Tax return money bought a new set of GM Fastburns and a Vortec (made for Scoggin-Dickey) TPI intake this week (all purchased from Sallee Chevrolet in Oregon).

Today, I took them to Total Engine Airflow (Bowling Green, KY. 270-782-6397) to be flow tested on their Flo-Pro bench (28" water).

The heads were straight out of the box. NOTHING done to them including leaving in the casting flash and other small bits that I WILL clean up before running them.

Intake port
.100 lift---63.1 cfm
.200---133.9
.300---173.3
.400---209.3
.500---237.3
.600---257.0

Exhaust port
.100 lift---42.2 cfm
.200---88.8
.300---128.9
.400---159.9
.500---180.3
.600---197.0

I then tested the intake by bolting it to the Fast Burn heads and repeating the test.

Intake port (with intake attached)
.100 lift---63.1
.200---128.1
.300---158.4
.400---183.9
.500---202.5
.600---215.3

I measured the intake's port opening (at the plenum runner side) at 1.58" to 1.63" using dial calipers. Plenty of meat to open up to 1-3/4" or larger.

The above numbers compare VERY favorably (better in most cases) to those posted for Pre-production Fast Burns that used 2.02 intake and 1.60 exhaust valves.

Production heads now use 2.00 intake and 1.56 exhaust valves.

I was going to "clean up" the ports (blend the valve pocket area, etc), but with those kind of numbers, I may just leave them alone.

Comments?

jms

 

I have no comments, other than that I can't wait to get my 400 going, I have a set of these heads to go on it. GM and others have repeatedly claimed that to touch these heads is to reduce their airflow. The few times i've seen magazines use these heads and claimed to have ported them, the rresults have been less than impressive.

Did you by chance CC the chambers? They are spec'd as 62cc, wondering how close they actually are....

 

Haven't cc'd them. They just came in yesterday and I wanted to flow them first chance (which was this afternoon) after getting off work this morning.

There are several 'flaws' (casting flash, etc.) that will have to be cleaned up. I just pulled out (from an intake runner) a piece of aluminum that was about 1/4" in size.

jms

 

This is great information, because there seems to be some serious folklore going around about the differences between different castings. Nobody ever had real numbers though.

But, now we do.

Stock runner diameter is 1.47"
The ACCEL baseplate runner diameter is 1.77"

Everybody says that the Vortec intake is a modified edelbrock casting, and there's been debate about how good the edelbrock casting is. If you measured 1.58-1.63" diameter, I think it finally gives us some real numbers to play with.

Apparently the size of the vortec intake is right smack between stock and the Accel. Now if we can just find somebody with a stock edelbrock base, we can put the rest of the rumors to bed.

BTW, did you take any flow measurements of just the base without the heads? I've got flow numbers for the stock base and the accel base, and I'd love to see how they compare to the vortec base.

 

I did not flow the base by itself.

The Fastburn heads have a slightly larger opening than the Fel-Pro # 1255 intake (to head) gaskets.

In turn, the Fel-Pro #1255 gaskets have a slightly larger opening than the intake's openings, therefore I figured the heads presented no restriction to the flow numbers on the intake.

At the intake's opening (plenum runner side), the round opening is about 1/16" to 1/8" smaller than the port seems to be, just 1/4" to 3/8" down the runners length.

In other words, the opening gets larger, a little way into the intake, following an initial lip at the gasket surface.

Don't hold me to these numbers (I don't have the tools to measure down inside), but I feel 1-3/4" port runner size is very easily achievable by just gasket matching the plenum side runner opening. Not to mention porting farther down throughout the runner.

On the other hand, I can't recall the injector boss size on my stock TPI intake. The Vortec TPI injector boss size is 'rather healthy' and as cast may present some restriction.

I have a crude, cheap, digital camera (that connects to my home computer) that I could take some pictures with and e-mail to someone, to post for me here if needed. My connection is slow.

jms

 

I'd be willing to post them if you wanted to email me