I couldn't get that link to work. If you increase valve size and open the pocket ( I believe that's what it's called) I wonder what the cc goes up to. Now if you open the pocket do you have to increase the runner cross sectional area so that you don't have a pressure drop right before the valve? Or would it be fine considering the pocket is smaller to support a smaller valve?

 

That is being mis-read by you Gkull , the valve size if you read the last sentence it states the Fast burn head size is 2.00 and 1.56 it is not a modded head. http://www.hotrod.com/techarticles/e...ylinder_heads/

("The heads were equipped with 2.02-inch intake and 1.60-inch exhaust valves-the exceptions include the Brodix Track-1 (2.080-inch intake valves) and the L31 Vortec (1.94-inch intake and 1.50-inch exhaust valves). The Fast Burn heads used 2.00-inch intake and 1.56-inch exhaust valves")


And ya disparaged car rags , They flow all those heads and you think the made up the numbers ? How come your not saying every flow rating is bad off by a ton ? Even 63Mako showed your flow numbers that matched the 170 port size iron vortecs making what you posted most likely those heads.


Now that you see good flow numbers and nope cant be a fast burn head . That is why it is so hard to get accurate info on them . People have so much inaccurate and wrong info that getting info on them has become almost impossible

 

Vortec head intake runner volume is @ 170cc , ok, knew that.

If you're asking me if I know of any intakes that may be raised runner that will fit under any hoodline - I don't.

Evidently conventional bolt pattern intakes also fit , and will most likely need to be port matched - if practical.

As far as intake manifold runner volumes - that would ,of course, be application required & product specific.

 

Yep there is a raised port intake that fits under the hood . 63mako

 

I see GM make a Fast Burn specific intake. Looked pretty tall. Let us know how your build turns out.

 

What is this? right from your link? I don't really care........... They are nice low cost heads, have fun an be happy I had a little 358 ci 9000 rpm motors in my dragster

The heads were equipped with 2.02-inch intake and 1.60-inch exhaust valves

 

Gkull you read that and are making a mistake THEY TESTED 6 sets of heads ..

"The heads were equipped with 2.02-inch intake and 1.60-inch exhaust valves-the exceptions include the Brodix Track-1 (2.080-inch intake valves) and the L31 Vortec (1.94-inch intake and 1.50-inch exhaust valves). The Fast Burn heads used 2.00-inch intake and 1.56-inch exhaust valves."


I realize you may not care but for people who search for answers on these heads it would be nice to have one topic that is easily found and has solid info.. Half the flow test numbers I have seen are for iron vortecs 170 runners yet people take them as gospel from other people who have no clue.

 

Here is a link to multiple flow results for Fast burn heads both out of the box and ported. (scroll down)
http://www.users.interport.net/s/r/s...ehdc.htm#Chevy
Look to be fair overall numbers for an as cast head. Porting by a good shop can really wake them up. (see the last 3 from the same shop Smithburg Racing 1. Out of box 2.Valve job W 2.02 valves 3. Ported.) The last one, ported, has huge numbers, up to 299 cfm @ .700 lift.
All that said if you can buy a set cheap they are likely ok. If you have to pay Summit's price of $1500 a pair there are way better options, especially if your then changing springs, porting the intake to fit, need guide plates to match up with existing configuration or porting the heads to achieve optimal flow. The intake manifold they use on the GM Fast Burn 385 crate 12366573 seems to be a standard vortec intake. Don't know how the port sizes align if they are for use with vortec head because the fast burns are 40 cc bigger ports. As for port velocity they are 202 CC - 210CC (depending on who is posting) intake ports according to the info I can find. Port velocity on that port should be identical to any other head with similar port sizes and is more suitable for a bigger CI engine or a high RPM operating range. For $1500 if I'm building a hot 350 I would go with the AFR 195 for similar money, less after mods. If I found a set of these as takeoffs or low mile used cheap I would not hesitate to run them. Just my take.

 

The info you can find is why I posted this topic, the fast burn gets so much bad info and inaccurate info it is sad. Port flow on a fast burn is unique to it. A diff 210 head will not have the velocity of the fast burn head. Your making basic claims that hold up most of the time but on the fast burn it is counter intuitive what GM designed.

The valves are un-shrouded from the factory , the combustion chambers ensure a Fast Burn by spark plug placement and milling that creates a swirling flame front. All things you would want and what many after market heads have to a large extent copied with the most success to go to AFR.

Guys with crate motors who get these heads , and there are more and more of them as they become the standard sbc head for GM , will at one time or another look for more info on this head , my topic was not really a debate on them but a place to offer up solid information others can use.

Example , and not to have any disagreement with Gkull , he read a statement that he only half read and posted the heads where modded. Wrong, if he read the whole statement he would see no mods where done and the 2.02 and 1.60 numbers stated meant all heads except 3 sets had that size , fast burns not one of them with 2.02 and 1.60 .. and had the stock valves.

