427 Dyno Results

First, a note of thanks to my pals Steve R and Kevin R, who spent most of the day at my shop today helping me out with the intake changing duties. Thanks guys!

In our last exciting episode (), I discovered that the Holley 1000 cfm 4150HP carburetor was far from 1000 cfm, and the addition of my Holley 1150 Dominator carb to the Victor intake on my 427 yielded a significant power increase. This morning I ran off to get more race gas (I'm running 110 octane leaded race fuel for all my tests), and also stopped at a friend's house to get his 1050 cfm three barrel Holley. On the intakes with the 4150 carb flange, I was torn between testing the three barrel and the Dominator on an adapter, so I had decided to try them both and see what happened.

Back at the shop, I tweaked the jets and lashed the valves on the engine with the Dominator carb still installed, and made a couple more pulls. The engine just touched 600 HP with this combination, Here's a graph comparing the Victor with the two carbs:



At this point I felt pretty confident that the additional airflow of the Dominator was the reason for the improvement, so it stood to reason that the Holley three barrel would also show an improvement over the 1000 cfm 4150HP Holley. I decided to put the three barrel on the Victor and test that next. This entailed installing my adapter back on the Victor to convert it to the 4150 pattern, and then installing the three barrel.

This morning I read some of the comments from my previous post stating that the mismatch between my adapter and the Dominator pattern on the Victor was the reason for the poor performance of the 4150 carb. I'm not buying one bit of that explanation, because I already tested for that on my 500HP stroker 390 engine. I do in fact have four Victors at my place, two with Dominator flanges and two with 4150 flanges. Testing on the other engine yielded no difference between the two port matched Victors, one Dominator flange and one 4150 flange, using the same 850 cfm Holley carb. Also, using the logic that the flange mismatch was the problem, the Holley 3 barrel carb would not show an improvement over the 1000 cfm 4150 carb. The actual results, however, showed that the 3 barrel carb was nearly as good as the Dominator:



The three barrel I borrowed was a pretty used up carb, and I thought it could be improved with some work to come even closer to the performance of the Dominator, but in the end I succumbed to the logic that three barrels just aren't available these days, so despite the performance of the three barrel I decided to proceed next with the Dominator on the 4150 adapter.

Next we swapped the Performer RPM intake back onto the engine, and installed the Dominator adapter and the Dominator carb. Unfortunately, this combination didn't work out so well. At the top end of the pull, this combination resulted in rough, uneven running of the engine. Where I expected to see this combination pulling away, it basically fell flat, barely outperforming the 1000 cfm 4150HP:



We ran this test three times with the same results in all cases. All the tune parameters, such as A/F, looked pretty good with this combination, but it just went really weird at the top end. Basically, it appeared to us that there was some kind of issue caused by the large adapter spacer, like an intake tract pulsing or resonance, that killed the top end power of this combination.

The conclusion that I drew after this was that I would probably be best off testing the dual plane intakes with the 1000 cfm Holley carb, and using the Dominator on the open plenum single plane intakes. If I had been really thinking this afternoon, I would have reconsidered the use of the three barrel on the Performer RPM intake. Hindsight being 20/20, I could have used to three barrel to prove or disprove the theory that the engine needed more air even with the Performer RPM. In fact, I may actually reinstall the Performer RPM tomorrow to test that; I'd really like to know the results of that test. However, today I just decided to proceed to the next manifold, and use the 1000 cfm Holley for all the dual plane intakes.

My friend Kevin had brought over his 427 MR dual plane intake, so we bolted that one on next, along with the 1000 cfm Holley. This manifold had looked pretty good on both the 425HP 428CJ, and my 500 HP 390 stroker, being down only 15 HP or so from the Performer RPM. On this engine, though, it was another story altogether. Much to my surprise, this manifold was down a LOT from the other intakes, peaking at only 480 HP! It also showed very poor upper RPM range stability, surging and pulsing, as can be seen in the dyno plot:



Again this evening, after the testing was completed, some second thoughts about this test have crept into my mind. I remembered that although this particular intake is a 427MR intake, it has been port matched to low riser ports. I'm using Mr. Gasket 202A intake gaskets on this engine, which match the heads. I'm wondering if the port openings of this intake are extending down below the bottom of the gasket? This would expose the bottom of the ports to the valley area of the engine, creating a big vacuum leak. We noticed during the warm-up with this engine that vacuum was lower than it had been with the other intakes. I have a call in to my friend Kevin to have him measure the port openings, so we can determine if this is indeed the case. So, at this time the results for this manifold should be considered preliminary only.

Finally we decided to install Joe Craine's Victor intake for the last testing of the day. Joe was kind enough to lend me this intake some time ago; it has been ported to flow nearly the same in all runners, at around 450 cfm. This is a 4150 intake, not a Dominator intake, so if I wanted to run the Dominator carb on this intake I would have to use the 4150 to Dominator adapter.

After bolting on the intake with the 1000 cfm Holley, we ran the test. Here are the results, graphed together with my port matched Victor using the same carb:



Joe's intake is up about 10HP pretty much across the board as compared to my intake. This is a very similar result to what I saw on the previous two engines when comparing Joe's ported PI intake with my unported PI intake. In those cases we saw an across the RPM range improvement of 5-15 HP.

(By the way, all the intakes I will be running on this engine are at least port matched to the MR ports, unless like the previous 427MR intake they are already larger than the head ports).

Next we pulled off the 1000 cfm Holley and bolted on the adapter and the Dominator. Man, what a goofy looking setup this is:



I had high hopes that we would see the same kind of improvement with this setup as I saw with the Dominator on my Victor intake. In fact, based on the previous test there was no reason why we wouldn't see 610 HP with Joe's intake. Unfortunately, it didn't work out that way; here is a dyno plot of Joe's intake with both the 1000 cfm carb and the Dominator carb:



The Dominator did not offer any substantial improvement. The only reasonable conclusion, I think, is that the manifold does not like the goofy adapter.

Tomorrow I think I will try bolting the 1050 three barrel onto Joe's intake, and see what happens. If I get back to 590-600 HP, then I think its safe to say that the adapter is the source of the problem. Which means that I can't run the Dominator carb on most of the intakes, and I may be forced to go back to the idea of using the three barrel to avoid limiting the performance of the engine with the different intakes.

I think its safe to say that there's a lot going on here, and I don't have a clear path to testing the intakes on this engine yet. More R&D coming tomorrow...

PS - Barry R! I need more 202A Gaskets! Oh, wait, I already called you about that...





Jay Brown
1968 Shelby GT 500 Convertible, 492" 667 HP FE
1969 R code Mach 1, 490" supercharged FE, 9.35 @ 151.20, 2007 Drag Week Runner Up, Power Adder Big Block
2005 Ford GT, 2006 Drag Week Winner, 12.0 Daily Driver
1969 Ford Galaxie XL, 460 (Ho Hum....)
1964 Ford Galaxie 500, 510" SOHC