cobra marty

Are the Edelbrock heads the only alumn. heads with the exhaust port in the same location? I think that the AFR and Dart both have raised ports which could be a problem as far as clearence is concerned.

SB

Brodix Race Rite's have standard intake + exh locations.

Good #'s for standard layoutr heads. Available out of box with 270cc Oval port or 294cc Rect port. Avaliable with a CNC combustion chamber that up's the flow even more.

Won't compete with a raised runner intake + exhaust port though.

Always check on the exhaust ports...some raised one's are near .300" and some go all the way up to .625" or so.

Ex manifold applications usually don't have much a problem since they use a good length of rubber tube to the tailpipes. Most tubular headers and some manifolds with real long risers will have issues.

rv

Kaama,
Thanks for the completed picture. That is good enough for me, you do not need to take any more. I have a couple follow-up questions:
1. Does that thermostat housing have the valve with the spring that acts as a bypass while the thermostat is closed and then closes the bypass once the thermostat opens?
2. Are the hoses to/from thermostat housing #12's?
3. Are the AN hose adapters 12AN to 1/2 NPT or 3/4 NPT.
4. Is the 18-22#'s of pressure at WOT or cruise?

Sounds like your setup is dialed in.
I also see you are using large tube full lenght headers. Did you have any insight on how your setup would do with elbow tops w/ 1 7/8" standard runner tubes?

Thanks,
Rick

rmbuilder

I have had the good fortune to be able to witness firsthand the performance of many of the boats owned by posters on this thread. One common trait of all these AFR headed engines is the application of power throughout the RPM range. This is due to the high flow numbers (low/mid/high lift) combined with a relatively small CSA. Not only are you moving significant quantities of air, you are doing so with very high port velocities. High peak flow numbers mean little without the column energy needed for proper cylinder fill. Without the proper port velocity and CSA, more energy is wasted initiating column motion and less inertia is present at IVO.

One factor less talked about is the combustion chamber program. These heads seem to always turn very good BSFC numbers, which is a strong indicator of chamber efficiency.
I plotted some BSFC/Torque graphs showing the fuel numbers relative to the torque output and in each case the curves are virtually inverse overlay, with lowest BSFC (.39-.41) occurring +/- 100 RPM of peak TQ (max VE).

WAGS382

See, I told you Bob knows his $hit.
The 305 cc Afr's and a small cam are all you need to achieve that 620 HP with your 502.
The "741" cam does not have the proper ratio from intake to exhaust duration and has more duration than you need, pushing that torque too far up the rpm range.
Jeff

Vinny P

I have had good luck and decent power with my NA 540 running AFR 315 CNC heads. Here are pictures of the ports as they came from AFR.

Thunderstruck

I run the AFR305s with custom cams from RMBuilder. Most people get the anodized option with the CNC port option. Bob (RMBuilder) knows his stuff. Got 605 hp at 5500 rpm on the dyno. I installed Crane HI6M modules with adjustable rev limiters to increase rpm range. My 32 AT runs 85 to 87 (added 6 to 7 mph) GPS depending on weather/load. Boat accelerates like a blower boat due to the high torque produced throughout the power band. Great idle. Call Bob Madera.

call me for more info

3375408228

Tom

CONDOR24

i changed out the stock hp500 cam in my motor for the crane "731" which AFR head combo would give me the best results ?, running lightning headers and nickerson holley carb.Also are my springs,guides and rockers applicable from my iron heads to the aluminum ones or do i need to purchase new stuff (sorry for my limited knowledge on this topic )

KAAMA

I cannot recall the the Crane 731 cam specs, but it might have too long of a intake/exhaust duration split for it to work well with the AFR heads. The head/cam combination have to work together for the engine to produce good results. I'm not saying a 731 cam wont still work, but you might as well retain the stock cast iron GM heads you now have and have some pocket port/bowl work done to them if you are going to keep that cam. With too much of an I/E split on the cam you'd still see some power increases with the AFR's, but without a properly selected cam you will be holding back their potential by not letting them do their job correctly.

Also, anything new would be good idea, although you can probably re-use the rocker arms you now have---just inspect them, but you may need a different length rocker arm stud for the AFR heads. I would highly suggest new springs, retainers, lifters, and pushrods. RMbuilder would be excellent to consult for your cam/valve train and will work with you & your engine builder.

Just make sure that whoever is doing the work does the job RIGHT and KNOWS what the heck he is doing...not by his sweet talking words---but by someone who has a lot of experience and a good reputation because there is a lot of $$$ involved and there won't be much room for error.

PatriYacht

Rockers will work. Pushrod length is different,you will need custom length pusrods. Get .080 wall thickness Comp 1 piece pushrods. Unless the springs are almost new, now would be a good time to get new ones.