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importance of and improving power curve

General engine tech -- Drag Racing to Circle Track

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randy331
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Re: importance of and improving power curve

Post by randy331 » Fri Nov 29, 2019 9:34 am

gmrocket wrote:
Thu Nov 28, 2019 8:13 pm
randy331 wrote:
Thu Nov 28, 2019 12:05 pm
Scan_20191128.jpg
This is our 421 cube pulling truck engine.

Top line is with the higher ratio rockers. 1.8/1.7 vs 1.7/1.6 it had.
Bottom line is the headers out of the pulling truck vs the dyno headers in the other 2 pulls.
The truck headers are fender well 1 3/4 tube x 3.5 collector, dyno headers are 1 3/4 x 1 7/8 step x 3 1/2 inch collector.
I'm happy with the flat power curve and it's hanging on to power past peak nicely, but I'm sure it can be better.
The bigger carb didn't gain anything. I was bettin that would.

So, we need to build our own headers that are closer to the dyno headers.

Does it just need more cam ?
I'm thinking maybe open the intake valve earlier ? Maybe open the ex earlier ?
A little faster lobe too ?
Just more cam ?

This is on a Stuska.


Randy
That thing never gives up..

Are both headers conventional collectors, no merge/pinch?

Since it likes the bigger two step and your gonna build a set anyway, it wouldn't hurt to try a 2" section after the 1 7/8 with some different lengths and a merge/pinch

Did it every dive up top?
Both headers are conventional collectors, no try Y or merge, just a 1 3/4 straight tube that we ran in the truck and the 1 3/4 1 7/8 step dyno headers. I have the truck headers here, I'll measure them. I know they are shorter than the dyno headers. I've measured them both before but don't know what I did with the lengths.

8500 rpm is as high as pulled on the dyno. That was the rpm range I wanted info on from this dyno session.

Randy

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Re: importance of and improving power curve

Post by randy331 » Fri Nov 29, 2019 9:55 am

CGT wrote:
Thu Nov 28, 2019 12:24 pm
Did you try any more or less timing last time you were on? Im just wondering if there couldnt be a little something there running way past peak like that...I hate I missed that dyno session. How long are the headers you tried?
No, this dyno session wasn't intended to be a final tune up for it, it was to look at a few things and get some direction to head. (bigger changes)
It was also less correction factor, air we will never pull the truck in so I see no need to chase final tune up.
That would also require a different ignition than what we run in the truck to be able to add timing up top.
It didn't want more than 31* last time in the rpm we pulled it.

Randy

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Re: importance of and improving power curve

Post by CGT » Fri Nov 29, 2019 11:48 am

Did you see the set of headers Joe has setting there in the dyno control room?....stainless sb2 flange? I'd like to see something like that on your 421..he purchased those at an auction...old nascar truck I believe. Nice looking set of headers.
"Never let your hobby ride you. Work while you work and play while you play"

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Re: importance of and improving power curve

Post by zums » Fri Nov 29, 2019 1:19 pm

Looks like rockers for the win all the way, are you looking to raise the power band rpm or just increase the power in a particular part of the curve , i know you said you had more plenum vac than you wanted, was that at the top of the pull or in the 82-8500 range,
Whats the deal at 7500, any idea?
Tom

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Re: importance of and improving power curve

Post by CGT » Fri Nov 29, 2019 2:03 pm

I was wondering about the 7500 rpm thing also..something going in and out of tune through there???
"Never let your hobby ride you. Work while you work and play while you play"

"Hobbies are a contradiction; they take work and turn it into leisure, and take leisure and turn it into work."

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Re: importance of and improving power curve

Post by randy331 » Fri Nov 29, 2019 8:44 pm

zums wrote:
Fri Nov 29, 2019 1:19 pm
Looks like rockers for the win all the way, are you looking to raise the power band rpm or just increase the power in a particular part of the curve , i know you said you had more plenum vac than you wanted, was that at the top of the pull or in the 82-8500 range,
Whats the deal at 7500, any idea?
Tom
Yes, the rockers were a win for sure, and yes I want to raise the power band rpm, and yes I want to increase power at all rpm . LOL :D
The pulling truck world is different than drag racing .

Not sure on the dip at 7500 rpm. Likely something out of tune there.

The big carb never showed over .9" vacuum even at 8500 rpm, but we didn't find any power there.
I'm re-thinking that.

This dyno session was just for info. It's coming apart for some work to the heads/intake and likely a new cam.

Was going to do a new 4.20 bore x 3.875 stroke tall deck block with 55 mm cam to put this top end on for next year, now my son don't want to pull,... so not sure I'll do that but I will re do some things on this one just to re dyno and learn.

Just figured I'd share the dyno results, and maybe get some ideas .

Randy

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Re: importance of and improving power curve

Post by randy331 » Fri Nov 29, 2019 10:52 pm

CGT wrote:
Fri Nov 29, 2019 11:48 am
Did you see the set of headers Joe has setting there in the dyno control room?....stainless sb2 flange? I'd like to see something like that on your 421..he purchased those at an auction...old nascar truck I believe. Nice looking set of headers.
No doubt we need to look at headers for the 421.

I seen that set he had sittin there your talkin about.

It looks like it likes lift/area and it wants different headers than we had on the truck.

Randy

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