Vortec or AFR Heads?

[Shawn]

Okay, I'm now leaning towards the AFR heads. I already have a performer manifold that will fit my 400 SBC with standard SBC heads. If I got the Vortec's they would need to be modified to accept more cam lift and sdpc has them already done for a package price since I would need a Vortec manifold too.

I have a guy selling some new AFR's for about $1000 and the Vortec head kits runs $900.

What do you guys think?


http://www.sdpc2000.com/catalog/217...ortec-Head-Kit-Edelbrock-Performer-Intake.htm
Our Vortec cylinder head kit provides you with everything you need to install the new Vortec heads on your vehicle. The following kit includes assembled Vortec heads, head gaskets, GM head bolts, GM stamped steel rocker arms, intake manifold, intake gaskets, 12 point intake bolts and additional required components as stated. This kit features our upgraded Vortec heads which have been modified to accept our high performance Z28 valve springs with lightweight LT4 retainers. This produces a high reving cylinder head that can handle up to 0.525" lift hydraulic camshafts. An Edelbrock Vortec Performer intake manifold is matched with this kit for optimum performance.



http://www.airflowresearch.com/pages/195sbc_sh.htm
The AFR Emissions Legal (versions from 1969-94 with heat riser, CARB EO #D-250-2), 195cc intake port small block Chevy cylinder heads are available in your choice of straight or L98 angle plug versions. These heads feature a 74cc or 68cc combustion chamber with a 64cc exhaust port and a 3/4” thick head deck (ideal for nitrous or blower applications). The 68cc chambers are designed for flat top or dished pistons; domed pistons will require additional machining. Standard valves are 2.020 intake and 1.600 exhaust with AFR’s hardened ductile iron interlocking valve seats. The exceptional flow characteristics, ideal operating range of 2000 rpm to 6500 rpm, 23º valve angle, and standard valve spacing make this the perfect street head for 350 cid to 400 cid engines from 1955-86. Available for 1987 to present engines with center bolt valve covers and 2 center intake bolts at 72º angle. No special parts are required.



http://www.chevyhiperformance.com/techarticles/83138/index1.html

When comparing cylinder-head flow data, it seems that everyone always looks at the maximum-lift flow data. But especially for street engines, the smarter move is to look at the mid-lift flow numbers. We decided to look more closely at the more popular iron and aluminum small-block heads at the 0.300-inch valve lift. Why 0.300-inch valve lift? According to knowledgeable engine gurus like the late Smokey Yunick and Zora Arkus-Duntov, concentrating on valve lifts at 65 to 68 percent of maximum valve lift contributes to both a strong overall torque curve and good horsepower. Number crunching 65 percent of 0.480-inch valve lift equals 0.312 inch.

We used this information to evaluate several small-block cylinder heads that we’ve flow-tested over the last four years. Since many of the heads that we tested used varying intake-valve sizes (from 1.94 to 2.08 inches), we multiplied the circumference of the valve (diameter times 3.1417 (pi)) times the valve lift to create a square inch area “flow window.” Then we divided this valve window area by the flow at 0.300-inch valve lift. By doing this, we eliminated the variable of valve diameter by creating a flow- per-square-inch criterion.

Here’s how this works using the GM Performance Parts Vortec iron cylinder head. The Vortec head uses a 1.94-inch intake valve to flow 190 cfm at 0.300-inch lift. We multiplied 1.94 inches times pi = 6.094 inches of circumference. This figure times the valve lift equals a flow window area (6.094 x 0.300 = 1.828 square inches). Then we divided the flow by the area (190/1.828 = 104 cfm per square inch). This number by itself really doesn’t mean much. But when we compared over 15 cylinder heads using this evaluation, the Vortec ranked fourth overall. This is just further reinforcement for how well this cylinder head flows between 0.100 and 0.400 inch of valve lift.

The following list includes the top 15 cylinder heads that flowed the best when averaged between 0.300 and 0.400 inch of valve lift. We should also state that all of these heads perform well. Should this mid-lift flow data be the only criterion for choosing a cylinder head for a 350ci/450hp street engine? The simple answer is no because it’s dangerous to base a decision on only one data point. But we would certainly encourage the use of this information as part of an overall decision on your next set of cylinder heads. Our lawyer has also advised us to say that your mileage may vary and the secretary will disavow any knowledge of our actions should we be caught. So there.

