SBC 350, Small Solid Street cams

[JAKEJR]

Yea, go to a 3.750" stroke.

10-4 I've read that until somewhere around 270ish, there's actually more area under the curve with a flat cam vs a roller. What say you?

Yep, I've read the same thing in one of the mags. IIRC, same article that said for a HR and a SR to give comparable performance, the SR needs 8-10 degrees more duration @ .050".

Jake

[CamKing]

IIRC, same article that said for a HR and a SR to give comparable performance, the SR needs 8-10 degrees more duration @ .050".

That's not always true, and depends a lot on the lash height the cam was designed for.

Here's 4 cams. All are the same seat duration(280), and the same .net lift(.525" w/1.5), and the same curve above the lash point.
Hydraulic Roller: 226@.050"
.012" Lash SR roller: 228@.050"
.018" Lash SR roller: 231@.050"
.024" Lash SR roller: 234@.050"

All 3 of those SR profiles will give comparable performance to the HR profile.

[pdq67]

Guys,

CamKing rate's his solid cams advertised durations at lashed.

That said, If you can't work something out with him, then call UDHarold at (662) 562-4933 and flat TALK to him.

And if you do, please say hello from ol' pdq67 for me! I bet Harold will talk your ear off.

He, He!! Great guy by me.

pdq67

[swatson454]

Yep, I've read the same thing in one of the mags. IIRC, same article that said for a HR and a SR to give comparable performance, the SR needs 8-10 degrees more duration @ .050".

Jake

It cam from David Vizard's latest SBC book and he was talking about the initial acceleration rates... "a roller versus a flat-tappet shows that, for cams below about 275 degrees, a flat-tappet delivers as much or more area under the lift curve than a roller."


Shawn

[LilRacr]

I can beleive the amount of area under the curve to a certain degree in small lobe flat tappets as you don't have alot of time to open the valve quick, that is one of the reasons I am very cautious about building this combination, from some of the cheap engine sim's I tinker with for fun shows that if I put everything together as it should be, and use basic head performance numbers that of the AFR 195 Vortec head the motor should make around 475hp and about the same torque with a roller cam based on simular lobes Mike has suggested. But my inexperience with such a small lobe is where my concern lies.

Anyone seen actual data or real life experiances with simular combinations?

My theory is correct sized high flow ports, small duration, yet high lift to move the air to get good idle characteristics yet great overall power.

[randy331]

Impressive! What type of bench do you use for testing your work?

The bench I use is an older SF300, it's in line with ports and information I have gotten from other consevative (non inflated)benches.

I would never get this in depth with a customers head unless there were rules attached, I would have started with a different head, but I had the castings and the means to do all the work, so we will see how they work in the end.

Are you flowing at 28", or flowing at a lower depression, and mathematicaly converting to 28"?

Randy

[CamKing]

Yep, I've read the same thing in one of the mags. IIRC, same article that said for a HR and a SR to give comparable performance, the SR needs 8-10 degrees more duration @ .050".

Jake

It cam from David Vizard's latest SBC book and he was talking about the initial acceleration rates... "a roller versus a flat-tappet shows that, for cams below about 275 degrees, a flat-tappet delivers as much or more area under the lift curve than a roller."

It's still wrong. I'll have to call David up.

[Keith Morganstein]

Yep, I've read the same thing in one of the mags. IIRC, same article that said for a HR and a SR to give comparable performance, the SR needs 8-10 degrees more duration @ .050".

Jake

It cam from David Vizard's latest SBC book and he was talking about the initial acceleration rates... "a roller versus a flat-tappet shows that, for cams below about 275 degrees, a flat-tappet delivers as much or more area under the lift curve than a roller."

It's still wrong. I'll have to call David up.

That's been out there for a while (doesn't make it correct of course)

Two lift curve graphs should clear things up.

[LilRacr]

Are you flowing at 28", or flowing at a lower depression, and mathematicaly converting to 28"?

Randy

No I can flow just about anything small block at 28", it's when I get into larger cubic inch combo's I have to drop back in depression convert to 28". With most stuff around and under 300cfm I can check flow at 32".

[A HotRod]

Bobby,
I hope you pull this engine / mileage / power experiment off good I've been gone the last week and want to do the same type of deal with my Chevy II.
I wish you the best,
Glenn

[LilRacr]

Glenn,

I am going to do my best to make it happen, I built many race combinations most say is a waste of time and they have made good power. Built pump gas bracket small blocks with basic parts that make over 600hp before it was commonly done(years ago). This is just another that I need to keep details straight and it should not have a problem to make decent power and still be able to cruise 300 miles on 15 gallons of pump gas.

Time will tell........ I will keep this post updated when done, but as I am starting into busy season again it may take several months to make it happen.