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N/A 331 on the Dyno 515 HP

42K views 34 replies 15 participants last post by  GT350HR 
#1 ·
I'm pleased with the results after dyno testing my new N/A 331.Here's a list of the goodies...

Factory 5.0 .030 Block
Scatt Crank & Rods
Mahle Dome Pistons (11.9 compression)
AFR 205 Heads
Custom Ground SR bump stick 250ish @ .050 .653 lift ground on 108 (Thanks Nat's Racing! )
Joe Sherman ported Victor Jr
750 Mighty Demon



Once on the Stuska dyno we had issues getting the 1 3/4 headers to fit with my AFR heads. even with spacers the headers we're hitting the plugs so we had to settle with 1 5/8 headers which more than likely hold back a few ponnies on my 331 but atleast it would give us a real good idea of what we we're working with..(Nat's Racing builds mostly circle track stuff and most of the guys run Chevy stuff...so we we're limited on header options).Anyways...after the break in we did some baseline pulls trying different timing jetting and some experimenting with spacers we we're very pleased with the results Timing was set at 33 total, 2 inch open spacer worked the best. My Mighty Demon liked lots of jet 80 / 88 (as Demons usually do) We made a best of 515 HP @ 7,243 RPM and 432 Ft Lbs of torque at 5,200. We could have made a bit more if we spun it higher (as it never peaked) but I wanted to be conservative ( It is a stock block). Looking back I would have liked to made another pull and take a round of jets out (as it was a tad rich) But we decided to call it a day...I think if we had 1 3/4 headers it would have gained an honest 10 HP but who knows.... But that's fine cause I'm not racing the dyno anyway.....I'll let my time slips do that for me LOL...I can't wait to get in my ride now I know they're not on this forum but a HUGE thanks to my friend Mike Marsella & Nat Chiavettone over at Nat's Racing in Swansea Massachusetts. Great work! Great people! Below are a few pics and video....Hope you guys enjoy it!




 
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#7 · (Edited)
Nice #'s, surprised you made them with 1 5/8 headers. It must be the head design because the Canfields or TW FAC heads seem to have no problem using 1 3/4 headers. I think the 1 3/4 headers would of let it breathed much better and upped power band. My custom 780cfm came with 74/84 jets, it seems your 331 is fairly rich on the front side. I see your running 2 breathers too.
Having over 500hp on a 331 is nothing to sneeze at. Be proud of your accomplishments. Your 331 is a rare breed...:):) Congrats. Put up some more pics. I know I can appreciate your hard work you've put into this.
 
#8 ·
Jeez Man, big numbers! would be big numbers for a 347!
We;re at 454hp with my new 347 & the builder is somewhat concerned because i'm using a stock Ford block(70;s)
According to him, once you get to lofty numbers close to 500 with a stock block, your on borrowed time.
I;m hoping he;s just a concervative guy
 
#9 · (Edited)
Jay Allen on sbftech.com has proven a stock mexican block is good for 694hp plus and has made that power around 7500rpms and brought it to 8500rpms where he stopped. As long as the valvetrain is dead-on and not running on SADI core material (off the shelf cams), it can be done. I emphasize a solid stable valvetrain/cam and a cam built with custom cam events in mind for the cubic inches.
 
#10 · (Edited)
Demons like bigger jets than Holleys.( I kept the stagger of primary /secondary around the same as BG.) A 750 Demon will flow about 820 cfm. I agree it was a bit fat...Maybe take round of jets out....On my car I have 1 3/4 Hooker Super Comps and it will lean out just by going to a bigger header but I will experiment at the track....Here are some pics for ya...

My 700 HP Expedition Well 200 in the front & 500 in the back

Got the clutch & blow shield on

Great intake / head port alignment

Taking a break for the camera

Almost done!

3 row radiator / Black Magic fan
 
#21 · (Edited)
Haven't posted in 3 years LOL. Here's the latest...Still going with the stock block set up...Only motor changes sense 2012 was a new set of valve springs and T&D shaft rockers with a lot more learning/tuning.... Enjoy!
https://youtu.be/fWA_h9NDKOU

<iframe width="560" height="315" src="https://www.youtube-nocookie.com/embed/fWA_h9NDKOU" frameborder="0" allowfullscreen></iframe>
 
#34 ·
Depends on your definition of long? Still running strong for 5 years...It is more like 540 ish HP now with more tuning and in perfect conditions it has gone a best of 9.80 @138.9 @ 2,700 lbs. I agree that you never know how long it will last, but there are a lot of variables to longevity.
 
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