Assembling parts for my 540 project, I'm close to the purchase of a set of AFR 335's, the CNC machined aluminum square port heads that are fully assembled. Below are the planned components, and I'd like to hear opinions on the power & torque estimates these parts will make:

* GMPP Gen 6 502 block, bored .030, 4.500" final size
* AFR 335 CNC square port heads, 335CC intakes, 121CC chambers
* SRP forged pistons, 10.2:1 compression ratio
* Callie's forged 4340 non-twist crankshaft (4.25" stroke)
* Eagle H-beam forged 4340 rods, +.250 (6.385" total)
* Holley Commander 950 MPFI 1,000CFM dry throttle body kit w/36 lb. injectors
* COMP hydraulic roller cam (specs yet to be determined)

All strapped into a '71 Chevelle 2-door coupe, Richmond 6-speed, Moser custom rear axle. My camshaft choice is still undecided and I would welcome suggestions on that as well. Overall, the car will be a Pro Touring cruiser and dragstrip performance is not important.

I'd consider 42 lb/hr injectors. Depending on other items I'd consider Holley's new BBC MPFI kits that come with 42 or 50 lb/hr injectors and wide band O2 with the same intake and TB you are looking at. These kits don't come with a pump and regulator. It is more hard core and saves you money taking out a few parts, but has the WB02 which is very nice.

The heads might be a bit big depending on the cam and RPM range.

What I thought too. Gregg, did AFR recommend those to you given your Pro-Touring useage? Assume rpm range will be 1800-5500 or so?


"dragstrip performance not important"

You're a wildman! 540ci for touring!

Guys...

No, I haven't consulted AFR on which head to use. Do you think the 315's would be a better choice? AFR's site listed them as recommended for BBC's up to 509CID, that's why I thought the next level of CNC offerings would be the choice (the 335's). What am I "giving up" or "leaving on the table" by using the larger flowing heads vs. smaller ones?

Gregg, I'm out of my league on this 540 stuff for sure. But for a very powerful street motor, it would seem that 310-315 would be best for the 1800-2500 cruise rpm. And the head size kinda effects cam choice to some extent.

Originally posted by riskyvt:
Guys...

No, I haven't consulted AFR on which head to use. Do you think the 315's would be a better choice? AFR's site listed them as recommended for BBC's up to 509CID, that's why I thought the next level of CNC offerings would be the choice (the 335's). What am I "giving up" or "leaving on the table" by using the larger flowing heads vs. smaller ones? Gregg,

I got AFR 315s for my 540 project. I thought the same thing about the 335s when I was deciding on heads. I talked to the guys at Shafiroff (where I got my shortblock) and they said the 315s would be perfect. My set up is pretty similar. Only I've got a solid roller, but my '70 will see street duty almost exclusivley. Talk to AFR. I bet they can guide you in right direction.
Looks good!

I have a set of AFR 315 on 4.25 stroke "454". I spoke with Tony @ AFR personally for a head recommend. I would highly suggest you speak to him personally, since he did design the heads, I don’t think you wont be sent in a wrong direction. He told me that these heads like a single pattern cam because of the high efficiency of the exhaust port.
I have a 4 speed with a tunnel ram and the low end torque is unreal. I am searching on a stronger street strip clutch set up now. Any thing over 2k rpm and smoke from the tires.
If I short shift it. The Clutch winds ups into fourth. :mad: I am very pleased with his recommendations for my setup.
Ohh!! As for a cam These head really work good with any good “aggressive” roller ramps and some where in the mid to high .600 lift will do ya good for some street action. My UD feels pretty good to me.
smile.gif

..."dragstrip performance is not important." In that case for sure go with the 315 heads.

On the engine dyno my "little" 496 showed 495 lbs torque at 2,500 rpm. With the 6 speed and thin sidewall pro touring tires you will be just a throttle blip away from a smoke show - even at well beyond any posted speed limits smile.gif

Thomas

Originally posted by riskyvt:
Guys...

No, I haven't consulted AFR on which head to use. Do you think the 315's would be a better choice? AFR's site listed them as recommended for BBC's up to 509CID, that's why I thought the next level of CNC offerings would be the choice (the 335's). What am I "giving up" or "leaving on the table" by using the larger flowing heads vs. smaller ones? =

Gregg,
The 335 is too big for what you are doing.
The AFR head is arguably the very best flowing & efficient out of the box head out there.

Going by your last sentence in your first post I would suggest at most the 325 with the CNC chamber.
The 315 or even the 305 with the CNC chamber option would be my choice.
If over 6000-6200 RPM is not important I feel you will gain nothing with the larger head & lose some torque at lower speed.
With the 315's, about 10.0 & a Hyd roller like a single pattern Isky with the HR546 or 547 lobe,,,
I'd go with the HR547 which is 294/248-.608 with 112 separation installed at 106-108 (I recommend a 1.8 rocker on the intake) & a Wieand stealth, RPM Air Gap or Vic Jr & a 950HP you would be looking at close to 650-675HP on an honest dyno.
The Stealth will make as much power as the Vic & more torque.
Just for info, you are giving up an easy 50+ HP with the Hyd roller vs. a solid roller.

