...so the Fastburn heads are what? -210cc intake? I think we can all agree that's way too big for a 350, right? I mean the venerable 383/AFR/219cam/SR combo only used 190cc right? Vortecs are 170cc, and I think the ZZ4/L98 are just a tad smaller (maybe TOO small). Regardless, not many people running anywhere NEAR that size on a 350. .....so GM put em on the ZZ4-Fastburn 350ci/385hp, which is almost the same as the now zz5. ....they cranking out 400 HP with a small zz4 cam, and 300ft/lbs at 1500 rpm. That's not too shabby. I guess my question is why? Obviously GM knows anyone dropping in that motor is gonna be happy. Is it the efficiency of the FB/vortec chamber? I mean I don't claim to have real world experience to really know the difference of running the same head, one small port and one big port and really seeing the difference over the entire curve, but accepted logic is that 210 is just WAY too big. BUT...obviously GM doesn't think so, and the numbers seem to agree.

I'm not looking at these heads. I'm not looking at a zz5. I was just reading on it and was just really surprised to see those heads on a 350, with good numbers. Looking for a little convo on the subject I guess. I'm curious.

 

I could only use guessology to say why. Only the back to back dyno comparisons can tell u what u want to know and whos got that much money to test the difference. We, the customer are always left the vulnerability of someones elses numbers claim. Ive found theres quite an lot of small businesses that prey on the performance enthusiasts but dont know anymore than the customers. I have to mention they troll the forums quite alot also and is the only way i can explain some of the personal attacks i receive for what i say. Some non-supporting vendors make nonsense and unsubstantiated claims then they send unidentified fake members w/o any kind of profile to support their false claims. Id really like to know how many trolls have the same MAC address.

Ok enough ranting. I admit i have no experience with the fast burn heads or know anything 'bout them other than they're GM's hot seller.

 

It all depends on your needs. If looking for an all-out race motor, get the Fastburns it takes a lot of RPM to fill up all that intake port volume, on the other hand if your goal is a dual-purpose motor that gives a reasonable mileage and good power get the Vortecs. Even with a lower volume intake port the Vortecs out-flow the Fastburns, so again, if high RPM isn't your goal, the Vortecs are the best deal.

 

they have big intake ports, but they are also very efficient ports. they are pretty much the LT4 Vette heads with the cooling passages and intake manifold bolt pattern configured for a gen 1 small block. those heads made their debut on the limited edition ZZ430 crate motor, which was a ZZ4 with the Fastburn heads in place of the L98 Vette heads, HOT cam kit with roller rockers, and vortec high rise dual plane intake and it was rated at 430HP and 430tq with a 750cfm carb, numbers that were no doubt on the low side based on the times people were knocking down at the drag strip..

those GM guys know now to engineer stuff, and the fact that those heads have been in the catalog for over 15 years now and are still being put on crate engines says a lot about how good of a design the really are.

 

Has anybody ever CC'd those heads?

I did on the AFR 195's and they don't even come close to 195 they measured 186 cc.

I also did the 195 Comp Elem. and they were only 189cc.

Sometimes they just use a number that isn't what the size really is.

 

I agree with that statement completely.....except that GMs numbers seem to disagree. I mean ideally wouldn't we want a head that has great torque down low, but can breath up top too? Who wouldn't? ...for a 210cc head to make 300 ft. pounds at only 1500 RPM seems pretty good!!!!! -on a 350 no less. I'm curious was a big AFR head would make? Anyhow, that was the point of my thread. Just to discuss. I'm not shopping for them.

That's interesting. GM is no stranger to fudging numbers here and there. ....maybe they are a little smaller. Still a big head though.

 

I know I am

 

Swwwweeeeeet!!!

I'm assuming you've got a carb on it? ...what size? ...and from your sig, you've got 3.27 gears too. How is it down low on the bottom end?

 

Fastburns arent to big. They have a larger port but small valve. They still move decent amount of air thru a small hole. Velocity is still fairly good. Efficient chambers too they arent bad but i think they cost way to much from gm as new.

 

Please note that GM REVAMPED the Fastbrun heads when they unveiled their latest crate motors. The new ZZ5 is the old FastBurn 385 with the only difference being the revised heads, which net 15 more HP (385 vs. 400).

Judging a head by total intake runner volume is a little like buying your cars by how much they cost per pound- a very crude measurement.

Even stock Vortec heads are around 170cc vs. about 155-160cc for a typical stock pre-vortec head. Why? They raised the port roof significantly. The added volume was in places that didn't significantly affect velocity through the port in the real world and they gained a TON for flow in the process. Where it mattered, velocity is still present in copious amounts. In some places they intentionally slowed down the velocity, BTW.

So is a 210cc GMPP Vortec-style head "too much" intake volume for a performance-oriented 350?.... probably not! It's probably about equivalent to an aftermarket head with 195-200cc intake port in terms of velocity where it matters.

That being said, GM is asking a VICIOUS premium for these things. Good? Yes. Good for the money spent? Debatable. More debatable than ever, actually.

 

Nope, its a good size.

 

Yup lol. I've got a holley 750dp on top. I swapped the crate intake for a GMPP vortec eliminator (highrise, airgap, single plane), and put in 1.5 RR's.

When funds/life allow I'd like to put in 1.6 RR's and the LT4 hot cam kit, but it's pretty wicked as it is now.

Yeah, 3.27's, posi. She'll get up and go, I haven't been to a track for hard numbers (need SFC's first). I'd like some 3.45's, maybe 3.70's...but that'll have to wait until I have overdrive, haha.

With my shift kit it'll bark each gear lol.

 

With a short runner EFI setup, you'd have even better low/mid range power and equal the carbs top end power.

 

Typically, yeah, I'd agree with that, but MY thinking, which may be wrong, was simply that a runner THAT big was pretty much and open and closed case of simply being too big. Clearly that's wrong, and I was just looking for some discussion on the topic. Lot of good info about that head.

 

I'm a little late to the party it seems but have to agree with what has been said already...

Yes a gen. rule 210cc heads would be way too large but you have to look at how the heads comes up with that port volume.

A tall skinny port will still keep the air speed (velocity) up, where a short wide port will not.

Plus you have to look at how the ports are designed.. IIRC the fast burn heads are raised port heads with the intake port floor something like .025" higher up than reg. heads. This gives a straighter path from intake port to intake valve

The fast burn ports are 1.205 x 2.270"

My Brodix IK 200cc head intake ports are 1.31" x 2.21"