So I knew the car felt strong during preliminary remote tuning drives, so I thought that dyno day would bring a good number. A 3.90 gear does hurt dyno numbers, but makes these cars much more fun to drive. I was shooting for 600 wheel, which would have been epic for a 403, but I thought we had a chance. Nick the owner of the car was hoping for 575-580. I used a local dyno for both final WOT AFR tuning and numbers. The shop owner called me and told me that I just set a new NA record in his shop. He builds Vettes…lots of vettes for many years. He’s built over a dozen Z06 cars and he wants to know what I did to this car to out perform any 427 he ever touched. Car did 662/579 on his DynoCom. I’m friends with the guy, but I told him that there’s no way that this 403 did those numbers. So I found another local shop with a Dynojet to compare this to. At the end of the deal I pretty much hit what I thought it would do…593/525. I’m not interested in hub dyno inflated numbers or any other inflated dyno numbers…looking for legit numbers for real data. This won’t impress some folks and I’m ok with that.
This is on pump 93 gas and mild timing. With this cars 12:1 compression, on E85 this thing would easily hit 615-620. It’s a hoss. The real winner here is the torque however. 525 ft lbs is built 427 numbers. The PDXS intake is a long runner unit that helps push torque, and the combination is set up to compliment it.

 

Dyno pull for your viewing pleasure…

 

This ought to be up for nicest grand sport in the country holy cow Scott!!

Incredible results and top shelf work. Thanks for sharing!

Who ground the cam for you? Mind sharing what lobes or is it secret squirrel stuff?

I bet a different intake would offer 600whp but average power would likely be down. The torque curve is faaaaat.

I didn’t need to see the Dynocom reading 10% high 😂😂 I need to get mine on a Dynojet and get some track numbers haha.

 

Great job Scott,well thought out
my Tuner told me the design LS3 XS intake was best intake he’s tried ,(for under the hood )
on a ls3 style engine
and according to the Eric Weingartner the AFR ls3 mongoose are the best flowing ls3 style heads out there

 

Thanks Spanks. Cam is a Comp. I worked with Tony on the cam. Lift is 675/672. Ground on a 114+3. Nothing special. They did put their polishing option on it, so it was beautiful.
The funny thing about talking LS3 intakes is that the GM unit is hard to beat out of the box. Yes, there are mods that help it but few aftermarket variants are available simply because the GM piece is simply that good. This XS was experimental to a degree due to the lack of good data out there. Some have tried it with success, and others didn’t like it. This proves that the combination must be capable of moving a LOT of air. I think the XS is like a 17ish liter intake…it’s got a LOT of plenum volume and has long runners.
I wish this guy would have started the pull at 3k. I’d bet it’s making 400 ft lbs at 3k. The car is ridiculously strong for a 403. It’s a 403 that thinks it’s a 417, and makes 427 torque. Maybe it identifies as a 427?…LOL

 

1.7 or 1.8 rockers?

 

That's funny, I do exactly the same thing.

 

1.8 YT 10mm rocker

 

Total secret squirrel stuff!!

Its a custom grind I spec'ed and had Comp build for us....I have been using some of their newer lobe designs the last couple of years with good success and this cam is another example of that

It has a good bit of lift with the 1.8 rockers I supplied (.675 / .672) which helps tap into and take advantage of the cylinder heads higher flow portion of the curve.

This head peaks right in the .675 - 700 lift range making it ideal for a hot street strip set up without having to lift the valve a ridiculous amount. They are very efficient

Even at .600 lift the head is already in the 370+ CFM range with a finished CNC port size the same as an unported stock LS3 casting (260 cc's)


Regarding the intake choice I agree that some other choices would have made more peak power but this intake is perfect for this and most street builds.....a mid length runner FAST would probably have required at least 6500 RPM before exceeding the numbers this intake generated but it would be down 40+ ft/lbs of torque at anything under 5500 RPM's

The car on the street would be so much less fun to drive.....and I bet the actual track results (drag strip) would have been very close because the average power thru the gear splits wouldn't have been that much more with a manifold more optimized for higher RPM

It would have made a stronger peak number and carried longer with the mid length FAST for sexier higher RPM numbers (would have easily cleared 600 wheel with a 403 small bore build!) but I like what we accomplished here and for a street car its 100% the right set up.

