flow numbers alone seem to suggest that the afr's flow the same or slighlty better till .500 lift.
And AFR says fast burn design is in use in their combustion chambers ,so which is a better head in the real world for sb350?
running 10.5 comp with a 222-230@.050 cam.

I have been looking at the fast burn heads for a 383 I want to build for my Chevelle. They are very interesting to say the least ! The power figures they claim from a 9.5 to 1 383 are very impressive. And the price is right...around $1200 a set last time I checked. I think they are the ones I am going to use. Maybe Gary from GMPP will chime in with a comment.

------------------
Bill Koustenis
Advanced Automotive Machine
Waldorf Md

1971 Heavy Chevy - original owner
Team Chevelle #100

what were the numbers ?
AFR claims 440hp/470lbs with 9:1 and
218/223 hydraulic cam.
I'd really like to know the advantages of the "fast burns" over the AFR's ,if there are any.

Both the AFR's and the Fast Burn heads are winners. The AFR's should outflow the FB in raw cfm, however the FB should have better swirl characteristics.

In the GM Performance Parts catolog it says "When tested on a 383 ci small block engine with 9.5 to 1 compression ratio and .540" lift roller cam, single plane intake manifold and 750 cfm Holley carburator, the Fast Burn heads produced 497 hp at an incredibly low 5,800 rpm".

For those interested in some of the most likely ingredients in the GMPP fast Burn 383, follow along: cam #12370847, intake #12496822 (Eliminator Vortec).

Although I had bought a Weiand mini-blower for use on the next Bomber engine, instead of that I am now in the midst of a 406 buildup that will use the Fast Burn heads, JE 16cc negative dome pistons for 10.5 comp ratio, and a Comp Cams solid roller cam #XR280, Eliminator intake etc. Anybody interested in a fully polished Weiand 142 mini-blower kit?

I have a hard time just using heads "straight out of the box", so I may do the tiniest amount of cleanup and possibly change out valves I'm still thinking about that part.

------------------
"Bomber" '67 El Camino
Beater comes back to life
350/TH350 14.90 @ 93mph!
350,000+ miles on car
Likely 100k+ miles on engine

Some thing else to consider is headers. From what I have heard you need custom headers for the AFR heads and you do not for the FB. Correct me if I am wrong.



------------------
66 327 Malibu

The AFR's on our 400 sbc didn't require special headers, all we had to do was bang the friggin pipe in so the friggin plug could clear it!!! http://www.chevelles.com/forum/mad.gif

Bomber,
Do like the book says and leave them heads alone ! http://www.chevelles.com/forum/smile.gif http://www.chevelles.com/forum/smile.gif
Its hard to resist isn't it ? It would be nice to see what they will do right out the box though !


------------------
Bill Koustenis
Advanced Automotive Machine
Waldorf Md

1971 Heavy Chevy - original owner
Team Chevelle #100

You may also want to consider valve guide material of each head. It seems like I read somewhere that the FB heads had cast iron guides (not 100% sure) where as the AFR's come with bronze guides. I've always been told that bronze guides were a must in high performance engines, especially with high lift roller cams. Maybe BILLK can share a little more insight on this issue. If all else were equal (ie. price, performance potential) I would go with the AFR's because of the bronze guides. Also I think the issue of custom headers only applies to the larger AFR's (220cc) with the spread center exhaust ports, not the 195cc street heads.

Bomber '67 - "I have a hard time just using heads "straight out of the box", so I may do the tiniest amount of cleanup and possibly change out valves I'm still thinking about that part."

