Header/q16 BBC dyno test

[randy331]

This a 468 BBC with 781 heads 12-1 comp, hvh intake with 1150 carb.
Thought this was an interesting comparison of headers.
We started out using the dyno shop 2 3/8 x 4" collector dyno headers so we could get EGts until we knew it was safe then we went to the ones he'll be running in the pulling truck. They are 2 1/4 x 3.5" collector, but aren't near as nice of exit off the head as the dyno headers.

...... dyno chassis
rpm.....hp....hp
5000...514...540
5100...524...556
5200...542...571
5300...560...583
5400...584...595
5500...596...609
5600...603...621
5700...617...628
5800...621...646
5900...646...657
6000...666...674
6100...682...686
6200...688...692
6300...691...699
6400...699...695
6500...706...703
6600...705...710
6700...706...710
6800...707...709
6900...710...710
7000...712...712

As you can see the smaller headers were much better down low with no real sacrifice of top end power.

This was 110 vp race gas vs Q16, jetting is up 4 sizes with Q16

.........110... Q16
rpm.....hp.....hp
5000...519....514
5100...527....524
5200...535....542
5300...554....560
5400...565....584
5500...581....596
5600...596....603
5700...616....617
5800...627....621
5900...640....646
6000...654....666
6100...670....682
6200...684....688
6300...685....691
6400...693....699
6500...696....706
6600...696....705
6700...689....706
6800...693....707
6900...691....710
7000...694....712

The Q16 seemed to help up top more than low rpm. Probably helped burn rate in that ugly 781 casting chamber.
Thought some may be interested in those 2 dyno tests.

Randy

[Carnut1]

Nice power with a set of 781's! Can you tell us how much work they have done to them? Thanks, Charlie

[steve316]

Glad to see you broke 700 hp with it .

[GARY C]

With that compression I wonder if the VP 113 would show a little better?

[sjre]

Excellent, I expected 700 but not at 7000 rpm. I kinda figured heads were were going to peak around 63-6500.

Thanks for the reply.

[FC-Pilot]

Depending on the application, if there is going to be any street time or lower RPM use I tend to error on the smaller side than the bigger side when it comes to Header size. I feel the lower RPM benefit out weighs the top end reward if I happen to go too small. Then again, that is just me. Thanks for posting up your findings.

Paul

[GARY C]

BTW how did the tq curve look? I am guessing it was good also or the HP #'s probably would have suffered.

[Walter R. Malik]

Randy ...
Pretty much what I would have expected to see ... it is all about the particular RPM range this engine will be asked to run.

Other than just jetting increases, I have experienced that using Q16 can be more advantageous with a somewhat different fuel curve than non-oxygenated fuel.

[randy331]

The heads have been ported, and the intake has been matched up and plenum worked on some. The intake still seems small at the runner entries. It could use some more work, but we'll probably look for a different one.

The TQ curve is nice, just short on the amount. 590 was best TQ. 1.26 Lbs/cube ain't stellar for something with vacuum, 12-1 comp, on Q16, but I probably traded some TQ just trying to make it peak higher and keep the valve train intact while it's pulling a sled.

We could have beat on it at the dyno some more and maybe found a little more power, but it's already on Borrowed Time, in fact that's it's name. LOL Mostly used stuff.

But, it's probably 200 HP up on his last years engine, so it should pull ok.

Randy

[GARY C]

The heads have been ported, and the intake has been matched up and plenum worked on some. The intake still seems small at the runner entries. It could use some more work, but we'll probably look for a different one.

The TQ curve is nice, just short on the amount. 590 was best TQ. 1.26 Lbs/cube ain't stellar for something with vacuum, 12-1 comp, on Q16, but I probably traded some TQ just trying to make it peak higher and keep the valve train intact while it's pulling a sled.

We could have beat on it at the dyno some more and maybe found a little more power, but it's already on Borrowed Time, in fact that's it's name. LOL Mostly used stuff.

But, it's probably 200 HP up on his last years engine, so it should pull ok.

Randy

With what your doing it probably needs the tq at a high rpm level to maintain wheel speed. Probably a whole different animal than most are use to.

[CGT]

Boone....dont know if I spelled that correctly....should be thrilled. Im not into pulling trucks but I like his, one of my favorite body styles. He is lucky you took an interest in his goal.

Seeing something as simple as a header swap and Q makes you realize what would be possible with ongoing development with stockish parts. 700hp with those parts is nothing to sneeze at for sure.

I think it will pull awesome on its "borrowed time" . Another good example of what can come from a hobbyists garage. It would be interesting to see if it responded to some more aggresive lobes, but I know rpm and revability is the goal. Good job.

[gnicholson]

2 1/4 headers are still to big in my opinion. 2 1/8 max or 2 by 3.5

[In-Tech]

2 1/4 headers are still to big in my opinion. 2 1/8 max or 2 by 3.5

I would bet a 2" x 8" stepped to 2 1/8" x 10" stepped to 2 1/4" x 12" to a 3" coned merge collector that grows to a 3 1/2" x 10" would work good for this cu.in/hp/rpm. But that's just me.

Good test Randy.

[digger]

What were primary length and collector length of each header tested ?

[mag2555]

I have a concern in that first test that at 5200 rpm the TQ and hp are 30 numbers different, it should much closer like in the second test!