Comments on these chambers' burn pattern?

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BradH
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Comments on these chambers' burn pattern?

Post by BradH »

Anyone have thoughts or comments on the burn pattern of these chambers? I don't really know enough to say anything one way or the other...

FWIW, this is the result of 25+ pulls on the dyno using a 50/50 blend of Sunoco 110 leaded and 93 E10 pump. Thanks - Brad
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Burn pattern.jpg
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Re: Comments on these chambers' burn pattern?

Post by JoePorting »

What casting is that? I don't recognize it. The exhaust port shows a lot of pitting. We're you running a lean mixture or lots of nitrous?

I thought I was the only one who made SBC Chambers that big. lol
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BradH
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Re: Comments on these chambers' burn pattern?

Post by BradH »

It's the poor man's approach to building a 15*-head stroker small block... with an absurdly high bob weight... a stock 3.75"-stroke BB Mopar.

Edelbrock Victors with the chambers CNC'd by a small Mopar-oriented shop. CR is a hair under 11.5 with flat-top 4.380" pistons and .040" quench.

No N2O, but most of the carbs tested were lean. It's not pitting, but the carbon buildup looks kinda that way.
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Re: Comments on these chambers' burn pattern?

Post by cgarb »

Poor man!?! You did say Mopar correct?
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Re: Comments on these chambers' burn pattern?

Post by cgarb »

OK, nevermind...now I know why your poor...lol.
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Re: Comments on these chambers' burn pattern?

Post by 1972ho »

Wouldn’t it be better to show the tops of the pistons.
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Re: Comments on these chambers' burn pattern?

Post by mag2555 »

Please post up a picture of the plugs.
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Re: Comments on these chambers' burn pattern?

Post by BradH »

1972ho wrote: Tue Apr 09, 2019 9:20 pm Wouldn’t it be better to show the tops of the pistons.
"Better"? Not necessarily, since I believe the chambers may indicate things that aren't obvious w/ seeing only the tops of the pistons. I'll get pics of the corresponding pistons when I get a chance.
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Re: Comments on these chambers' burn pattern?

Post by BradH »

mag2555 wrote: Wed Apr 10, 2019 6:52 am Please post up a picture of the plugs.
I'll get pics of the plugs when I get pics of the pistons.
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Re: Comments on these chambers' burn pattern?

Post by Newold1 »

Curious what leakdowns would measure on the cylinders if it was done before teardown?

What were air/fuels measured on dyno pulls?

Were any jet changes made between pulls?

As others here asked, what do piston tops and plugs look like?
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Re: Comments on these chambers' burn pattern?

Post by Krooser »

cgarb wrote: Tue Apr 09, 2019 9:08 pm OK, nevermind...now I know why your poor...lol.
When a 800hp fake Chevy dirt motor sells for less than $30,000 you will have a point.
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Re: Comments on these chambers' burn pattern?

Post by Powertrip »

What is the quench clearance?
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Re: Comments on these chambers' burn pattern?

Post by BradH »

Piston tops for 1 & 3 (same as chambers shown) and 8 & 6
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Piston tops 1_3.jpg
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Piston tops 8_6.jpg
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Re: Comments on these chambers' burn pattern?

Post by BradH »

Plugs for 1/3/5/7 and 8/6/4/2
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Plugs 1-3-5-7.jpg
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Plugs 8-6-4-2.jpg
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Re: Comments on these chambers' burn pattern?

Post by BradH »

FWIW, we ran timing at 34 / 36 / 38; 34 wasn't that good, 36 was better, 38 was a tad better than 36 at peak HP. I was thinking it was going to "like" 35-ish like the old heads, but the additional timing made a significant improvement.

I brought a few 4150 carbs, but they weren't dialed in well at the time (new stuff I hadn't tested before). We spent some time working with two in particular (a 1.50" v downleg and a 1.58" v annular), but the AFRs were still in the high 13s. We then tested a smaller shop carb (1.40"? v downleg) that was in the high 12s to low 13s IIRC (don't have the printouts in front of me) that made as much power as the bigger carbs that needed additional tuning time.

Oh, no before or after leakdown tests. This was a re-hone & re-ring job on the shortblock, but with new heads, cam & intake.
Last edited by BradH on Thu Apr 11, 2019 9:59 pm, edited 1 time in total.
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