You may need to clean up a little flashing on the Fast Burn heads but thats all. It is not recommended to do any port work to them though. I'd leave the valves alone. You can mill the snot out of the Fast Burn heads because they have over .400" thick deck.
I copied this from Sallee Chevrolet & quoting Gary at GMPP ......
"If you want to improve your heads, clean the flash in the ports, blend the ridge left by the throat cutter behind the valves and blend the bowls. We get about 20 HP doing this on a 350. I would consider a cam with similar lift and duration ground on wider lobe seperation to build more cyinder pressure, this will wake your motor up a bunch."
I hope you don't mind http://www.chevelles.com/forum/wink.gif
http://www.sallee-chevrolet.com/Discus/board.html


------------------
Dale
Lowered '67 Elcamino
ZZ430HP / 4L60
"Canyon Carver"
www.chevelles.com/showroom/elkydriveway1.jpeg (http://www.chevelles.com/showroom/elkydriveway1.jpeg)

My $400 '93 FireBird
http://www.chevelles.com/showroom/D:%5cMyPhotos%5cFireBird.JPG

So I guess at this point it's toss up ?
I think the FB's have angle plugs,and don't they take a special intake ?

They have the bolt patern for either the Vortec or standard intake.


------------------
JT
71 SS Vortec 355

Speed Demons (http://www.angelfire.com/co/KellyMotorsports)

I had likewise narrowed my head selection down to these two. The $400 smaller price tag from the General made my choice a little easier.

------------------
Fueling the addiction:
67 Malibu (sb406/700R4)
70 SS454 M/C (roller 468/Switch-Pitch TH400)
74 Jensen ('94 4.3/2004R)
73 Jeepster ('96 4.3/700R4)
72 Chevy C10 ('99 Vortec 355/200R4)
50 Merc Woodie (Being chopped, dropped, and planted on a Caprice chasis, '00 Vortec 350/700R4)

"A drag race is like a gun-fight....... there IS no 'second-place winner'

Wouldn't claim to be an expert on AFR heads so won't comment on same.
Some things to consider on Fast Burn heads, use Vortec style intake or raised runner Bow-Tie. Intake ports are raised .240". Exhaust requires LT1/LT4 style flange due to raised "D" shaped ports. Heddman and Sanderson both make this style header. Don't change the valves! Some engine builders have recommended to customers that they install aftermrket stainless valves. This eliminates one of the Fast Burn heads' key advantages...lightweight stainless hollow stem valves and retainers. These weigh about half of a conventional stainless valve. Also, don't use cam manufacturers' recommendation for cam springs when using a aftermarket cam, unless they FULLY UNDERSTAND that your valves and retainers are as light as they are. You will end up with too much spring, not a horrible thing just unnecessary. Stock fast burn springs are good for .525" lift and about 7000 rpm. The 497hp 383 example in the catalog used FB heads that had been cleaned up a little (not radically ported)...this was done without my knowledge and I didn't find out until after the catalog was printed. Also the cam had alot of duration, which is required anytime you try to feed a 383 or 400 inch engine due to the increased piston speed and long stroke and the effects they have on cylinder fill. The cam was not the one listed in the catalog. Just read what I wrote, sounds like I'm making excuses. I'm not, just don't want anyone to be disapointed. Stock FB heads and the 540 lift cam in the catalog, with 9.6 CR, 4.0" bore, 3.8" stroke, dual plane vortec intake, 750cfm Holley will make 440 hp at about 5800 and 450 ft lbs at 4000.

I, too, had narrowed it down to these two heads, but I ordered the AFR 190s. Here's why:

1. I really wanted to retain my Q-Jet with its divorced choke. The AFRs can be ordered with heat risers and the FBs cannot.

2. The AFR 190s flow MUCH better at lower lifts, which was important for my application and cam. What is impressive to me is how well the AFRs exhaust ports flow... they actually flow better than L98 intake ports! The bottom-line for me is that they will yield better fuel economy (as well as power, of course!), which is what a good flowing exhaust port will do, if the right cam is selected.

3. The FBs have 210cc intakes and the AFRs have 190cc intakes, and I felt the slightly smaller ports would be more appropriate for my usage.

4. I also wanted to retain my existing intake manifold (Performer) and my existing headers (Hedman Elite 1-5/8"), which I had bought within the last year. The AFRs allow me to do that.

