[NHRASuperStock455SD]

Carb:

We are over 700HP with the Q-jets and cast iron heads. I would do a Q-jet as they out pull a Holley evertime, easier to tune at the track.

Dyno:

Could you publish the page that has the input numbers for dyno conditions? Did they match the dyno room? I noticed you didnt have the SCFM numbers so you didnt run the outside air through the turbines with the hat on the carb, but rather the air in the dyno room?

Correction factor numbers are derived from those inputs, and are very critical for getting the right info.

I always like to see when the engine stops gaining cfm pulling through the carb. It indicates issues showing up.

Engine:

Are you using like 1 3/4 headers on this big motor? 4300 peak torque indicates a very small header. 455's need at very least 2 inch and most of the time 2 1/4. A very fast Pontiac you all know runs even bigger! He woops on Chevys, Fords and Mopars.

I ran 1 3/4 on a dyno once and got 4300 peak torque and 5300 peak HP, put the bigger headers on and got 4700 and 6200. Pontiac guys kill me when they use 1 3/4 and then want to know why their HP peaks are low. They also want to know why their exhaust gaskets blow out all the time. (probably taking 30HP to push the exhaust gases out)

Another thing I would look at in this motor is valve spring, as in, you might not have enough.

I just saw a dyno sheet on a big Pontiac motor after huge, I mean huge headers, man what a difference. My 455SD picked up 3 tenths when going from a 2 inch to a 2 1/4. Thinking about going to 2 3/8.

Lynn

[formulabird428]

the Kauffman's suggested a 1 3/4 header, because it works on their heads quite well. However, I had them test a set of 2" primaries, and the dyno results are IDENTICAL. I'm talking, within 2 hp all across. Same thing with torque, about +/- 5hp across all rpm's. Max hp/torque occurred at same values too...

does that sound strange?

[tom s]

Lynn,its a 428.I just had a 428 street motor on the dyno and it made 475 HP too 6200 with a factory dual plane intake and a 700 AFB and 1 5/8 headers.Way smaller cam and less CR and 260CFM heads.Lot less HP also.Tom

[jm455ho]

Originally Posted by formulabird428

the Kauffman's suggested a 1 3/4 header, because it works on their heads quite well. However, I had them test a set of 2" primaries, and the dyno results are IDENTICAL. I'm talking, within 2 hp all across. Same thing with torque, about +/- 5hp across all rpm's. Max hp/torque occurred at same values too...

does that sound strange?

We tried 1 3/4 and 1 7/8 headers on our 455 with KRE290 heads and found a significant increase in the midrange with the bigger headers. Up to 31 lbft torque increase at 4600 rpm. #41 is 1 3/4 header and #56 is 1 7/8 header in the attached graph.

[formulabird428]

Originally Posted by jm455ho

We tried 1 3/4 and 1 7/8 headers on our 455 with KRE290 heads and found a significant increase in the midrange with the bigger headers. Up to 31 lbft torque increase at 4600 rpm. #41 is 1 3/4 header and #56 is 1 7/8 header in the attached graph.

wow. very interesting. how could my combo be so similar? maybe the combo is at the point...where the carb/intake/camshaft is such a limiting factor...header size doesn't come into play yet?

that would be my only guess.