Santa came early

I was chewing the fat with a co-worker last week, talking about winter projects (and possibly retirement for him). I mentioned the possibility of going with a single plane intake on the 396 for next season, he said something about having one in his garage that he had taken off of his boat.

He brought it in the next day, it's a Holley Strip Dominator 300-4 http://www.holley.com/300-4.asp, BBC oval port. He wasn't particularly attached to it, so now it's in the trunk of the Camaro! His boat was a "mud-sucker", but the coolant passages look as good as most antifreeze used intakes I've seen.

So, come next April, we'll see how a single plane does on the baby Rat. The cam is supposed to be good for 2400-6800 RPMs, but I shifted at 6200 last season because it just didn't keep pulling after that. Could either be due to the intake itself, or the carb not being big enough. Whichever it was, this should change things.

 

gonna want a lot lot lot more rear gear ratio.
What rpm and MPH are ya trapping at now? tire diameter?

 

I'm running a 27" tire. It traps at a little over 5800 RPMs, 100 mph, at altitude. At sea level, it's a lot higher, but I didn't run it all out the last time I was down low.

 

According to the math either your tire is effectively a lot shorter ,the tach is pooched, or the trans torque converter is slipping a lot (more than 10%)

I'm thinking you should change to a 4.56:1 rear gear. Your converter will couple a lot better on the top end and the engine will stay in the single plane manifold's best power band for the whole track.
I measure the effective diameter of my slicks by measureing from the ground to the center of the axle/center cap.
usually 1" less radius which makes the effective diameter 2" shorter. so a "27" tire is only effectively 25" tall.
whats your 60 times? 8th mile et and MPH?

But even accounting for this, the math indicates more than 10% slippage. Or the tach is wrong.

Don't be suprised, I found my tach (A Sun Pro knock off) was about 700rpm off at high rpm. Had to replace it. Auto Guage, much better. Was over reving the motor.

 

The converter probably is slipping. 2 years ago at sea level, when still running the 270 hydraulic cam, it was running out of r's at about 1200'. I'm sure a better converter would reduce that slippage.

The rears are 10.50-27x15 Hoosier Quicktime Pro DOTs, currently with tubes run at 19 psi. 60's are 1.85's at altitude, 1.75's at sea level. 1/8th miles are 8.8's @ 80 mph at altitude (Jr dragsters outrun me - don't have good data at sea level with current setup).

Don't forget this is a 3900 lb car with the aerodynamics of a 4x8 sheet of plywood. . .

 

Went out and actually got the logbook. 1/8th's are actually 8.5's @ 80 mph at altitude. The rest is close enough.