 

If afr copied gm on there fast burn design, why do afr heads out flow gm's fast burns?

 

I'm sure the port velocity has to be determined not only by the port volume (regardless of brand ), but also the amount of air being passed (cfm). A 210cc port of any brand will have lazier flow than a 170 vortec or a 180 AFR.

BUT, if the 210 has great swirl (and I'm sure the Fast Burns do) it will certainly help.

They are a very interesting , and high quality cyl head !

 

The heart shaped "swirl" combustion chamber has been around for 80 years since the 30's. Check Harry Ricardo. They were used on the mid 50's Lincoln engines the hot rodders used in that era. "hot rod Lincoln" engines were the ultimate in the day. I was building these for the old school guys in the 70's. It morphed into the bathtub shaped chamber we are used to seeing to reduce costs. GM started using it again and refined it after the aftermarket adapted it to high performance heads (AFR was making custom "Fast Burn" chambers in the 70's) and was mass producing them in the early 90's. It is the most efficient chamber design but the hemi chamber will make more power especially at really high RPM. Fuel burns faster and more completely increasing power and mileage. That said you can probably give a lot of credit to the EPA and federal government for it's use. The vortec head was designed to deliver the most power and also meet emissions and fuel mileage requirements. It was a truck head introduced in 1996. It is the "hot rod Lincoln" head design of today, cheap and effective. The fast burn is an aluminum, bigger port, bigger valve vortec design. The vortec was designed for lower RPM torque for trucks. The fast burn is designed for a higher rpm performance car engine. Both are best used with flat top pistons if possible. AFR has 1 goal, the most flow through the smallest port to produce the most power, ports and chambers are CNC. As you notice the newer ones flow upward of .600 lift. The vortec design was for maximum efficiency but a more durable smaller lift cam, flow tops out @ sub .500. They are "as cast" and cost of production plays into it as well.

 

Thanks for the explination. So basically they all copy they Lincoln design chamber.

 

Yes, from 50 years ago.

 

GM had a patent on Fast burn .. Not sure if it still exists however it was one head AFR did not claim any modeling or mods to, however AFR and GM where tight , worked together and AFR worked with LT1 , LT4 heads which preceded the Fast burns . Point in fact AFR and GM engineers worked hand in hand in the early days of AFR.

The ideas may be old just like beehive springs are a very old idea from the 1920's but they where put to use by GM. And for a head to flow so little based on some posts , and are able to support 500 plus hp out of the box is sorta hard to swallow when you look at flow charts claiming 232 or whatever was posted. .

Also porting of the head , no combustion chamber work needed , valve sizes can be made bigger but porting is all done behind the valves if you do any at all

 

I would tend to believe this over some car rag over inflated numbers from 1999 hot rod. You are talking about 15+ year old technology in those GM fastburn heads. The above numbers are wonderful for a budget aluminum head. You can even find roller cammed motors making upper 400 hp using GM fast burn heads

The worthless discussion on head port cc and port velocity Anybody that really understands port flow knows that it is the volume of the whole port including the intake manifold. Total runner length is also a factor.

 

So your saying cross sectional are has no part in flow and velocity has not effect on low rpm performance?

 

I am saying that the whole discussion of cross section and head port volume is only part of the equation. Some people are just hung up on worthless discussions about some cross section needs some kind of flow at some low lift The cam lobe spends only an instant of time at lower lifts because of the lobes steep ramps.

A long TBI intake port can have 1000 cc of volume and still limits a 350 ci motor to less than 6000 rpm. A large single plane like a Edelbrock Super Victor Jr. and a 227 cc heads might add up to 1000 cc and the 358 ci race motor can do 8500 rpm

 

Flow link from our own forum to set a base line.

http://forums.corvetteforum.com/c4-t...w-numbers.html

L98 head flows about 194 at 500 .. 2cfm increase in air flow on heads can gain 1 hp.

ZZ4 uses L98 heads at 355hp , make no other change except ADD fast burn heads and gain 30 to 40 hp . ( GM states 30) Many dynos posted 35 and 41 hp increases with just the head swap.

If you do the math the Fast burn is 253 min flow intake at 500. Making Gkulls numbers wrong just based on simple math alone , And making my flow test post with a 6 head comparison more likely to be accurate.

It also supports Summit , GM and other sellers that claim out of the box fast burn supports 500 plus hp.

Now if you clean up the cast flash , increase valve size and port the bowls leaving the combustion chamber alone you should easily get close to 300 cfm on these heads ,, Add Beehive springs , retainers , seats and locks and you can utilize these heads effectively for 600 hp and then some.

Yes some may not care one way or the other but with the fast burn being used on GM crates as a main stay it is information those group of owners who will be happy to have.

 

users.erols.com/srweiss/tablehdc.htm#Chevy this is a site I got from Straub it's a little difficult to interpit but it shows out box fast burns as well as worked on fast burns.