5. I am convinced that the AFR heads are assembled with parts that are at least as good as those used on the FB heads, but what really sold me was paying a visit to AFR, physically examining the heads and seeing the quality of the casting and machining. After reading about the extraneous flashing on the FBs (and then seeing it when I examined some heads at a local dealer), I was a bit turned off to the FBs because I did not want to fool around with cleaning them up.

6. Gary from GMPP did make some important points about the superiority of the FB combustion chambers, and I do believe the FB heads have better combustion chambers than the AFRs, but there were too many factors (as listed above) that weighed in the AFRs favor IN MY APPLICATION AND SITUATION, and that's why I bought the AFRs.

Of course, it didn't hurt that AFR is 15 miles from here and I was able to visit their facility and talk to one of the owners, and ultimately tailor my heads to my needs. I thinks that's kinda cool.

I ordered a '97-'00 HD L31 Vortec 350 crate motor (which just arrived today) and am going to put the heads on this engine and sell the Vortecs that came on it. I am switching out the stock roller cam for a CompCams XR258HR-10, adding hardened pushrods, Crower SS roller rockers and then I'll be good to go.

Oh yes, this is going in my '76 C20.

Big O Dave

combustion chamber and plug angle seem to be key factors here ,but how does each one affect performance ,econmoy ,etc. and what makes the FB better?

I'm not going to take sides. We often trap ourselves when we look at just #s. When Chev brought out the OC BB head, flow benches showed increased airflow, but real world results were mixed. That was a result of a reduction of the swirl/tumble that keep the mixture, a mixture. If we just look at airflow #s, we'll find you can lay back the back wall of the combustion chamber and increase flow, but get an over all reduction of power, or only gain at high rpm with a lazy engine at low rpm.

Modifications to a head that increase swirl/tumble will most often show a decrease in airflow through the port, but increases in torque [from which we calculate HP] and sometimes a reduction of fuel used at the same power level. This is what Chev is doing with the FB head. Note they remind us not to mess with the intake port. A flow bench may show a port job increasing airflow, but a loss in power can result.

AFR heads have been the standard others have been compared to. The FB head is taking the swirl/tumble induced burn quality to a new level. I'd bet we'll see some inovative new combustion chambers from others as well in the near future.

This could get very interesting, and we'll all learn something I'm sure!

I understand the greater flow of the AFR's in raw cfm, but the attention that G.M. paid to swirl on the FB heads impressed me more - as previously said, keeping the mixture a mixture will result in power gains.

For Gary at GMPP, thanks for your input here, as well in other forums. I do understand the benefits of the lightweight LT4 valves, retainers, and springs - but.. Just like the GMPP 383 engine going beyond a .525 lift (to the .540 lift) I'm using a Comp Cams XR280 solid roller on my 406, which is .570/.576 lift reduced to .554/558 after lash - which means that I cannot use the as supplied LT4 ovate springs (which I think are some of the finest springs made for applications that can use them). The GMPP catolog says the FB head will accomodate up to 2.02 x 1.60 valves. There are a few things going on here: the excellent LT4 valves, retainers, and springs just plain work well on most small blocks, G.M. knows that the majority of FB heads will go on 350's, rather than 383's or 406's, and so the smaller valve size makes more sense, without doing any porting, I can install valves with undercut stems and more attention paid to valve angles and increase flow without changing port or combustion chamber - so that I (expect) that the swirl characteristics will be retained.

...hence my weariness of the "huge" 210cc runners.AFR also now sells 185 cc head that flow only minus 5 cfm at 500 lift ,called the "high swirl & tumble ..."(although this could be marketing since they still seem to push the 190cc head.)
O.K. score so far ,
FB: lightweight valvetrain,d shaped exhaust ports,raised intake runners (not always necesary ,huh?),and the Great Almighty "FAST BURN"

AFR :flows like crazy,works with your intake,
smaller intake runners (promotes velocity ,I believe)

Do AFR combustion chambers suck ?
Are the fast burn combustion chambers all that super spectaular?