The 300 Club

1. AFR 190
2. Canfield 220
3. Canfield 195
4. Vortec iron
5. AFR 180
6. AFR 210
7. TFS 195
8. Holley 300-570
9. World Sportsman II 200
10. Dart Iron Eagle 220
11. Edelbrock Performer RPM
12. World S/R Torquer
13. Brodix -8
14. Stock 882 iron
15. Edelbrock Victor Jr.

 

[Greg72]

I've heard nothing but good things about AFRs...

In fact, it seems like the only reason people don't ALWAYS buy them is due to economics (AFRs seems to also be the MOST expensive option too!)

Their flow numbers seem great....and have always been backed up by independent magazine testing, so it's not just marketing hype. The observation about "flow under the curve" vs. "peak flow" makes a lot of sense to me as well... a big, meaty flow curve would sure seem a lot more sensible on a street car....where a pure "full throttle" drag car might be able to get away with a high peak flow-type head....and save a few bucks in the process.

 

[theperfectgarage]

Right on, great research you,ve done. If I read right, the vortec kit did not come with the vortec performer intake. there both great choices but seeing as you have the old style intake, go with the afr's. With these choices I dont see how you could lose.

 

[sled_dog]

I have heard before(who knows if its believable) that the people at AFR helped GM design the Vortec heads. AFR uses the same combustion chamber design as Vortec heads from what I've always been told.

Like Greg said, if I could afford aftermarket heads, it would be AFR for me. ANd like you noted, all added up they come out to relatively similar pricing.

 

[Shawn]

I found a place selling AFR's for about $1200 brand new with free shipping. Its not much more than some of the other heads out there.

Its also tempting just to purchase the standard Vortecs (with no mods) and run a smaller cam. The heads are less then $500 new or $250-300 on ebay (used). Still need a special manifold though ($200).

 

[dyeager535]

We discussed this a bit before, aren't the Torquers (II?) using a fast burn chamber now, and a fair bit less expensive than the AFR's, something like $800/pr?

They seemed to be a pretty good piece all things considered.

 

[Shawn]

We discussed this a bit before, aren't the Torquers (II?) using a fast burn chamber now, and a fair bit less expensive than the AFR's, something like $800/pr?

They seemed to be a pretty good piece all things considered.

Yeah, $800 at Summit. They're #12 on the list for flow. I wonder if thats the newer design that they tested.

 

[dyeager535]

Yep, I was wrong, thinking of the sportsman II's. From Worlds page, the torquers are still crappy chambers, Sportsmans are fast burn. And they are ranked about middle of the pack in your first post.

For me, when looking at Vortecs, flow and chamber are great (which is why they are good heads) but all the other issues are what turn me off on them.

 

[Shawn]

Yep, I was wrong, thinking of the sportsman II's. From Worlds page, the torquers are still crappy chambers, Sportsmans are fast burn. And they are ranked about middle of the pack in your first post.

For me, when looking at Vortecs, flow and chamber are great (which is why they are good heads) but all the other issues are what turn me off on them.

Yeah, too bad GM didn't make them with better springs that could take more lift. other than that, a really NICE head.

Found this article which is part II of my 400 sbc build up:

http://airflowresearch.com/articles/article39/A-P1.htm

 

[beater_k20]

for $1000, i'd go with the AFRs, not only do you get a better flowing set of heads, but you get aluminum heads as well. from your previous posts, i can tell you like performance. while Vortecs are decent performing heads, the AFRs are much better in several areas. you will be much happier with them.

 

[dyeager535]

Yes if you can afford them, no argument here that AFR's are the way to go.

For just a couple hundred more per pair, you can't really go wrong.

I'd certainly trade a bit of low end for some more topend. If you always kept the RPM's down then the low end numbers would the only thing important, but if you like the throttle, you need some top end.

 

[sled_dog]

Not sure what you feel the advantage of an aluminum head is, weight is about the only real existing advantage...

If they made AFRs in a steel head, man that would be sweet.

 

[beater_k20]

Not sure what you feel the advantage of an aluminum head is, weight is about the only real existing advantage...

lightweight, better heat dissipation, which means less hot spots in the combustion chamber, and less chance of detonation.

 

[Shawn]

Yes if you can afford them, no argument here that AFR's are the way to go.