Don't know much about FI at all but I would assume you will make as much or more power with better drivability

If you email me I can probably save you a few dollars on the AFR's & the Cam & Lifters.
We have pretty fair pricing on both ;)

For what you want to do, I wouldn't go too nuts on the cam. Big hydraulic rollers don't pull a ton of vacuum in my experience. I'd definately keep in under 244@.050 if not a little smaller if going hr. I'm a fan of solid rollers with EFI. You'll get a lot more vacuum. Run good lifters and a moderate cam.

Off topic here but are the 502 Gen VI blocks limited on their over bore size? Why not a an aftermerket block or stay at the stock over bore doesn't that give like a 534? I remember seeing ones advertized using the Gen VI block just in case you need to re-do it in the future.

Guys will say its too small, but the 2nd largest Crane SR would be a nice, gentle cam for the street.

Trouble with Crane is, they redid their website, it it flat out sucks. CLearly done by a web guru with little auto experience.

Originally posted by Doug F.:
For what you want to do, I wouldn't go too nuts on the cam. Big hydraulic rollers don't pull a ton of vacuum in my experience. I'd definately keep in under 244@.050 if not a little smaller if going hr. I'm a fan of solid rollers with EFI. You'll get a lot more vacuum. Run good lifters and a moderate cam. =
As I said, what I know about FI you could fit in a thimble & also the reason for the 112 separation for the 547 lobe which should give you pretty decent vacuum in a 540.
Actually should be rather mild on a single pattern cam.
The other lobe (HR546) is 284/238/.578 & you'd definitely want a 1.8 rocker.
You need to get the valve open to take advantage of the outstanding flow of the heads.
I'd like at least.650 but I think that's a little hard with a hyd roller & short duration.

I agree completely with Doug on the solid roller.
You can run a lobe with good seat timing & still have a real cam. :D

The problem with most hyd lobes that are over 244 is the seat timing is up there which increases overlap & hurts vacuum.
The HR547 Isky lobe is only 294 which is pretty good for a 248 @ .050 lobe.
For instance the Comp X3347 (intake lobe for the XR294) lobe is only 242 @ .050 but still 294 at the seat compared to the above lobe ;)
Harold may have some even more aggressive lobes with less seat timing that would work even better but he will need to answer that.

Originally posted by Doug F.:
For what you want to do, I wouldn't go too nuts on the cam. Big hydraulic rollers don't pull a ton of vacuum in my experience. I'd definately keep in under 244@.050 if not a little smaller if going hr. I'm a fan of solid rollers with EFI. You'll get a lot more vacuum. Run good lifters and a moderate cam. I'm a little confused here. I thought one of the advantages of the aftermarket ECUs (and one of the reasons they were created) were their programming ability - not that the early OEM ECUs weren't but the learning curve is/was considerably steeper. Perhaps its easier with more vacuum but why can't the engine combo be tuned with whatever you have to work with?

You can program aftermarket EFI for any cam. At a certain point you should go alpha-N, which is never desireable on a street car. At that point you're talking 280@.050+ race cams(just a real rough number, many other variables apply, let just say below 3-5" of vacuum at idle). However, some dynamics and principles still apply no matter what whether carb or EFI. If you have a manual trans and except to be able to lug an engine, even if it is a 540 down real low with a big cam, it is going to chug and not run smooth. Better with an EFI, but not smooth.

For what this person seems to want to do, I think they would much rather have decent low end smoothness, torque and power, than give that up for the 20-30 HP up top they would get. It's cool to have a lumpy engine for a while, but if it is a stick and you drive it a lot, it gets old. He's still gonna have 600+ HP no matter what cam he uses. Might as well have 600 HP and a smooth engine.

Now if you have a weekend car with a 4000 converter, cam it up, but a Hyd. roller is all done around 6000 RPM (valve train stability) from my experience, if you are lucky.

Solid roller gives the best of all worlds if you use good parts.


From my limited experience, compared to say Mike's which is a lot more with engine combos, the heads mean the most. The cam is second. A small cam makes good power with very good heads. It takes a big cam to make very good power (upstairs, ala stock eliminator) with poor heads, then you lose all the low end.

For a street car, best correct heads, and a moderate cam.

Also the cam will determine how rich you have to run at idle and cruise and how well it will run closed loop. If you have a larger cam you will most likely need a wideband O2 sensor so you can idle and cruise at 13-14:1. A narrowband at 14.7:1 is usually too lean. A wideband is a good investment anyhow.