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Discussion Starter · #1 ·
One of my bracket race buddies took his engine to the dyno last week. Like most of us, was hoping for bigger numbers than he ended up with. Heres what he has:
Dart 9.5 deck SBC block
4.25 stroke crank
4.125 bore
6.300 rod
15.7 to 1 compression
Brodix 18* heads, 386-280 @.800 with 1.6 rockers
Brodix HV1000 intake, 1/2 spacers pinned on, gasket matched, light plenum work, 1 inch spacer.
Moroso vac pump
Cam is 274/286 @.050 108 lobe sep.
The engine peaked @6300 making 712 hp, peak torque was 670 at 5000 rpm. The engine was dynoed on alchohol.

What you guys think?
 

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Discussion Starter · #3 ·
A little weak is what Im thinking also.
The tune up isnt known?
The shop didnt have any headers with any egt's or wide band O2 sensors that fit that cylinder head, only SB2 stuff.
It made its best power with 27 degrees timing in it.
I would like to see a larger intake plenum, and a larger camshaft myself.
 

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The heads are weak, the intake is weak, and he's not filling the cylinders with 4.250 stroke.... just too much piston speed, and the cam is a little small....

Is there a reason for the alky?

It really just depends on his goals..... it should run fast, and I bet it makes power over a very broad range.... gear it, converter it right.....
 

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Discussion Starter · #5 ·
The alky runs cooler in the summer months, cheaper too.
Yes the toque curve is pretty broad, thats pretty much what he was looking for.
The car is a 78 Camaro, 2977 lbs without driver.
5.43 gear
32 inch tire
The car ran consistant 6.16's(1/8th) with the 427 that let go.
He was wanting to run in the 5.80s.
I dont think he will make it there though.

What manifold would you put on it Chris?
 

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Thats a big stroke and small cam, and intake combo, plus that low flow for that many cubes its a lot for a 383 but not a big small block, you dont have near enough head on that kind of stroke, the piston moves to fast to fill the cylinder with a limited top end. Should pull stumps and be reliable if he does not try to over rev it that piston speed will kill it.
 

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Discussion Starter · #8 ·
I could be mistaking on the Brodix intake part number. No they are not the 18x heads.
 

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That stroke is the killer, as the valve opens the piston speeds its way down the cylinder faster than it can fill, Valve events with a restrictive intake and head will not help it enough, A larger runner intake may help it a lot that intake cant flow what the heads do, I bet you have a lot of vacuum in the intake runners at WOT
 

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Discussion Starter · #13 ·
Im thinking the Brodix part number is HV1813 for the intake manifold.
The camshaft is going to be changed, my buddy finally agrees his is too small.
Im thinking something like 283-296 @.050 112 lobe seperation.
Can someone do a "resticted" type intake lobe that could help with the cylinder filling?

Also Chevy guys? What intake manifold would you use on this combination? Maybe the Edelbrock Glidden?

The cylinder heads are what they are, cant change them now, like was mentioned, good numbers for a 383 inch engine.

Thanks for everyones input.
 

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I am not sure how you tune a methanol motor without EGT. Plugs don't color enough even if you run it so fat it makes you cry 3 blocks away.
The other thing is did they monitor intake air flow? If they did VE (Volumetric Efficiency) can be calulated and would should low numbers like under 90% confirming what the guys are saying about the cylinders not filling.
 

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The alky runs cooler in the summer months, cheaper too.
Yes the toque curve is pretty broad, thats pretty much what he was looking for.
The car is a 78 Camaro, 2977 lbs without driver.
5.43 gear
32 inch tire
The car ran consistant 6.16's(1/8th) with the 427 that let go.
He was wanting to run in the 5.80s.
I dont think he will make it there though.

What manifold would you put on it Chris?
I'd put as much cross section in the manifold as I could obtain in the casting..... and then some.

Realistically, you have a big block with small block heads on it.
 
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