I'm looking at different heads for my new big block. Wow, talk about an overwhelming amount of choices! I'm totally lost...

Engine: Merlin II, 540 cubes. I just order the Holley Commander 950 rectangular port EFI yesterday. The oval Holley system has some flow restriction that I though I'd avoid. The 540 should be fine with square ports.

I don't want anything too extravagant, I'm trying to stay in the $2000 complete area. The Canfields are looking very good, since you can get them assembled with your choice of CNC combustion chamber size (110-124) for around $1999. Not bad. Your choice of 305cc or 350cc intake ports.

Other heads in my price range: Dart Pro-1 in 310, 325, or 345cc., Dart Iron Eagles, Brodix 2, 2+, 2xtra, Edelbrock RPM-R, Merlin 310cc rectangulars in iron or aluminum, GM rect ports. Anything else I should look at (as if this isn't enough:))

Current plan is for a hydraulic (or maybe solid) roller cam. Dyno2000 puts this engine with the Comp Cams XE294HR-10 hyd. roller and the 305cc Canfields at around 618hp/663tq. The Canfield 350's go 652hp/676tq.

I've spend a considerable amount of time playing with these combos in Dyno2000, but I'm not sure I believe what it's saying. In this program, the smaller intake port heads (around 305-310) don't make any more low end power at 2000 rpms than the larger 345-360 heads. How can that be? The program is recommending very large ports, but I'm not sure that is accurate. What's going on? I'd be happy to post the dyno files for anyone that wants a look.

Thanks!



[Modified by Flareside, 4:50 PM 1/1/2002]

 

Joe:
Have you considered the AFR heads? The flow numbers of the heads seem pretty impressive to me. They have three different intake runner sizes - 315cc, 335cc, 357cc. You can check out the heads at:
http://www.airflowresearch.com/BBCheads.htm

 

Hey, thanks Bence! I had read about those heads a while back, but I thought they were more expensive. Flatlander has them for $1799 complete. Not bad. Cheaper than the Canfields I've been looking at. Do you know if anybody has flow numbers for the smaller port versions? (305's and 325's)

-Joe

 

One thing to keep in mind is the exhaust ports. If the heads use raised ports (and many of them do), you can't use regular headers. You'd be looking at custom headers at big $$$.

Personally I like Edelbrock heads for a street driven car. My Edelbrock oval ports have not given me any trouble and make good power.

 

Joe:
Sorry, I checked around and was unable to find any flow numbers for the smaller runner heads. :(

 

Markus, are you sure about the custom headers? The Darts are raised .3" and the Canfields are .6". The headers are that tight under the car?

 

Its not easy to over cam or over "head" a 540. What compression are you planning to run? How tight will you spin this engine?

Jim Moore (427Hotrod) with his 540 runs the big Brodix-2Xtra's and made more torque and HP than my 540 w/ fully ported Brodix -2's. His cam is also slightly bigger, more evidence these big engines like lots of airflow.

Most of the aluminum head manufacturs (Dart, Brodix, Canfield, AFR) use raised exhaust ports which may require custom headers. Depending on your choice of headers (off the shelf vs. custom), the Edelbrock rectangular port heads may be the way to go. I would recommend at least having them pocket ported and matched to your intake as the big 540 with a decent cam will move quite a bit of air. A fully ported set will really wake up your 540, but will cost a bit more than your $2000 budget. Although heavy, the Merlin iron heads flow well, and also use the stock exhaust port location. The lower initial price of the Merlins may allow you to have them ported and stay reasonably close to your budget.

Good luck,

Mark


[Modified by ML67, 11:43 AM 1/2/2002]

 

With all due respect it looks as if you have given your 540 a restriction with your manifold choice,cfm choice.The best heads are now of now concern.Go Edelbrock.

 

Mountainmotor, I'm not sure I'm following you. The intake is a Holley high-rise single plane rectangular port with a 1000 cfm 4 hole throttle body. How restrictive could that be? They also offer a 2000 cfm dominator flanged version, but I think that's overkill.
See:




[Modified by Flareside, 5:41 PM 1/2/2002]

 

Hi Mark,

I'm not planning to rev this thing very high, that's why I'm going with big cubes. I'd like to keep compression around 10:1 or so, because I probably won't run a cam as radical as Jim's. I'll have to take a harder look at the Edelbrock heads. In Dyno2000 they don't produce nearly the horsepower that the others do.

-Joe

 

Joe,
You might want to look at chevyhiperformance.com........they have a compilation of their head flow tests for all of the major manufacturers there.

 

Well , you know my thoughts already. Go BIG!!!

I know of a fellow here that says he made 660 hp with his 540 with ported GM rectangular ports (Edelbrocks) with a .660 something solid roller cam. He didn't have flow numbers, the guy at the shop just did 'em the old style way.

Another made 670 hp or so with Dart 320's and a huge .750 or so cam. He is detuning it some now.

The Canfield stuff has a great reputation. I would look at them seriously. I haven't looked at the AFR ones in person yet but I bet they are nice.

Mark is right about the costs. My Brodix are essentially out of the box with a little clean up by me. They were pretty nice but I'm sure some real flow bench time could help out. That will be the next stage. A fully ported set of iron Merlins could put out some good power. I'm sure you can get 375 easily or even close to 400 cfm out of a set of them with some serious work.

I would lean toward a set of big aluminum ones that are nice out of the box. It will help with pump gas.

