Old school generic hft cams vs newer and faster...

[travis]

On a mild to moderate performance street build...

Is it possible that an old school hft cam could actually perform better than a newer design, faster action cam?

For example...typical 350 Chevy or 351w Ford, 9 to 10-1 compression, dual plane, 600-750 carb, 2500-3000 stall, 3.50-3.73-4.10 gears, etc. Ported stock heads or small 160-180cc aftermarket vs a bigger, lower port velocity head like a 200cc sportsman or 210cc budget aftermarket aluminum head. Would or could the engine perform better and/or have better street manners with the bigger port heads and an older design, slower acting cam?

My thinking is (whether it’s right or wrong) is that a smaller, higher velocity port could handle a faster opening valve without a drastic drop in port velocity, where a bigger, lazier port might work better with a slower opening valve to help keep port velocity up. I could also see this same scenario playing out with say a mildly ported head with a 1.94” intake valve vs a heavily ported head with bigger 2.05” intake valves, where the bigger valve head could want a slower cam to help keep port velocity up.

I’m trying to get a better understanding of how port volume or port velocity plays into a street or mild race type engine build.

[CamKing]

Your thinking is backwards.
When we have an engine with a port that is too big, and lazy, we have to reduce duration, and increase lift, to band-aid the big port. It needs an extremely fast valve motion

Where we see inline like a slower valve action, is with boosted engines and ports, where the port size is small, for the amount of mass moving thru it.

[travis]

Where we see inline like a slower valve action, is with boosted engines and ports, where the port size is small, for the amount of mass moving thru it.

So would the slower acting cam work better, but possibly to a lesser extent, with a small fast port?

I’ve been playing with EA3.4, and it does predict better overall performance with older style, slower acting cams with smaller heads, but many times these sims don’t always jive with reality

[F-BIRD'88]

If you want the "Older"" hyd ft designs to perform best give the motor compression and don't be afraid to play with installed position and added rocker ratio .
Especially is that older design is dynamicly stable.

The trouble with some of the older generic off the shelf stuff is the LSA's are (may be) wrong for your purpose.

Like CamKing hinted at, they tend to work well with street type boost. (If stable)

[F-BIRD'88]

Another lil trick with "older" hyd cams is running the Intake rockers with a hair of lash. Which is tweekable for purpose.
The older hyd street designs tend to have +/- 10 deg more seat duration, running a bit of lash allows you to tweek that a bit. (If say you want to take that to the max you could run 8 solid l:fters on the intakes with a friendly slight running lash for say a street sleeper/cheater) (the valves will need lash attention)
Can combine with a + rocker ratio tweek too.

Cam Games

[CamKing]

Where we see inline like a slower valve action, is with boosted engines and ports, where the port size is small, for the amount of mass moving thru it.

So would the slower acting cam work better, but possibly to a lesser extent, with a small fast port?

I’ve been playing with EA3.4, and it does predict better overall performance with older style, slower acting cams with smaller heads, but many times these sims don’t always jive with reality

The problem with running an old style cam, is it's inefficient, compared to today's cam designs. For any application, you need a given amount of valve lift area, to fill the cylinder. Some applications will require faster valve action then others, but none will like having too much seat duration for the application. With the old style lobes, to get the valve lift area required, you have to go with a design that has too much seat duration, for the application. This bleeds off cylinder pressure, and lessens the draw on the intake from the exhaust, during overlap.

If the engine needs a slower valve action, there are plenty of modern designs with slower valve action, that don't have way too much seat duration for the application