Tomorrow I begin an intake manifold comparo on my brother's 428. Here are the engine specs:
- 428 + .030", stock rods, forged pistons at about 10:1 CR, CJ pan/windage tray
- C6AE heads, CJ valves and very minor port cleanup
- Crane dual pattern hydraulic cam, 272/284, 216/228 @ .050", .531"/.561"
- FPA headers, Holley 750 vacuum secondaries carb
We got the engine set up and fired on the dyno tonight, so we are ready to start testing tomorrow. This engine has been a project of my brother's for over 10 years, and he's not a big engine guy, so I wanted to check it out a little before we fired it. It is completely rebuilt, and has not run before tonight. First we ran a compression test, and got the following number for cylinders 1-8:
165, 190, 175, 150, 185, 180, 185, 180.
I was a little concerned about the variation, especially on #4 at only 150 psi. Next we ran a leakdown test; again, for cylinders 1 - 8:
7%, 6%, 8%, 40%(!!), 5%, 7%, 5%, 8%.
Cylinder #4 was leaking badly through the exhaust valve, and showed 40% leakdown. I don't know if this was a defective valve job, or a result of the engine sitting for the past 8 years since the valve job was completed. In any case, after discussing it we decided to continue with the testing, and pull the head for a valve cleanup after the dyno testing was completed.
So, that is what I know about the components of this engine and its general condition. We had an oil pressure scare early in the evening, but it turned out to be nothing, and the engine fired right up and seemed to run well on the dyno. Tomorrow we will start testing. We are going to try the following intakes:
Police Interceptor
Stock cast iron Cobra Jet
Edelbrock Streetmaster
Edelbrock F427
Edelbrock Performer RPM
Blue Thunder 428CJ
I'm hoping that we will be done testing the intakes by the end of the day Sunday. All the intakes are in UNPORTED condition; no port matching, plenum work, or anything else has been done to them. Also, we will run all of the intakes with the heat riser blocked, but we will run the PI intake with the heat riser open AND blocked, to see if there is a difference.
If you want to play, rank the intakes for peak HP. We will be running the engine from 2500 to 5500 RPM during the dyno pulls. Here are my guesses from best to worst for peak HP:
Blue Thunder
Performer RPM
Cobra Jet
PI
F427
Streetmaster
I could be way off, but one thing for sure: by the end of this weekend barring unforeseen circumstances, I will KNOW which is best.
What do you guys think??
Jay Brown
1968 Shelby GT 500 Convertible, all aluminum 489" 1030 HP Supercharged FE
1969 XL Convertible, 460
1969 R code Mach 1, 706 HP 511" all aluminum FE, 10.457 @ 127.47, 2005 Drag Week Winner, Naturally Aspirated Big Block
