Don Terrill’s Speed-Talk

With my engine build I am going to do a solid lifter valvetrain. My initial thoughts were to use a solid roller for the advantageous cam profile. I have gotten mixed reviews for what I'm after, a big inch engine that produces a lot of power, but more or less reliable on the street. Some have suggested that I'd be better off going with a solid flat tappet instead. This has me wondering two things.

1. Is running a solid flat tappet truly MORE reliable than a solid roller lifter (assuming all tolerances are correct and proper lash is maintained)?

2. How much difference in power could I expect to see in an engine running solid flat tappet vs. solid roller?

I ran power simulations on the computer, and on my pump gas 406 the solid roller sim showed a 50 plus hp improvement. Neither the cam I had nor the solid roller I swapped in were ideal, but I dropped over 2 tenths with the change. On a street driven car, it's going to spin the tires endlessly, making the increase in power moot.

The roller will make more power.

IMO a correctly done SFT is way more reliable.

If you are accustomed to flat tappet stuff, solid roller spring pressures are scary. You can build a nice short block or buy a nice set of heads for the price of a compete solid roller valvetrain.

Let's start where all discussion's like this should start!
How big a motor are we talking about?
What is the weight of the car?
And what is power number your looking for?

I'll try to do this in order of the replies:

So why exactly is a SFT more reliable? Is it just because you remove the failure risk of the needle bearing lifter? I know a roller will make more power. I think that goes without saying. I'm looking to see what the compromise is.

I'm not afraid of the price of the solid roller, just more curious about the performance difference.

As far as the engine is concerned, lets go with somewhere between 521-557", 10.5:1 compression.

Ok , are we talking Mopar, Chevy, Ford, and now much hp do you need to put a smile on your face?

The correct mechanical roller cam will make more power, and be more reliable. Especially with a 521" big Block.
A big inch engine like that will need a good amount of valve lift to make good power. The more lift, the more spring pressure you'll need to control the valve train. As you increase the spring pressure on a cast iron flat tappet cam, you greatly reduce the reliability. A BBC flat tappet cam with .650" valve lift, is nowhere near as reliable as a roller with .650" lift.

mag2555 wrote: ↑Thu Oct 12, 2017 12:17 pm Ok , are we talking Mopar, Chevy, Ford, and now much hp do you need to put a smile on your face?

All of it.....

J/K. Enough to put the car comfortably in the 9's on a consistent basis. 3000 lbs without driver.

CamKing wrote: ↑Thu Oct 12, 2017 12:18 pm...The more lift, the more spring pressure you'll need to control the valve train. As you increase the spring pressure on a cast iron flat tappet cam...

This is exactly what I was thinking. That why I was confused when some folks suggested to use a SFT. With high lift, high spring pressure, 0.700+ lift, I'm thinking you're just inviting the lifter and cam to become one with each other.

Low 9s @ 3200 lbs calls for some 750 hp dependant on aerodynamics and even for a 500 cid motor that's cake!

nickpohlaandp wrote: ↑Thu Oct 12, 2017 12:12 pm I'll try to do this in order of the replies:

So why exactly is a SFT more reliable? Is it just because you remove the failure risk of the needle bearing lifter? I know a roller will make more power. I think that goes without saying. I'm looking to see what the compromise is.

I'm not afraid of the price of the solid roller, just more curious about the performance difference.

As far as the engine is concerned, lets go with somewhere between 521-557", 10.5:1 compression.

It might have helped to put this info up front. There's a world of difference between a street driven 383 and a 500+ inch street strip big block.

nickpohlaandp wrote: ↑Thu Oct 12, 2017 12:27 pm

CamKing wrote: ↑Thu Oct 12, 2017 12:18 pm...The more lift, the more spring pressure you'll need to control the valve train. As you increase the spring pressure on a cast iron flat tappet cam...

This is exactly what I was thinking. That why I was confused when some folks suggested to use a SFT. With high lift, high spring pressure, 0.700+ lift, I'm thinking you're just inviting the lifter and cam to become one with each other.

We do a bunch cams for big inch BBC engines in off-shore boats. They have to be extremely reliable. They have to be able to idle for maybe 45 minutes at a time, and run wide-open for an hour at a time. My customers have all switched to mechanical roller cams.

CamKing wrote: ↑Thu Oct 12, 2017 1:10 pm...My customers have all switched to mechanical roller cams.

Which lifters are they using? Are they using needle bearing rollers, or bushed rollers with pressurized oil supply (like babbit)?

CamKing wrote: ↑Thu Oct 12, 2017 1:10 pm...

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