And don't automatically assume a big head or intake means less low rpm power. If they are designed properly, big flowing heads will make more low end than smaller stuff. The best of both worlds. Look at Montys small block. There has been lots of propaganda put out in the last 20 years that has caused many engines to be built way too mild considering what is available.

There is no such thing as too much airflow. Maybe too much volume for the airflow you have and rpm range you're shooting for, but the more air the better.

Even my big stuff peaked TQ at 4100 rpm and HP @ 6200 on the chassis dyno. How much lower do you really want it? If you get it much lower you're going to choke it up.

You gotta be careful with the Dyno programs. My experience is they are a little optimistic. I mean they might get within 5 % or so , but at this level that's 35 hp! The best use of them is to play with trends and see what they do without getting too hung up on the actual numbers.

How does Holley rate the CFM of the EFI? What pressure drop do they use to rate it? Is it the same 1.5" that is used for 4 bbl carbs?


Jim



[Modified by 427Hotrod, 12:54 AM 1/5/2002]

 

Here's another way to think of it...

Let's say ovalports with 269 cc or so work great on 396's. Will turn 7000 rpm.

On a 427 they will make power to 6400 or so pretty well.

On a 454 they are good to 6000 or so. Depending on mods.

On a 496 they are strangling it. Maybe low 5000 range unless you have ported Merlins or lots of work on OEM ones.

Now look at rectangular port ones with 315/325cc.

They kill a 396 down low. You gotta twist it hard. Top end running is great though.

Now you jump 31" to a 427. Still kind of iffy but they start working. Start coming on strong at about 5500 or so. Gotta twist in the 7000+ range to really benefit them.

Jump only 27" to a 454 and all of a sudden they start to make some sense. They come alive around 5000 and the bottom end is still pretty good with the long stroke. Look at the LS6 and LS7's.

Jump another 42" and put them on a 496 and you're doing good. The sucker starts acting like the 427 one did with oval ports. Strong out to 6400 or so and the additional stroke really makes bottom end come alive some more.

Now, go and add ANOTHER 44" to that and how can you expect them to feed it above 5000 rpm or so. You just created the same situation as the 496 and oval ports. Makes a great motor home/tow truck motor though!

Big motors need AIR.

This is pretty simplistic/generalistic and makes lots of assumptions but you get the point.


Jim

 

Ok Jim, I think I get it now ;) That's the best explanation and example I've seen, and it really makes sense. It's a big help to have the experiences of you guys to educate the rest of us!

At the moment, I'm thinking about the Merlin Jenkins 345cc heads that Mark suggested (thanks Mark!). They come in iron or aluminum. This head does seem to give up around 25hp up top in Dyno2000 as compared to 345cc raised exhaust port heads (Brodix, Dart, Canfield), but I guess we know how accurate that program is. I'd really like to avoid custom headers if I can.

I'm not sure how Holley arrived at their cfm rating. I just assumed it used the standard 4 barrel rating. It's a good question and I'm looking for the answer.

Does anybody know if the new AFR heads have raised exhaust ports? I'll fire off an email to them.

Thanks!

-Joe



[Modified by Flareside, 2:07 PM 1/5/2002]

 

That Holley Manifold I believe to be a perfect match to the Fel Pro 1275,which is a great match for the Edelbrock 454R#6065 heads.I guess what I should have replied with is why with a manifold like that would you want to dump the intake into a very large VR 345? The combination would be a mis match along with your chosen cam which by itself is suspect to being a little too short on duration at 0.50 and with ..540 intake lift a better head is not needed.
If it were me I would use the above Edelebrocks or the Dart 320's with a custom ground Engle Extreme series flat tappet solid lifter asking them for a EP-55 intake lobe and an EP-58 exhaust lobe ground on a 112 Lobe center angle with 4 degrees of advance ground into it putting the intake centerline on a 108 Centerline that makes this cam:
296 advertised-259@0.50 .628 lift intake
302 advertised- 268@0.50 .638 lift exhaust using 1.72 Rockers
This is just my opinion on what would work best for you.I am certain there are other opinions as well but if you don't cam it up a bit you will soon get sick of the overkill bottom end power.This will give you the best of both.

 

Hi Mountainmotor,

I never actually intended to buy that Comp cam, I was just using it in the software to compare different heads. I guess in retrospect I should have went with something with a higher lift. I'm still totally undecided on a cam. I'll probably stay away from the solid rollers because this engine will make more power than I'll really need anyway. If I lost a lifter and trashed my $8k engine, I think I would have a breakdown! ;)

The cam you spec'd sounds similar to what Mark and Jim are running.

-Joe

 

Hey Joe I have the Air Flow research catalog and price list right here in front of me and there is no mention of the big block heads havving raised exhaust ports. Any other questions about them just let me know. Bill. I am looking forward to following your buildup.

 

Uh oh Bill, what are you doing with that catalog? :lol: Upgrading?

 

Right now just window shopping Joe but I feel the tug of that " if I am going to do this then I might as well do that " syndrome but the AFR's are one sweet looking head. Another head you might want to look at is the Victor Jr. race heads from Edelbrock as the JR. doesn't have raised exhaust ports and I believe has 325 cc intake ports. They are basically a CNC ported version of the Performer 454-R heads. I still can't even decide on a cam let alone heads.

 

Also, Joe I happened to be looking at " How to build and modify Chevy Big Block Engines " and it makes a reference to the Merlin heads as having a raised exhaust port. Not sure if thats true or not.