Not ranting just questioning.

To be honest with you, the biggest reason I went with the AFRs is because I could use all of my old stuff.

I believe that the FBs are more "leading edge" and will probably produce more peak hp, but for me, the AFRs were close enough and considering I could use my old stuff, they fit my needs best.

Once I get them bolted (studded?) on, and my engine installed and running (and sorted out), I'll let you all know how they work out.

Incidentally, I'm kinda running an "experiment" here. I've read Vizard's and Lingenfelter's books, and played around with DD/DD2000 for a few months; I'm giving Vizard's philosophy of using very free-flowing heads combined with a (relatively) conservative cam to produce a W-I-D-E powerband with good peak power and strong low-end torque.

Basically, Vizard feels that if you are trying to achieve a specific horsepower level, for example 350hp, you basically have two options:

Option 1: Build your engine with the stock (or mildly ported) heads and use an aggressive cam that gives the peak power you want but moves the powerband up higher in the rpm range. This option sacrifices low-end power and response.

Option 2: Build your engine with free-flowing, aftermarket heads such as the AFRs or FBs, and use a mild, short duration/high lift cam. This option theoretically yields the same peak power as Option 1, but significantly more low-end, Vizard says, because the larger-ported (but not TOO large) heads detract from the low-end LESS than the aggressive cam would.

So I'm giving it a shot. The cam I've chosen, CompCams XR258HR-10, is 206/212 @ .050" and lifts the valves to .480"/.487". According to DD2000, this cam/head combo and my carb and manifold, should yield about 346hp @ 5,000rpm and 402lbft @ 2,500rpm (and 395lbft @ 2,000rpm).

My heavy C20 should put this "theory" to the test - we'll see if this combo will yield strong low-end torque along with the predicted peak power.

Big O Dave

So what are flow #s for these Fastburn heads, cant find them published anywhere. Even if they are a bit less than Gary said Id like to get a ballpark idea. :confused:

combustion chamber and plug angle seem to be key factors here ,but how does each one affect performance ,econmoy ,etc. and what makes the FB better?


We have ported a lot of these heads, and have seen some awesome improvements in air flow and on track performance. The AFR head will win the hp war on the dyno but the fast burn head is a great street strip head and makes the best power with less total timing, because of the fast burn chamber and spark plug location. Most of the time they make best power at 30-32* of total timing!

Here is a link to some flow number from our data base
http://www.j-performance.com/index.php?option=com_content&task=view&id=28

Just fyi...this thread was started in 2000....8 years ago...somehow it's been brought back from the dead.

Things have changed a bit since then...including pricing and the products available. The Fastburn's are $1260 from Jegs. They haven't been updated in quite some time (I don't believe). The new AFR 195 Eliminators have chambers that are arguably just as efficient as the Fastburn's chambers and they flow a LOT better at almost every lift with a smaller port...and they're about $180 more than the Fastburns. And, you don't have to use a Vortec intake...no contest IMO unless you just really want GM parts. Out of the box, I'd be willing to bet a large sum of money that the AFR's would out-perform the Fastburn's on the dyno and at the track. Not that they're a bad head...just that technology has caught up and passed them in the last 8 years (funny..that seems to happen a lot with GM these days).

I have a engine customer w/a 81 vette runs 12.flats @115.5 w/stock fastburns & Beehive springs added.
These numbers were run before we found 25hp on a chassis dyno so faster et's should come soon made 370hp peak rwhp.
Combo is
406cubes,fastburns,RPM Performer,10.5 comp ratio hyd 286H comp cam,750VS Demon
3.73 rear,tight TCI 10" converter &700r4.
Tires were BFGoodrich radial TA's & car is very driveable with 12" of vacuum idleing.

My money's on the AFR's. But that's because I just bought a pair of 195 Comp Eliminators and they do work. 540 hp at 6100, 525 tq at 4600 and idles at 850 rpm out a 406. I'm thinking of getting a set of the 195 Eliminator Street's for my 383.