For just a couple hundred more per pair, you can't really go wrong.

I'd certainly trade a bit of low end for some more topend. If you always kept the RPM's down then the low end numbers would the only thing important, but if you like the throttle, you need some top end.

I'm with you. I like both but I find myself in the upper RPM quite often...

The question now is 180's or 190's. The guy I know has 190 cc heads for a good deal. I'm wondering if 190cc would be too much.

lightweight, better heat dissipation, which means less hot spots in the combustion chamber, and less chance of detonation.

I read many times you can run more compression with alum.

 

[dyeager535]

I would think when building a 400, the larger runners can't be a bad thing. Especially when talking upper end.

While the article you mention places some of the heads down compared to the Vortec, they did average those across .3-.400 lift numbers. Again talking stock to stock, the Vortecs are 1.94/1.5's, the Sportsmans (for instance) are 2.02/1.6. Valve size isn't everything, but a larger engine at higher RPM's is going to see at least some benefit from the larger valves. At least they won't be a choke point. No idea what the AFR's run.

Aluminum's only real advantage is weight savings, along with perhaps ease of repair, but on a non-racing engine, I don't think the repair aspect is very much a factor.

Aluminum heads can/need to run more compression because they do bleed heat so well. Heat=power, which is why iron heads (identical construction) in controlled testing make more power than aluminum. I think that's a *fairly* new realization, at least in the aftermarket, because you started to see actual comparisons iron to AL in heads, and the consensus eventually seemed to be that iron heads make more power. But if you up the compression in aluminum heads at least in a 1/4 mile car, you will probably break even between the two.

Personally, weight reduction is never a bad thing. On these trucks though, the weight savings of aluminum heads alone is probably pretty negligible. Still cool though.

Now couple those heads with an AL engine block and you are on to something lol.

 

[sled_dog]

The general consensus is 1 point of compression up to even out the power lost with aluminum heads. That was my point, iron vs aluminum, iron wins. A polished Iron combustion chamber will be better with less hotspotting or detonation issues.

The best place to remove weight in an engine is of course rotating assembly, but like said, lost weight is lost weight. In a truck of any kind(except all out drag or race) I'd run aluminum heads.

 

[Shawn]

Here's a good article on iron vs alloy

http://chevyhiperformance.com/techarticles/83858/

Conclusion

We still believe that iron heads have the ability to make more horsepower than aluminum heads, but we also think that the difference is probably less than an average of 5 lb-ft of torque. Given this, the power difference is slight enough that other variables can contribute as well. In this case, the two sets of heads were not identical enough to reveal the basic inherent advantage of the iron heads.

Wouldn't 1 point of more compression give you more than 5 lb-ft of torque?

 

[dyeager535]

Again, I think that is based on the heat lost during combustion in AL heads....same compression, EXACT same heads, the iron head is making more power. Bump the AL compression up, and what they are saying is that on the same engine, the AL heads would be somewhere around 5ft lbs better than the irons.

The gain from compression IS higher than that 5ft lbs, BUT since the AL starts at a lower number than iron in the first place, the NET gain in power is slight.

 

[Shawn]

Another thing to consider is fuel.

http://www.diabolicalperformance.com/hotrodoctane.html

Don't build a high-compression engine (>10:1) with some old cast iron double-hump heads and expect to get maximum power out of 87-octane gas. On the other hand, by using new aluminum heads with modern fastburn chambers, you might get by with 87 octane gas, with more compression than you would have guessed. Technology comes to the rescue again! A generalization of the results of their test would be to say that using some good heads, you can run 10:1 on the street and run 87 octane and set your timing to around 34 or 36 total and probably be OK without any detonation and only give up 5 to 10 hp compared to using 114 octane racing fuel with idealized timing. For the street, that sounds like the way to go. Why pay 20 to 30 cents per gallon more for gas when you don't have to? If your engine is built with aluminum fastburn heads, decide which octane you're willing to pay for and then adjust your timing to eliminate detonation.

It would be nice to run the standard grade of fuel on my 400 and not have to pay for the high octane stuff at the pump while running 10:1.

 

[dyeager535]

Well, again, it comes down to aluminum saving you weight.

If 9:1 on iron heads (fast burn chambers are going to let you run 87 at that compression easily) make as much power as 10:1 AL heads, there is no difference except that you have more compression.