Real happy with the outcome of this build (exceeded my higher expectations) and Scott did a great job with the assembly and blueprinting of the short block

Good stuff guys.....catch up soon

-Tony


PS......The difference in the dyno's was something else....this is why dyno numbers are almost useless to compare unless they are taken on the same dyno.

No different than flowbench numbers even when guy's aren't fudging the number to make them look better....LOL

Most testing equipment spits out different numbers.....that's why its always ideal to have a baseline run on the same dyno before you mod your car....that's the only true way to see what you really accomplished

While I would have liked to believe the original Dynocom hub dyno numbers it was pretty obvious by the torque output that to me they had to have been inflated but it doesnt take away the fact it was the highest NA car they had seen on that dyno and the owner of the shop was very impressed.

Hub dynos almost always read higher due to the fact that the engine isn't having to accelerate the weight and mass of the rear tires. That's a huge difference at the end of the day

What was cool was the shape of the two curves from two different locations was the same and that makes sense....that's exactly how it should have been

 

I like the "ish" under the pushrod length, lol

solid build.

 

Thanks for posting Tony. I hadn’t included the original dyno sheet, so I’ll throw it up for comparison sake…

 

One hell of a well thought out build! Nick is going to be miles of smiles. I would guess in drag set up it will go low low 10s pretty slick and likely high 9s. The 3.90 gears and mantic clutch are 100% perfect for the combo imo. Great job to all involved and nothing better than having someone like Scott giving the personal attention to your build and assembly. Can’t wait to see it in person!

only thing I don’t see is a trans/diff brace. I highly suggest it in the near future

 

I just got one of these after a discussion with Scott. He's right. This tool is so simple you'll wonder why you didn't think of it first. It is also dead nuts accurate. It makes using the old style checkers and counting bolt turns look like stone age methods. Thanks for the tip, Scott.....

 

I'm gonna order one as soon as I can find one. There website doesn't let me click on a link to buy.

 

I'll also add that I agree completely with Tony and Scott about dyno results. Dynos are a tool. Nothing more. I have stayed with the same tuner, and dyno, for 20 years. Rich Gala is a great tuner, and uses the same Mustang dyno he used at Wheel to Wheel over 20 years ago. He is now partners at Billy Briggs Racing Engines. They are an 80 mile drive one way for me. But by using the same dyno and tuner all these years, I can compare apples to apples. If I gain, great. If not, what went wrong, and why? Many guys use dyno numbers for their own personal billboard for power numbers (i.e. "racing" dynos). I could probably find someone else to fudge the numbers. But then I'd only be lying to myself....

 

Summit sells them also.....

 

Big 10-4 on dynos only being a tool.
ALSO.... it's totally about the COMBO. I think some folks lose touch with this fact. The parts NEED to work in close concert with each other.
It's Tony Mamo's strict adherence to these principles that help make him the moving force in engine builds that he is.
I always love reading his posts and learn from most all of them

 

That setup sounds like a good time especially with a stick! I highly recommend to use Pep Boy Futuras for the break in period 😄 and take vids of 4 gear burnouts

 

Hell yea! So excited for Nickypoo to be able to beat on this thing with confidence!.

Great dyno #'s.....good choice on a clutch. It should rip.

I told nick it should make 600+ whp. I know some think that's alot but for a 400ci~ ls that's where it should be if the engine is for a hotrod. Maybe I'm the outlier on that but a little thought can go a long way on a combo.

 

Thanks Philly-cheese! It may run like that with you or Dougie-fresh at the wheel, probably not my tank *** 🤣.
I think that brace would be a great plan, as she's a chonk. All that weight/power/gear will probably spell disaster.