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Author Topic: 408 Stroker for street Stage 1 estimate and Stage 2 dyno result!!  (Read 2025 times)
Junior Member
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Posts: 75

« on: July 30, 2017, 01:42:53 AM »

Hi to everybody from Vato's Race Engine!

It's been a while since i posted anything,been superbusy at work,and after work doing engines for other's,porting head's and helping friend's at the track(Pro Stock and Street cars).And setting up my own flow bench (finally) with air speed sensor's has needed some renovation time at home.

This is one of the engines that I planned for customer,he had 360 in his '70 Duster,and he insisted to use Hyd Roller cam and wanted good torq street motor with more than 420hp.(There's another Duster with 400-420 in his hometown and you get the picture icon_smile_big)
I told him that if I build it,and if i can port the head's and intake,it will make 500hp.He wanted to drive it with like this and gather some money for port job.

Car has 3.55 gear's and 2500stall so this build is truly a street engine.
After engine mod's he swapped Hughes 3500stall for "new" engine

So build stage 1 was:

-360 block with .030" bore
-Scat rotating assy
-9.72:1 Compression
-Comp Cams Mutha Thumbr Hyd.Roller 235/249@.050 and .557/.542 107lsa
-Cometic Head gasket
-Edelbrock RPM heads
-Mancini 1.6 roller rockers
-TTI Stainless headers,stepped
-650 Holly db
-Mopar Single plane intake

My estimate was it woud produce 430-440hp@4-4500rpm range and torq 440-460@35-4000range.
Low peak rpm is based from 170cc head's that are really small for 408 with this kind of cam.

I did not have the opprtunity to dyno it,customer performed build and just drove it.Shame....
Estimate was based on Pro Engine Analyzer with 2% error calibration and new combo fell right in the 2% when compared to actual dyno number.It is accurate but you reallyreallyreally need ti make sure that all specs are dead accurate.

Stage 2 with engine dyno result's:

Ported head's with following mod's
-Modified chamber's edges and gave it notch beneath intake valve
-Removed head bolt bulge
-Ported entire intake and exhaust runner's,port average CA(cross sectional area) was calculated as close to get Hp in upper RPM as needed.I knew that with this cam,i needed 57-6000Peak Rpm to break 500hp mark.
-Opened every intake port opening to SAME size,there were REALLY big toleranses from factory,and wall thickness on pushrod varies a lot!This was tricky,wall thickness varied from 0,077" to 0.109" and allthough on some port's there was still lot more thickness,i had to play with thinnest one and i really took it to the limit to a measured port window size 1.00"x2.25" total 2.25" window size.

-Ports went from 170cc to 185cc,and yes,i did ported and measured every runner to exatly same size;)

-Stock runner flowed 256cfm@ .600,after my work they gave 285cfm @ .600 lift.It was pretty good numbers from 185cc runner,and mainly the increase % from orginal was what i really watch,for the peak lift from the cam.

-Chamber's went from 64cc to 70cc,that was planned, since on those head's,quench area from stock is terrible 0.055" allready,so as i milled head's 0.038" and used Cometic that had 0.27" gave me quench 0.044"

-New Compression 10.47:1 and measured 178psi

Did some mod's on intake also and short block build.
When engine was brought to me,i measured rotating torg with torgue wrench on crank.I do this to all engines i build.After 2year's of street driving,it still needed 34ft lbs to turn.After my assembly,it needed 22ft lbs with new rings and bearings.

Dyno time!

With single plane intake,750carb and some spacer swapping(4-hole,open,4-hole tapered) it made:
@2500rpm  211hp and 448ftlbs
Peak torg 508ftlbs @4500-4700rm
Peak Horsepower 507hp @ 5700rpm
And the nice part:
From 2500 to 6000rpm,torg does not fall under 444ft lbs!!!

Then i threw a curve bal to the dyno and for the owner...i swapped Edelbrock RPM AirGap from the box,no mod's and runner's that were smaller than on head's.

Power 496hp@5400rpm and 525ftlbs@4300rpm!!

at 3600rpm torg difference was 27ftlbs and @4000 it was 31ftlbs!!

Average 2750-5750rpm was
-single plane 396hp/481lbs
-Dual plane 403hp/493lbs

Yes he did buy that RPM from me after dyno icon_smile_big

I will try to post some pictures from head's and build up,also from dyno sheet's from both intake's and flow chart from head's

Sorry to make this so long,but this turned to really good engine and i was really pleased and happy how it performed

As i heard from owner,his A-body is now really handfull to drive and burnout's are a walk in the park cheers

I hope that this was not to hard to read.

Please feel free to comment!

Vato's Race Engine

Junior Member
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Posts: 75

« Reply #1 on: August 04, 2017, 12:33:47 PM »

Here are some photos and dyno sheet for both intakes
Torgue is in Nm,so you need to dividet 1.35 to get ftlbs

Best SinglePlane,Mopar race manifold

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Best Dual Plane,Edelbrock Rpm Air Gap,OTB

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Junior Member
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Posts: 75

« Reply #2 on: August 04, 2017, 12:41:21 PM »

Solid line is Dual plane,and the reason torque is behind single plane at 2500-2800 is that it was really hard to get O2 sensors to calm down right vs left when dyno was loaded.On single plane,they were in line better right from beginning.But at 2800rpm,dualplane took of and held lead all the way to 5000
That's torgue differen't that you can feel!

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And yes,it was run with 3" exhaust,and 18" mufflers.

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Flow Chart Stock(vakio) vs Ported

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