Head size thoughts

[rich grsc]

So just a general what do you think question. :confused: A 347BB, would you prefer a 190 head or a 205 head. It's a running discussion among some friends. :o

[Railroad]

All around, 190. Do not know what the BB is after 347. ,,,,probably feel dumb after finding out.

[weendoggy]

I run 185's on my BB (big bore Boss Block) 347. Hhmmm, would that make it a BBBB? :confused: All good, no issues, plenty of power/torque.

[rich grsc]

BB, big bore

[Rebostar]

I run AFR 185's on my 331W stroker and 205 Edelbrock's on my 427W. in the Cobra. The 47 Merc has a 427W with AFR 195"s. I would think the 190's would be a perfect fit for a 347.

[canuck1]

I think it depends on your cam and what you expect to get out of the motor. Look at the head manufacturer's specs to see what it flows at different valve openings and compare that to the cam you're likely to run. If you can get adequate flow through a 190 without needing a > .600" valve lift to get there, then the smaller heads are the answer. Often the smaller port will flow at least equal to the larger port at more reasonable lift rates, so there's no advantage to the larger port size for that application.

Sean

[bobl]

Obviously there are many variables that could make one head work better than another. The big bore would support a 2.08 intake valve which the bigger head would probably have. If both heads are "as cast" and from the same Mfg. the bigger head will make more top end power at the expense of a slight torque loss below 3500 rpm or so. If you are looking at top end power, bigger is almost always better. If the cam doesn't have enough lift and duration to take advantage of the bigger head than it could very easily under perform. There are numerous higher end CNC heads with smaller runners that will out flow the bigger as cast heads. IMO the AFR 195 works better than any head I've tested on a 347, except for the cost.

Bob

[MB750]

Higher runner volume = higher RPM performance.

I don't race, so 185cc for me is good enough.

[J R Jones]

AI Overview
The primary difference between 195cc and 205cc small block Ford (SBF) heads is the intake runner volume, which affects engine performance characteristics, primarily air flow velocity versus peak horsepower.
195cc Heads: Generally recommended for smaller displacement engines (like 302/5.0L and 347 strokers) or street-oriented applications where strong low-end torque, throttle response, and drivability are desired. The smaller runner volume promotes higher air velocity at lower RPMs, improving efficiency in that range.
205cc Heads: Designed for larger displacement stroker engines (such as 331, 347, 363, or 392+ cubic inches), higher-RPM race applications, or forced induction setups where maximum airflow for peak horsepower is the main goal. The larger volume can reduce air velocity at lower RPMs compared to the 195cc head, potentially sacrificing some low-end street manners for top-end power.

But you knew that already.
jim

[PaulProe]

Rich, I chose to go with the 205 heads on my build. When you add the larger studs and pushrod retainers to the 195, the price is almost the same as the 205's. Joe was able to make big power on mine with the Borla manifold. And the low end torque was well within my expectations.

[StangRacer]

So just a general what do you think question. :confused: A 347BB, would you prefer a 190 head or a 205 head. It's a running discussion among some friends. :o

It really depends on what you are trying to accomplish and what heads you are using. For example, a TFS Twisted Wedge head at 190 is significantly different than a standard inline head at 190 because the intake port is shorter. This is much like the "trick" NHRA Super Stockers use to beat the port volume rule. They will mill the intake face of the head to make the port physically shorter thereby having less port volume.

If you are comparing two inline valve heads, such as the AFR, Edelbrocks, etc..., the 205 head will make more power and lose very little, if anything, to the 190 head at lower RPM as long as the cam events are correct. The cam duration is what determines the power band. Many get caught up in flow numbers and the numbers published at 28 inches of water don't really give the entire story. At some point the smaller port heads are going to start to back up and the flow through the port goes in the toilet because the velocity is too high where the larger volume head will keep filling the cylinder.

For a 4.125 bore 347 I would go with the 205 every time. Just tell the cam designer your intended use and desirable RPM range.

[rich grsc]

As I said, just a general discussion. Wanted to see the thoughts out there by guys that build some of their own engines. I spent a fair amount of time at SEMA with two of the better known head companies, listening to their theories on head size and airflow.
I wish we had gotten around to the head discussion at diner. Would like to hear what Joe told you, Know Tim asked about cam & distributor gears, you & I are the only ones in agreement.

[MB750]

There's rules of thumb, and then there's theories. Since IC engines have been around for over a century, much of what they're capable of has been vetted out. Case in point, cam phasers that alter cam timing based on certain engine parameters is some of the latest tech (coyote), and now electric superchargers are starting to show up in the skunk-works divisions of major manufacturers (Honda V3 motorcycle prototype) with intentions on smaller displacement without the loss of power.

I think smaller displacement w/ boost is gonna reign supreme in the coming decades, at least until the IC engine is phased out for something else.

[Jeff Kleiner]

Smart guys listen to bobl. Just sayin' ;)

Jeff

[narly1]

I think smaller displacement w/ boost is gonna reign supreme in the coming decades, at least until the IC engine is phased out for something else.

With the recent news reports of widespread engine recall from the major car manufacturers there is growing sentiment that perhaps the small displacement w/ boost approach has reached its limits.

Earl

[rich grsc]

Funny how quick it goes off topic. Oh, my car is gray.

[Shamilton289]

As others have said, it depends on your intended use. You can build these cars with 600-800hp but how are you going to put that power to the pavement? Since I won’t be running wide-open throttle at the drag strip I would prefer the power band down low instead of up high, and I would go with the 1.90 head

[Ford & Jeep Fan]

THese cars are so light weight you will not notice the difference.