in a wash tub from a Roller Lifter failure.)

Tom V.

https://www.chevelles.com/threads/so...tappet.119279/

Here is a post from Harold Brookshire (RIP) from UD posting about this subject.

I looked at that post by Harold and say they are not similar cams.

"They were both 288/296 at .020", 255/263 at .050". The flat tappet was 166/173 at .200", .540"/.556" valve lift. The roller tappet was 176/183 at .200", .626"/.626" valve lift. Both cams used .026" valve lash, hot."

"The only real difference is in the shape of the lift curve. Both cams shut the valve on the seat at the IDENTICAL seating velocity."

My question would be how much difference would there be in HP if I put 1.75:1 rocker arms on the flat tappet cam?

Stan

I did see the lift was quite a bit more. The flat tappet cam could very well pick up some of the lost HP if you put a rocker on it that would increase the lift. How much does a rocker change affect duration if any? Trying to learn more everyday.