GMPP #12464298 Flow Numbers

[user-9274568]

Anyone flowed a stock Fast Burn #4298 GM Head? Any help would be appreciated.

Chad

[rmbuilder]

Intake Fast Burn
.100"........ 65
.200"........ 133
.300"....... 183
.400"........ 225
.500"........ 254
.600"........ 244
.700"........ 248

Exhaust Fast Burn
.100"........ N/A
.200"........ 98
.300"....... 129
.400"........ 150
.500"........ 171
.600"........ 179
.700"........ 184

2.00" intake/1.55" exhaust
202 cc intake port
78 cc exhaust port
Bob

[SStrokerAce]

Looks a lot like a stock LT4 casting.

[user-9274568]

0.100 62/55
0.200 136/104
0.300 187/133
0.400 232/158
0.500 266/180
0.600 275/193

So these numbers from Pace GM are inflated BAD..

Thanks for the info

[Ryan Stone]

Not that it makes much difference given the fact that the numbers are not larger across the board (also how close are GM's tolerances for ports?), but... I would think you should post the depression as well such that an accurate comparison could be made. I know 28" seems to be the standard, but it could not hurt to make sure you are both on the same page.

-Ryan

[user-9274568]

Well my favorite GM partsman "loaned" me a #4298 head. I have a friend who thinks he wants a set. I flowed them on my bench on a 4.00 fixture at 28. I used a Ferrea valve with a 30 degree backcut.

.100 67
.200 130
.300 187
.400 238
.500 261
.600 256
.700 250

I never thought I would be able to borrow a head, so I wanted to ask. The GM numbers looked high to me, so I wanted some real info. Thanks for all the help. Maybe the difference mine and rmbuilder was the valve.

[PRH]

Not to bring this back from the dead, but in doing a little digging I was surprised to see there wasn’t an abundance of flow data readily available for the fast burn heads.

These numbers are from what I assume is the earlier version, based on the casting number being lower.
These are for part number 19300955/casting number 12367712, tested in ootb form on a 4.00” bore @28”, no tube on exhaust:

2.00/1.55 GM valves and stock VJ-
Lift——— I/E
.100—— 64/47
.200——132/95
.300——183/125
.400——226/146
.500——256/156
.600——248/161

[1980RS]

Not to bring this back from the dead, but in doing a little digging I was surprised to see there wasn’t an abundance of flow data readily available for the fast burn heads.

These numbers are from what I assume is the earlier version, based on the casting number being lower.
These are for part number 19300955/casting number 12367712, tested in ootb form on a 4.00” bore @28”, no tube on exhaust:

2.00/1.55 GM valves and stock VJ-
Lift——— I/E
.100—— 64/47
.200——132/95
.300——183/125
.400——226/146
.500——256/156
.600——248/161

Sort of look like what my stock Large Port Vortec heads flowed

[dfarr67]

Not to bring this back from the dead, but in doing a little digging I was surprised to see there wasn’t an abundance of flow data readily available for the fast burn heads.

These numbers are from what I assume is the earlier version, based on the casting number being lower.
These are for part number 19300955/casting number 12367712, tested in ootb form on a 4.00” bore @28”, no tube on exhaust:

2.00/1.55 GM valves and stock VJ-
Lift——— I/E
.100—— 64/47
.200——132/95
.300——183/125
.400——226/146
.500——256/156
.600——248/161

A few years ago I was building a 385 for the truck and ended up going with AFR mainly because they were assembled and I banked on their quality as a bolt on piece- for a vortec application so there was only a few choices between E-tec 170/200 or GM Fastburn. Information and feedback was very slim on the Fastburns including exhaust port/header interface for GM TBI application headers and some weird intake cc size- I see not much has changed- is the market more for rules/competition vs public consumption....I couldn't pony up for an unknown. The E-tecs were supposed to be good after some work put into them- but why bother.

[PRH]

The exhaust ports on the fast burn heads I had here really didn’t make any sense to me.
They’re pretty huge, and they’re raised a bit....... and they don’t flow that great.

The pattern left from the header gaskets that had been run on that set of heads appeared as though the top of the header opening was well below the top of the port exit in the head.

It would seem to make more sense to have the port exit size/shape in the head be a good match for what would be a typical sized header to get used with the heads.
Since these heads come on crate engines that make around 400hp, you’d expect that most of those things will get put in vehicles running 1-5/8 or 1-3/4 headers....... which I doubt have an opening big enough to properly mate with the exhaust port size/shape of the FB heads.

The stock iron vortec heads have a nice small exhaust port opening.
With a little reworking of it, and the 1.55 valve...... I’m sure it could easily match or exceed the flow of the FB exhaust port.
In my mind, they should have used a modified exhaust port from a stock vortec head, one that retained the small sized port exit, as the basis for the FB exhaust port.

[CGT]

The exhaust ports on the fast burn heads I had here really didn’t make any sense to me.
They’re pretty huge, and they’re raised a bit....... and they don’t flow that great.

The pattern left from the header gaskets that had been run on that set of heads appeared as though the top of the header opening was well below the top of the port exit in the head.

It would seem to make more sense to have the port exit size/shape in the head be a good match for what would be a typical sized header to get used with the heads.
Since these heads come on crate engines that make around 400hp, you’d expect that most of those things will get put in vehicles running 1-5/8 or 1-3/4 headers....... which I doubt have an opening big enough to properly mate with the exhaust port size/shape of the FB heads.

The stock iron vortec heads have a nice small exhaust port opening.
With a little reworking of it, and the 1.55 valve...... I’m sure it could easily match or exceed the flow of the FB exhaust port.
In my mind, they should have used a modified exhaust port from a stock vortec head, one that retained the small sized port exit, as the basis for the FB exhaust port.

Yes, the exhaust port makes no sense. I fought real hard over the summer to get headers to fit my fastburns in my personal car. Great heads, but they have their downsides...like price, exhaust port size and bolt hole location, valve seats etc.

[dfarr67]

Yes, the exhaust port makes no sense. I fought real hard over the summer to get headers to fit my fastburns in my personal car. Great heads, but they have their downsides...like price, exhaust port size and bolt hole location, valve seats etc.
Top

That killed it for me- exhaust headers are hard enough to fit for long term leak free function. There were at least two generations of these heads as well.

[PRH]

There are probably other examples of this situation occurring, but I can’t think of any off the top of my head........
Back when the Ford Motorsport J302 heads came out, they had a much different exhaust port exit than any std Ford heads. It was a wide vertical “D”.
Hooker came out with a specific header to use with those heads on the small Windsor block in a Fox body.
They were 1-3/4 x 3, and they matched up with the heads pretty well.