408 dyno test

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92b

92b

FABO Gold Member
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Dynoed this 408 today. Young guy's first build.
440.3 TQ @ 3500
323.1 HP @ 4300
Corrected to J 607 std.
summit 1789 cam
stock heads
performer intake
600 QF slayer w/ 1" 4 hole top open bottom spacer
Stock distributor from salvage yard
Dyno headers 1 5/8 - 1 3/4 x 3" x19" collector
16" vac @ 750 idle only 3 deg. advance. Vac can was dead on arrival.
Time 35 deg. @ 4500
Whistled @ 8.4:1
Going in a 4x4 pick up
16415204753251105646940234962430.jpg
 
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Outstanding! Welcome to another young gun! Pride and respect from an old man. Can't wait for his next build.
 
Those are impressive number for such a mild cam and low compression .
Should even get decent mileage !
 
It'll only get better once you pick up a fully functional distributor and dial the curve in.

Nice little stump puller ya got.
 
I’m surprised the HP peaked at that low of an rpm.
The TQ peak occurred at what I would consider a pretty normal, and sufficiently high rpm, that I would have expected it to end up making peak HP a little higher.

Any idea which stock heads were used?
 
PRH said:
I’m surprised the HP peaked at that low of an rpm.
The TQ peak occurred at what I would consider a pretty normal, and sufficiently high rpm, that I would have expected it to end up making peak HP a little higher.

Any idea which stock heads were used?
Click to expand...
Imo it's timing. Its a big part of that, read about the distributor.

As for the heads..they could flow less than as cast depending on A. Valve job B. The valve job with no blending done @2.02 ...now picture the flow curve...then the low lift cam.
 
OP says timing is 35@4500, shouldn’t be a big problem with that.

Non-working vac advance is a non-issue, as it does nothing at WOT anyway.

My curiosity on the heads was more along the lines of them perhaps being 318 heads.

Nice looking dyno cell btw......:thumbsup:
 
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PRH said:
OP says timing is 35@4500, shouldn’t be a big problem with that.

Non-working vac advance is a non-issue, as it does nothing at WOT anyway.

My curiosity on the heads was more along the lines of them perhaps being 318 heads.
Click to expand...
More power below that is where I went with that.
I do not see any components that make big power in ootb form listed. Performer intake...stock heads with unknown valve job and valve. I assume the cam is .441 aka .420 lift after all the bad angles. Whichever head...
..To me.. in this build..If the .300 lift is in the toilet...that's a lot of it.
Maybe I'm missing that you mean he needs some 302 heads? ;) jk
We're on the same thing..
 
PRH said:
I read the 3deg advance as the ignition timing at idle.
Click to expand...
Yes, 3 degrees ignition lead at idle. It has a lot of mechanical advance. I don't think manifold vac on the advance is right for every application but in this case it might be a good fit. It has a stable vac signal of 16" at 750 and 18" at 1000rpm. I don't like to use manifold vac if it is a week unstable signal at idle. A working vac adv canister should strengthen the idle even more and help part throttle and cruise. As long as it doesn't add too much timing. Too bad it didn't work.
I don't know where the cam is degreed at and neither did the owner. I think he had someone degree it for him but he didn't know what the number was.
I looked when we primed the motor but couldn't find a casting number. On the bottom side maybe?.
My guess is probably just a standard valve job on the heads.
 
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This gives me hope for my 4×4 408 build...
Forged dishes
Around 9.3:1 or so .
Solid cam 224@50 470 lift
Rebuilt 202 valve slightly ported 596 heads..
Dual plane air gap Speedmaster intake..
Holley street demon 750..
New set of cheap headers...
With just a little more of this and a little more of that I'm hoping to hit this kind of torque and Power...
 
With such low compression, more timing everywhere should improve numbers: tq, hp, mileage.
Recently, I worked on a similar 8ish:1 CR engine that had initial timing set at 0*. I advanced the initial to 15* & added another 15*[ at idle ] with vac adv connected to man vacuum.
Idle vacuum, in gear, increased from 13.5 to 16".
 
Go to 4secondsflat.com and get there distributor kit to limit mechanical advance. Bump the timing up to 15*’s (actually run as much as you can) and limit the mechanical to 16/17. (And adjust it again later for more or less) This is a ball park starting point. You’ll really wake up that engine big time!
 
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