ECeptor

My BBC guru tells me its a toss up between AFR's and Canfields for 502's and up. His opinion is all the others are a cut below those two.

If looking for a simple 500hp 454, then the Edelbrocks are a good economical choice.

KAAMA

Well said---just tossing in a cam such as a Crane "741" or "731", etc, in these engines with late design aftermarket heads such as with AFR heads isn't the simple answer anymore these days.

HARDCORE A/O

This is great news for me. Jim V is actually working on a set of AFR 345 ("as cast") as we speak. He is going to flow them before and after and I'll post the numbers once I get them.
It is correct that all of the exhaust ports are the same for the 305, 325 and 345 "as cast" heads as well as the 315, 335 and 357 CNCed heads. However, AFR installs a tuliped exh. valve in the exhaust for the two larger heads in both series, which increases the flow. Apparently, AFR has determined that the exh. vs. int. flow ratio would be too high with the tulip valves in the 305 and 315 heads (like above 80%).
Another thing to note is that at least the 345 "as cast" head (I'm not sure about the 305 and 325) has CNC work in the bowls, and this probably contributes to the seemingly high "out of the box" flow figures that we see on the AFRs.

axapowell

I'm going to have to disagree with your last statement. Gen VI 502, stock HP 500, 800 holley carb, Dart 6200 intake, HVH 1" super suckerspacer, CMI elbow tops, AFR 315 (CNC'd 305's), Crane 168741, Crane extended body roller lifters (dog bone style), Crane ignition (HI-6M and coil), 1.7 ratio rockers on the exhaust, 1.8 ratio on the intake, stock JE pistons, stock rods, and the stock steel crank. PROVEN combo 625HP.

If you would like me to supply the GPS speedo results and RPM range, I would be happy to do so. But, 1999 353 Formula Fastech, loaded (9500 lbs) that went from a 78 mile an hour boat to a 87 mile an hour boat! That's it. Proven!

Dave

woody1

How many people here have cams custom ground? And Im not talking about calling a 9 dollar an hour comp cams hotline tech that picks blindly from the catalog? I bet the truthful answer is very, very few

KAAMA

Guess I can't argue too hard with you on that Dave! I wonder what the same engine would do with a cam where the I/E split is closer together on the same dyno...either way those are very good numbers and nice pick up in speed for a shelf cam. Guess I'll have to eat my words and sweat this one out!

I am actually using a cam that is smaller in .050" duration numbers with a closer I/E split than the Crane 741 in my 565cid engines---but then .050" duration numbers don't alwyas mean anything either.

SB

Results aren't near as bad when not correctly specing a camshaft with a high quality designed head than err on a camshaft for a low tech big port (OEM GM) cyl head.

A large lazy port is a disaster waiting to happen.

Let's also not forget that the combustion chamber has a lot to do with a cyl heads performance to. Modern combustion chambers are getting much, much better.

I have a good head thinking question : is the 'bad' port in a BBC head really the actual bad port.

rmbuilder

The BBC AFR heads come in three basic (Intake port/Machine finish) configurations.
Chamber:
124cc/121cc/119cc/114cc flat mill/102cc angle mill

Port:
305 cast /315 CNC
325 cast /335 CNC
345 cast /357 CNC
The program accounts for the 10/12 cc increase in port size

Finish:
As Cast:
As cast intake/exhaust/combustion chamber. This head receives (standard) a CNC bowl finish program that extends approx 2" below the seat/throat.

CNC Chamber:
The 2" seat/throat with a complete CNC chamber program. This greatly assists in torque production due to chamber efficiency, which is not necessarily reflected in raw flow numbers.

CNC Port:
Full Port/Chamber program.

Valve selection: (tulip proprietary to AFR)
305/315/325/335- Standard Valves:
7630- 1 Piece SS 1.880", 11/32", chrome stem, +. 100" Nail Head HF #F801259

345/357- Tulip Valves:
7631- 1 Piece SS 1.880", 11/32", chrome stem, Tulip HF # 1297

Optional Valve:
7633- 1.880" Tulip Inconel HF #F 802297

The tulip/tulip Inconel valve does significantly elevate the flow level of the exhaust port.

Why the nail head valve standard in the 305/315, 325/335 heads and the tulip in the 345/357 versions?
Very often these smaller port heads are improperly cammed (N/A applications) in relation to the Intake/Exhaust bias (80%+). Due to the fact that the 305/315/325/335 versions are most often utilized in moderate RPM/Displacement (under 600 CID/7000 RPM/NA) combinations, flow potential is not necessarily optimized to minimize the effects of excessive exhaust duration bias. Simply put, if you miss on the exhaust duration it's not as detrimental to TQ production with the nailhead.

AFR does, however, always recommend the tulip up valve in "a properly cammed application" regardless of the mechanical parameters. The tulip is standard in the 345/357 CNC due to the fact they are properly used in very large displacement/RPM combinations as they are less sensitive to over exhausting via the volume of exhaust gas present and the RPM/time available to evacuate the spent charge.

Looking at an engine as an integrated system it makes sense that whenever you make significant progress in any area/areas it becomes necessary to re-evaluate the collateral components, including the camshaft.

Bob

cstraub

All my customers do...

SB

Cstraub - yes they do.

Bob - great information and a great example for my thread :
http://www.offshoreonly.com/forums/s...d.php?t=137657 that not so many people have seen interest in for some reason. I would think some or many would - but I guess throwing in a cam that 'looks good' is fine for most.

I personally like to experiment but heh, that's me....the crack pot.