462 Dyno Day 48s / RAIII Exh Manifolds ...
 

hi fellas,

wasn't sure whether to jump in here or not but pretty sure we all like "dyno day" posts .. and I feel I couldn't have pulled this off without the street section and you all (I'm sure ive read every. single. build post. multiple x's) so I thought I'd share.

the previous iteration of this motor that my dad and a machinist friend built in the mid 90s but wasn't run regularly till last season, was not cutting it. besides making metal, it developed a knock last fall. I've had this '69 judge since high school '82 and besides losing its original QJ (um, doh) .. motor is original to the car.

I've been a full time musician my whole life and have been lucky to work with and learn from many musicians from previous generations. this is how we maintain the Thread and learn. I bring this up 'cause when I started looking around for a builder in my area I kept hearing, over and over, about a nearby builder who was in his 80s and had been building race motors for 60+ years. I did visit a bunch of shops and every one of them seemed capable and likely, to build a badass motor but when I finally made the trip down to Nat Chiavettone's place and talked w/ him in person I knew he was a guy I could trust and relate with: friendly, confident, nothing to prove and zero drama.

along these lines i have got to bring up JayS here .. I've had jay on speed dial for the past year and he's fielded every half baked question I've thrown at him, w/ patience and friendliness. THANK YOU, Jay! couldn't have done it w/o you and I've learned a chit ton from you.

because the car's a judge I really wanted to stick w/ the iron 48s and raIII exhaust manifolds. I wanted the motor to be solidly in the 400s hp wise and into 500 ft lbs tq so I talked w/ nat about bringing heads down to Darrin at Nitemare in Ct. Darrin ended up doing a mild port job, opening heads up to 245/195cfm. nat completed heads himself. we decided to go all forged: a scat 4.25" crank, rods, and dished pistons w/ cr just over 10:1. cam is a bullet hydraulic roller 236/244 @ .050, 560 lift. I had QJ rebuilt last season for the 400 w/ 041 which wasn't even close to adequate for this 462. took a little playing with to dial it in. intake manifold was port matched. motor was dyno'd with what nat describes as junk headers., said the only Pontiacs he builds anymore, owner's are going w/ aluminum round port heads. he thinks most of the power loss I'll see when motor is in car will be from crushed 2 1/4" exhaust and mufflers not the raIII manifolds. before next season I'll remedy this.

motor's going in top of October. while it was getting done I had car's original m20 rebuilt but w/ "Italian" m22 wide ratio gear set. rear end is a 12bolt w/ 373s. fingers crossed I'll get a couple of solid months driving before it's too cold.

anyway, sorry for long winded post that reads like some corny award acceptance speech but who else can I share with if not the board here?

thanks again for all y'all's expertise, mike

486/547-wow great build and beautiful car!! I need to get glasses like Nat in that pic

Congrats on a nice build there!

It’s shows that properly port iron D port heads even on a large CID motor can make great power for a street / strip motor, and that wide flat over 1000 rpm wide peak torque band is very much what you want for a fun easy to drive anywhere street car.

The Dyno details also show that it’s calibration was accurate for the info it was providing.

Enjoy it since we still have some good driving days ahead here before winter .

Nice build, good job. Thanks for sharing

Those are great numbers, but your A/F ratio says there's more to be had. Considering your compression ratio, I'd be more comfortable with a WOT ratio closer to 12.0 and a BSFC number of .44 or .45 on average. I think your going to have the chance of engine knock on the street when you're running at thermostat temperature.

I agree I think it could hit 500HP with some more more work, especially with 4 tube headers instead of the 3 tube. I suggested it wasn’t worth spending a bunch of extra time and money looking for every last HP though because when he puts the engine back in the car it will have RA manifolds and eventually a nice full 2.5” exhaust. Much higher numbers and my guess is he would have had to retune the carb when it goes back in the car. I thought his builder did a nice job. I am guessing between the RA manifolds and full exhaust the AFR will drop down into the 12s in the car. If I recall correct it is also a 93 octane combo.

It’s going to be a fun ride for sure. It was entertaining watch everything fall in place, Mike gave great updates on the progress.

Good point on having the manifolds and exhaust system on the engine in the car. A little octane boost might be called for depending on air & water temps for "anti-ping" insurance.

Very similar build to mine and hp/ trq #’s are almost identical. Nice build!

Nice build and beautiful Judge!

thanks fellas ..

I saw AFR too (had to look up what BSFC meant!). Nat (and Jay) both told me it'd probably be closer to 12 w/ manifolds and full exhaust.
Guess I listen and check plugs once I'm mobile?

car's def a 10-footer ie what was once nice paint, even though car literally spent 25 years protected in my dad's garage, the lacquer is cracking all over, even flaking off trunk. hopefully taking care of trunk this winter.

jay, ha .. entertaining w/ great updates = where's the freakin' off button on this thing?

forgot to mention above that cam has a 112 LSA and 108 ICL

Congrats! Good power for a relatively mild build!

Are those numbers corrected? The barometric pressure was 30.56 ?

thanks, mchell .. I just looked at dyno sheet and it reads "correction method: standard" .. and I assume 30.56 is uncorrected #?
can't wait to get car together its been year it hasn't been on the road (and 25 years before that ha)

Nice!
 

Excellent numbers, congrats and I'm sure you will love the power!
What intake did you use?

car's original stock intake, just port matched fwiw.

and right back at you, builds you're working on look like alot of fun ; )

Badass stock running "400".

It’s a badass 462 now, not a 400.

That`s why I used the quotes.;)


The manifolds on a judge will throw em off.

What does BSFC have to do with Air Fuel Ratio and engine knock?

Stan

Love stealthy builds like this!

BSFC is a measurement of engine efficiency, calculated as the fuel consumption rate in pounds per hour divided by the horsepower produced at at the measured rpm. The result is the amount of fuel need to produce 1 horsepower for one hour at the engine rpm when the measurements were taken. Lower numbers indicate more efficient conversion of BTU energy to motion than to waste heat. His BFSC and A/F numbers indicate the engine is doing a very good job of burning all the fuel entering the cylinders, but the engine can likely produce more horsepower at a given rpm with a decrease in the A/F ratio (corresponding to a higher BSFC), and given the fact the coolant temperature was only 101 in an engine with 10:1 cr, his 12.7 and higher A/F ratios are only going to get leaner, increasing the chance of pre-ignition and an accompanying loss of power.

BSFC is definitely not the most important thing to look at, but it should correlate to volumetric and combustion efficiency. In my experience, numbers around .44 to .46 represent a good balance between power, efficiency and manageable combustion temperatures. Of the engines we had in the labs at GMI in the mid 70s, we got the best efficiencies from the 3.8L Buick V6 under development. When measuring the BTU loss to coolant, oil and exhaust, we were getting 31-33% of the energy in the fuel to the flywheel.

The best I saw was the 1973 Firebird with a turbocharged 350 built for the clean air car competition. Everything in the intake system was built undersize. It was a very small turbo pulling through a Holley staged 2-barrel from a Vega. The turbo fed a three pound coffee can plenum that had 1 inch copper tubing going to each intake port to keep velocities high. We also had one of the very first lock-up converter turbo 350 transmissions in the car. That setup managed to reach 41% thermal efficiency and delivered better mileage on the city circuit than the highway. But NOX emissions were high and there weren't any catalytic converters yet.