tomcat

I finally had a chance to read the article and although the comparison was not a simple head swap, in some ways it makes more sense to change the whole intake-head-cam package because that's what you have to do in real life. The stock heads and intake are not going to work with the solid roller cam they used.

I think the best way to evaluate the stock GM package versus the AFR package is to estimate volumetric efficiency from the reported HP figures. This is more meaningful than comparing flow bench numbers.

Stock - 530 HP @ 5500, ~88% volumetric efficiency

AFR - 700 HP @ 5500, ~100% volumetric efficiency

Can't complain about 100% V.E. I guess the question is, "Can you live with a torque peak at 5000 RPM in a boat?" The test boat was a 21 footer so low end was not an issue. The speed increase of 17 mph tends to back up the horsepower claims.

I'm looking forward to hearing results of these heads on a 540 or larger displacement with a hydraulic roller cam.

H2Xmark

that just goes to show that supercharging is not the only way to get a good speed increase.

Strip Poker 388

I think the AFR heads have the exhaust port raised ,so this will change where your exhaust exits the transom or change the tail pipes.

Madmax

Hey Tomcat....

for those of us that can't find that magazine cause they live in a hick-town can you give me a quick overview of the engine? Cubes? Cam? Compression? Intake?

Thanks.!

tomcat

Madmax: They really didn't give much info in the article.

The base engine was a 502 GM crate engine with GM Performance castings (rectangular port). They don't say iron or aluminum. Compression ratio of 8.5:1. 530 HP.

A mild street mechanical roller (254/260 0.660 lift), a Victor Jr. intake and a set of fully CNC ported AFR 315cc heads with the tulip valve upgrade. 741 HP.

H2Xmark: It's the RPM that's the problem. I love the sound of a 6400 RPM big block as much as the next guy, but I don't really want one in my boat. I'd rather have that much power @ 5200 RPM with 7 psi of boost.

RLW

I am getting ready to build a 540 with AFR heads. This will be a 5500 rpm motor with durability being paramount. 9:1 compression and hydraulic roller cam.
All out HP and Torque is not the criteria.
If you go to the AFR website, they give you some flow numbers on some of their heads. What caught my eye was the 305 "CNC Chamber" heads. Not to be confused with the 305"As Cast" or the 315"CNC Ported" heads.
The 315 "CNC Ported" starts out as the 305 "As Cast" head. The 305 "CNC Chamber" head outflows the 325 "As Cast" head until it hits the .600 lift mark. I really don't see myself going much past that valve lift number anyway.
The 315 "CNC Ported" is only about 4% better than the 305 "CNC Chamber" head.
Is that 4% worth another $750 for a fully CNC Ported head?
Is the 305 to small for a 540 motor? Wouldn't the port velocity be better with the 305 head?
Does anyone have any input in regards to intake volume requirements on a mild 540?
Thanks for any replies.
Russ

Monty

I'm dyno testing my 540's this Friday with AFR 315CNC heads, Crane 741 hyd roller, Holley 850, Victor Jr intakes, etc.

I bought the heads bare with nothing more than the CNC work and copper-berrylium seats installed. I used Del West valves, D/W titanium retainers and locks, and Isky (actually PSI) Tool Room springs, with Crower stainless steel rockers.

We flow tested the AFR 315 CNC's on a Superflow and with Manley Extreme Duty valves the results were within 5 cfm or so of AFR's claims. Some were a little lower, some were a little higher.

I ended up going with Del West Inconel exhaust valves, and D/W stainless intakes, which we put a 30* back cut on. Retesting showed and improvement in the intake flow as much as 20 cfm at most lifts.

I built my engines for the most area under the curve between 2000 and 5500 rpm, with reliability and durability being more important than peak power as well. If you're interested, I'll post the dyno results this weekend.

RLW

Monty,
I was hoping you would respond. I have done my share of searches on 540's and your name always popped up. I have been following your replies and posts.
I find it interesting that you are using a Holley 850 carb. It seems that most builders want to use a 1050. I was thinking a 950 would be a good choice.
Did you machine in a wide contact area on the exhaust seat for improved heat transfer?
What was the reason for the copper beryllium valve seats?
Is it for both the intake and the exhaust?
Would you share what cam you are using and it's profile and your compression ratio?
Thanks!
Russ Withiam

Bob280Silencer

This must be the winter of "540s"!I'm building one also.315AFR CNC,741 cam but efi instead of carb.HP500efi platform so wanted to keep the efi system.I'm going to try 9.2 cr,ordered JE pistons with 11cc inverted dome.With al.heads i think that ratio will be fine.Will post dyno results later.Monty,are you installing the cam advanced? BOB

ursus

This should be a great combination, as you noted there is not a big advantage to the 315,325 when using less than .60 lift and so their advantage is really in the 5000+ rpm range. The 305's will make good torque in the 3500-5000 range , I believe AFR recos the 305 as cast or chamber heads for 540's unless it is an all out race motor , talk to them about your cam choice/combo.

Yes we are interested